1Department of Anthropology, Rutgers, The State University of New Jersey, 2Department of Anthropology, The University of Texas at Austin
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Reconstructions of paleohabitats provide critical contextual information for understanding hominin evolution. The morphology of species from relevant sites understood in terms of functional relationships to habitat (termed ecomorphology) offers a direct link to habitat. Ecomorphology has been preferred as a “taxon-free” approach.
Bovids are common in ecomorphological analyses, but bovid phylogeny and habitat are not uncorrelated raising the possibility (as argued by Klein and colleagues) that analyses are anything but “taxon free.” We analyze two relative dimensions of the bovid metatarsal previously found to have strong associations with habitat (relative midshaft width and relative metatarsal length) using PGLS to estimate potential phylogenetic effects.
Eleven measurements were taken on 361 bovid and 11 antilocaprid metatarsals from 74 extant bovids and one extant antilocaprid. Ratios of length and midshaft width versus a geometric mean size proxy were fit to PGLS models using the phylogeny of Hernández Fernández and Vrba. A first set of models including the ratios and size proxy showed the expected strong phylogenetic signal with lambda of 0.94 for relative length and 0.74 for relative midshaft width. Models including habitat resulted in a lambda of 0.88 for relative length and lambda bounded at zero for relative midshaft width and yielded significant habitat effects.
Clearly, phylogeny, morphology, and habitat all march together. Notably, bovid metatarsal midshaft width appears less likely to be confounded by phylogeny. We suggest that the way forward for ecomorphology is grounded in functionally relevant observations and careful consideration of phylogeny designed to bracket probable habitat preferences appropriately.