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In recent years a number of reports on new descriptions and ancient lineages have suggested that the Western Ghats represent a major hotspot of amphibian diversity and probably a relict habitat (Dutta et al., 2004). In the last five years, 13 new species of amphibians have been discovered from the Western Ghats. Of these, nine are anurans (Dubois et al., 2001; Krishnamurthy et al., 2001; Bossuyt, 2002; Biju and Bossuyt, 2003; Kuramoto and Joshy, 2003; Biju and Bossuyt, 2005a, b; Das and Kunte, 2005) and four are caecilians (Ravichandran et al., 2003; Giri et al., 2003; Bhatta and Prashath, 2004; Bhatta and Srinivas, 2004). Our description of a new species based on morphogenetic analysis from the same biodiversity hotspot adds to the growing list of amphibians from the region, clearly indicates the hotspot status of the region, and reinforces the current notion that there are several new species yet to be discovered (Aravind et al., 2004) requiring proper methods for describing new species.
We described the new species based on morphometry, molecular analysis, and acoustics, which complemented the taxonomic description of the species. Also, the observation that the amplected pair of P. neelanethrus sp. nov. descended to the ground without any water body nearby was probably indicative of ground nesting and direct development to a froglet, which are characteristic of the genus (Marmayou et al., 2000).
The study also revealed that although traditional approaches based on morphometric comparisons and acoustics provided an initial indication that P. neelanethrus was a new species, its identity and overall taxonomic relationships could most reliably be inferred based on molecular analysis. Furthermore, it is important to note that the specimens of the putative new species from different localities carried identical rDNA sequences, which strongly suggests that the isolated, disjunct small populations spread over a considerable part of the central Western Ghats were indeed P. neelanethrus sp. nov., which is expected to be a very poor disperser.
Philautus neelanethrus sp. nov. was found mainly in the mid-altitudinal range (500–700 m asl) characterized by evergreen/ semi-evergreen/moist deciduous forest patches in the central Western Ghats, and most importantly in Myristica swamps, which are considered to be living fossils among the vegetation types prevailing in the region (Chandran and Divakar, 2001). The phylogenetic and molecular-dating analysis suggests that P. neelanethrus sp nov. is a relatively old taxon among other species of Philautus endemic to the Western Ghats. Systematic sampling carried out in the Sharavathi River basin shows that forest patches (as mentioned above) are a prerequisite for this species to survive; these patches are not found in many parts of the study area due to multiple anthropogenic disturbances. These unique features, the relatively older origin of the taxon but presence of its extant population in restricted, non-overlapping and non-contiguous patches, suggests that there had been significant habitat fragmentation in the Western Ghats leading to the present day disjunct populations. The species thus appears to be a useful, indirect bioindicator of the ecological health of the Western Ghats, where the remaining evergreen/semi-evergreen/moist deciduous forests are becoming patchy and insularized.
A number of recent studies have documented habitat fragmentation in the Western Ghats due to various anthropogenic activities, viz, construction of dams for hydropower, extension of agricultural fields into forested areas, and urbanization (Vasudevan et al., 2001; Gururaja et al., 2003; Aggarwal, 2004). We emphasize here that such fragmentation of natural forest habitats has led to the formation of ecological barriers. These barriers have curtailed poor dispersers like P. neelanethrus sp. nov. from dispersing into adjoining similar habitats, leading to the formation of metapopulations. Such metapopulations are always at high risk of extinction due to progressively decreasing native habitats, inbreeding stress, invasion by introduced species, etc. Thus the new species is clearly an indicator of forest fragmentation, at the same time warning of the consequences of fragmentation of the remaining biodiversity in the region and calling for immediate conservation measures to be initiated.
The supplementary data for this article can be found online at http://dx.doi.org/10.2108/zsj.24.525.
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