Ecomorphology in Neotropical snakes: a study with the tribe Pseudoboini

Author(s)

Laura Rodrigues Vieira de Alencar

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2010-08-27

Examining board members

Marcio Roberto Costa Martins; Ronaldo Fernandes; Ricardo Jannini Sawaya

• Advisor: Marcio Roberto Costa Martins

Abstract

Snakes of the tribe Pseudoboini are ecological diversity, considered as a monophyletic group and have a known phylogeny. Thus, the analyses of possible associations between the morphology and the ecology of this group in an evolutionary framework became possible. In the present study, we analyze the diet of pseudoboine species, and we test hypotheses of possible adaptative relationships between morphology and diet, and between morphology and microhabitat use in pseudoboine snakes. We also explore how these traits evolved during the diversification of the tribe. Nine species were considered as diet generalists and 13, as diet specialists, being six lizard specialists, three small mammal specialists, two snake specialists, one a lizard egg specialist, and one a bird egg specialist. An increase in the consumption of small mammals was not associated with an increase in robustness and head volume. Lizard, small mammal and snake specializations occurred independently at least twice in terminal taxa during the diversification of the tribe. A specialization in bird eggs seems to be an autapomorphy of Rhachidelus brazili. Robustness decreased in the ancestor of Siphlophis species, and increased substantially in R. brazili. Head volume descreased in the ancestor ofSiphlophis species and in Oxyrhopus petola, and increased substantially in Phimophis guianensis, in the ancestor of O. trigeminus and O. rhombifer and in R. brazili. Siphlophis cervinus, S. compressus, S. pulcher and D. anomalus were considered as semi-arboreal. The semi-arboreal habit reconstruction indicates that this habit evolved independently at least twice during the diversification of the group. We did not find indications of the effect of vegetation use on body size, robustness, head shape and the number of ventral scales per body unit. However, vegetation use seems to have led to an increase in tail length. Body size substantially decreased in P. guianensis and substantially increased in Clelia rustica and in the ancestor of C. clelia and C. plumbea. The number of vertebrae per body unit decreased substantially in C. rustica, in the ancestor of C. clelia and C. plumbea, and in Pseudoboa haasi. It substantially increased in the ancestor of O. trigeminus and O. rhombifer, and in O. melanogenys and P. guianensis. Tail length significantly decreased in C. rustica, Boiruna maculata and P. haasi, and increased substantially in the ancestor of the genus Siphlophis, in O. petola, D. anomalu ,R. brazili and in the ancestor of Pseudoboa spp.. Head width decreased substantially in Pseudoboa neuwiedii and increased significantly in S. compressus, P. guianensis and in B.maculata. Strong influence of phylogenetic inertia and/or the effect of alternative selective agents could be related to the absences of these possible adaptative 69 relationships. An ancestor with a morphology adequate to a diet based on small mammals and to arboreality could also have influenced the results. Knowing the outgroup of the tribe Pseudoboini would help to further clarify the relationships between morphology and ecology of these snakes. (AU)