The influence of body size and sexual dimorphism on speciation within Anura



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Many adaptive radiations demonstrate clear relationships between morphological variation and diversity, hinting that trait plasticity leads to increased potential to diversify. This study will examine this pattern within frogs (Anura). Body size is the focal morphological feature of this study due to its ease of collection and close relationship with the niche of an organism. Unlike most large-scale studies, this one takes into account both male and female body size and the extent of sexual size dimorphism (SSD). This allows us to determine not only whether body size relates to diversification rate but also whether body size evolution in one sex is more indicative of changes in diversification rate than the other and what impact SSD has on diversity. The results show that rates of male and female body size evolution as well as extent of sexual size dimorphism were all significantly positively correlated with speciation rate. The relationship between body size and speciation supports the idea that morphological plasticity and enhanced diversification go hand-in-hand. Both sexes rate of body size evolution had a similar relationship with speciation, indicating neither sex is more important for diversification. Increased sexual size dimorphism suggests this selection for extreme variation promotes diversity. Overall, rates of phenotypic evolution and speciation were closely linked across all of Anura.