Rhacophorid treefrogs have different reproductive modes: some go through a tadpole stage and some have direct development, and the adults of some species produce foam nests. Philautus is the only genus characterized by direct development. The production of foam nests has been reported in the genera Polypedates, Rhacophorus, Chiromantis and Chirixalus. Recent molecular studies did not provide a robust hypothesis concerning the origin of these reproductive modes in the Rhacophoridae. In order to better understand the evolution of these reproductive modes, we tried to clarify relationships within this group, using DNA sequencing. Our data set consists in a large number of new sequences (1676 base pairs corresponding to threee genes) for five outgroup ranoids and 48 Rhacophoridae, including 16 undescribed species from Sri Lanka and southern India, and all homologous data available in Genbank. After the inclusion of Philautus from India, our data show that the separation of Philautus into clades does not coincide with their geographic distribution. Our data point to the existence of a clade, including the genera Rhacophorus, Polypedates, Chiromantis and Chirixalus, which confirms the results of Wilkinson et al. (2002) and suggests that the ability to produce foam nests has emerged only once in the Rhacophoridae, as already stated by these authors.
The morphology of tadpoles has long received too little attention in taxonomic and phylogenetic contexts, beyond the use of Orton’s general tadpole types, despite the potential of larval characters for resolving problems in systematics. A possible explanation for this neglect is the ontogenetic variation of external morphology. In order to understand the value of larval characters in taxonomy and systematics, it is necessary to determine the developmental stage at which characters reach their definitive size, form and colour before meaningful comparisons can be made within and between species. Here I use the tadpole of Rana (Sylvirana) nigrovittata as a model organism to assess ontogenetic character variation. Morphometric measurements were taken, and external oral and internal buccal characters were assessed separately for each developmental stage from 26 to 38. Coefficients of variation were calculated for each morphometric character at each stage of development to test the character’s efficiency in reflecting the morphology of the tadpole. Most morphometric characters taken from the body described the shape of the animal well and varied little among individuals, whereas those taken from the tail were less reliable and those of the oral disk were quite variable due to contraction during fixation. A developmental 'climax' for most characters was reached by specimens between stages 32-40, indicating that they are best suited for morphological intra- and interspecific comparisons.
Amphibian populations are dramatically declining, while their inventory is far from being achieved. Tadpoles are usually overlooked from biodiversity survey, whereas their consideration will optimize species counts and knowledge of their ecological and developmental requirements is essential in conservation planning. Two mitochondrial markers, 16S (397 new sequences obtained) and COI (343 new sequences obtained), are used to test DNA barcoding on a set of larval and adult Asian amphibians represented by 83 recognized species from 65 sites. The advantages and drawbacks of each marker are assessed, COI barcoding being advocated for global DNA barcoding, whereas 16S suits for taxonomically or geographically restricted DNA barcoding. About half of the collected tadpoles were badly identified or incompletely named in the field. All tadpole sequences (except one case of probable introgressive hybridization) were correctly assigned to their respective species. Finally six clusters of tadpole sequences without conspecific adults were revealed, stressing the importance of collecting and taking into account tadpoles in biodiversity survey and conservation planning.
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