Browsing by Author "Mulvaney, Jake Matthew"

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    Landscape and Paleoclimatic influences on the genetic population structure of four forest-dependent passerines in the Eastern Cape of South Africa
    (Stellenbosch : Stellenbosch University, 2021-12) Mulvaney, Jake Matthew; Cherry, Michael; Matthee, Conrad; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Anthropogenic activity has placed increasing pressure on the restricted, fragmented forest biome of South Africa. Recent assessments of forest-dependent avifauna strongly indicate the vulnerability of this taxon to deforestation, and ongoing forest exploitation. Half of the forest- dependent bird species in South Africa have reportedly experienced range declines over the past quarter century, most notably within forests of the Eastern Cape province that are incorporated in the Maputaland-Pondoland-Albany Biodiversity Hotspot. These apparent declines have motivated a need to understand the population dynamics, and forest connectivity patterns of forest-dependent avifauna within the country, to better inform conservation efforts seeking to preserve the genetic integrity of these vulnerable bird species. This study investigated the population genetic structures of four range-declining forest- dependent Oscine passerines across the Eastern Cape and southern KwaZulu-Natal provinces of South Africa: Batis capensis (range decline: 1.30%), Cossypha dichroa (range decline: 19.53%), Phylloscopus ruficapilla (range decline 20.69%), and Pogonocichla stellata (range decline 23.02%). These four bird species are small-bodied (<50g) insectivores, that preferentially inhabit the temperate Afromontane forests, and represent a globally important functional group vulnerable to forest fragmentation. The landscape genetics study conducted on these four species revealed that reported range declines did not correspond closely to the genetic responses of these bird species to anthropogenic activity. Batis capensis showed substantial geneflow disruption, and declining effective populations, whereas P. ruficapilla and P. stellata populations appeared comparatively stable, although P. stellata did exhibit geneflow disruption. Only the South African endemic C. dichroa displayed simultaneous decline in distribution and effective population size, alongside geneflow disruptions, highlighting a vulnerability to forest loss and degradation. Landscape resistance modelling revealed the importance of both forest and coastal/mesic thicket for maintaining geneflow within these species. A phylogeographic study investigated the regional species-climate relationships of B. capensis, P. ruficapilla and P. stellata. The effective populations of these species were found not to have been constrained during the last glacial maximum – a climate event speculated to have resulted in drastically restricted forest distributions across South Africa. Furthermore, lowland scarp forests were affirmed as climate refugia for B. capensis and P. stellata, while the Afromontane forests of the Amatole Mountains and central Transkei appear to have harboured regional source populations of P. ruficapilla. Finally, comprehensive mist-netting of regional forests during sampling collection for the genetic studies afforded an opportunity to compare the effectiveness of point counts and mist- netting survey techniques at representing aspects of regional forest bird community structure. These comparisons found that point counts alone were sufficient to reliably assess these bird communities, with mist-netting contributing negligibly towards species detection. Combined survey efforts under-represented forest-edge foragers, woodland and grassland habitat generalists (collectively comprising ~63.6% total diversity), large birds, Palaearctic migrants, and carnivores (raptors), highlighting the potential shortcomings of these survey techniques in determining bird community composition. Overall, this study provided novel insights into forest connectivity; and past forest dynamics of forest-dependent insectivorous passerines within previously poorly investigated forests of the southern Maputaland-Pondoland-Albany Biodiversity Hotspot, and provides recommendations for future field surveys of these forests.