Karthikeyan Vasudevan

Molecular Evolution of Vertebrate Neurotrophins: Co-Option of the Highly Conserved Nerve Growth Factor Gene into the Advanced Snake Venom Arsenalf

Neurotrophins are a diverse class of structurally related proteins, essential for neuronal development, survival, plasticity and regeneration. They are characterized by major family members, such as the nerve growth factors (NGF), brain-derived neurotrophic factors (BDNF) and neurotrophin-3 (NT-3), which have been demonstrated here to lack coding sequence variations and follow the regime of negative selection, highlighting their extremely important conserved role in vertebrate homeostasis. However, in stark contrast, venom NGF secreted as part of the chemical arsenal of the venomous advanced snake family Elapidae (and to a lesser extent Viperidae) have characteristics consistent with the typical accelerated molecular evolution of venom components. This includes a rapid rate of diversification under the significant influence of positive-selection, with the majority of positively-selected sites found in the secreted β-polypeptide chain (74%) and on the molecular surface of the protein (92%), while the core structural and functional residues remain highly constrained. Such focal mutagenesis generates active residues on the toxin molecular surface, which are capable of interacting with novel biological targets in prey to induce a myriad of pharmacological effects. We propose that caenophidian NGFs could participate in prey-envenoming by causing a massive release of chemical mediators from mast cells to mount inflammatory reactions and increase vascular permeability, thereby aiding the spread of other toxins and/or by acting as proapoptotic factors. Despite their presence in reptilian venom having been known for over 60 years, this is the first evidence that venom-secreted NGF follows the molecular evolutionary pattern of other venom components, and thus likely participates in prey-envenomation.

Efficiency of Adaptive Cluster and Random Sampling in Detecting Terrestrial Herpetofauna in a Tropical Rainforest

Abstract We sampled forest floor herpetofaunal communities in a monsoonal rainforest in South India for three consecutive years to evaluate the use of cluster sampling in estimating species composition and density. Our initial experimental design consisted of comprehensive random searches of multiple 25m2 quadrats (SRS) for animals. After our initial season we found that most quadrats had zero animals detected and, when encountered, animals were spatially aggregated. To increase sampling efficiency and derive more precise density estimates, we shifted to adaptive cluster sampling (ACS). We compared the relative sampling efficiencies of ACS to SRS and the ability of the 2 methods to detect rare species. Adaptive cluster sampling failed to yield the more precise density estimates as predicted by statistical theory. However, ACS yielded more individual and rare species detections. Our results suggest the ACS assumptions should be carefully evaluated prior to use because it may not be appropriate for all rare, spatially aggregated populations.

Trophic Ecology of Lapemis curtus (Hydrophiinae) along the Western Coast of India

Abstract Stomach contents were obtained from 165 individuals of Lapemis curtus. Food was present in 90% of the stomachs, but only on 59 occasions prey could be identified to family level. Five fish families constituted the diet of L. curtus of which, Clupeidae and Cynoglossidae dominate. There was no significant difference in the proportion of the fish families represented in the diet with the size or sex of the snakes. There was variation in this proportion with the time of the day. The proportion of Cynoglossidae in the diet showed marked difference with time of the day. The study found no geographic variation in the feeding ecology of L. curtus in this region when compared to similar studies elsewhere. This species is a generalist in its feeding habits since it feeds on fish that inhabit different depths in the water column. These results suggest that L. curtus may be an ambush forager. During the trawls, the fish families that constituted 95% of the sea snakes diet were also being harvested.

DENSITY AND DIVERSITY OF FOREST FLOOR ANURANS IN THE RAIN FORESTS OF SOUTHERN WESTERN GHATS, INDIA

The structure and composition of forest-floor anuran diversity in the biologically rich rain forests of southern Western Ghats were studied. The study was carried out in the relatively undisturbed rain-forest tract of Kalakad-Mundanthurai Tiger Reserve. A quadrat search method was used to estimate species richness and density of the forest floor anuran community. Sample locations were distributed across three distinct watersheds in the reserve. In total, we captured 509 individuals belonging to 20 species. The density of anurans was 149 individuals ha−1 on the rain-forest floor, and along streams their densities exceeded 300 individuals ha−1. Total diversity across all watershed locations was partitioned into within and among watershed components, corresponding to alpha and beta diversity. We found high levels of species turnover (high β diversity) among watersheds, a process that may partly explain the high species richness and large number of endemic anuran species known to occur in the rain forests of the Western Ghats. Anurans density was low and comparable to other studies conducted in South-East Asian forests. A re-examination of the reports on anuran densities revealed that Central American anuran densities were an order of magnitude higher than South Asian and South American anuran densities. Existing hypotheses do not adequately explain the differences in anuran densities in different parts of the world.

The devil is in the detail: estimating species richness, density, and relative abundance of tropical island herpetofauna

BackgroundOne of the basic premises of drawing samples from populations is that the samples are representative of the populations. However, error in sampling is poorly recognized, and it goes unnoticed especially in community ecology. By combining traditional open quadrats used for sampling forest floor herpetofauna with intensive bounded quadrats, we explore the effect of sampling error on estimates of species richness, diversity, and density in the Andaman Islands.ResultsFisher’s α measure of species diversity and second order jackknife estimate of species richness were not sensitive to number of individuals sampled. Sampling error resulted in underestimation of density in both frogs and lizards. It influenced relative abundance of individual species resulting in underestimation of abundance of small or camouflaged species; and also resulted in low precision in lizard species richness estimates.ConclusionsSampling error resulted in underestimation of abundance of small, fossorial or camouflaged species. Imperfect detection from less intensive sampling method results incorrect estimates of abundance of herpetofauna. Fisher’s α for species diversity and second order jackknife for species richness were robust measures. These have strong implications on inferences made from previous studies as well as sampling strategies for future studies. It is essential that these shortfalls are accounted for while communities are sampled or when datasets are compared.

Literature based species occurrence data of birds of northeast India.

Abstract The northeast region of India is one of the world’s most significant biodiversity hotspots. One of the richest bird areas in India, it is an important route for migratory birds and home to many endemic bird species. This paper describes a literature-based dataset of species occurrences of birds of northeast India. The occurrence records documented in the dataset are distributed across eleven states of India, viz.: Arunachal Pradesh, Assam, Bihar, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura, Uttar Pradesh and West Bengal. The geospatial scope of the dataset represents 24 to 29 degree North latitude and 78 to 94 degree East longitude, and it comprises over 2400 occurrence records. These records have been collated from scholarly literature published between1915 and 2008, especially from the Journal of the Bombay Natural History Society (JBNHS). The temporal scale of the dataset represents bird observations recorded between 1909 and 2007. The dataset has been developed by employing MS Excel. The key elements in the database are scientific name, taxonomic classification, temporal and geospatial details including geo-coordinate precision, data collector, basis of record and primary source of the data record. The temporal and geospatial quality of more than 50% of the data records has been enhanced retrospectively. Where possible, data records are annotated with geospatial coordinate precision to the nearest minute. This dataset is being constantly updated with the addition of new data records, and quality enhancement of documented occurrences. The dataset can be used in species distribution and niche modeling studies. It is planned to expand the scope of the dataset to collate bird species occurrences across the Indian peninsula.

A new genus and species of arboreal toad with phytotelmonous larvae, from the Andaman Islands, India (Lissamphibia, Anura, Bufonidae)

Abstract A new bufonid amphibian, belonging to a new monotypic genus, is described from the Andaman Islands, in the Bay of Bengal, Republic of India, based on unique external morphological and skeletal characters which are compared with those of known Oriental and other relevant bufonid genera. Blythophryne gen. n. is distinguished from other bufonid genera by its small adult size (mean SVL 24.02 mm), the presence of six presacral vertebrae, an absence of coccygeal expansions, presence of an elongated pair of parotoid glands, expanded discs at digit tips and phytotelmonous tadpoles that lack oral denticles. The taxonomic and phylogenetic position of the new taxon (that we named as Blythophryne beryet gen. et sp. n.) was ascertained by comparing its 12S and 16S partial genes with those of Oriental and other relevant bufonid lineages. Resulting molecular phylogeny supports the erection of a novel monotypic genus for this lineage from the Andaman Islands of India.

Fine Scale Habitat Selection in Travancore Tortoises (Indotestudo travancorica) in the Anamalai Hills, Western Ghats

Abstract Travancore Tortoises (Indotestudo travancorica) are endemic to the Western Ghats, south India. Landscape level surveys showed no clear habitat selection by the species. Therefore, we used radiotelemetry to study home-range size and fine-scale spatial movement habitat use of four tortoises from 2008–10. Minimum convex polygon home-range sizes of four tortoises varied between 5.2 and 34 ha. Tortoises spent a majority of their time in evergreen forest edge that had bamboo–lantana–grass. Eighty-two percent of the locations in the evergreen forest, and 95% of the locations in the bamboo–lantana–grass habitat, were at the edge of these habitats. Therefore at a fine scale, tortoises used the forest edge, possibly because it provided opportunities for foraging and thermoregulation.