Geographic variation in selected African mammalian taxa: a comparison of modern and fossil conspecifics
Authors: Reynolds, S.C.
Editors: Bishop, L.C. and Turner, A.
Conference: School of Biological and Earth Sciences, Liverpool John Moores University
This study examines the nature and extent of intraspecific variation in four African mammalian taxa: the Reck’s springbok Antidorcas recki (Schwarz, 1932) the impala Aepyceros melampus (Lichtenstein, 1812) the spotted hyaena, Crocuta crocuta (Erxleben, 1777) and the Plains zebra, Equus burchellii (Gray, 1824). These taxa co-occur in East and southern African Plio-Pleistocene fossil sites. Modern conspecifics are known for all taxa except for the extinct springbok (A.recki) which is here compared to the descendant species Antidorcas marsupialis (Zimmermann, 1780).
The four focal species are investigated for geographic body size differences and for body size changes through time. Multivariate methods are used to characterise cranial and dental variation in modern samples from East (‘East’) and southern African (‘South’) regions. Statistical comparisons are made between samples of modern and Plio-Pleistocene fossil specimens of each species. Results of this study show that modern intraspecific variation in Crocuta, Equus and Antidorcas is primarily size-related, while Aepyceros shows mainly shape differences. The same pattern of geographic variation is not identified in the fossil conspecifics of these taxa. Significant differences between the ‘East’ modern and fossil conspecifics outnumber differences between modern and fossil samples of the South region. The South sample not only shows fewer changes but these indicate a different pattern of change to the East samples. Body size changes in various mammalian taxa through time have previously been interpreted as indicating climatic and environmental shifts. The size-related changes identified in this study may indicate that climatic and environmental shifts in the East African region were greater than contemporaneous changes in southern Africa. Studies of Plio-Pleistocene climates and environments seem to corroborate this body size interpretation. Evidence suggests that a greater degree of climatic and environmental change occurred in the East African region during this period. This study suggests that climatic and environmental shifts influence mammalian body size changes, both in present and past conspecifics, but that not all species have changed in the same way nor to the same extent.
Preferred by: Sally Reynolds