Browsing by Author "De Klerk, Helen Margaret"

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    Biogeography and conservation of terrestrial afrotropical birds
    (1999) De Klerk, Helen Margaret; Crowe, Timothy M
    This study aimed to describe patterns of distribution in terrestrial Afrotropical birds, to investigate the causes of these patterns, and examine how aspects of distributional patterns may be used to prioritize local regions for conservation attention. Presence-only data were gathered and digitized at one-degree square scale for 1686 terrestrial bird species that breed on or regularly visit sub-Saharan Africa as non-breeding migrants. Biogeographical analysis of the 1437 species that are globally restricted to sub-Saharan Africa (Afrotropical endemics) revealed a suite of geographical areas that have a homogenous and characteristic avifaunal composition, termed avifaunal zones. The approach used in this study ensured representativeness in the resultant biogeographical classification scheme, which was not biased towards avifaunas that are species rich or that contain many narrow endemics, and further included avifaunas that consisted of few, but taxonomically and ecologically distinct species (e.g. the Namib Province). Analysis of zonal boundaries exhibiting high levels of turnover, defined specifically as species replacement, were distinguished from zonal boundaries that are characterised by species richness gradients. For instance, the northern forest-savanna boundary between the Guineo-Congolian and Northern Savanna Subregions was shown to consist of a sharp ecotone between forest and savanna, whereas the boundary between the Northern Savanna and Northern Arid Subregions was shown to be dominated by species drop-outs. This shows that whereas the Northern Savanna Subregion represents a unique avifauna that is distinct from that of the Guineo-Congolian Subregion, the Northern Arid Subregion is merely a depauparate subset of the Northern Savanna avifauna. Patterns of species richness and narrow endemism where shown to differ between species groups that exhibit different life history characteristics (e.g. residents vs. migrants) and distributional characteristics Atrotropical endemics vs. nonendemics). Differences can probably be attributed to island biogeography and aerography theory.