Dissertations / Theses on the topic 'Mating system evolution'

Species of Valerianaceae in South America represent one of the best examples of rapid diversification on a continental scale. The phylogeny of Valerianaceae has received a lot of attention within the last 10 years, but relationships among the South American species are fairly unresolved. Results from previous studies have not been well resolved with traditional genetic markers, most likely due to its recent and rapid radiation. Species in this clade exhibit a variety mating systems and inflorescence types. For the first part of this research I used several traditional plastid markers, and 3 new low copy nuclear markers to better resolve the phylogeny and then explore mating system evolution within the clade. For the second part of this research I collected high-throughput “next-generation” genomic sequence data from reduced representation libraries obtained using genotyping-by-sequencing (GBS) protocols, along with several phylogenetic methods, to try to further resolve the phylogeny of this group.

Sex chromosomes experience distinct evolutionary environments, due to their unusual pattern of inheritance, and studies of sex chromosome evolution can shed light on the fundamental evolutionary forces acting across the genome as a whole. Here, I combine genomic and transcriptomic data across a wide range of avian species to explore the evolutionary processes governing sex chromosome evolution. Birds are female heterogametic and therefore it is possible, via comparisons with male heterogametic species, to identify the fundamental factors driving sex chromosome evolution, versus those associated with sex. In this thesis, I uncover a complex mosaic of recombination suppression between the Z and W chromosomes, characterized by repeated and independent divergence of gametologs, together with ongoing genetic exchange. Additionally, I highlight the role of mating system, and interplay between evolutionary forces, in driving coding and expression evolution on the Z and W chromosomes. My findings indicate that although the Z chromosome is masculinized for male-specific effects, the magnitude of genetic drift acting on Z-linked genes is elevated in promiscuous relative to monogamous mating systems. In contrast, evolution of the female-limited W chromosome is governed predominately by purifying selection. Together, my results suggest that the role of the Z chromosome in encoding sexual dimorphisms may be limited, but that W-linked genes play a significant role in female-specific fitness. In conclusion, my findings reveal the power of mating system in shaping broad patterns of genome evolution.

High levels of inbreeding are expected to cause a strong reduction in levels of genetic variability, effective recombination rates and in adaptation compared with related outcrossing populations. The evolution of mating systems can thus have profound effects on the evolution of genome structure and diversity. In this thesis I test these predictions, using the plant genus Arabidopsis as a model system. I examine patterns of genome organisation, DNA sequence polymorphism and divergence in the highly self-fertilizing Arabidopsis thaliana, and compare them to those of its self-incompatible, outcrossing relative Arabidopsis lyrata. From comparisons of rates of substitution, there is no evidence for a higher rate of amino acid substitution in A. thaliana, suggesting that slightly deleterious amino acid mutations may not be the primary source of protein evolution in these species. In contrast with results from published data, analysis including polymorphism data also reveals no difference in the ratio of nonsynonymous to synonymous polymorphism between species, suggesting that there may not be a general elevation of amino acid polymorphism in A. thaliana. Comparisons of intron length reveal evidence for consistently smaller introns in A. thaliana, perhaps reflecting the action of directional selection on noncoding DNA length in an annual plant. Analysis of codon usage bias at orthologous loci shows evidence for consistently higher GC content at third codon positions in A. lyrata. Comparisons of base composition in introns and polymorphism patterns for preferred and unpreferred synonymous mutations show no evidence for a shift in mutation pattern or rates of biased gene conversion between species, suggesting that the difference in codon bias might reflect a relaxation of natural selection in A. thaliana. However, comparisons of codon usage between species using a measure of codon bias based on relative abundance of tRNA genes reveals no significant difference between species, and there is no evidence for a difference in the relative rates of preferred and unpreferred substitutions. As there is a good correlation between the frequency of preferred codons defined by tRNA abundance and levels of gene expression, these results suggest a neutral explanation for the difference in GC content. Comparisons of multilocus neutral variability between A. thaliana and A. lyrata show the expected decrease in average within-population diversity in A. thaliana, but this is complicated by strong geographic structuring of variability in A. lyrata, probably associated with recent demographic history. Consistent with an influence of demographic history, analysis of intralocus linkage disequilibrium suggests a strong deficiency of the effective rate of recombination in A. lyrata. In contrast, A. thaliana shows approximately the amount of linkage disequilibrium expected in a highly self-fertilising species. These results suggest a possible role for population admixture in northern, postglacial populations of A. lyrata. A whole-genome analysis of transposable elements in A. thaliana indicates that recombination rate heterogeneity does not play an important role in driving their distribution in this species, and that gene density is the primary determinant of TE abundance in the genome. Combined with evidence from other complete eukaryotic genomes, this pattern is consistent with a role of inbreeding in reducing effective rates of recombination genome-wide, and thereby reducing the effect of recombination rate heterogeneity on genome structure. Polymorphism analysis of 18 foci located in regions of contrasting recombination rate in an Icelandic population of Arabidopsis lyrata reveals no evidence for the expected positive correlation between recombination rate and nucleotide diversity. A maximum likelihood analysis of polymorphism and divergence for these data shows evidence for significantly elevated diversity compared with divergence at a centromeric locus, suggesting the possibility of balancing selection in this region. Alternatively, recent demographic history may have contributed to an uncoupling of the expected relationship between recombination and variability, and an inflation of the variance in diversity across loci. The results of this thesis provide some evidence for the evolution of genome structure between related Arabidopsis species, but no strong evidence for differences in the efficacy of natural selection. These results emphasize the importance of understanding the influence of population history on the action of natural selection at the molecular level.

It is not clear whether genes of the innate immune system of vertebrates are subject to the same selective pressures as genes of the adaptive immune system, despite the fact that innate immunity genes lie directly at the interface between host and pathogens. The lack of consensus about the incidence, type, and strength of selection acting on vertebrate innate immunity genes motivated this study. The goal of this work was to elucidate the general principles of innate immune receptor evolution within and between species. A phylogenetic analysis of the Toll-like receptor 5 (TLR5) in primates showed an excess of nonsynonymous substitutions at certain codons, a pattern that is consistent with recurrent positive selection. The putative sites under selection often displayed radical substitutions, independent parallel changes, and were located in functionally important regions of the protein. In contrast with this interspecific pattern, population genetic analysis of this gene in humans and chimpanzees did not provide conclusive evidence of recent selection. The frequency and distribution of a TLR5 null mutation in human populations further suggested that TLR5 function might be partially redundant in the human immune system (Appendix A). Comparable analyses of the remaining nine human TLRs produced similar results and further pointed to a biologically meaningful difference in the pattern of molecular evolution between TLRs specialized in the recognition of viral nucleic acids and the other TLRs (Appendix B). The general picture that emerges from these studies challenges the conventional idea that pattern recognition receptors are subject to an extreme degree of functional constraint dictated by the recognition of molecules that are essential for microbial fitness. Instead, TLRs display patterns of substitution between species that reflect an old history of positive selection in primates. A common theme, however, is that only a restricted proportion of sites is under positive selection, indicating an equally important role for purifying selection as a conservative force in the evolution of this gene family. A comparative analysis of evolutionary rates at fifteen loci involved in innate, intrinsic and adaptive immunity, and mating systems revealed that more promiscuous species are on average under stronger selection at defense genes (Appendix C). Although the effect is weak, this suggests that sexual promiscuity plays some role in the evolution of immune loci by affecting the risk of contracting infectious diseases.

Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2005.
Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0033. Adviser: Lynda F. Delph. "Title from dissertation home page (viewed Feb. 9, 2007)."

The Mercurialis annua L. (Euphorbiaceae) species complex comprises a group of closely related lineages that present a wide range of sexual-systems, making it a valuable model for the study of plant sexual-system evolution. Within this polyploid complex, diploid populations are dioecious, and polyploid populations either monoecious or androdioecious (males coexist with functional hermaphrodites). The primary aim of this thesis was to use patterns of genetic diversity to elucidate the evolutionary origin and maintenance of the sexual-system diversity in M. annua. The phylogeny of the M. annua complex was reconstructed using chloroplast and ITS DNA sequence. This, in conjunction with morphometric analysis, showed that both hexaploid M. annua, and a novel species from the Canary Islands (newly described here as Mercurialis canariensis), were allopolyploid in origin. Such an origin for hexaploid M. annua suggests that androdioecy may have been able to arise in this group as a consequence of hybridisation between a monoecious lineage, tetraploid M. annua, and a dioecious lineage, M. huetii. Artificial crosses were used to show that hexaploid M. annua has disomic marker inheritance, and a statistical approach was developed to quantify genetic diversity and differentiation in polyploids with disomic inheritance. Strong gradients in genetic (allozyme) diversity at a pan-European scale were used to infer the existence of separate glacial refugia for dioecious and monoecious races of M. annua, at the eastern and western ends of the Mediterranean basin, respectively. A metapopulation model had previously been proposed to explain the ecological maintenance of androdioecy in M. annua. Here, population-level patterns of genetic diversity were used as an indirect test of this model. The discovery of lower within-population diversity, and of greater genetic differentiation between populations, for monoecious populations than for androdioecious populations was consistent with the metapopulation model, and suggests that androdioecy is maintained by the occurrence of regular local extinction.

Evolution is not always straight-forward, as selection pressures may differ between different generations of the same species. This thesis focuses on the evolution of life history of the model species, the Green-veined White butterfly Pieris napi. In central Sweden P. napi has two generations per year. The directly developing summer generation is short-lived and time stressed, compared to the diapausing generation. In paper I polyandry, defined as female mating rate, was shown to differ between generations but was unaffected by environmental factors. In paper II both males and females of the direct developing generation were shown to eclose more immature than the diapausing generation, indicating larval time constraints. Consistent with this, diapausing males mated sooner than direct developers. Directly developing females, however, mated sooner after eclosion than diapausing females, even though they are more immature. This was shown to negatively affect fecundity, but can pay off when the season is short. Paper III shows that directly developing males have less sex pheromones at eclosion than diapausers, and the differences in sex pheromone production is consistent with developmental time constraints and the differences in mating system. In P. napi and other polyandrous butterflies, males transfer a large, nutritious ejaculate at mating. Large ejaculates confer advantages under sperm competition, but as they are costly, males should adjust ejaculate size to the risk of sperm competition. In paper IV we found that males transfer on average 20% larger spermatophores under high male competition than at low competition. The same effect could be observed if we added male sex pheromone to the air in a mating cage without male-male competition. Paper V shows that males of the two generations respond differently to an increase in male-male competition, with diapausing males transferring larger spermatophores than direct developers at high male competition risk.

At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 5: Submitted manuscript.

Studies of mating systems and social organisation have been central to understanding of the evolution of social behaviour. The European badger Meles meles is a good species in which to study these processes, as its complex social system provides an opportunity to investigate how both natural and kin selection shape the evolution of mating systems and social structure. In this thesis, I use behavioural and genetic data to describe the mating system and social organisation of a high-density badger population and examine the occurrence of cooperative breeding. I genotyped 915 (85%) badgers trapped in Wytham Woods (1987–2005), 630 of which were cubs, and assigned both parents to 331 cubs with 95% confidence. This revealed a polygynandrous mating system, with up to five mothers and five fathers per social group. Mounting behaviour was also polygynandrous and I show the strongest evidence to date for multiple-paternity litters. I demonstrate, for the first time, that groups consisted of close and distant kin: approximately one third of group members were first-order kin, and overall group members had slightly lower relatedness levels than half-siblings. Within groups, adult and yearling females had higher pairwise relatedness than males, and neighbouring groups contained relatives. These findings result from the high level (42%) of extra-group paternities, 86% of which were assigned to neighbouring males. For the first time I show that females avoided inbreeding by mating with extra-group males; however, incestuous matings did occur. Promiscuous and repeated mountings were observed, which may reduce male–male aggression and infanticide, but may also promote sperm competition, genetic diversity, and / or genetic compatibility. Just under a third of adult males and females were assigned parentage each year and I quantify, for the first time, reproductive skew within badger groups. Correlations between relatedness, group productivity, and reproductive skew were not consistent with the predictions of incomplete-control models; rather, resource availability may play a role. Older and younger badgers displayed reduced annual breeding success, with male success increasing initially with experience. The Restraint, Constraint, and Selection Hypotheses did not explain the age-related breeding pattern in females. Variance in lifetime breeding success (LBS) was greater for males. Males that only bred within or only outside of their groups had half the LBS of males that did both. Females that were assigned maternity probably bred cooperatively and allonursed non-offspring, which has not been demonstrated previously. No benefit was established, however, in terms of litter size, probability of offspring breeding, or offspring lifetime breeding success, with more mothers in a group. In conclusion, badger social groups are fostered through kinship ties. Polygynandry and repeated mounting may have evolved originally to reduce male–male aggression and infanticide by males, through paternity masking. Although plural breeding occurs, group living appears to be costly. Motivation to disperse may be reduced through high-levels of extra-group paternities, which may also reduce inbreeding. Cooperative breeding among mothers may represent a low-cost behaviour with indirect benefits due to high levels of relatedness between female group-members. Badger sociality therefore represents an early stage in the evolution of social behaviour.

Studies of demography and population structure give insight into important evolutionary processes such as speciation and diversification. In the present work I perform such studies in the genus Capsella, which has three species: C. grandiflora, an outcrossing diploid, C. rubella a selfing diploid, and C. bursa-pastoris a selfing tetraploid. These three species make a good model system for evolutionary studies because they encompass two major plant evolutionary processes: mating system shifts and polyploidization. To conduct my studies I have gathered a large number of samples across the distributions of each species and scored them both phenotypically and genotypically: more specifically we measured flowering time and collected DNA sequence data. In the tetraploid C. bursa-pastoris we applied an association mapping approach which takes population structure into account to search for genetic variation associated with variation in flowering time. Flowering time is an important and highly adaptive trait which is frequently subject to natural selection. We found evidence of association between flowering time and several single nucleotide polymorphisms (SNPs) within the flowering locus C (FLC) and cryptochrome 1 (CRY1). In the case of FLC these SNPs code for nonconsensus splice site variation in one of the two copies of the gene. The SNPs could potentially have functional consequences and our results imply that non-functionalization of duplicate genes could be an important source of phenotypic variation. Using a novel coalescent based approach, we investigated the polyploid origin of C. bursa-pastoris and find evidence supporting a recent autopolyploid origin of this species. In the two diploid species, I use sequence data to investigate population structure and demographic history and to assess the effects of selfing on C. rubella. Observed patterns of population structure and genetic diversity in C. rubella can be explained by a combination of both demographic history and mating system. Observed patterns in C. grandiflora suggest that the investigated populations do not deviate strongly from the SNM, which has rarely been found in modern demographic studies. Finally, we investigate the effect of sampling strategy on demographic inference. Extensive sampling both within and across our populations allow us to empirically test the effect of sampling strategy on demographic inference. We complement the empirical analysis with simulations and conclude that the effect of sampling strategy is in many cases weak compared with that of demographic events. Nevertheless, these effects are real and have the potential to lead to false inference and therefore sampling strategy should be carefully considered in demographic studies.
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 725

Orientador: Célio Fernando Baptista Haddad
Resumo: As forças de seleção natural e sexual atuam sobre os indivíduos e podem os levar ao isolamento reprodutivo. O acúmulo de modificações evolutivas pode levar ao surgimento de novas entidades. Espécie é unidade basal em biologia; assim, com sua exuberante biodiversidade, a Mata Atlântica é uma floresta neotropical fundamental para estudos de processos evolutivos em anfíbios anuros. Reunindo os gêneros Cycloramphus, Thoropa e Zachaenus, a família Cycloramphidae agrupa espécies de anuros saxícolas e terrestres, todas endêmicas da Mata Atlântica brasileira. Pelos seus hábitos especializados de vida e reprodução, os cicloramfídeos formam um grupo atrativo para estudos evolutivos. Na presente tese são apresentados quatro capítulos que abordam três escalas distintas da evolução: a diversificação entre espécies, populações e indivíduos. São abordados: (1) a filogenia molecular multilocus de Cycloramphus-Zachaenus, demonstrando que a evolução da terrestrialidade no clado se correlaciona com o dimorfismo sexual em tamanho; (2) a diversificação fenotípica associada a diversificações genéticas em populações de C. boraceiensis e C. dubius, demonstrando que estas duas espécies-irmãs saxícolas apresentam zona de contato e hibridação; (3) o sistema de acasalamento promíscuo e as relações sociais em C. boraceiensis, demonstrando que tamanho das fêmeas e dos machos e parentesco genético influenciam a formação dos casais; e (4) o sistema de acasalamento poligínico com fidelidade na espécie saxíco... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Natural and sexual selection forces act on individuals and may lead to reproductive isolation. The increase in evolutionary modifications may lead to the emergence of new entities. Species is the basal unity in biology; thus, with its exuberant biodiversity, the Atlantic rainforest is a fundamental Neotropical forest for studies of evolutionary processes in anuran amphibians. Comprising the genera Cycloramphus, Thoropa, and Zachaenus, the family Cycloramphidae gathers saxicolous and terrestrial anuran species, all endemic to the Brazilian Atlantic rainforest. Because of their specialized life and reproductive habits, cycloramphids are an attractive group for evolutionary studies. In the present thesis we show four chapters that address three distinct scales of evolution: the diversification among species, populations, and individuals. We goaled: (1) the multilocus molecular phylogeny of Cycloramphus-Zachaenus, demonstrating that the evolution of terrestriality in the clade is correlated with the sexual size dimorphism; (2) the phenotypic diversification associated with the genetic diversifications in populations of C. boraceiensis and C. dubius, demonstrating that these two saxicolous sister species show a contact zone and hybridization; (3) the promiscuous mating system and the social relations in C. boraceiensis, demonstrating that female and male sizes, and mate relatedness influence pair formation; and (4) the polygynic mating system with fidelity in the saxicolous specie... (Complete abstract click electronic access below)
Doutor

Cis-regulatory changes in e.g. promoters or enhancers that affect the expression of a linked focal gene have long been thought to be important for adaptation. In this thesis, I investigate the selective importance and genomic correlates of cis-regulatory variation and divergence in the genus Capsella, using massively parallel sequencing data. This genus provides an opportunity to investigate cis-regulatory changes in response to polyploidization and mating system shifts, as it harbors three diploid species, the outcrosser Capsella grandiflora and the selfers Capsella orientalis and Capsella rubella, as well as the tetraploid Capsella bursa-pastoris. We first identify cis-regulatory changes associated with adaptive floral evolution in connection with the recent switch to self-fertilization in C. rubella and show that cis-regulatory changes between C. rubella and its outcrossing close relative C. grandiflora are associated with differences in transposable element content. Second, we show that variation in positive and purifying selection is important for the distribution of cis-regulatory variation across the genome of C. grandiflora. Interestingly, the presence of polymorphic transposable elements is strongly associated with cis-regulatory variation in C. grandiflora. Third, we show that the tetraploid C. bursa-pastoris is of hybrid origin and investigate the contribution of both parental species to gene expression. We show that gene expression in the tetraploid is partly explained by cis-regulatory divergence between the parental species. Nonetheless, within C. bursa-pastoris there is a great deal of variation in homeolog expression. In summary, this thesis explores the role of cis-regulatory changes for adaptive morphological changes in connection to a shift in mating system, the role of cis-regulatory divergence between progenitor species for an allopolyploid as well as the impact of positive and purifying selection on cis-regulatory variation within a species.

Black scavenger flies are characterized by sexual behaviours that are very unusual in insects. I have studied two of the most remarkable elements of their mating systems: the timing of copulations immediately after an oviposition bout (post-oviposition matings) and the males' escorting of ovipositing females. In a study of the patterns of sperm precedence in one sepsid species, I found that the sepsids' peculiar timing of matings is not associated with unusual patterns of sperm precedence: sepsid males displace rival sperm and achieve a large last male advantage, which is the most common outcome of sperm competition in insects. I discuss the potential significance of sperm transfer mechanisms for the sepsids' timing of matings, and I consider factors that may favour the maintenance of post-oviposition matings in sepsid populations. In a survey of sepsid mating patterns, I found that post-oviposition matings are typical of many black scavenger flies and that mating systems characterized by the absence of copulations with gravid females may have arisen early in the family's evolutionary history. In several black scavenger flies, ovipositing females are commonly accompanied by an escorting male, and in all but one of the species I have studied, escorting is pre-copulatory. In several species, I found pronounced geographic variation in the expression of this trait. I argue that sepsids share certain characteristics which may have facilitated multiple independent origins of escorting behaviour. In order to investigate the adaptive significance of escorting, I have conducted a comparative study of patterns of sexual size dimorphism and sex ratios at oviposition sites in conspecific populations that show great divergence in the expression of this trait. The results of this research support the pre-copulatory mate guarding hypothesis for the adaptive significance of escorting behaviour, and they suggest that conspecific populations vary significantly in the degree or nature of sexual selection acting both on morphology and behaviour of males. Furthermore, in a study of the genetic architecture of escorting behaviour, I found that the observed behavioural variation has a genetic basis: the expression of escorting behaviour is a quantitative trait with a significant sex-related component of inheritance.

The aim of this thesis was to study the evolution of reproductive systems and reproductive traits in the fungal genus Neurospora. More specifically, I have investigated the evolutionary forces shaping the genes involved in sexual reproduction, focusing on mating-type (mat) and pheromone receptor (pre) genes. Neurospora contains species exhibiting three different mating systems, i.e., heterothallism (self-incompatibility), homothallism (self-compatibility) and pseudohomothallism (partial self-incompatibility). First, a robust phylogeny of Neurospora was established. The phylogenetic analyses revealed multiple independent transitions in reproductive life style during the evolutionary history of the genus. We argued for a heterothallic ancestor of the genus, although our subsequent ancestral reconstruction analyses favored a homothallic ancestor. To be able to settle the ancestral mating system, we zoomed in on the structural architecture of the mat-locus in four homothallic species of Neurospora, thought to have arisen from independent transitions. Our results led us to suggest two different genetic mechanisms (translocation and unequal crossover) to explain the transitions in mating system from heterothallism to homothallism. We pointed out that the mating-system transitions in Neurospora are unidirectional, and suggested that transposable elements might be driving the transitions. In conclusion, we suggest a heterothallic ancestor for Neurospora, and that at least six transitions to homothallism and two transitions to pseudohomothallism have occurred in its evolutionary history. Further, we used the phylogeny of Neurospora as a framework to test if the evolution of pre-genes (pre-1 and pre-2) in hetero- and homothallic Neurospora is dependent on mating systems and/or even the homothallic clades themselves (i.e., mating-system and/or switch-dependent). The molecular evolution results suggest that pre-1 and pre-2 are overall functional in both homothallic and heterothallic Neurospora. The molecular evolution of pre-1 seems to be independent of mating-system or homothallic clade, and we detected signs for positive selection in the C-terminal tail. For pre-2 we found no support for mating-system dependent evolution, but indications for switch-dependent evolution. In this study we also included expression analyses of both pre- as well as mat-genes, with the prospect to assess functionality and regulation. During this thesis work, we also performed a phylogenetic study were we found that reproductive genes might be more permeable to introgression than other genes, which is in contrast to theoretical expectations. In the last study, we confirmed the co-existence of two alternative splice variants of the pheromone receptor gene pre-1 in Neurospora crassa, and performed expression profiles studies using quantitative RT-PCR. I hope this thesis work will further strengthen Neurospora as a model for research in evolutionary genetics.

The drivers of fidelity and divorce of pair-bonded individuals, along with their fitness consequences, are of great interest as they influence mating systems, population structure and productivity, and gene flow. Socially monogamous birds offer an ideal opportunity to study divorce since they show great variability in the extent to which pair bonds are maintained. However, there has been little consensus as to whether divorce is a behavioural adaptation to improve a mating situation, or a consequence of other processes. Moreover, the biological and ecological correlates of fidelity are difficult to address because previous work has been based on indirect and potentially biased methods. Finally, in terms of process, the link between the process of mate choice and subsequent mating decisions has been largely inaccessible to study. My doctoral thesis addressed these significant gaps in our understanding of cause, process and consequence in the formation and dissolution of pair bonds in socially monogamous birds. I accomplished this in three principal ways. First, I conducted a robust phylogenetic meta-analysis on 84 studies across 64 species to assess the existing empirical evidence that divorce in socially monogamous birds is adaptive (in terms of breeding success). This analysis revealed that divorce is, in general, adaptive as it is both triggered by relatively low breeding success and leads to improvement in success. Next, I developed a novel probabilistic multievent capture–mark–recapture framework that provides joint estimates of survival and fidelity while explicitly accounting for imperfect detection, capture heterogeneity, and uncertainty in pair status. By applying this model to breeding data on a wild great tit population I showed that birds that remain faithful to their partner exhibit higher survival rates and are more likely to remain faithful in the next breeding season than do birds that change partners. Subsequently, I confirmed the generality of a survival benefit by applying the model to breeding data on other tit populations. Then, by applying the model to data from a population of mute swans, I showed that fidelity decreases the likelihood of skipping breeding and mortality in this long-lived species, and that these effects depended on age, individual quality, and immigration status. Finally, I investigated how the timing of pair formation influences breeding success and divorce probability using five years of data on the over-winter social behaviour of great tits. I showed that early pair formation had a positive effect on fitness components, influencing the likelihood of divorce only indirectly, through breeding success. Further, my work revealed that males, but not females, with higher numbers of the female associates in winter, and males whose future breeding partners were ranked low amongst these, divorced more often. My research makes a significant contribution to our understanding of divorce and fidelity, and generates a number of important implications for future studies. First, my work establishes that divorce is adaptive for breeding success. Second, my results highlight that survival is an important (and likely, widespread) fitness consequence of pairing decisions. Third, I provide a novel statistically rigorous modelling framework for estimating fidelity-rates and testing hypothesis about fidelity that overcomes many of the inherent biases in traditional estimates. Fourth, it provides the first evidence for a selective advantage of early pair formation in wild, thus highlighting that there are benefits to pair familiarity that manifest via social associations of individuals prior to breeding. Finally, my work reveals the selective pressures operating via the social environment can ultimately influence the mating strategies individuals adopt.

The evolution of selfing from outcrossing is one of the most frequent mating system transitions in angiosperms. Plants that are highly selfing typically exhibit a suite of morphological traits termed a "selfing syndrome," including reduced corollas and reproductive structures, loss of corolla pigmentation, little anther-stigma separation, and a low pollen/ovule ratio. The overall consensus among scientist is that the morphological changes that accompany the transition to selfing are adaptive and thus a product of natural selection. Few attempts, however, have been made to determine whether traits of the selfing syndrome are truly an operation of natural selection or if genetic drift could be the acting force. My dissertation examines the roles that natural selection and genetic drift played in the evolution of the selfing syndrome in Ipomoea lacunosa. With the use of field observations, crossing data, and molecular analyses, I show that I. lacunosa has evolved increased selfing ability, decreased anther-stigma distance and smaller, white flowers, compared to its closest relative I. cordatotriloba. Furthermore, using a standard QST - FST comparison, I evaluated the relative importance of selection and drift in the evolution of the selfing syndrome in I. lacunosa. I also identified the genetic basis of flower color divergence between I. lacunosa (white) and I. cordatotriloba (purple) and examined patterns of variation to determine if selection or genetic drift caused the divergence. Analyses revealed that the traits of I. lacunosa characteristic of the selfing syndrome have evolved as a product of natural selection, not genetic drift.

Dissertation

To understand how mating systems evolve, we depend on both (i) theoretical explanations and predictions, supported by mathematical modelling, and (ii) quantitative tools to test predictions rigorously. This thesis is divided equally between these two aims. The first three papers explore the evolution of mating systems using analytic and simulation models. I begin by considering a long-standing puzzle in marine invertebrate systems: the widespread association between a species' body size, whether it is hermaphroditic or has separate sexes, and its mode of fertilisation (i.e. whether eggs and sperm are released into the water or retained by the adult until fertilisation). I argue that local competition among eggs for fertilisation can explain these patterns, which arise in taxa as diverse as sea stars, corals and polychaete worms (Paper 1). I then turn to egg trading – the alternating exchange of egg parcels during mating by simultaneous hermaphrodites – which is one of the best-supported cases of reciprocity between non-relatives. I show that egg trading is under positive frequency-dependent selection and should evolve most easily when potential mates are encountered frequently (Paper 2). Once evolved, egg trading selects for female-biased sex allocation. I explain how this bias allows simultaneous hermaphroditism to persist stably, even in motile species living at high population densities, where simultaneous hermaphroditism is otherwise predicted to be unstable (Paper 3). These three papers contribute to the resolution of Williams' paradox – the mismatch between the empirical distribution of hermaphroditism and our theoretical expectations – by providing finer-grained predictions for when hermaphroditism should occur. The last three papers provide quantitative tools for the measurement of natural (and particularly sexual) selection. I argue that pre-mating sexual selection should be understood as a two-step causal process: traits affect mating success, which in turn affects reproductive success. Most previous work has focussed too narrowly on one or the other of these steps, leading to confusion about what sexual selection is and how we should measure it. I provide a new statistical framework that integrates both steps in the sexual selection pathway, and includes a third path whereby traits directly affect reproductive success. This leads to better estimates of the strength of sexual selection on traits (Paper 4). I then compare various indices of sexual selection, often used in comparative work, that do not rely on trait measurements. I show that the recently defined Jones index outperforms all others in predicting the actual strength of sexual selection, because it accounts for both steps in the sexual selection pathway (Paper 5). Lastly, I provide a new way to quantify the total selection acting on a trait, including both directional and non-directional selection (Paper 6).

Yes
A crucial step in the transition from outcrossing to self-fertilization is the loss of genetic self-incompatibility (SI). In the Brassicaceae, SI involves the interaction of female and male speci-ficity components, encoded by the genesSRKandSCRat the self-incompatibility locus (S-lo-cus). Theory predicts thatS-linked mutations, and especially dominant mutations inSCR, arelikely to contribute to loss of SI. However, few studies have investigated the contribution ofdominant mutations to loss of SI in wild plant species. Here, we investigate the genetic basis of loss of SI in the self-fertilizing crucifer speciesCapsella orientalis, by combining genetic mapping, long-read sequencing of completeS-hap-lotypes, gene expression analyses and controlled crosses. We show that loss of SI inC. orientalisoccurred<2.6 Mya and maps as a dominant trait totheS-locus. We identify a fixed frameshift deletion in the male specificity geneSCRand con-firm loss of male SI specificity. We further identify anS-linked small RNA that is predicted tocause dominance of self-compatibility. Our results agree with predictions on the contribution of dominantS-linked mutations toloss of SI, and thus provide new insights into the molecular basis of mating system transitions.
Work at Uppsala Genome Center is funded by 550 RFI / VR and Science for Life Laboratory, Sweden. The SNP&SEQ Platform is supported by 551 the Swedish Research Council and the Knut and Alice Wallenberg Foundation. V.C. 552 acknowledges support by a grant from the European Research Council (NOVEL project, 553 grant #648321). The authors thank the French Ministère de l’Enseignement Supérieur et de la 554 Recherche, the Hauts de France Region and the European Funds for Regional Economical 555 Development for their financial support to this project. This work was supported by a grant 556 from the Swedish Research Council (grant #D0432001) and by a grant from the Science for 557 Life Laboratory, Swedish Biodiversity Program to T.S. The Swedish Biodiversity Program is 558 supported by the Knut and Alice Wallenberg Foundation.

Understanding how floral traits covary with one another and with mating patterns is an important step in understanding how and why mating systems evolve. I examined the evolution of floral and mating system variation in Camissoniopsis cheiranthifolia (Onagraceae), a species that exhibits divergence in key floral traits expected to be associated with variation in the relative importance of outcrossing vs. self-fertilization. I combined geographic surveys of floral variation with genetic estimates of the proportion of seeds outcrossed (t) and confirmed that t covaried with corolla width and herkogamy in a predictable way both within and among populations. I then performed geographic surveys, manipulative experiments and genetic analyses to evaluate the potential role that; inbreeding depression (ID), interactions between flowers, pollinators and florivores, and reproductive assurance (RA) may have played in shaping and/or maintaining the geographic pattern of mating system variation in this species. The main selective factor maintaining outcrossing in large flowered (LF) populations appears to be ID, which was much stronger in LF compared to small flowered (SF) populations. These results are also consistent with purging of ID in SF populations. Increased selfing appeared to alleviate pollen limitation (PL) because it was associated with higher and less variable fruit set and reduced florivory by a microlepidopteran. However, evidence that florivores preferentially attacked larger flowers was equivocal. LF experienced stronger PL than SF populations suggesting that one condition for the evolution of selfing via RA is met in outcrossing populations. Floral emasculation experiments revealed that the timing of selfing also covaried with flower size among and within populations. SF self-pollinate before flowers open but LF do not, suggesting that selfing evolved in response to chronic outcross PL. Negative side effects of emasculation were detected which prevented a clear interpretation of the RA value of selfing. Given that much of what is known about RA comes from emasculation experiments, my results suggest that the assumptions of this approach, which are rarely verified, require more serious consideration. Taken together my results suggest that C. cheiranthifolia has evolved multiple stable mixed mating systems perhaps in response to selection for RA.
Thesis (Ph.D, Biology) -- Queen's University, 2012-12-30 14:13:46.366

Thesis (M.S.)--Florida State University, 2004.
Advisor: Dr. Alice A. Winn, Florida State University, College of Arts and Sciences, Dept. of Biological Science. Title and description from dissertation home page (viewed Jan. 18, 2005). Includes bibliographical references.

Bryophytes, by their haploid dominant life cycle, possess several unique qualities ideal for study of mating patterns. In particular, the possibility of intragametophytic selfing in some species, and the vegetative propagation of gametes allow for a unique window into the haploid stage that is intractable in other groups. Despite these advantages, there have been relatively few studies on mating patterns bryophytes in natural populations. Sphagnum (peatmoss) is an excellent case study in the interactions between sexual condition, ecology, and mating patterns. In the first Chapter, we use microsatellites to characterize the genetic diversity and mating patterns in fourteen species of Sphagnum, diverse in sexual condition (separate vs combined sexes in the haploid stage) and ecology (microhabitat variance along the water table). We find that genetic diversity and mating patterns are related only in species with separate sexes, that sexual condition and ecology have interacting effects on inbreeding coefficients, and that inbreeding depression is not a common phenomenon in Sphagnum. In the second Chapter, we conduct an intensive survey of one population of Sphagnum macrophyllum, to detect whether variance in haploid fecundity and mating success is related to diploid fitness. We find a relationship between mating success and fecundity (a signal of sexual selection), and fitness of the diploid generation is connected to the parentage of the haploid generation. Finally, in Chapter 3 we use phylogenetic comparative methods to track the phylogenetic signal in microhabitat preference in Sphagnum. We find extremely fast rates of evolution along the micronutrient gradient, but high phylogenetic signal along a hydrological gradient. Given that Sphagnum species living high above the water table have reduced water availability, phylogenetic signal in the hydrological gradient has macroevolutionary implications for mating systems in Sphagnum.

Dissertation

There are few other structures in nature from which evolution has generated such wide diversity as the flower or inflorescence, and this diversity is commonly attributed to the influence of their animal visitors. By outsourcing their mate choice to pollinators, plants have left themselves - and especially their flowers - subject to the selective forces imposed by the behaviour, cognition and perception of the pollinators that serve them. The orchids provide some of the most remarkable and extreme examples of adaptations to specific animal pollinators. Perhaps one of the most peculiar of these strategies is sexual deception, whereby male insects are lured to the flower by mimicry of the female sex pheromone. This seemingly unlikely strategy has evolved multiple times independently on different continents in different parts of the orchid phylogeny which raises the question of what adaptive advantages might underlie such a strategy. This multidisciplinary thesis studies gene flow and pollinator behaviour in two sympatric sexually deceptive orchids in the genus Chiloglottis. The two species attract their specific wasp pollinators through emission of distinct species - specific semiochemicals. Since floral volatiles play a pre-eminent role in pollinator attraction, Chiloglottis provides an excellent case study for examining the interaction between floral volatile chemistry, pollinator behaviour and the evolutionary dynamics of populations. The thesis begins with a review of floral volatiles and their role in pollinator attraction and plant speciation. The literature is used to develop a research framework of six testable hypotheses under which we might productively explore the influence of floral volatiles on plant evolution. These hypotheses are then explored in the study system over the following chapters. A study of pollinator specificity, neutral genetic differentiation and floral chemistry demonstrates that the chemical mimicry crucial to sexual deception is responsible for reproductive isolation and potentially even speciation. Mating system and paternity analysis provide the first genetic evidence for multiple paternity in orchid broods. Extensive outcrossing is found to predominate and paternity assignment shows evidence for long distance pollen flow supporting the hypothesis that sexual deception promotes outcrossing and so minimizes the potentially deleterious effects of selfing. Lastly, an innovative new method is developed for tracking wasps in the field. Application of this technique to a population of orchid-pollinating wasps reveals detailed information about their movement and mating behaviour. The findings support the conclusion that sexual deception is a superb adaptive solution to the problem flowers face of simultaneously attracting pollinators and persuading them to leave quickly.

This thesis explored aspects of diversity in the ascomycete genus Pleospora and the new family Aliquandostipitaceae. In Pleospora, the main focus was on mating system evolution. I found that homothallism in Pleospora evolved in three different ways from heterothallism. One origin of homothallism resulted from a horizontal transfer across lineages involving a MAT locus. The approach chosen to investigate mating system evolution in Pleospora was based on delimiting the polyphyletic genus Pleospora to Pleospora sensu stricto, inferring a robust species phylogeny of Pleospora sensu stricto and cloning and examining the master regulator locus of sexual development in ascomycetes, the MAT locus. Conclusions were then drawn by integration of the total evidence. Research of mating system evolution in Pleospora was initiated by confirmation of the monophyly of Pleospora isolates with Stemphylium asexual states. This group contained the type of Pleospora, and was thus called Pleospora sensu stricto. Contributing towards a monophyletic genus Pleospora, the marine species P. gaudefroyi collected in British Columbia, and lacking a Stemphylium asexual state, was transferred to the new genus Decorospora. Phylogenetic 18S rDNA analyses and Shimodaira-Hasegawa and Kishino-Hasegawa tests rejected the null hypothesis of monophyly for the two taxa. Instead, Pleospora gaudefroyi grouped distantly from P. herbarum, at the base of the family Pleosporaceae confirming the importance of a Stemphylium asexual state for the definition of Pleospora sensu stricto in this case. Since no existing genus was available to accommodate P. gaudefroyi, the new genus Decorospora had to be erected. To generate a species phylogeny of Pleospora sensu stricto, 114 ingroup taxa with Stemphylium asexual states were used. Phylogenetic analyses based on ITS, GPD, EF-1alpha and vmaA-vpsA DNA sequences with four different algorithms showed that Pleospora sensu stricto contained 22 phylogenetic species. Morphological species generally correlated well with phylogenetic species, except for the type P. herbarum whose phylogenetic species contained the four additional morphological species P. alfalfae, S. vesicarium, P. tomatonis and P. sedicola. Another conflict between morphological and phylogenetic species concept could arise in the phylogenetic species S. xanthosomatis that also contained an isolate of S. lycopersici, which, however, was not certain to represent the type of the species. Three phylogenetic species, one of which was exclusively collected in British Columbia, did not contain any morphological species and might be new to science. The protein-coding gene EF-1 alpha, parts of which where used for phylogenetic inference in Pleospora sensu stricto, contained an unusual intron in the phylogenetic species S. lancipes, S. trifolii and Stemphylium sp. strain P246. The intron was up to 1678 bp long, more than 1400 bp longer than introns in other species of Pleospora, it encoded a protein and was delimited at the 5'-end by the non-canonical splice site GGT, instead of GT. The ORF encoded by the introns of all three Pleospora species was most similar to a hypothetical zinc finger protein from the filamentous ascomycete Gibberella zeae. In case of experimental verification, this would be the first report of a 'parasitic' intron splice site in fungi. To continue investigations of mating system evolution in Pleospora sensu stricto, the MAT locus was PCR amplified using primers targeting the conserved motives alpha box and HMG box on the MAT1-1 and MAT1-2 genes respectively. A chromosome walking approach was then used to recover the MAT flanking regions and neighboring genes. It was shown that Pleospora sensu stricto contained three kinds of MAT regions, comprising either a MAT1- 1 or MAT1-2 idiomorph, or both MAT1-1 and MAT1-2 idiomorphs fused end to end, with the inverted MAT1-1 gene placed between ORF1 and MAT1-2. The genes flanking the MAT regions were ORF1 upstream, and BGL1 downstream of the idiomorphs, as in the close relative Cochliobolus. The idiomorphs of Pleospora sensu stricto were well delimited upstream of the MAT genes, terminating 16 or 17 amino acids inside ORF1 for respectively MAT1-1 and MAT1-2. The downstream boundary of the idiomorphs of Pleospora sensu stricto was poorly defined. There were no important differences between MAT genes from fused and separate MAT regions of Pleospora sensu stricto. MAT1-1 genes from both separate and fused regions were 1193 bp in length and contained one intron of 53 bp inserted at position 218. MAT1-2 genes were all 1093 bp long and comprised one intron of 55 bp inserted at position 491. The fused MAT regions of Pleospora sensu stricto consisted of MAT1-1 and MAT1-2 idiomorphs fused end to end, with MAT1-1 and flanking regions inverted. The gene arrangement found in the fused MAT regions was hypothesized to have evolved from ancestors with separate MAT regions by a crossover following the inversion of MAT1-1. The crossover was possibly facilitated by a short, 4 bp long stretch of DNA sequence similarity between MAT1-1 and MAT1-2 idiomorphs, resulting from the inversion of MAT1-1 plus flanking regions. MAT locus architecture and phylogenetic species correlated well. All phylogenetic species of Pleospora sensu stricto with more than one isolate contained both MAT1-1 and MAT1-2 isolates with separate MAT regions, or only isolates with fused MAT regions. MAT regions also correlated with mating systems in Pleospora sensu stricto. Species with fused MAT regions were homothallic, whereas species with separate MAT regions were heterothallic except one group that was ho mothallic. In all homothallic isolates with separate MAT regions, only MAT1-1 was detected. To evaluate the number of times a switch between mating systems occurred in the evolution of Pleospora sensu stricto, the species phylogeny was compared to the MAT phylogenies, in conjunction with the results from structural analyses of the MAT loci. MAT data of Pleospora sensu stricto suggested a single origin of the fused MAT regions from separate MAT regions. The single origin was supported by the monophyly of the fused MAT regions in MAT phylogenies, as well as the complicated structure of the fused MAT regions that was unlikely to have evolved twice independently. Whereas combined MAT evidence suggested a single origin of the fused MAT regions, the species phylogeny suggested at least two independent origins of the fused MAT regions. The conflicting evidence between MAT data and the Pleospora sensu stricto species phylogeny was consistent with a single origin of the fused MAT regions followed by a horizontal transfer across lineages, by sexual or asexual means. The one time evolution and subsequent horizontal transfer of the fused MAT region constituted two different evolutionary origins of the homothallics with fused MAT regions. A third origin of homothallism in Pleospora sensu stricto was in the group with a separate MAT locus containing a forward-oriented MAT1-1 gene. Homothallism in this case may be do to unknown mutations in other than the MAT genes, as possibly in the homothallic Neurospora africana. The last part of my thesis dealt with two new species in the new family Aliquandostipitaceae. Both Aliquandostipite khaoyaiensis and A. sunyatsenii were collected in Asia, and comprised several features not previously reported in ascomycetes. Novel morphological features were the presence of two types of fruitbodies side by side on the substrate, and the widest hyphae reported in ascomycetes. Overall morphological appearance suggested that species of Aliquandostipite were related to members of the order Pleosporales. However, molecular analyses of the 18S rDNA showed that species of Aliquandostipite did not belong to the Pleosporales, but instead grouped with uncertain affinity in the class Dothideomycetes.
Science, Faculty of
Botany, Department of
Graduate

Tese dout., Ecologia, Universidade do Algarve, 2007
Chez les algues brunes du genre Fucus, le caractère dioécie/hermaphrodisme a évolué plusieurs fois et l’hybridation est possible entre taxa possédant des systèmes de reproduction contrastés. Ces singularités en font un excellent modèle pour étudier l’évolution des systèmes de reproduction aussi bien à l’échelle macro que micro-évolutive. Une approche phylogénétique basée sur l’analyse de séquences chloroplastiques démontre que, comme chez les plantes supérieures, l’hermaphrodisme est ancestral chez ces algues. Cependant, les taxa F. vesiculosus, F. spiralis et F. ceranoides sont compris dans un râteau irrésolu, mettant en question leur statut d’espèce. Par l’utilisation de marqueurs du flux génique nous avons démontré que les trois espèces étaient bien isolées reproductivement quoique incomplètement. Afin d’étudier l’importance de la barrière aux flux géniques, nous avons concentré notre analyse à l’échelle d’un estran, zone de transition entre F. vesiculosus et F. spiralis. Différentes approches, alliant génétique et biologie des populations ont été utilisées. Comme attendu selon les modèles écologiques de l’évolution des systèmes de reproduction, l’espèce hermaphrodite montre un très faible ratio sperme/ovule tandis qu’une réallocation des ressources vers la fonction mâle est constatée chez l’espèce dioïque. Nos résultats démontrent que l’hybridation est fortement limitée spatialement par de faibles capacités de dispersion et un fort taux d’autofécondation chez F. spiralis. Elle est due au sperme F. vesiculosus fécondant les ovules de F. spiralis. Ces résultats apportent de nouvelles preuves de l’importance des régimes de reproduction lors du processus de spéciation.

Bees have had an intimate relationship with humans for millennia, as pollinators of fruit, vegetable and other crops and suppliers of honey, wax and other products. This relationship has led to an extensive understanding of their ecology and behavior. One of the most comprehensively understood species is the Western honeybee, Apis mellifera. Our understanding of sex-specific investment in other bees, however, has remained superficial. Signals and cues employed in bee foraging and mating behavior are reasonably well understood in only a handful of species and functional adaptations are described in some species. I explored the variety of sensory adaptations in three model systems within the bees. Females share a similar ecology and similar functional morphologies are to be expected. Males, engage mainly in mating behavior. A variety of male mating strategies has been described which differ in their spatiotemporal features and in the signals and cues involved, and thus selection pressures. As a consequence, males’ sensory systems are more diverse than those of females. In the first part I studied adaptations of the visual system in honeybees. I compared sex and caste-specific eye morphology among 5 species (Apis andreniformis, A. cerana, A. dorsata, A. florea, A. mellifera). I found a strong correlation between body size and eye size in both female castes. Queens have a relatively reduced visual system which is in line with the reduced role of visual perception in their life history. Workers differed in eye size and functional morphology, which corresponds to known foraging differences among species. In males, the eyes are conspicuously enlarged in all species, but a disproportionate enlargement was found in two species (A. dorsata, A. florea). I further demonstrate a correlation between male visual parameters and mating flight time, and propose that light intensities play an important role in the species-specific timing of mating flights. In the second study I investigated eye morphology differences among two phenotypes of drones in the Western honeybee. Besides normal-sized drones, smaller drones are reared in the colony, and suffer from reduced reproductive success. My results suggest that the smaller phenotype does not differ in spatial resolution of its visual system, but suffers from reduced light and contrast sensitivity which may exacerbate the reduction in reproductive success caused by other factors. In the third study I investigated the morphology of the visual system in bumblebees. I explored the association between male eye size and mating behavior and investigated the diversity of compound eye morphology among workers, queens and males in 11 species. I identified adaptations of workers that correlate with distinct foraging differences among species. Bumblebee queens must, in contrast to honeybees, fulfill similar tasks as workers in the first part of their life, and correspondingly visual parameters are similar among both female castes. Enlarged male eyes are found in several subgenera and have evolved several times independently within the genus, which I demonstrate using phylogenetic informed statistics. Males of these species engage in visually guided mating behavior. I find similarities in the functional eye morphology among large-eyed males in four subgenera, suggesting convergent evolution as adaptation to similar visual tasks. In the remaining species, males do not differ significantly from workers in their eye morphology. In the fourth study I investigated the sexual dimorphism of the visual system in a solitary bee species. Males of Eucera berlandi patrol nesting sites and compete for first access to virgin females. Males have enlarged eyes and better spatial resolution in their frontal eye region. In a behavioral study, I tested the effect of target size and speed on male mate catching success. 3-D reconstructions of the chasing flights revealed that angular target size is an important parameter in male chasing behavior. I discuss similarities to other insects that face similar problems in visual target detection. In the fifth study I examined the olfactory system of E. berlandi. Males have extremely long antennae. To investigate the anatomical grounds of this elongation I studied antennal morphology in detail in the periphery and follow the sexual dimorphism into the brain. Functional adaptations were found in males (e.g. longer antennae, a multiplication of olfactory sensilla and receptor neurons, hypertrophied macroglomeruli, a numerical reduction of glomeruli in males and sexually dimorphic investment in higher order processing regions in the brain), which were similar to those observed in honeybee drones. The similarities and differences are discussed in the context of solitary vs. eusocial lifestyle and the corresponding consequences for selection acting on males
Bienen und Menschen verbindet eine lange andauernde und enge Beziehung. Diese enge Beziehung hat zu einem ausgeprägten Wissen über die Ökologie und das Verhalten geführt. Die am besten untersuchte Bienenart ist die westliche Honigbiene, Apis mellifera. Der ausgeprägte Kasten- und Sexualdimorphismus hat das Studium der Geschlechterunterschiede vereinfacht und vorangetrieben. Unser Wissen über geschlechtsspezifische Investitionen bei Bienen ist jedoch in vielerlei Hinsicht lückenhaft geblieben. Die Signale und Achtungssignale die im Paarungsverhalten eine Rolle spielen sind nur bei einer Handvoll Arten hinreichend bekannt und funktionelle Anpassungen an diese sind in wenigen Arten beschrieben. In dieser Arbeit habe ich sensorische Anpassungen an geschlechtsspezifische Verhaltensweisen in drei Bienengruppen genauer untersucht. Weibchen und Arbeiterinnen haben generell eine ähnliche Lebensweise. Männchen beschäftigen sich fast ausschließlich mit der Partnersuche. Infolgedessen, zeigt die Sensorik der Männchen eine größere Vielfalt an morphologischen und funktionellen Anpassungen als die der Weibchen. Im ersten Abschnitt dieser Arbeit habe ich Anpassungen des visuellen Systems von 5 Honigbienenarten (Apis andreniformis, A. cerana, A. dorsata, A. florea, A. mellifera) untersucht. Ich finde eine deutliche Korrelation zwischen Körper- und Augengröße bei beiden weiblichen Kasten. Königinnen haben relativ kleinere Augen als Arbeiterinnen, was der verringerten Rolle visueller Wahrnehmung im Lebenszyklus dieser Kaste entspricht. Die Arbeiterinnen unterschieden sich sowohl in ihrer Augengröße als auch in der funktionellen Morphologie. Die Unterschiede passen jeweils zu der artspezifischen Ökologie. Drohnen aller Arten haben auffällig vergrößerte Augen, jedoch sind sie in zwei Arten (A. dorsata, A. florea) überproportional vergrößert. Zusätzlich zeige ich, dass bestimmte Augenparameter mit dem artspezifischen Paarungszeitpunkt korrelieren, und schlage vor, dass die Lichtintensität eine Rolle bei der Feststellung des richtigen Paarungszeitpunktes spielen könnte. In der zweiten Untersuchung habe ich die Augen von zwei Drohnenphänotypen von A. mellifera untersucht. Neben normalen Drohen werden in der Kolonie auch kleinere Drohnen aufgezogen, die unter einem geringeren Fortpflanzungserfolg leiden. Meine Ergebnisse zeigen, dass sich die Phänotypen vermutlich nicht in der räumlichen Auflösungsfähigkeit, jedoch in der Lichtempfindlichkeit der Augen von normalen Drohnen unterscheiden. In der dritten Untersuchung habe ich die Augenmorphologie bei 11 Hummelarten untersucht. Ich beschreibe in dieser Studie Anpassungen der Arbeiterinnen, die vermutlich mit der Habitatwahl im Zusammenhang stehen. Hummelköniginnen sind, im Gegensatz zu Königinnen der Honigbiene, in der ersten Zeit nach der Koloniegründung auf sich allein gestellt und müssen alle Aufgaben, die später von den Arbeiterinnen übernommen werden, selbst ausführen. Dementsprechend sind die Augen beider Weibchenkasten ähnlich in ihrer relativen Größe und funktionellen Morphologie. Vergrößerte Augen der Männchen können in Arten verschiedener Untergattungen gefunden werden und der Phänotyp ist im Laufe der Evolution mehrfach unabhängig entstanden, was ich mit phylogenetisch vergleichenden Methoden zeige. Die Augenmorphologie der vier untersuchten großäugigen Arten ist sehr ähnlich, was auf konvergente Evolution hinweist. Die Augenmorphologie der restlichen Arten unterscheidet sich hingegen nicht deutlich von jener der Weibchen. In der vierten Untersuchung habe ich mich dem Sexualdimorphismus der Solitärbienenart Eucera berlandi gewidmet. Männchen haben größere Augen und sowohl größere Facetten als auch eine höhere räumliche Auflösung im frontalen Gesichtsfeld als Weibchen. In einem Verhaltensversuch habe ich die Auswirkungen der Größe von Weibchendummies auf die Detektion getestet. In 3-D Rekonstruktionen der Weibchenverfolgung zeigte sich dass die Winkelgröße des Objektes, eine von der Distanz unabhängige Größe, eine wichtige Rolle spielt. Im Zusammenhang mit den gefundenen Daten diskutiere ich die Parallelen zu anderen Insektenarten. In der fünften Studie untersuche ich das olfaktorische System von E. berlandi. Männchen haben extreme lange Antennen. Um die anatomischen Grundlagen der geschlechtsspezifischen Antennenmorphologie zu untersuchen habe ich die Antennen beider Geschlechter im Detail studiert. Zusätzlich bin ich dem Dimorphismus entlang der olfaktorischen Bahn bis ins Gehirn gefolgt. Männchen zeige funktionelle Anpassungen (z.B. längere Antennen, eine höhere Anzahl an olfaktorischen Sensillen und Rezeptorneuronen, stark vergrößerte Glomeruli im Antennallobus, eine zahlenmäßige Reduktion der Glomeruli und geschlecherspezifische Investition in höhere Integrationszentren im Gehirn) an die Weibchendetektion