Linking microhabitat structure, morphology and locomotor performance traits in a recent radiation of dwarf chameleons
Faculty of Sciences. Biology
Functional ecology / British Ecological Society. - Oxford
, p. 702-713
University of Antwerp
Evidence that morphological traits associated with particular environments are functionally adapted to those environments is a key component to determining the adaptive nature of radiations. Adaptation is often measured by testing how organisms perform in diverse habitats, with performance traits associated with locomotion thought to be among the most ecologically relevant. We therefore explored whether there are relationships between morphology, locomotor performance traits (sprint speed, forefoot and tail grip strength on broad and narrow dowels) and microhabitat use in five phenotypic forms of a recent radiation of dwarf chameleon - the Bradypodion melanocephalum-Bradypodion thamnobates species complex - to determine whether morphological differences previously identified between the forms are associated with functional adaptations to their respective habitats, which can be broadly categorized as open or closed-canopy vegetation. The results showed significant differences in both absolute and relative performance values between the phenotypic forms. Absolute performance suggests there are two phenotypic groups - strong (B.thamnobates and Type B) and weak (B.melanocephalum and Types A and C). Relative performance differences highlighted the significance of forefoot grip strength among these chameleons, with the closed-canopy forms (B.thamnobates, Types B and C) exceeding their open-canopy counterparts (B.melanocephalum, Type A). Little to no differences were detected between forms with respect to sprint speed and tail strength. These results indicate that strong selection is acting upon forefoot grip strength and has resulted in morphological adaptations that enable each phenotypic form to conform with the demands of its habitat. This study provides evidence for the parallel evolution of forefoot grip strength among dwarf chameleons, consistent with the recognition of open and closed-canopy ecomorphs within the genus Bradypodion.