Diet, morphology and performance in two chameleon morphs: Do harder bites equate with harder prey?
Applied Biodiversity Research Division, South African National Biodiversity Institute, Claremont, Cape Town, South Africa; Department of Biodiversity and Conservation Biology, University of the Western Cape, Bellville, South Africa; Département d'Ecologie et de Gestion de la Biodiversité, UMR 7179 C.N.R.S/M.N.H.N., Paris, France; Department of Biology, University of Antwerp, Antwerpen, Belgium; Department of Botany and Zoology, University of Stellenbosch, Matieland, South Africa
Ecologically induced morphological variation has been identified as a mainstay in evolutionary theory. Species that inhabit different habitats are likely to display morphological and functional differences related to the exploitation of different dietary resources available in each habitat within limits imposed by trade-offs. Here, we examine two populations of the Cape Dwarf Chameleon, Bradypodion pumilum, from fynbos (heathland) and woodland to investigate whether head morphology and bite performance are related to diet within and between populations. Stomach contents are compared with prey availability to test whether chameleons are selective with respect to prey size, hardness and evasiveness. Our data show that for adult chameleons from the fynbos (Kogelberg; n = 44), mean and maximum prey size are tightly correlated with head morphology and performance. In woodland habitat (Stellenbosch; n = 52), only maximum prey size is correlated with head morphology and performance. Fynbos chameleons showed no preference with respect to prey hardness, while those from woodland ate less hard and/or sedentary prey than available, thus preferring items that were soft and/or evasive. Finally, fynbos chameleons have a diet of sedentary and/or evasive prey similar in proportions to that available. Our results suggest that diet is not directly related to selection on the head morphology and biting performance of B. pumilum in woodland habitat, but that it may be important for selection in fynbos due to a reduction in overall prey availability. © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London.
adaptation; diet; ecomorphology; evolutionary theory; fynbos; heathland; lizard; performance assessment; prey availability; prey selection; prey size; stomach content; trade-off; woodland; Bradypodion pumilum; Chamaeleonidae; Squamata