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Biogeography
The wide geographic range of Bovidae, and the fact that many bovid clades are restricted in their distributions, makes this group ideal for biogeographic investigation. The Miocene evolution of Bovidae took place against the backdrop of major climatic and physiographic changes, including the closure of the Tethys Gateway (Berggren 1972), opening of the East African and Red Sea rift valleys (Ghebreab 1998), gradual global cooling (Zachos et al. 2001), the Messinian salinity event (Hsü et al. 1973), and the global expansion of C4 grasslands at low latitudes (Cerling et al. 1997). As such, the search for correspondence between global environmental changes and major biogeographic events in the evolutionary history of Bovidae is a main focus of any synthetic treatment of the bovid fossil record.
Bovids are diagnostic components of biogeographic zones defined on the basis of whole fossil faunas. For example, the fossil bovids from the late Miocene Baynunah Formation (United Arab Emirates,
Gentry 1999) suggest an overlapping of the North African, Greco-Iranian (=Sub-Paratethyan), and Oriental (south Asian) Provinces. These traditional biogeographic provinces, outlined for the late Miocene by
Bernor (1984), continue to remain relevant for discussion today, as do the topics addressed by past syntheses of bovid paleobiogeography (Gentry 1968;
Thomas 1984a).
Systematic and paleontological work of the last two decades has significantly improved the resolution at which bovid paleobiogeography can formulate and test hypotheses. For one, the production of more robust phylogenies, particularly by way of molecular methods, has allowed for the rapid development of phylogeographic studies. Such studies have worked to reconstruct ancestral areas for higher clades (e.g.,
Hassanin and Ropiquet 2004) as well as the geographic range expansions and contractions of individual species (e.g.,
Arctander et al. 1999). Additionally, the fossil record has been sufficiently improved to allow for new appraisal of late Miocene biogeographic trends. Higher resolution paleobiogeographical studies are now possible that reveal developing zoogeographies both among and within biogeographic provinces in the late Miocene. For example, marked differences appear to have differentiated the Southern Balkan vs. Anatolian faunas of the late Miocene Greco-Iranian Province (Kostopoulos 2009).
The presence of a monophyletic Caprini+Alcelaphini+Hippotragini (unnamed clade) provides a good opportunity for paleobiogeographic studies as the living Caprini are almost entirely Eurasian while recent Alcelaphini and Hippotragini are African (the latter are present in Arabia as well). On the basis of fossil and molecular phylogenetic evidence,
Ropiquet and Hassanin (2005) proposed that Caprini originated on Mediterranean islands in the late Miocene. In addition to major cladogenetic and dispersal events, the record of rare and isolated occurrences of bovid taxa outside their expected geographic range is another important indicator of biogeographic interchange. For example, caprines have a very limited record of presence in Africa, and Plio-Pleistocene fossil caprines like Bouria and Makapania are taken to be immigrants southwards from Eurasia. The age of occurrence of these fossil caprines in Africa happens also to correspond to pronounced global cooling events (Vrba 1995). Both Alcelaphini and Hippotragini have a limited Plio-Pleistocene record (Pilgrim 1939) outside of Africa, namely in the Siwaliks, and Alcelaphini may have also occurred in the late Miocene of Italy with Maremmia (e.g.,
Thomas 1984a). Additional possible African occurrences in Europe include possible reduncines from late Miocene Sicily and Turkey (Seguenza 1902;
Köhler 1987;
Gentry 1999). Late Miocene links between sub-Saharan Africa and southern Asia are also apparent in the shared presence of bovid taxa such as the reduncine Kobus porrecticornis (see
Haile-Selassie et al. 2009). In light of the apparent barriers to exchange between southern Asia and the Greco-Iranian Province (Beden and Brunet 1986), shared occurrences of Bovidae between the Siwaliks and parts of Africa begs further investigation.
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