Evidence of adaptive evolution in the cranial morphology of tropidurid lizards from coastal Peru 

Ken Sebastian Toyama

Abstract


Head morphology is known for being a good predictor of diet characteristics in lizards. Head height and width are considered to be the most important head dimensions being related to a higher bite force, which allows certain lizards to consume different prey items. In this study head dimensions are compared between four species of the South American lava lizard genus Microlophus, which were paired considering their main diet (herbivorous and insectivorous). Head height, width and length were measured for each species and compared between them independently of body size. It was found that head height and width were strongly related with the diet of each species, as the ones with a semi-herbivore diet showed bigger values for these traits. Additionally, the head was longer in insectivorous species, which is a result not reported before. The different morphologies of the study species support a possible case of adaptive evolution, since both types of diet and head morphology arose from different clades in the Microlophus phylogeny. Consequently, the results of this study give evidence of a strong link between species and their constraints on specific diets. Further ecomorphological studies are needed to enrich the knowledge about this subject which is relatively understudied in South American desert lizards. 


Keywords


Ecomorphology; diet; herbivore; lizards; desert; South America

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