Abstract
Spatial variation in the environment may be an important source of morphological variation in many organisms. Tadpoles are valuable model organisms for studies of morphological variation, and in particular, the evaluation of the relationship between environmental and morphological variables. In heterogeneous environments, such as the temporary ponds found in the Cerrado savanna of central Brazil, understanding how environmental variables influence the morphological variation found in tadpole populations can provide important insights into this phenomenon. The present study thus aimed to (i) describe the morphometric variation in tadpoles found in different populations of Dendropsophus nanus and Dendropsophus minutus in the Cerrado of southern Maranhão state (Brazil), and (ii) relate this variation in tadpole morphology to the characteristics of the local ponds. Tadpoles were collected from 11 pounds in southern Maranhão, and the morphological space among the different populations was compared using NPMANOVA, separately for each species. The degree of association between the environmental and morphological matrices was then tested using a Stepwise Multiple Linear Regression. The morphological (tadpole morphometry) and environmental (pond characteristics) data matrices were obtained by ordination techniques. Considerable morphometric differences were found among populations in both species. In D. nanus, the morphometric variation was correlated with that of the substrate, whereas in D. minutus, morphometry was associated with the vegetation found in the pond. Overall, then, the study demonstrated that distinct environmental variables influenced significantly the morphometry of the tadpoles of each frog species.
Key words
anuran larvae; Dendropsophus minutus; Dendropsophus nanus; Maranhão; morphology; savanna
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