Palghat Gap Research Articles

The past and current distribution of the lesser-known Indian endemic Madras Hedgehog Paraechinus nudiventris (Mammalia: Eulipotyphla: Erinaceidae)

The Madras Hedgehog Paraechinus nudiventris (Horsefield, 1851) is a species endemic to a few isolated patches in southern India threatened by habitat loss and direct take. Little is known about its historical distribution or present climatic needs, both of which could provide important baselines for conservation and habitat restoration. The current distribution of Paraechinus nudiventris was modelled using occurrences collected in the field and from community reports. Based on the current climatic niche estimated from Maxent, Madras Hedgehog distribution was projected into southern India during the last interglacial gap (120,000–140,000 YBP), and last glacial maximum (22,000 YBP) and mid-Holocene (~6,000 YBP). During the (Last Interglacial Gap) LIG the suitable habitat was restricted to the Palghat gap in the southern Western Ghats mountains and a small region in south Sri Lanka, although it is unclear whether the suitable climates in Sri Lanka were occupied and then extirpated, or never colonized. The present climatic niche of the species is confined to lower elevations and semi-arid plains of southern and central Tamil Nadu in India. The contemporary models can be used to update the IUCN range map for P. nudiventris in India, as well as identify suitable habitats for this species to guide local conservation strategies.

Two new nocturnal species of South Asian Cnemaspis Strauch, 1887 (Squamata: Gekkonidae) of the wynadensis clade from the southern Western Ghats, India

We describe two new medium-bodied, nocturnal species of South Asian Cnemaspis from the southern Western Ghats, Tamil Nadu, India in an integrative taxonomic framework. The two new species are phylogenetically and morphologically allied to the wynadensis clade and can be distinguished from other species of the wynadensis clade and each other by a combination of nonoverlapping morphological characters including body size, homogeneous dorsal pholidosis, the number of femoral pores and poreless scales separating these series, the number of ventral scales across the midbody and longitudinal scales from mental to cloaca, the number of dorsal granules around the body; and an uncorrected pairwise ND2 sequence divergence of 8.2–22.9 % (16S 4.2–12.2 %) from all other members in the clade. These are the first members of the wynadensis clade known from south of the Palghat Gap apart from C. bireticulata, a putative junior synonym of C. sisparensis that is likely to be distinct owing to morphological differences and geographic distance. Cnemaspis sanctus sp. nov. is from low coastal hills in Kanyakumari District at the southern tip of the Western Ghats and Cnemaspis persephone sp. nov. is from the Anaimalais, Anaimalai Tiger Reserve. Many more undescribed species of the wynadensis clade and South Asian Cnemaspis are likely to be found across the southern Western Ghats.

Avifaunal assemblage patterns in Bharathapuzha River Basin, Kerala, India

Bharathapuzha, the second largest west-flowing river in the Western Ghats, originates from the northern and southern parts of the Palghat gap and debouches into the Arabian Sea at Ponnani. This river is exposed to high levels of anthropogenic pressures. This study looks into avifaunal assemblage patterns and the factors influencing the structure of bird communities in different ecological zones of the Bharathapuzha River Basin. The syntropic birds and flocking birds contribute variations in the bird community assemblage in the river basin. For the water-dependent and water-associated birds, mudflats, water flow, riverside vegetation, and distance from the forest were found to be the influencing factors in the migratory season. The study also emphasized the importance of protecting these river-associated habitats for the conservation of birds.

Crustal and Lithospheric Variations along the Western Passive Continental Margin of the Indian Peninsula

The western passive continental margin (WPCM) of the Indian Peninsula is one of the world's largest and most remarkable escarpments, signifying a boundary between oceanic and continental lithospheres. It traverses distinct lithological units, majorly the SGT, WDC, and DVP, each characterized by distinct geological structures, geochronological histories, and petro-physical properties. Despite numerous research efforts, the exact mechanisms governing the WPCM evolution and its developmental connections remain unclear due to limited data and significant uncertainties. In our study, we meticulously analyzed global and local models, focusing on the Western Ghats (WG), to examine crust and lithosphere thickness. Our analysis revealed significant uncertainties in crustal and lithospheric variations, with a maximum difference of 10.68% in crust thickness and 20.04% in lithospheric thickness across different major lithological formations in the WG. These differences can have a substantial impact on the geodynamic analysis of lithospheric structures and tectonic evolution. Additionally, we developed a 2-D lithospheric density model over the WG, crossing the major geological units, which delineates the crust and lithospheric structure between the eastern and western sides of the escarpment. Our results, in conjunction with geomorphological data, suggest that the WPCM’s thick lithosphere with elevated topography illustrates a continuous upwarp, supported by flexural compensation of uplifted terrain. The movement of the Indian plate, primarily in the N-S and NW-SE directions, subsequently modified the entire escarpment. This model offers insights into the evolution of the WPCM and potentially contributes to the formation of the NE-SW fault in the southern part of the South Indian Shield, with potential implications for the Palghat gap.

Phylogeographical patterns are governed by geography in endemic polymorphic snail Indrella ampulla (Gastropoda: Ariophantidae)

Abstract Genetic diversity within a species can be shaped by abiotic factors, such as climate and geography. We aimed to ascertain the relative importance of these two abiotic factors to Indrella ampulla, a monotypic snail species from the Western Ghats, India, that has three colour morphs with some overlapping distributions. We also wanted to investigate whether these colour morphs represent divergent lineages or incipient species. We sequenced one nuclear and two mitochondrial genes from 32 individuals of I. ampulla. We used phylogenetic, population genetic, and niche modelling tools to address these questions. The results suggested that the colour morphs were not reciprocally monophyletic and exhibited considerable niche overlap, suggesting that they cannot be considered as incipient species. Furthermore, the results showed that the impact of palaeoclimatic oscillations in shaping the genetic diversity of this species cannot be determined conclusively. The Palghat Gap seems to have shaped the genetic diversity in this group to a certain degree. The colour morph distributed south of the Palghat Gap did not show admixture and exhibited the least amount of niche overlap with the other morphs. The geography of the landscape seems to have played a prominent role in shaping genetic diversity in this species.

Rediscovery and systematics of Rhinophis fergusonianus Boulenger, 1896 (Serpentes: Uropeltidae) from Indias Western Ghats.

The shieldtail snake Rhinophis fergusonianus Boulenger, 1896 was previously known only from the holotype specimen collected approximately 130 years ago from an imprecise Indian locality (Cardamom Hills). We report the rediscovery of this species from four localities, from low-elevation hills on both sides of the Palghat Gap in the southern part of the Western Ghats of peninsular India. We document new specimens of R. fergusonianus and provide a reassessment of the systematics of the species based on external morphology and DNA-sequence data. We also provide a revised key to the identification of Indian species of Rhinophis.

Characteristics of the strong winds on the exit region of the Palghat gap during the Indian summer monsoon season

Characteristics of the strong winds on the exit region of the Palghat gap during the Indian summer monsoon season

Bioacoustics, breeding ecology and range of the Kerala warty frog Minervarya cf. keralensis from north of the Palghat gap, central Western Ghats

Minervarya cf. keralensis has been detected for the first time north of the Palghat gap in the central Western Ghats, a range extension of about 85 km. This species calls and breeds in the post-monsoon period (Jan–March) and exhibits axillary amplexus. Male call characteristics, natural history observations, and distributional complexities are described. Currently, the Minervarya nilagirica group that includes M. keralensis, show a complex distribution pattern in peninsular India that is worthy of further phylogeographic study.

A multitude of spots! Five new microendemic species of the Cnemaspis gracilis group (Squamata: Gekkonidae) from massifs in the Shevaroy landscape, Tamil Nadu, India

South Asian Cnemaspis are one of the most diverse clades of gekkonids in South Asia with their highest diversity in the Western Ghats and Sri Lanka. These geckos include only a few nocturnal species and are largely diurnal or cathemeral and restricted to relatively cool habitats. One of the prominently diurnal subgroups in South Asian Cnemaspis is the bangara clade, which includes six species distributed in southern India on the eastern slopes of the Western Ghats, the southern Eastern Ghats and Palghat Gap. In this paper, we describe five more species of the bangara clade from the Shevaroyan landscape, including three from Kollimalai and one each from Yercaud and Pachaimalai, all in Tamil Nadu. These new species show 4.6–19.7 % uncorrected sequence divergence on the mitochondrial ND2 gene from each other and known species of the bangara clade and are morphologically diagnosable in body size, the number of paravertebral tubercles between limb insertions, the number of dorsal tubercle rows, the number of ventral scale rows across the belly, the number of femoral and precloacal pores and poreless scales separating these series, and aspects of colouration. The discovery of these five new species adds to the growing discoveries of cool-adapted species in southern India outside the Western Ghats and highlights the role of sky-islands in diversification. The Shevaroyan landscape shows high levels of microendemism with eight species distributed in an area of < 2000 km2, and all these species restricted to much smaller areas of actual distribution. With an area of < 500 km2 respectively, the massif of Pachaimalai has a single endemic and the massifs of Yercaud and Kollimalai have three endemic Cnemaspis species each.

Report of Euphaea pseudodispar Sadasivan & Bhakare, 2021 (Insecta: Odonata) from Kerala, India

The newly described damselfly, Euphaea pseudodispar Sadasivan & Bhakare, 2021 (Insecta: Odonata) is reported from Wayanad in Kerala state for the first time. This observation suggests that it is distributed from the northern Western Ghats to the southern part of central Western Ghats up to Wayanad, north of the Palghat gap. This study highlights the need for extensive field surveys of Odonata in the Western Ghats of India.

Biogeographical and diversification analyses of Indian pseudoscorpions reveal the Western Ghats as museums of ancient biodiversity

The tropical forests of the Western Ghats (WG) of India are considered ‘refugia’ harbouring highly diverse and endemic taxa but these refugia are under immense anthropogenic pressure. Most phylogenetic studies have explained diversity patterns across the WG using vertebrates, however, the processes impacting the highly endemic invertebrate fauna are still poorly understood. Here we investigate the evolutionary history of an ancient and widespread arachnid lineage (Pseudoscorpiones: Chthoniidae: Tyrannochthoniini) in the WG through a variety of biogeographical and diversification analyses, including sequence data from three markers for 45 terminals from the WG and 22 from Africa, East and Southeast Asia, Australasia and the Neotropics. Our results show that WG Tyrannochthoniini are rendered paraphyletic by African taxa, a result consistent with continental drift. WG Tyrannochthoniini are further split into two major clades, a southern WG clade and an African-central WG clade, due to vicariance along a major biogeographical barrier, the Palghat Gap. Central WG pseudoscorpions diverged from their African relatives at the Jurassic-Cretaceous boundary, coinciding with the separation of India from Africa. Despite ancient vicariance, six dispersal events occurred across the Palghat Gap, beginning in the Early Cretaceous as India was rafting towards Southeast Asia and ending by the early Miocene, implying that the Palghat Gap became impermeable to dispersal for these humid-adapted organisms during Miocene aridification. Although the ancestor of WG Tyrannochthoniini originated in lowland WG forests, three dispersal events into high montane Shola forests occurred most likely as a result of Late Cretaceous orogenesis and Neogene uplift, allowing lineages to occupy niches at higher elevations. An exponentially declining diversification rate, typical of older lineages, supports the ‘museum’ model of diversification for WG Tyrannochthoniini. Our study sheds light on the historical biogeography of relictual soil-arthropods in the WG and emphasises the role of WG forest refugia in preserving ancient invertebrate biodiversity.

Species distribution modeling and assessment of environmental drivers responsible for distribution and preferred niche of critically endangered and endemic ornamental freshwater fish species of the genus Sahyadria.

India has different bioclimatic zones and supports diverse aquatic habitats rich in biodiversity. For effective conservation of the endangered species in its habitat, it is essential to know the distribution of fish species in the environmental range, and for this, species distribution models are the efficient and innovative tools. The present study used the MaxEnt modeling technique for developing probability distribution models highlighting the distribution of fish species by analyzing the known occurrence records of Denison barb under genus Sahyadria (Sahyadria denisonii Day 1865 and Sahyadria chalakkudiensis (Menon et al., Rec Zool Surv India 97:61-63, 1999)) in relation to environmental variables typically incorporating seasonal and temporal variability. AUC of the models for Sahyadria species depicted good fitness. Both species were found sensitive to "solar radiation," "temperature seasonality," and "temperature annual range" and assessed as significant predictors. The sensitivity and distribution of both species to these environmental variables were found correlated with their breading and spawning seasons. "Precipitation" was determined as one of the significant climatic envelopes influencing the distribution of the species associated with river flow. The models showed the distribution of S. denisonii in the higher precipitation areas compared to S. chalakkudiensis. The probability distribution model with respect to the distribution of both species indicates a lineage barrier at Palghat Gap supporting the earlier studies. At the latitudinal scale, prediction of the suitable ecological habitat provides a detailed insight into the distribution of all genetic lineages of the genus Sahyadria. Evidently, the findings of this study can assist in determining ecological niches for endangered species of other areas and may aid in field surveys as well as developing conservation plans.

Cryptic diversity of Rhinolophus lepidus in South Asia and differentiation across a biogeographic barrier

Peninsular India is an important region for mammalian diversification and harbors major biogeographic barriers. However, little is known about the role of this region in the diversification of bats though it harbors high chiropteran diversity. In this study, we used phenotypic, acoustic, and genetic markers to assess the diversification of Rhinolophus lepidus bats in South Asia. We first investigated if peninsular India is associated with speciation of R. lepidus. Further, we tested if the Palghat Gap acts as a biogeographic barrier to gene flow in this species. Our results revealed cryptic genetic diversity in peninsular India suggesting that this region holds at least one endemic species level lineage of the R. lepidus species complex.  Analyses of populations of R. lepidus across the Palghat Gap in the Western Ghats revealed clinal variation in phenotype, with bats south of this barrier being bigger and emitting echolocation calls of higher frequency. We also observed that populations on either side of the Palghat Gap have remained genetically isolated since the mid-Holocene.

Spatial patterns of phylogenetic diversity and endemism in the Western Ghats, India: A case study using ancient predatory arthropods.

The Western Ghats (WG) mountain chain in peninsular India is a global biodiversity hotspot, one in which patterns of phylogenetic diversity and endemism remain to be documented across taxa. We used a well‐characterized community of ancient soil predatory arthropods from the WG to understand diversity gradients, identify hotspots of endemism and conservation importance, and highlight poorly studied areas with unique biodiversity. We compiled an occurrence dataset for 19 species of scolopendrid centipedes, which was used to predict areas of habitat suitability using bioclimatic and geomorphological variables in Maxent. We used predicted distributions and a time‐calibrated species phylogeny to calculate taxonomic and phylogenetic indices of diversity, endemism, and turnover. We observed a decreasing latitudinal gradient in taxonomic and phylogenetic diversity in the WG, which supports expectations from the latitudinal diversity gradient. The southern WG had the highest phylogenetic diversity and endemism, and was represented by lineages with long branch lengths as observed from relative phylogenetic diversity/endemism. These results indicate the persistence of lineages over evolutionary time in the southern WG and are consistent with predictions from the southern WG refuge hypothesis. The northern WG, despite having low phylogenetic diversity, had high values of phylogenetic endemism represented by distinct lineages as inferred from relative phylogenetic endemism. The distinct endemic lineages in this subregion might be adapted to life in lateritic plateaus characterized by poor soil conditions and high seasonality. Sites across an important biogeographic break, the Palghat Gap, broadly grouped separately in comparisons of species turnover along the WG. The southern WG and Nilgiris, adjoining the Palghat Gap, harbor unique centipede communities, where the causal role of climate or dispersal barriers in shaping diversity remains to be investigated. Our results highlight the need to use phylogeny and distribution data while assessing diversity and endemism patterns in the WG.

Morphological groupings within Euphlyctis (Anura: Dicroglossidae) and description of a new species from the surroundings of Thattekad Bird Sanctuary, Kerala, India.

The skittering frog genus Euphlyctis is known to have a distribution range from Arabian Peninsula to Bangladesh through India and Sri Lanka. Although species descriptions were initiated about two centuries ago in the genus with a small number of species described, taxonomic identities and genetic information for many species are still incomplete / inaccurate. Here, we report the systematic status of this group, discuss a series of taxonomic issues, and describe a new species. Based on morphological characters and colour patterns, and their reciprocal monophyly in the molecular tree, two morphological groups, 'cyanophlyctis group' and 'hexadactylus group' are established within the genus Euphlyctis. We discuss the genetic identity for E. cyanophlyctis, described 220 years ago from the Indian subcontinent, from the surroundings of its type locality. E. mudigere is proposed as a junior synonym of E. cyanophlyctis as it was described from populations here considered to originate from the general distribution area of the latter taxon, and without substantial genetic divergence from other populations here attributed to E. cyanophlyctis. The potential of resurrection of Euphlyctis seistanica due to distinct genetic population in Iran is discussed; this lineage appears to be genetically rather similar to E. kalasgramensis, and the species distinctness of these two lineages requires further study. The validity of E. kalasgramensis is also discussed in the context of the historically earlier nomina, Rana bengalensis and Rana leschenaultii due to distribution range overlaps. The prospects of establishing either Rana cyanophlictis variety fulvus or Rana cyanophlictis variety flavens from Sri Lanka are also mentioned. Based on a comparative account, we report the discovery of a new species of skittering frog Euphlyctis kerala sp. nov. which has a restricted distribution in the western coastal plains of India, south of the Palghat gap. [http://zoobank.org/urn:lsid:zoobank.org:act:02B1DE04-C40C-4AAD-AC87-EF97673A4BF5].

The Malay Cardamom Meistera aculeata (Roxb.) Škorničk. & M.F. Newman (Zingiberaceae: Alpinioideae) from the Palghat gap: a new record to Kerala, India

Meistera aculeata (Roxb.) Škorničk. & M.F.Newman (Zingiberaceae, subfamily - Alpinioideae) a lesser known species, has been located from the Palakkad (Palghat) Gap region in the Walayar Hill ranges of the southern Western Ghats and reported here as an addition to the flora of Kerala. A detailed taxonomic description along with photographs are provided.

Description of a new species of Xylophis Beddome, 1878 (Serpentes: Pareidae: Xylophiinae) from the Western Ghats, India.

We reassessed the systematics of the Indian (semi)fossorial snake Xylophis perroteti (Duméril, Bibron Duméril, 1854) based on morphological and DNA sequence data for type, historical, and new specimens. A population from the Anamalai Hills is distinct from broadly topotypic X. perroteti from the Nilgiri Hills (from which they are separated geographically by the lowland Palghat Gap) on the basis of both external morphology and DNA sequence data. We describe the Anamalai form as a new species, Xylophis mosaicus sp. nov. The new species is more closely related to X. perroteti than to X. stenorhynchus and X. captaini. A new key to identify the species of Xylophis is presented.

Record of Oldenlandia hygrophila Bremek. (Spermacoceae: Rubiaceae), a lesser known herb from Palghat Gap of Western Ghats, Kerala, India

Oldenlandia hygrophila Bremek., a lesser known taxon has been relocated from the type location in the Palghat (Palakkad) gap region of southern Western Ghats, Kerala, India, and is described. Setiform cuticular protuberances all over the plant, branching pattern, stipule length, axillary solitary blue flower, corolla lobes not spreading during anthesis, size of flower, presence of hyaline hairs inside corolla tube, calyx lobe reaching one-fourth of the corolla tube, exerted anthers with glabrous filaments, sub - globose capsule and seed surface pattern are some of the peculiar features which makes this taxa different from other Oldenlandia species. After its type collection in 1972, this endemic taxa could not be relocated from its type locality till date.

A deeply divergent lineage of Walkerana (Anura: Ranixalidae) from the Western Ghats of Peninsular India.

The frog family Ranixalidae is endemic to the Western Ghats of Peninsular India and contains two genera, Indirana and Walkerana. The three known species of Walkerana are restricted to different hill ranges south of the Palghat Gap, an ancient valley in the Western Ghats. In this study, we report the discovery of a deeply divergent lineage of Walkerana from the high elevations of the Elivalmalai hill range. This finding extends the geographic range of the Walkerana clade to the north of the Palghat Gap. The new species Walkerana muduga sp. nov. is genetically and morphologically divergent, and geographically isolated from its sister lineages. We also recovered a potential new lineage in the adjoining hill ranges suggesting the presence of additional new species in this genus north of the Palghat Gap.

Seasonal vegetation shift and wetland dynamics in vulnerable granitic rocky outcrops of Palghat Gap of southern Western Ghats, Kerala, India

Low altitude granitic hillock systems prevalent in Palghat (Palakkad) Gap region of southern Western Ghats were analyzed for seasonal dynamics in wetland taxa associated with marshy ephemeral flush vegetation, small ephemeral pools and deep rock pools. Due to characteristic habitat features, such systems harbor a unique pattern of microhabitats and associated floristic components. Wet phase in rocky outcrops in the monsoon season establishes a hydro-geomorphic habitat that supports establishment of wetland taxa like Eriocaulon, Drosera, Utricularia, Dopatrium, and Rotala. Seasonal shift in the floral associations was evident in tune with wetland dynamics. Wet rocks support ephemeral flush vegetation which display some unique plant associations of species of Eriocaulon, Utricularia, Drosera, Cyanotis, Murdannia, and Lindernia. Small ephemeral pools displayed taxa like Rotala malampuzhensis R.V. Nair, Dopatrium junceum (Roxb.) Buch.-Ham. ex Benth., D. nudicaule (Willd.) Benth., Monochoria vaginalis (Burm.f.) C. Presl, and Cyperus iria L. Rocky pools are the habitats of aquatic angiosperms like Nymphaea nouchali Burm. f., Ludwigia adscendens (L.) H. Hara, Utricularia aurea Lour. and Hydrilla verticillata (L.f.) Royle. The study documented 121 plant taxa from 37 families during a wet phase from rocky outcrops of the study area. Gradual shift in vegetation is evident as water recedes from granitic hillocks. During the period from December to March, the rocky pools dry up which results in a shift in the vegetation pattern where Poaceae members form the dominant elements. As most of the rocky outcrops are exposed to extreme temperature and acute water shortage, the taxa inhabiting such ecosystems tend to evolve much faster than in other habitats. Moreover, the vicinity of these hillocks in the Palghat Gap region to human settlements, face threats like fire, grazing, quarrying, dumping of wastes etc. which may cause considerable loss to the very sensitive plant communities which are not yet fully documented.