Resilient forest faunal communities in South Africa: a legacy of palaeoclimatic change and extinction filtering?

Authors

  • Michael J. Lawes,

    Corresponding author
      *Michael J. Lawes, School of Biological and Conservation Sciences, Forest Biodiversity Research Unit, University of KwaZulu–Natal, Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa. E-mail: lawes@ukzn.ac.za
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  • Harriet A. C. Eeley,

    Corresponding author
      *Michael J. Lawes, School of Biological and Conservation Sciences, Forest Biodiversity Research Unit, University of KwaZulu–Natal, Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa. E-mail: lawes@ukzn.ac.za
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  • Nicola J. Findlay,

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    • Present address: Nicola J. Findlay, Grassland Science, KwaZulu–Natal Department of Agriculture and Environmental Affairs, P/Bag X9059, Pietermaritzburg 3200, South Africa.

  • Dale Forbes

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    • Present address: Dale Forbes, Asociación Amigos de las Aves, Apdo. 2306-4050, Alajuela, Costa Rica.


*Michael J. Lawes, School of Biological and Conservation Sciences, Forest Biodiversity Research Unit, University of KwaZulu–Natal, Pietermaritzburg, P/Bag X01, Scottsville 3209, South Africa. E-mail: lawes@ukzn.ac.za

Abstract

Aim  To examine the influence of climatic extinction filtering during the last glacial maximum (LGM; c. 18,000 yr bp) and of the subsequent recolonization of forest faunas on contemporary assemblage composition in southern African forests.

Location  South Africa, Mozambique, Swaziland, Zimbabwe.

Methods  Data comprised presence/absence by quarter-degree grid cell for forest-dependent and forest-associated birds, non-volant mammals and frogs. Twenty-one forest subregions were assigned to one of three previously identified forest types: Afrotemperate, scarp, and Indian Ocean coastal belt. Differences among forest types were examined through patterns and gradients of species richness and endemism, assemblage similarity, species turnover, and coefficients of species dispersal direction. The influence of contemporary environment on assemblage composition was investigated using partial canonical correspondence analysis. Several alternative biogeographical hypotheses for the recolonization of forest faunas were tested.

Results  Afrotemperate faunas are relatively species-poor, have low species turnover, and are unsaturated and infiltrated by generalist species. In northern and central regions, communities are supplemented by recolonization from scarp forest refugia, and among frogs by autochthanous speciation in localized refugia. Scarp faunas are relatively species-rich, contain many forest-dependent species, have high species turnover, and overlap with coastal and Afrotemperate faunas. Coastal forests are relatively species-rich with high species turnover.

Main conclusions  Afrotemperate communities were affected most by climatic extinction filtering events. Scarp forests were Afrotemperate refugia during the LGM and are a contemporary overlap zone between Afrotemperate and coastal forest. Coastal faunas derive from post-LGM colonization along the eastern seaboard from tropical East African refugia. The greatest diversity is achieved in scarp and coastal forest faunas in northern KwaZulu–Natal province. This historical centre of diversity has influenced the faunal diversity of nearly all other forests in South Africa. The response of vertebrate taxa to large-scale, historical processes is dependent on their relative mobility: forest birds best illustrate patterns resulting from post-glacial faunal dispersal, while among mammals and frogs the legacy of climatic extinction filtering remains stronger.

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