Ishan Agarwal

Topographically complex tropical landscapes often harbour cryptic biodiversity structured by geography and the environment, where morphologically conserved taxa may conceal deeply divergent evolutionary lineages. We examined whether two traditionally described morphological groups (morphotypes) of the Western Ghats-endemic skink genus Ristella are monophyletic and occupy distinct environmental niches and how climatic and topographic factors influence their distribution and diversification. We quantified niche divergence using spatial data on climate, elevation, and canopy cover and constructed a dated multilocus coalescent phylogeny (∼4 kb; three mitochondrial and three nuclear loci) to assess phylogenetic congruence with niche separation. Ancestral range evolution and ancestral state reconstruction analyses were used to evaluate the role of climatic stability in shaping diversification. Phylogenetic analyses indicate that one morphotype is monophyletic, whereas the other comprises two non-sister clades, suggesting convergence or retention of ancestral traits. Our results also reveal clear environmental niche separation between morphotypes, particularly in elevation, canopy cover, temperature, and precipitation. Diversification probably began in the climatically stable southern Western Ghats, with most phylogenetic splits occurring post Late Miocene, consistent with aridity-driven vicariance. These findings underscore the role of climatic stability in Ristella diversification, revealing early ecological divergence followed by relative niche stability within major lineages.

Gangaichthys indonepalicus gen. et sp. nov ., is described from the Indo-Gangetic Plain, Bihar, India. This is the first stygobitic chaudhuriid and first subterranean fish from the alluvial aquifers of the Gangetic Basin and Indo-Gangetic Plain, with all three specimens collected from borewells. As the first subterranean member of the family Chaudhuriidae it is readily diagnosed from other genera and species of the family by a unique set of morphological characters linked to its stygobitic habit such as reduced eyes, the complete absence of body pigmentation, and apparent absence of ribs. In addition to its stygobitic characters, Gangaichthys is distinguished from all known chaudhuriid genera by the following osteological characters: neural spines laterally narrow and tapering to a point posteriorly or dorso-posteriorly, no spinelike projection on neural arch in front of neural spine; preorbital extension of ectopterygoid does not reach beyond coronoid process of dentary; metapterygoid elongate. Gangaichthys indonepalicus gen. et sp. nov . may further be distinguished from all known chaudhuriid genera and species by the presence of 64 vertebrae (28 abdominal, 36 caudal), and in having a single pectoral fin-ray, six caudal fin-rays, 37 dorsal, and 35 anal fin-rays. Molecular data place Gangaichthys indonepalicus gen. et sp. nov . within Chaudhuriidae, and it is > 20% divergent from two genera of the family for which there is comparative mitochondrial CO1 sequence data.

A new species of ground-dwelling gecko of the genus Cyrtodactylus (Geckoella) is described from the low elevation Terai-Duar region of southeastern Nepal using molecular and morphological data. Cyrtodactylus teraiensis sp. nov . is the first new species of the C. nebulosus species complex, the remaining members of which are distributed in the northern Eastern Ghats and Satpuras; a lectoype for C. nebulosus is also designated. The new species is the first Geckoella described from outside peninsular India and distributed north of the Indo-Gangetic Plains. Cyrtodactylus teraiensis sp. nov . forms the deeply divergent sister taxon to Indian members of the C. nebulosus complex with 15.7–18.1% uncorrected mitochondrial sequence divergence from them, and 21.0–28.5% from other Geckoella . The new species is also recognised in tree-based delimitation methods and can be morphologically distinguished from other Cyrtodactylus and Geckoella species by a small body size (snout to vent length, SVL up to at least 45.5 mm), length of original tail < SVL, 16–18 rows of dorsal tubercles, 30–32 ventral scales across belly at midbody; dorsal colour pattern of four or five paired spots between neck and hindlimb insertions alternating with two or three much smaller paired spots. The divergence between Cyrtodactylus teraiensis sp. nov . and Indian members of the C. nebulosus complex is estimated to have occurred in the Middle Miocene, and it may be that tropical forest expansion during the Mid-Miocene Climatic Optimum allowed dispersal across the Indo-Gangetic Plains.

India, one of the world’s most biodiverse countries and now the most populous, stands at a critical intersection of ecological wealth and intense anthropogenic pressure. Its unique geological history, once part of Gondwana and later colliding with Asia, has profoundly shaped its biota, resulting in high levels of endemism and evolutionary distinctiveness. Despite a deep cultural reverence for nature, much of India’s biodiversity, its distribution, evolutionary origins, and future trajectory remain poorly understood. At the heart of shaping a resilient future for biodiversity science in India lies the urgent need for a modern, accessible, and integrated biodiversity research. Here, we assess the current state of biodiversity science in India, drawing from taxonomic and biogeographical studies that rely heavily on natural history collections. For many taxa and ecosystems, data remain scarce or outdated, often based on collections from the 19th and 20th centuries, with critical gaps in molecular, distributional, and phenotypic trait information. Existing data are frequently fragmented, inaccessible, or poorly integrated. These limitations hinder the ability to understand biogeographical patterns or monitor biodiversity change during the Anthropocene. We argue that a national institution dedicated to biodiversity research is urgently needed to coordinate the documentation, analysis, and conservation of India’s natural heritage for future generations.

Two new species of Cyrtodactylus from the khasiensis group are described using morphological characters supported by molecular analyses based on the mitochondrial ND2 gene. Cyrtodactylus makwanpurgadhiensissp. nov. and C. churesp. nov. from the Siwalik Mountains in central Nepal are at least 11.2% divergent from other Nepalese congeners and 16.7% from each other and can be distinguished by a combination of morphometric and meristic traits. The description of two new species from the Siwalik Mountains underscores the conservation significance of this region, a relatively young, dry, and geologically unstable range of the Himalayan orogen. Despite serving as a border between the lowland (Terai) and Himalayan range, it remains underrepresented in both biodiversity assessments and conservation planning in Nepal. Our findings suggest the need for a robust and targeted species research program and to prioritise this landscape for conservation actions.

We conduct a review of the known species of Cyrtodactylus from Nepal based on type and topotypical material, resulting in the synonymization of one species and description of three additional species from Central Nepal. The five species of Cyrtodactylus from Nepal are members of the Indo-Burma clade and are at least 11.7 % divergent from known congeners based on the mitochondrial ND2 gene. The results show that C. nepalensis and one of the new species are allied to the C. fasciolatus group while the other two new species and C. martinstolli are members of the mountain subclade within the khasiensis group. The new species can be readily distinguished from congeners in the Himalaya by a combination of body size, meristic characters including number of dorsal tubercle rows and mid ventral scales across the belly, the number and arrangement of pores in males and females, and subcaudal condition.

We describe a new species of small-sized Calotes from mid-elevation (~1270 m asl.), swidden or shifting cultivation areas in the Subansiri river basin, Upper Subansiri District, Arunachal Pradesh, India. Mitochondrial sequence data (ND2) recovers Calotes sinyik sp. nov. as the closely related sister taxon to an unnamed species from Medog, Tibet; the two falling in a broader clade including C. paulus + C. zolaiking and species of the C. emma and C. mystaceus groups. The new species is 7.8% divergent in ND2 sequence data from the unnamed lineage from Medog and deeply divergent (≥ 21.6–28.1%) from other congeners. The new species can easily be distinguished from regional congeners by its small adult body size (maximum snout to vent length of 65 mm) and heterogenous dorsal scales, and from its closest relatives C. paulus and C. zolaiking by having 54 or 55 midbody scale rows and 42 or 43 vertebral scales. It is likely that many more allied species remain to be discovered from Northeast India, which remains poorly surveyed across taxonomic groups.

We describe five new species allied to Cnemaspis beddomei from the Southern Western Ghats, Tamil Nadu, India using morphological data and mitochondrial sequence divergence. The new species are members of the beddomei and anamudiensis subclades within the beddomei clade and are from boulder habitats in evergreen forests in Tenkasi (Cnemaspis tenkasiensis sp. nov.), and the Agamalai (C. agamalaiensis sp. nov.), Anaimalai (C. anaimalaiensis sp. nov. and C. valparaiensis sp. nov.) and Palani Hills (C. anuradhae sp. nov.). The new species can be distinguished from other members of the beddomei clade and each other by a combination of non-overlapping morphological characters including body size, distinct colouration in males, the number or arrangement of dorsal tubercles around the body and paravertebral tubercles, the number of ventral scales across midbody and longitudinal scales from mental to cloaca, tail tuberculation and arrangement of subcaudal scales, besides uncorrected pairwise ND2 and 16S sequence divergence of ≥ 5.4 % and ≥ 2.3 %. The beddomei clade is another example of extreme micro-endemism, all 23 known species are evergreen forest dwellers and are each known from just one or a few closely spaced localities, with three non-sister species known from within one kilometre straight-line distance of each other on the Valparai Plateau, Anaimalai Tiger Reserve. The beddomei subclade is distributed from Agasthyamalai to the Anaimalais while the anamudiensis subclade is restricted to the Anaimalai, Palani and Kannan Devan Hills.

We describe two new species of South Asian Cnemaspis from far northern peaks of the Northern Western Ghats of Maharashtra, India. The two new species are the most northernly distributed representatives of the girii clade and are phylogenetically and morphologically allied to C. uttaraghati. The new species are 15.0% divergent from C. uttaraghati in pairwise uncorrected ND2 sequence data, 9.9 % from each other, and over 17.5–18.8% from other members of the girii clade. The two new species can easily be distinguished from most members of the girii clade by a combination of non-overlapping morphological characters such as body size (maximum snout to vent length 35–43 mm), low number of dorsal tubercle rows (6–11), having irregular paravertebral tubercles, and high subdigital lamellae counts; and from each other and C. uttaraghati by the number of midventral scales across belly, the number of subdigital lamellae, and the number of poreless scales separating series of femoral pores. The new species and C. uttaraghati are distributed within 10–25 km of each other, providing an example of extreme micro-endemism in the Northern Western Ghats.