The results of our phylogenetic analysis allow us to investigate evolutionary relationships among all nominal species within the Western Ghats-Sri Lanka biodiversity hotspot, and with the Southeast Asian taxa by extending the geographical range of our dataset.
The Maximum Likelihood tree (Fig. 4) depicts four major clades, which are highly resolved, with various associated distribution patterns within the Western Ghats-Sri Lanka biodiversity hotspot: the Hylarana aurantiaca and Hylarana flavescens groups are restricted to the Western Ghats; the Hylarana temporalis group is found only in Sri Lanka; the Hylarana malabarica group has a wide distribution in India and Sri Lanka, along with Hylarana cf. leptoglossa from Northeast India (Fig. 4).
The other Southeast Asian taxa, including Hylarana nigrovittata — type species of the genus Sylvirana (Dubois, 1992), were found to be basal to the above-mentioned Western Ghats and Sri Lankan groups. However these associations were not strongly supported, probably due to insufficient taxon sampling to resolve these relationships. The clade containing Hylarana erythraea (type species of the genus Hylarana) formed the most basal split with strong support. Though some relationships among the Southeast Asian taxa remained unresolved due to poor data sampling from outside the study area, most branches in our trees were well supported and the overall topology was in agreement with earlier studies (Che et al., 2007; Pyron and Wiens, 2011).
Seen in the context of Che et al. (2007) and Pyron and Wiens (2011) our results suggest that most of the Western Ghats-Sri Lankan congeners form an endemic radiation (Fig. 4). This includes the Hylarana aurantiaca and H. flavescens groups from India, and the H. temporalis group from Sri Lanka. The H. malabarica group which has one species each from India and Sri Lanka, forms a well-supported clade with South East Asian H. cf. leptoglossa. Given that previously recognized generic level taxa (Sylvirana and Hydrophylax) included in our study form sister clades at the base of the phylogeny, further taxonomic focus is needed to ascertain if the endemic Western Ghats-Sri Lankan radiation warrants a higher level taxonomic status.
Three (out of four) Northeast Indian taxa nested with Southeast Asian species rather than the species from the Western Ghats, except Hylarana cf. leptoglossa, which was closely related to the Hylarana malabarica group (Fig. 4). This group also contained the single sample from Central India (SDBDU 2011.596), which nested with the Hylarana malabarica haplogroup 1. The identity of this sub-adult specimen could not be confirmed morphologically. Our results suggest that among the Western Ghats-Sri Lankan groups, the Hylarana malabarica group is more closely related to the Southeast Asian taxa. This is also evident from the distribution of species in the subgenus Hydrophylax (Dubois, 1992), whose taxonomic status remains unresolved (Che et al., 2007). Though our sampling is insufficient to comment on the dispersal and distribution of Hylarana throughout its range, the results of our study provide the first molecular evidence for the diversity and distribution of Hylarana species across the Western Ghats and Sri Lankan biogeographical region, and may assist future studies to resolve the existing uncertainty about taxonomic positions of taxa contained in the genus Hylarana.