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Journal articles on the topic 'Reversed sexual size dimorphism'

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Published: 4 June 2021

Last updated: 30 January 2023

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1

Cooper, Mark. "Centrobolus anulatus (Attems, 1934) reversed sexual size dimorphism." Journal of Entomology and Zoology Studies 6, no. 4.13 (July 1, 2018): 1569–72. http://dx.doi.org/10.22271/j.ento.2018.v6.i4.13.16.

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2

Mueller, Helmut C. "Evolution of Reversed Sexual Size Dimorphism: Sex or Starvation?" Ornis Scandinavica 20, no. 4 (December 1989): 265. http://dx.doi.org/10.2307/3676490.

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3

Montgomerie, Robert, and Arne Lundberg. "Reversed Sexual Dimorphism in Raptors: Which Sex Changed Size?" Oikos 56, no. 2 (October 1989): 283. http://dx.doi.org/10.2307/3565349.

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4

McGillivray, W. Bruce. "Size, sexual size dimorphism, and their measurement in Great Horned Owls in Alberta." Canadian Journal of Zoology 63, no. 10 (October 1, 1985): 2364–72. http://dx.doi.org/10.1139/z85-349.

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The degree of reversed size dimorphism between male and female Great Horned Owls in Alberta was examined by measuring 18 skeletal and 7 external characters on museum specimens. Females are significantly larger than males on all characters except skull width, which is larger in males. The degree of sexual size dimorphism is highest for flight characters and weight and weaker for skull, body core, and lower limb elements. High variances associated with external characters make the use of Storer's dimorphism index an unreliable measure of between-sex differences. External characters show weak intercharacter correlations and are poorly correlated with size as defined by first principal component scores obtained from skeletal characters. Despite significant differences between an ideal size axis and eigenvectors of both correlation and covariance matrices, the three are shown to be equivalent in estimating size. Inequality among character variances bias the interpretation of covariance-based principal component analyses supporting the use of correlation matrices to determine patterns of shared variation. The high degree of intercharacter differences in sexual size dimorphism indicate that single characters provide poor estimates of size.

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5

Catry, Paulo, Richard A. Phillips, and Robert W. Furness. "Evolution of Reversed Sexual Size Dimorphism in Skuas and Jaegers." Auk 116, no. 1 (January 1999): 158–68. http://dx.doi.org/10.2307/4089462.

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6

Lundberg, Arne. "Adaptive Advantages of Reversed Sexual Size Dimorphism in European Owls." Ornis Scandinavica 17, no. 2 (May 1986): 133. http://dx.doi.org/10.2307/3676862.

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7

Hakkarainen, Harri, Erkki Korpimäki, and Erkki Korpimaki. "Reversed Sexual Size Dimorphism in Tengmalm's Owl: Is Small Male Size Adaptive?" Oikos 61, no. 3 (September 1991): 337. http://dx.doi.org/10.2307/3545241.

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8

BLOMQVIST, DONALD, OLOF C. JOHANSSON, UNO UNGER, MIKAEL LARSSON, and LARS-ÅKE FLODIN. "Male aerial display and reversed sexual size dimorphism in the dunlin." Animal Behaviour 54, no. 5 (November 1997): 1291–99. http://dx.doi.org/10.1006/anbe.1997.0532.

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9

Bunce, Michael, Trevor H. Worthy, Tom Ford, Will Hoppitt, Eske Willerslev, Alexei Drummond, and Alan Cooper. "Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis." Nature 425, no. 6954 (September 2003): 172–75. http://dx.doi.org/10.1038/nature01871.

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10

Phillips, Richard A., Deborah A. Dawson, and Douglas J. Ross. "Mating Patterns and Reversed Size Dimorphism in Southern Skuas (Stercorarius skua lonnbergi)." Auk 119, no. 3 (July 1, 2002): 858–63. http://dx.doi.org/10.1093/auk/119.3.858.

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Abstract Numerous explanations exist for the evolution of reversed size dimorphism in raptorial species. A recent study concluded that reversed size dimorphism in skuas and jaegers was probably not attributable to breeding-role specialization, but that there was evidence for sexual selection, and in particular intrasexual competition by females for males. Our study tested the applicability of those conclusions for Southern (or Brown) Skuas (Stercorarius skua lonnbergi) breeding in South Georgia. Clutch volume was related positively to size and condition of females and negatively to condition of males, but there was no evidence of assortative mating for size or condition within pairs. Potential explanations for the discrepancy between this and previous studies are that size is less closely correlated with individual quality because of highly diverse foraging strategies, territory quality is a confounding factor, or because lower aggression in Southern Skuas reduces the necessity for small females to avoid large males.

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11

MUELLER, HELMUT C. "THE EVOLUTION OF REVERSED SEXUAL DIMORPHISM IN SIZE IN MONOGAMOUS SPECIES OF BIRDS." Biological Reviews 65, no. 4 (November 1990): 553–85. http://dx.doi.org/10.1111/j.1469-185x.1990.tb01238.x.

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12

Wu, Hui, Haitao Wang, Yunlei Jiang, Fumin Lei, and Wei Gao. "Offspring sex ratio in Eurasian Kestrel (Falco tinnunculus) with reversed sexual size dimorphism." Chinese Birds 1, no. 1 (March 2010): 36–44. http://dx.doi.org/10.5122/cbirds.2009.0019.

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13

Samuk, Kieran, Davis Iritani, and Dolph Schluter. "Reversed brain size sexual dimorphism accompanies loss of parental care in white sticklebacks." Ecology and Evolution 4, no. 16 (July 27, 2014): 3236–43. http://dx.doi.org/10.1002/ece3.1175.

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14

Temeles, Ethan J. "Reversed Sexual Size Dimorphism: Effect on Resource Defense and Foraging Behaviors of Nonbreeding Northern Harriers." Auk 103, no. 1 (January 1, 1986): 70–78. http://dx.doi.org/10.1093/auk/103.1.70.

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Abstract Sexual differences in resource defense and foraging behaviors during the nonbreeding season are detailed for Northern Harriers (Circus cyaneus) in California. Female harriers hunted more frequently in high (>0.5 m) vegetation than males. In addition, females hunted at slower speeds and used different hunting behaviors than males. Females in high vegetation showed a significantly greater response (i.e. attack) rate to approaching harriers than males, and females won nearly all (28/29) aggressive interactions with males. These results suggest that sexual differences in harrier foraging behavior during the nonbreeding season result from females excluding males from preferred foraging areas and males adopting alternative foraging strategies. Foraging strategies of harrier sexes are compared with foraging strategies of sexes of birds in which males are larger than females to examine the role of body size in determining sexual foraging strategies.

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15

Slagsvold, Tore, and Geir A. Sonerud. "Prey size and ingestion rate in raptors: importance for sex roles and reversed sexual size dimorphism." Journal of Avian Biology 38, no. 6 (October 23, 2007): 650–61. http://dx.doi.org/10.1111/j.2007.0908-8857.04022.x.

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16

LORMEE, HERVE, CHRISTOPHE BARBRAUD, and OLIVIER CHASTEL. "Reversed sexual size dimorphism and parental care in the Red-footed Booby Sula sula." Ibis 147, no. 2 (March 30, 2005): 307–15. http://dx.doi.org/10.1111/j.1474-919x.2005.00404.x.

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17

McDonald, Paul G., Penny D. Olsen, and Andrew Cockburn. "Selection on body size in a raptor with pronounced reversed sexual size dimorphism: are bigger females better?" Behavioral Ecology 16, no. 1 (July 7, 2004): 48–56. http://dx.doi.org/10.1093/beheco/arh118.

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18

Lopes, Cassiane Furlan, Fabiano Stefanello, Christian Bugs, Cristina Stenert, Leonardo Maltchik, and José Ricardo Inacio Ribeiro. "Sexual dimorphism in Belostoma angustum Lauck (Insecta: Heteroptera: Belostomatidae) may be related to paternal care." Biological Journal of the Linnean Society 129, no. 2 (November 30, 2019): 288–314. http://dx.doi.org/10.1093/biolinnean/blz178.

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Abstract The structures involved in parental care are often dimorphic. Female Belostoma angustum water bugs lay eggs on the hemelytra of their mates, where the eggs are brooded until hatching. Males use their hind legs to carry, aerate and protect the eggs. After controlling for covariance between variables, we fitted a series of structural equation models (SEMs) and evaluated the existence of sexual dimorphism in the size of the body and hind legs, in the shape and centroid size of the hemelytrum, and among the static allometry slopes of the size-related differences. Landmarks were used to capture phenotypic variation, by eliminating all non-shape variations with a Procrustes superimposition. Neither the shape of the hemelytrum nor its centroid size was related significantly to the aforementioned linear body measurements. Instead, the differences in the size of the hind legs were mediated by body dimensions only in males. We also found that males were wider and had longer heads than females, according to the SEM intercept values. Our findings suggest that sexual dimorphism in B. angustum may be related to a balance between sexual role reversal and viability costs.

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19

Drummond, Hugh, and Maria Guerra. "Reversed Sexual Size Dimorphism and Parental Care: Minimal Division of Labour in the Blue-Footed Booby." Behaviour 132, no. 7-8 (1995): 479–96. http://dx.doi.org/10.1163/156853995x00162.

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AbstractReversed sexual size dimorphism in avian species (females larger than males) may be an adaptive consequence of different roles of males and females in parental care. We examined the alleged division of labour in two-chick broods of the blue-footed booby, using behavioural observation and frequent weighing of chicks. In the first week of parental care, males and females fed broods at similar frequencies and provided similar masses of food, but females brooded more than males when broods were 5-10 d old. Subsequently, females provided a greater mass of food and frequency of feeds than males until chicks were at least 35 d old (mass) and 60 d old (frequency), while attending the brood for just as much time as males until chicks were at least 35 d old. Males and females did not differ in the tendency to feed (frequency and mass) the first-hatched chick differentially. In nearly all components of parental care examined here, and in other studies, the female's contribution is equal to or greater than the male's. Only in clutch attendance and nest defence does the male contribute more than the female, but his small size seems unlikely to enhance performance in these activities. Overall, small size appears potentially to limit male provisioning of the brood, and is unlikely to be an adaptation for division oflabour in parental care. This result casts doubt on the relevance of the division-of-labour hypothesis for adult size dimorphism.

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20

Fernández-Montraveta, Carmen, and Jesús Marugán-Lobón. "Geometric morphometrics reveals sex-differential shape allometry in a spider." PeerJ 5 (July 26, 2017): e3617. http://dx.doi.org/10.7717/peerj.3617.

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Common scientific wisdom assumes that spider sexual dimorphism (SD) mostly results from sexual selection operating on males. However, testing predictions from this hypothesis, particularly male size hyperallometry, has been restricted by methodological constraints. Here, using geometric morphometrics (GMM) we studied for the first time sex-differential shape allometry in a spider (Donacosa merlini, Araneae: Lycosidae) known to exhibit the reverse pattern (i.e., male-biased) of spider sexual size dimorphism. GMM reveals previously undetected sex-differential shape allometry and sex-related shape differences that are size independent (i.e., associated to the y-intercept, and not to size scaling). Sexual shape dimorphism affects both the relative carapace-to-opisthosoma size and the carapace geometry, arguably resulting from sex differences in both reproductive roles (female egg load and male competition) and life styles (wandering males and burrowing females). Our results demonstrate that body portions may vary modularly in response to different selection pressures, giving rise to sex differences in shape, which reconciles previously considered mutually exclusive interpretations about the origins of spider SD.

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21

ANDERSSON, MALTE. "Evolution of reversed sex roles, sexual size dimorphism, and mating system in coucals (Centropodidae, Aves)." Biological Journal of the Linnean Society 54, no. 2 (February 1995): 173–81. http://dx.doi.org/10.1111/j.1095-8312.1995.tb01030.x.

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22

Krüger, Oliver. "The Evolution of Reversed Sexual Size Dimorphism in Hawks, Falcons and Owls: A Comparative Study." Evolutionary Ecology 19, no. 5 (September 2005): 467–86. http://dx.doi.org/10.1007/s10682-005-0293-9.

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23

Emlen, Stephen T., and Peter H. Wrege. "Size Dimorphism, Intrasexual Competition, and Sexual Selection in Wattled Jacana (Jacana Jacana), A Sex-Role-Reversed Shorebird in Panama." Auk 121, no. 2 (April 1, 2004): 391–403. http://dx.doi.org/10.1093/auk/121.2.391.

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AbstractWe studied sexual size dimorphism, intrasexual competition, and sexual selection in an individually marked population of Wattled Jacanas (Jacana jacana) in the Republic of Panama. Males are the sole incubators of eggs (28-day incubation) and primary providers of chick care (50–60 days). Females were 48% heavier than, and behaviorally dominant over, males. Females also showed greater development of secondary sexual characters (fleshy facial ornamentation and wing spurs) than males. Both sexes defended territories throughout the year against same-sex conspecifics. Competition for territorial space was intense, and many individuals of both sexes did not become breeders. Resident females further competed with one another to accumulate multiple mates, resulting in a mating system of simultaneous polyandry. Female and male residents (territory holders) were larger, heavier, and more ornamented than adult floaters of the same sex. Larger and heavier females also had more mates than smaller females. Body size was thus a critical predictor of success in intrasexual competition for territories (both sexes) and for mates (females). Three measures of sexual selection—(1) sex difference in the opportunity for sexual selection, (2) female-to-male ratio of potential reproductive rates, and (3) operational sex ratio—each indicated that sexual selection is currently operating more strongly on females than on males (female-to-male ratios ranged from 1.43:1 to 2.22:1). Values of 1.61:1 and 1.43:1 represent the first published quantitative estimates of the opportunity for sexual selection for any sex-role-reversed bird. Our study supports the theory that when increased parental care entails reduced opportunities for future reproduction, asymmetries in parental care behaviors of the sexes can influence the intensity of competition for mates and the direction and strength of sexual selection.

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24

Rawashdeh, Ma'amon A., and Ikhlas Fawaz Bani Bakir. "The Crown Size and Sexual Dimorphism of Permanent Teeth in Jordanian Cleft Lip and Palate Patients." Cleft Palate-Craniofacial Journal 44, no. 2 (March 2007): 155–62. http://dx.doi.org/10.1597/05-197.1.

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Objective: To provide a detailed description of crown size dimensions in the permanent dentition of Jordanian cleft lip and palate patients and to compare the findings with those of other populations. Method: The mesiodistal crown diameters of the permanent teeth of 47 patients with unilateral cleft lip and palate (UCLP), 25 patients with bilateral cleft lip and palate (BCLP), and 74 controls were measured. Results: The cleft group (UCLP and BCLP patients) generally demonstrated a smaller tooth size for both the maxillary and mandibular arches than did the control group. A sexual dimorphism pattern with males having larger teeth than females was observed for controls and UCLP patients. More males with BCLP had smaller teeth than did females. In the maxilla, the UCLP cleft-side teeth showed the largest percentage (4%) of sexual dimorphism, whereas the BCLP teeth achieved the highest percentage (3.4%) in the mandible. The UCLP cleft-side maxillary lateral incisors (13.2%) and BCLP mandibular canines (6%) displayed greater sexual dimorphism in crown size than did any other tooth class. Conclusions: Tooth size reduction occurred across all permanent tooth types and among early and late-forming teeth in cleft patients compared with the controls. This reduction was more pronounced in the maxillary incisor field. Males with UCLP and control males had larger teeth than did females, whereas a reversal of the normal dimorphism pattern was observed in patients with BCLP.

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25

Longland, William S. "Reversed Sexual Size Dimorphism: Its Effect on Prey Selection by the Great Horned Owl, Bubo Virginianus." Oikos 54, no. 3 (March 1989): 395. http://dx.doi.org/10.2307/3565301.

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26

RISPOLI, V. F., and A. B. WILSON. "Sexual size dimorphism predicts the frequency of multiple mating in the sex-role reversed pipefishSyngnathus typhle." Journal of Evolutionary Biology 21, no. 1 (November 22, 2007): 30–38. http://dx.doi.org/10.1111/j.1420-9101.2007.01470.x.

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27

Pérez-Camacho, Lorenzo, Sara Martínez-Hesterkamp, Salvador Rebollo, Gonzalo García-Salgado, and Ignacio Morales-Castilla. "Structural complexity of hunting habitat and territoriality increase the reversed sexual size dimorphism in diurnal raptors." Journal of Avian Biology 49, no. 10 (October 2018): e01745. http://dx.doi.org/10.1111/jav.01745.

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28

Mulvihill, Robert S., Robert C. Leberman, and D. Scott Wood. "A Possible Relationship between Reversed Sexual Size Dimorphism and Reduced Male Survivorship in the Ruby-Throated Hummingbird." Condor 94, no. 2 (May 1992): 480–89. http://dx.doi.org/10.2307/1369220.

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29

Bondrup-Nielsen, Søren, and Rolf Anker Ims. "Reversed sexual size dimorphism in microtines: Are females larger than males or are males smaller than females?" Evolutionary Ecology 4, no. 3 (July 1990): 261–72. http://dx.doi.org/10.1007/bf02214334.

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30

ROSSITER, STEPHEN J., ROGER D. RANSOME, CHRISTOPHER G. FAULKES, DEBORAH A. DAWSON, and GARETH JONES. "Long-term paternity skew and the opportunity for selection in a mammal with reversed sexual size dimorphism." Molecular Ecology 15, no. 10 (June 23, 2006): 3035–43. http://dx.doi.org/10.1111/j.1365-294x.2006.02987.x.

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31

Tarr, Simon, Shai Meiri, James J. Hicks, and Adam C. Algar. "A biogeographic reversal in sexual size dimorphism along a continental temperature gradient." Ecography 42, no. 4 (October 16, 2018): 706–16. http://dx.doi.org/10.1111/ecog.03593.

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32

Ganbold, Onolragchaa, Richard P. Reading, Ganchimeg J. Wingard, Woon Kee Paek, Purevsuren Tsolmonjav, Ariunbold Jargalsaikhan, Otgontsetseg Khuderchuluun, and John Azua. "Reversed sexual size dimorphism: body size patterns in sexes of lesser kestrels (Falco naumanni) in the Ikh Nart Nature Reserve, Mongolia." Journal of Asia-Pacific Biodiversity 12, no. 3 (September 2019): 363–68. http://dx.doi.org/10.1016/j.japb.2019.04.003.

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33

Massemin, S., Erkki Korpimäki, and Jürgen Wiehn. "Reversed sexual size dimorphism in raptors: evaluation of the hypotheses in kestrels breeding in a temporally changing environment." Oecologia 124, no. 1 (July 21, 2000): 26–32. http://dx.doi.org/10.1007/s004420050021.

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34

Aisenberg, Anita, Carmen Viera, and Fernando G. Costa. "Daring females, devoted males, and reversed sexual size dimorphism in the sand-dwelling spider Allocosa brasiliensis (Araneae, Lycosidae)." Behavioral Ecology and Sociobiology 62, no. 1 (June 12, 2007): 29–35. http://dx.doi.org/10.1007/s00265-007-0435-x.

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35

Niemc, Aleksandra, Magdalena Remisiewicz, Joel Avni, and Les G. Underhill. "Sexual dimorphism in adult Little Stints (Calidris minuta) revealed by DNA sexing and discriminant analysis." PeerJ 6 (August 8, 2018): e5367. http://dx.doi.org/10.7717/peerj.5367.

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Background The sex of an individual organism plays such an important role in its life cycle that researchers must know a bird’s sex to interpret key aspects of its biology. The sexes of dimorphic species can be easily distinguished, but sexing monomorphic bird species often requires expensive and time-consuming molecular methods. The Little Stint (Calidris minuta) is a numerous species, monomorphic in plumage but showing a small degree of reversed sexual size dimorphism. Females are larger than males but the ranges of their measurements overlap, making Little Stints difficult to sex in the field. Our aim was to develop reliable sexing criteria for Little Stints in different stages of primary moult during their stay on the non-breeding grounds in South Africa using DNA-sexed individuals and discriminant function analysis. Methods We caught 348 adult Little Stints in 2008–2016 on their non-breeding grounds at Barberspan Bird Sanctuary. To molecularly identify the birds’ sex we used P2/P8 primers and DNA isolated from blood samples collected in the field. We used Storer’s dimorphism index to assess the degree of sexual size dimorphism. Then we divided our sample into two groups: before or during and after primary moult. For each group we developed two functions: one using wing length only and the other a combination of morphometric features including wing, tarsus and total head length. Then we used a stepwise procedure to check which combination of measurements best discriminated sexes. To validate our result we used a jack-knife cross-validation procedure and Cohen-kappa statistics. Results All the morphometric features we measured were bigger in DNA-sexed females than in males. Birds with fresh primaries had on average 2.3 mm longer wings than those with worn primaries. A discriminant function using wing length (D1) correctly sexed 78.8% of individuals before moult, and a stepwise analysis showed that a combination of wing length and tarsus (D2) correctly identified the sex of 82.7% of these birds. For birds with freshly moulted primaries a function using wing length (D3) correctly classified 83.4% of the individuals, and a stepwise analysis revealed that wing and total head length (D4) classified 84.7%. Discussion Sexual size differences in Little Stints might be linked to their phylogenetics and breeding biology. Females are bigger, which increases their fecundity; males are smaller, which increases their manoeuverability during display flights and hence their mating success. Little Stints show an extreme lack of breeding site fidelity so we did not expect a geographical cline in their biometrics. Sexing criteria available for Little Stints in the literature were developed using museum specimens, which often shrink, leading to misclassification of live birds. The sexing criteria we developed can be used for studies on Little Stints at their non-breeding grounds and on past data, but should be applied cautiously because of the overlapping ranges.

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36

Dudás, György, and Krisztián Frank. "Sexual size dimorphism in the tail length of the Caspian Whip Snakes, Dolichophis caspius (Serpentes, Colubridae), in south-western Hungary." Acta Herpetologica 16, no. 2 (September 17, 2021): 129–31. http://dx.doi.org/10.36253/a_h-10306.

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Sexual size dimorphism is widespread among snakes and has also been observed in lengths of body appendages such as in tails. Males typically possess longer tails than females and this dimorphism in tail length has generally been attributed to the importance of the tail in mating and reproduction. We used body size measurements, snout-vent length (SVL) and tail length (TL) as well as a body condition index (BCI) as a measure of quality in Caspian Whip Snakes from Hungary, in order to shed light on sexual dimorphism patterns. The SVL of males (1061 ± 133 mm, n = 25) were significantly longer than that of females (887 ± 208 mm, n = 41). However, the proportion of TL to total length was lower in males than in females (0.257 ± 0.018 and 0.274 ± 0.017, respectively). The BCI of females (386 ± 10) was significantly higher than that of males (343 ± 15). Females having proportionally longer tails compared to males seems to be the reverse of the usual trend. Selective pressures on the tails of female snakes are less obvious, as tail length may be linked to more than one function, and hence be simultaneously subjected to more than one type of selective force.

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37

Emlen, Stephen T., and Peter H. Wrege. "Size Dimorphism, Intrasexual Competition, and Sexual Section in Wattled Jacana (Jacana jacana), a Sex-Role-Reversed Shorebird in Panama." Auk 121, no. 2 (April 2004): 391–403. http://dx.doi.org/10.2307/4090403.

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38

Olsen, Jerry. "Reversed Sexual Dimorphism and Prey Size Taken by Male and Female Raptors: A Comment on Pande and Dahanukar (2012)." Journal of Raptor Research 47, no. 1 (March 2013): 79–81. http://dx.doi.org/10.3356/jrr-12-48.1.

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39

Emlen, Stephen T., and Peter H. Wrege. "SIZE DIMORPHISM, INTRASEXUAL COMPETITION, AND SEXUAL SELECTION IN WATTLED JACANA (JACANA JACANA), A SEX-ROLE-REVERSED SHOREBIRD IN PANAMA." Auk 121, no. 2 (2004): 391. http://dx.doi.org/10.1642/0004-8038(2004)121[0391:sdicas]2.0.co;2.

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40

Fu, J., C. J. Weadick, and K. Bi. "A phylogeny of the high-elevation Tibetan megophryid frogs and evidence for the multiple origins of reversed sexual size dimorphism." Journal of Zoology 273, no. 3 (November 2007): 315–25. http://dx.doi.org/10.1111/j.1469-7998.2007.00330.x.

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41

Kalmbach, Ellen, Ruedi G. Nager, Richard Griffiths, and Robert W. Furness. "Increased reproductive effort results in male-biased offspring sex ratio: an experimental study in a species with reversed sexual size dimorphism." Proceedings of the Royal Society of London. Series B: Biological Sciences 268, no. 1481 (October 22, 2001): 2175–79. http://dx.doi.org/10.1098/rspb.2001.1793.

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42

Puniamoorthy, Nalini, Martin A. Schäfer, and Wolf U. Blanckenhorn. "SEXUAL SELECTION ACCOUNTS FOR THE GEOGRAPHIC REVERSAL OF SEXUAL SIZE DIMORPHISM IN THE DUNG FLY, SEPSIS PUNCTUM (DIPTERA: SEPSIDAE)." Evolution 66, no. 7 (March 16, 2012): 2117–26. http://dx.doi.org/10.1111/j.1558-5646.2012.01599.x.

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43

Graves, Gary R., Seth D. Newsome, David E. Willard, David A. Grosshuesch, William W. Wurzel, and Marilyn L. Fogel. "Nutritional stress and body condition in the Great Gray Owl (Strix nebulosa) during winter irruptive migrations." Canadian Journal of Zoology 90, no. 7 (July 2012): 787–97. http://dx.doi.org/10.1139/z2012-047.

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The largest irruptive migration of the Great Gray Owl ( Strix nebulosa Forster, 1772) recorded since 1831 occurred in Minnesota, USA, during the winter of 2004–2005. We tested the hypothesis that morphometric indicators of nutritional stress covary with stable isotope signatures in a sample of 265 owls killed by vehicle collisions. The ratio of carbon to nitrogen in muscle (C/Nmuscle) was shown to be a reliable proxy of nutritional stress. δ13C values for liver and muscle were significantly higher in owls in poor condition, reflecting the depletion of lipid reserves in fasting individuals. On the other hand, δ15N values for liver and muscle were marginally lower or unchanged in owls in poor condition. Stomachs of emaciated owls were less likely to contain prey, implying that many nutritionally stressed individuals were too weak to hunt and were near the tipping point of irreversible fasts. In a broader context, sexual differences in the correlative relationships between stable isotope signatures, C/N, and body condition suggest that the consequences of reversed sexual size dimorphism extend to physiological processes during the nonbreeding season.

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Kelly, Clint D. "Effect of nutritional stress and sex on melanotic encapsulation rate in the sexually size dimorphic Cook Strait giant weta (Deinacrida rugosa)." Canadian Journal of Zoology 94, no. 11 (November 2016): 787–92. http://dx.doi.org/10.1139/cjz-2016-0108.

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Nutritional condition and sex are known to influence efficacy and investment in immune function. A poor diet is costly to immune function because it limits the resources (e.g., protein) available to effector systems (e.g., melanotic encapsulation), whereas males and females are expected to differ in how they allocate resources to fitness-related traits. Males are expected to invest less in immunity, and more in mating, than females, but this pattern could be reversed if fitness is more condition-dependent in males than in females. I tested the effects of nutritional condition and sex on melanotic encapsulation rate in the Cook Strait giant weta (Deinacrida rugosa Buller, 1871), an orthopteran insect exhibiting strong female-biased sexual size dimorphism that is, at least in part, the result of strong sexual selection for small male size. I found that male D. rugosa have a stronger encapsulation response than females, while nutritional condition has only a small positive effect on this particular effector system in both sexes. Whether the observed sex difference in encapsulation ability is due to a physiological constraint in females or whether males allocate more resources to this effector system because their fitness is more condition-dependent than female’s remains to be determined.

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Zheng, Yuchi, Shuqiang Li, and Jinzhong Fu. "A phylogenetic analysis of the frog genera Vibrissaphora and Leptobrachium, and the correlated evolution of nuptial spine and reversed sexual size dimorphism." Molecular Phylogenetics and Evolution 46, no. 2 (February 2008): 695–707. http://dx.doi.org/10.1016/j.ympev.2007.09.019.

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Schoenjahn, Jonny, Chris R. Pavey, and Gimme H. Walter. "Why female birds of prey are larger than males." Biological Journal of the Linnean Society 129, no. 3 (January 16, 2020): 532–42. http://dx.doi.org/10.1093/biolinnean/blz201.

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Abstract The causes of the reversed sexual size dimorphism (RSD; females larger than males) in birds of prey are subject to a centuries-old, passionate debate. A crucial difficulty is to distinguish whether the postulated benefits derive from the proposed causal process(es) or are incidental. After reviewing the existing literature, we present a methodology that overcomes this difficulty and renders unnecessary any speculative a priori distinctions between evolved function and incidental effects. We can thus justify the following novel version of the well-known nest defence hypothesis as the most likely to explain the phenomenon in all birds of prey that show RSD: if the female predominates in actively defending the eggs and young against predators, then she is the heavier sex, and her relatively greater body mass is adaptive. That is, heavier females are favoured (independently of males) by natural selection. The attractiveness of this hypothesis is that it has the potential to explain the phenomenon in all raptors exhibiting RSD, can deal with the exceptional cases in this group, explains the direction of the dimorphism, focuses on a key factor in the reproductive success of most raptors, is parsimonious, i.e. does not require supporting hypotheses, and is supported by a substantial body of evidence.

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Maurer, Golo, Claire Smith, Marc Süsser, and Robert D. Magrath. "Solo and duet calling in the pheasant coucal: sex and individual call differences in a nesting cuckoo with reversed size dimorphism." Australian Journal of Zoology 56, no. 3 (2008): 143. http://dx.doi.org/10.1071/zo08049.

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Duetting and female vocalisations have rarely been studied in tropical non-passerines. In coucals, a subfamily of nesting cuckoos, these behaviours have evolved under unusual conditions of male-biased parental care and reversed sexual size dimorphism. Here we provide the first detailed description of the structure and occurrence of sex-specific calls and duets in a monogamous coucal species, the pheasant coucal, Centropus phasianinus. Pheasant coucals of either sex use two types of far-reaching (>1 km) calls in their solo and duet displays: the ‘descending whoops’ call and, less frequently (25%), ‘scale’ calls. Both calls are series of very deep hooting notes that the larger females produce at lower frequency than the males (~326 versus 480 Hz). Descending whoops calls also vary among individuals but this difference is not consistent enough for individual identification. Most duets (63%) comprise a single scale call by each partner and the sexes start duets with equal frequency. Duetting triggers neighbouring pairs to duet too, suggesting a role in territory defence. Calling is most intense in the morning and early in the breeding season. The cryptic behaviour of coucals makes their calls an important tool for studies on their mating system, survey work and taxonomic research.

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Crews, D., M. A. Diamond, J. Whittier, and R. Mason. "Small male body size in garter snake depends on testes." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 249, no. 1 (July 1, 1985): R62—R66. http://dx.doi.org/10.1152/ajpregu.1985.249.1.r62.

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In the red-sided garter snake (Thamnophis sirtalis parietalis) adult females are larger than adult males; this difference is apparent within 3 wk of birth, a time coinciding with high circulating levels of androgens. To study the ontogeny and regulation of this sexual dimorphism, male neonates were either castrated, castrated and given Silastic capsules containing testosterone or estradiol, or given a sham operation at 8, 9, or 10 wk of age. Female neonates were either given a Silastic capsule containing testosterone or dihydrotestosterone or given a sham operation at 8, 9, 10, or 14 wk of age. The sex difference in body size and growth rate in neonates was abolished by castration; the pattern of growth of castrated males was similar to sham-operated females. Androgens in the amounts administered failed to reverse the effects of castration, because castrated male and female neonates receiving exogenous androgens grew at the same rate as did sham-operated females. Males castrated as adults grow larger than adult males given a sham operation, indicating the inhibitory role of the testes on body size exists after sexual maturity. Treatment of adult males with testosterone, however, prevented the increase in body size after castration, suggesting that the mechanism regulating weight gain in the garter snake depends on gonadal androgen.

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Yen, An, Hsiao-Jou Wu, Pin-Yi Chen, Hon-Tsen Yu, and Jia-Yang Juang. "Egg Incubation Mechanics of Giant Birds." Biology 10, no. 8 (August 1, 2021): 738. http://dx.doi.org/10.3390/biology10080738.

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Finite element analysis (FEA) was used to conduct mechanical analyses on eggshells of giant birds, and relate this to the evolution and reproductive behavior of avian species. We aim to (1) investigate mechanical characteristics of eggshell structures of various ratite species, enabling comparisons between species with or without reversed sexual size dimorphism (RSSD); (2) quantify the safety margin provided by RSSD; (3) determine whether the Williams’ egg can have been incubated by an extinct giant bird Genyornis newtoni; (4) determine the theoretical maximum body mass for contact incubation. We use a dimensionless number C to quantify relative shell stiffness with respect to the egg size, allowing for comparison across wide body masses. We find that RSSD in moas significantly increases the safety margin of contact incubation by the lighter males. However, their safety margins are still smaller than those of the moa species without RSSD. Two different strategies were adopted by giant birds—one is RSSD and thinner shells, represented by some moa species; the other is no RSSD and regular shells, represented by the giant elephant bird. Finally, we predicted that the upper limit of body mass for contact incubation was 2000 kg.

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Puniamoorthy, N., W. U. Blanckenhorn, and M. A. Schäfer. "Differential investment in pre- vs. post-copulatory sexual selection reinforces a cross-continental reversal of sexual size dimorphism inSepsis punctum(Diptera: Sepsidae)." Journal of Evolutionary Biology 25, no. 11 (September 17, 2012): 2253–63. http://dx.doi.org/10.1111/j.1420-9101.2012.02605.x.

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