The evolution and diversification of diet in elapids
Kgaditse, Mimmie Mamafolo
A central goal in macroecology is understanding the factors that have shaped broad-scale patterns among extant natural communities. Diet is widely cited as a key factor involved in shaping snake diversification. Amongst serpents, the adaptive radiation of elapids is unparalleled in terms of their sheer global distribution. My study was aimed at evaluating the variation in diet and how trends evolved throughout the radiation of the elapids. Based on the published natural history data of 303 elapid species, a cluster analysis revealed seven groups of species within which diet types were similar. The broad diet clusters included snake consumption, feeding on fish, ectotherms, endotherms, lizards, a generalist diet and lastly, a terrestrial invertebrate group that was the least prevalent diet type. Maximum Parsimony, Maximum Likelihood and Stochastic Character Mapping were used to trace the ancestral dietary condition in the Elapidae. Reconstructions demonstrated that starting from an ophiophagous ancestor, elapids still largely retain their early feeding habits. Despite the emergence of novel feeding patterns in the group, the predominantly conservative diet patterns suggest that niche conservatism has shaped elapid foraging dynamics. Members of the lineage characteristically feed on elongate ectothermic prey (e.g., squamates, caecilians, eels, earthworms) possibly owing to morphologically-mediated gape constraints. Phylogenetically corrected comparative methods were used to assess the influence of differences in body size, lifestyle and global scale spatial distribution of diet evolution. While lifestyle and distribution considerably influenced how diet patterns evolved, body size was not a significant determinant of the prey types taken. The lack of body size-diet association may be because larger-bodied elapids also opportunistically supplement their diet with smaller prey items. Overall, the findings indicate that recent ecological factors (e.g., lifestyle) coupled with long established factors (phylogeny, biogeography) have shaped elapid natural history patterns. This study is the first of its kind to offer a family-level, phylogenetically-based analysis on the evolutionary and contemporary feeding dynamics of the world’s most widespread snake family.
A dissertation submitted to the School of Animal, Plant and Environmental Sciences, Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa in fulfilment of the requirements of the degree of Masters of Science. Johannesburg, South Africa. July, 2016.
Kgaditse, Mimmie Mamafolo (2016) The evolution and diversification of diet in elapids, University of Witwatersrand, Johannesburg, <http://wiredspace.wits.ac.za/handle/10539/21722>