The evolution of diet in the Lamprophiidae

Naik, Hiral
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Studying feeding biology in a phylogenetic context helps elucidate the factors that significantly influenced the evolutionary history of organisms. The snake lineage is one of the most morphologically and ecologically diverse clades of vertebrates due to a variety of traits (e.g. venom, body shape, gape size and habitat use) that have enabled their exceptional radiation. Recently, the Deep History Hypothesis (DHH) has been used to explain how divergence, deep in the evolutionary history of snakes, has resulted in present day niche preferences. The Competition-Predation Hypothesis (CPH) contrastingly attributes current ecological traits to recent species interactions. Diet has been a key factor in shaping snake diversity and ecology, and it has often been used as a proxy to understand current snake community structure and evolutionary trends in snakes. I tested the validity of the two evolutionary hypotheses in the Lamprophiidae, a family of primarily African snakes. Furthermore, the evolution of lifestyle, fang types and body size in the Lamprophiidae was examined. Having sourced dietary data for ~300 species, a Hierarchical Cluster Analysis was performed, to group diet into eight broad clusters. A generalist diet comprised of lizards, aquatic vertebrates, small mammals, snakes and reptile eggs, was characteristic of 46% of extant species. Stochastic Character Mapping was performed to generate 50 possible evolutionary hypotheses, the majority of which suggested a generalist ancestral feeding condition with a tendency towards specialisation. Although the generalist feeding trait has largely been retained in many extant lamprophids, some species have a more specialised diet. From the phylogenetic reconstruction, it is evident that the ancestral lamprophid consumed a generalist diet in a terrestrial environment with a relatively small body size (400-600 mm) and possessed back fangs. Body size and fang morphology were correlated with diet indicating that these selective pressures have influenced the variety in prey consumption. A phylogenetic signal from Pagel’s lambda confirmed the divergence in diet while traits such as lifestyle, fang types and body size were constrained. Thus, the validity of DHH and CPH depends on the characters assessed and in this case, a combination of historical and contemporary influences is responsible for shaping the lamprophid community as a whole. The divergence in diet in the lamprophids is most likely influenced by competition or predation, as their interactions with other species within their habitat could be responsible for shaping their diet. This proves to be the case for the lamprophidae, however, studies on other groups of snakes, in different regions of the world have found that phylogeny is more influential on diet patterns. This study shows the importance in understanding ecological factors as a determinant of community ecology. Key words: Divergent evolution, snake ecology, morphological trait reconstruction
A dissertation submitted in fulfilment of the requirements of the degree of Master of Science to the School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa . July 2017.
Naik, Hiral (2017) The evolution of diet in the Lamprophiidae, University of the Witwatersrand, Johannesburg,