Species distribution and assembly patterns of frog larvae in rainforest streams of Madagascar.

Many tropical rainforests harbour species-rich assemblages of frogs and, consequently, of tadpoles. These larvae are often morphologically highly diverse, especially in their oral structures. Whether this might represent an important axis of ecological partitioning in frog assemblages remains an untested hypothesis. In general, it is poorly known how diverse tadpole assemblages are organised. Using information from Madagascar's remarkably species-rich stream tadpole assemblages, we analysed the distribution and co-occurrence of 44 species. We also assessed the importance of phylogenetic history and eco-morphological adaptation for habitat selection at two functional and two spatial levels. We show that both rare and common species exist in most morphological clusters and phylogenetic groups of tadpoles. Habitat characteristics of the streams and surrounding forest influence species composition. Whereas there is a general trend in preferring wide and deep streams without a steep slope for most species, some of the morphological clusters separate along specific habitat variables. Stream choice is influenced both by phylogenetic history and morphological adaptation. Within streams, tadpoles partition microhabitat mainly according to their morphological cluster but without phylogenetic signal. Species dissimilarities of habitat selection on both spatial scales are not correlated. We found no evidence for competition in the tadpole assemblages studied. [ABSTRACT FROM AUTHOR]