Abstract
The Western Ghats (WG) is an escarpment on the west coast of Peninsular India, housing one of the richest assemblages of frogs in the world, with three endemic families. Here, we report the discovery of a new ancient lineage from a high-elevation massif in the Wayanad Plateau of the southern WG. Phylogenetic analysis reveals that the lineage belongs to Natatanura and clusters with Nyctibatrachidae, a family endemic to the WG/Sri Lanka biodiversity hotspot. Based on geographic distribution, unique morphological traits, deep genetic divergence, and phylogenetic position that distinguishes the lineage from the two nyctibatrachid subfamilies Nyctibatrachinae Blommers-Schlösser, 1993 and Lankanectinae Dubois & Ohler, 2001, we erect a new subfamily Astrobatrachinae subfam. nov. (endemic to the WG, Peninsular India), and describe a new genus Astrobatrachus gen. nov. and species, Astrobatrachus kurichiyana sp. nov. The discovery of this species adds to the list of deeply divergent and monotypic or depauperate lineages with narrow geographic ranges in the southern massifs of the WG. The southern regions of the WG have long been considered geographic and climatic refugia, and this new relict lineage underscores their evolutionary significance. The small range of this species exclusively outside protected areas highlights the significance of reserve forest tracts in the WG in housing evolutionary novelty. This reinforces the need for intensive sampling to uncover new lineages and advance our understanding of the historical biogeography of this ancient landmass.
Highlights
Ancient lineages hold significant information for understanding the biogeographic past of different regions (Fjeldsaå & Lovett, 1997)
Given the deep divergences between Nyctibatrachus, Lankanectes, and the new lineage, the age of the MRCA of these three lineages fall within the range of the stem age of Nyctibatrachidae and the crown age of Natatanura, recently estimated to be in the Late Cretaceous or Paleocene (∼57–76 Ma) (Van Bocxlaer et al, 2012; Pyron, 2014; Yuan et al, 2018)
We demonstrate that this new species is morphologically diagnosable from other natatanuran taxa endemic to the Western Ghats (WG)
Summary
Ancient lineages hold significant information for understanding the biogeographic past of different regions (Fjeldsaå & Lovett, 1997). In South Asia, the Western Ghats (WG) escarpment of Peninsular India and the island of Sri Lanka have long been recognized as rainforest refuges (Wallace, 1876; Mani, 1974) These regions are an evolutionary repository for amphibians with hundreds of frog species from nine families: Bufonidae Gray, 1825; Dicroglossidae Anderson, 1871; Micrixalidae Dubois, Ohler & Biju, 2001; Microhylidae Günther, 1858 (1843); Nasikabatrachidae Biju & Bossuyt, 2003; Nyctibatrachidae Blommers-Schlösser, 1993; Ranidae Batsch, 1796; Ranixalidae Dubois, 1987; and Rhacophoridae Hoffman, 1932 (1858) (see Dutta et al, 2004; Van Bocxlaer et al, 2009; Biju et al, 2011, 2014; Vijayakumar et al, 2014; Dinesh et al, 2015; Dahanukar et al, 2016). Three of these frog families (Micrixalidae, Ranixalidae, and Nasikabatrachidae) are endemic to the WG, while a fourth, Nyctibatrachidae, consists of two subfamilies: Nyctibatrachinae which is endemic to the WG, and Lankanectinae which is endemic to Sri Lanka
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