Добірка наукової літератури з теми "Southern scrub-robin"

From 2013 to 2015 we recorded an isolated, highly fragmented and previously undocumented population of the southern scrub-robin within the arid shrublands of the Great Victoria Desert. In this region, the southern scrub-robin persists in scattered and intermittent areas of long-unburnt mulga (Acacia spp.) shrubland, with a dense shrubby understorey dominated by Aluta maisonneuvei and Eremophila shrubs. The Great Victoria Desert supports the only known desert population as the southern scrub-robin otherwise occurs in the temperate and semiarid shrublands of southern Australia and occurs in the desert at the arid extreme of its range. Fire is highlighted as a significant threatening process due to the species’ restricted occurrence (less than 5% of the landscape in the region), low reproductive rate, limited dispersal capability and persistence within long-unburnt and fire-sensitive habitats. As forecast environmental changes are likely to render the arid extremes of the species’ range unsuitable, this outlying, desert population is potentially declining and of conservation significance.

In April 2013, a transect c. 1100 km long with 100 points arranged in 5 sections was designed in northern Namibia between Ruacana Watefall (W) and Kongola (E) to study avian diversity in relation to gradual changes in precipitation (c. 350 mm in W to c.600 mm in E). In total, 81 bird species were recorded in all 100 points, but in particular section, the numbers were low, ranging from 22 to 38 species. In overall, the most frequent and most numerous (dominant) were the following species: Cape Turtle Dove, Blue Waxbill, Grey-headed Sparrow, Laughing Dove and Fork-tailed Drongo. Together they comprised 42.2 % of all individuals recorded. All of them, except for the Fork-tailed Drongo, were granivores. Only nine species were recorded in ten or more points. Besides the above-mentioned dominant species, the following other were in this group: Black-chested Prinia, Black-throated Canary, Pied Crow and White-browed Scrub Robin. In particular section the number of dominant species ranged from 5 to 7, without a gradient. Two species, the Cape Turtle Dove and Blue Waxbill, remained dominant in all fi ve sections. Th e Laughing Dove and Fork-tailed Drongo — in four sections, and the Grey-headed Sparrow — in three sections. Although, no gradient in species diversity, evenness, and dominance structure was recorded, signifi cant diff erences between two most western and two most eastern sections were apparent. Two species were more frequent and numerous in the eastern than in the western sections: White-browed Scrub Robin and Cape Turtle Dove; while the following species were more frequent and numerous in the western than the eastern sections: African Palm Swift , Black-chested Prinia, Black-throated Canary, Blue Waxbill, Grey-headed Sparrow and Pied Crow.

In Australia anthropogenic development has resulted in substantial loss and modification of natural habitats. This development has occurred most intensively around the continent’s southern and eastern coastal areas where fertile soils and climates appropriate for agriculture are located. Consequently, a diverse range of species found within this region frequently suffer from fragmented distributions that alter evolutionary processes and result in increased population structure and the erosion of genetic diversity. Augmenting the effect of habitat clearing and alteration, climate change is predicted to result in increasing temperature and decreasing rainfall in many regions of Australia. What makes anthropogenic climate change a major threat is that its impact will occur in ecosystems already suffering fragmentation and other perturbations associated with human activity. This thesis seeks to characterise the molecular demography of the ground-dwelling southern scrubrobin (Drymodes brunneopygia), a species whose future is at risk from both habitat loss and climate change. I begin by reviewing the current use and potential role of molecular demography to inform species distribution modelling for conservation. My study of the southern scrub-robin itself begins with the development of microsatellites. Employing these microsatellites, I investigate genetic diversity and recent migration across intact and fragmented mallee vegetation in southern Australia. Our assessment of habitat protection for this species reveals that large areas of contiguous native vegetation are most often conserved toward the climatically extreme, northern distribution of the southern scrub-robin. Conversely, we find that genetic diversity and larger effective population size are concentrated in southern regions, which are dominated by agriculture. Subsequently I investigate the composition and structure of different mallee understorey vegetation types, and the nature of their resources and risks to dispersing southern scrub-robins in both the historic (pre-clearing) and contemporary landscapes. Landscape types with an open or inaccessible understorey were shown to increase population genetic structure in the southern scrub-robin, in particular chenopod habitat. Conversely, landscape types that offered a dense, accessible understorey structure decreased genetic structuring, possibly due to increased predator protection and foraging opportunities during dispersal. I proceed by investigating the relationship between genetic diversity and habitat quality at southern scrub-robin home sites. Genetic diversity was diminished by the presence of feral predators and weed infestations, suggesting the control of invasive species should be a conservation priority for the southern scrub-robin. I also confirm the fundamental requirement of a dense shrubby understorey for this species, suggesting that control of feral herbivores may also be of conservation benefit. Finally, I consider the role that adaptation to change can play in securing the future of the southern scrub-robin in an era of habitat loss and climate change. Simultaneously considering the effects of distance and the environment, I identify substrate and temperature conditions among the most important environmental variables associated with spatial patterns of genetic diversity. To prioritise regions for additional conservation actions, I consider predicted genetic uniqueness, land use, current and future habitat suitability and the amount of pressure existing genetic-climate relationships are expected to experience.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2012