Biology subjects

Bharti, D. K.

Publications and source records attributed to Bharti, D. K..

3 recordsLinked to original sources

bioRxiv2025

Comparing the genetic diversity of two threatened Rhyticeros hornbill species with contrasting geographic range sizes

Island endemics exhibit low genetic diversity due to founder effects and geographical isolation, increasing their vulnerability to inbreeding depression. The Narcondam Hornbill (Rhyticeros narcondami), restricted to the 6.8 km2 Narcondam island in the Andaman archipelago, has the smallest range size among hornbills, a globally threatened group of birds. We compared the genetic diversity of the Narcondam Hornbill with the Wreathed Hornbill (Rhyticeros undulatus) distributed from the Eastern Himalaya to Bali. We generated DNA sequences for four mitochondrial markers ; Cytochrome B (Cytb), cytochrome c oxidase subunit I (COI), NADH dehydrogenase subunit 2 (ND2) and displacement loop (D-loop) regions) from 14 Narcondam Hornbill faecal samples and for three markers (Cytb, COI and ND2) from 19 Wreathed Hornbill tissue samples from north-east India. Our results suggest markedly lower genetic diversity in the island endemic Narcondam Hornbill compared to the Wreathed Hornbill. Specifically, Cytb and COI showed no genetic variation in the island endemic, compared to three to five haplotypes in the Wreathed Hornbills. In the ND2 region, Narcondam Hornbills showed seven haplotypes among 13 samples compared to the Wreathed Hornbills six haplotypes among eight samples. The observed genetic diversity in the D-loop in the Narcondam Hornbill was lower than other island-endemic hornbill species in the Philippines. The extremely low genetic diversity in the Narcondam Hornbill likely stems from a small founder population and/or past hunting pressures that reduced its numbers to approximately 30% of its current population of 1000 birds, rendering the Narcondam Hornbill susceptible to environmental and human-driven changes.

genetics↗

bioRxiv2022

Genetic diversity varies with species traits and latitude in predatory soil arthropods (Myriapoda: Chilopoda)

AimTo investigate the drivers of intra-specific genetic diversity in centipedes, a group of ancient predatory soil arthropods. LocationGlobal Time periodPresent Major taxa studiedCentipedes (Class: Chilopoda) MethodsWe assembled a database of over 1200 mitochondrial cytochrome c oxidase subunit I sequences representing 120 centipede species from all five orders of Chilopoda. We used this sequence dataset to estimate genetic diversity for centipede species and compared its distribution with estimates from other arthropod groups. We studied the variation in centipede genetic diversity with species traits and biogeography using a beta regression framework, controlling for the effect of shared evolutionary history within a family. ResultsWe observed a wide variation in genetic diversity across centipede species (0 to 0.1713), which falls towards the higher end of values among arthropods. Overall, 21.51% of the variation in mitochondrial COI genetic diversity in centipedes was explained by a combination of predictors related to life history and biogeography. Genetic diversity decreased with body size and latitudinal position of sampled localities, was greater in species showing maternal care and increased with geographic distance among conspecifics. Main conclusionsCentipedes fall towards the higher end of genetic diversity among arthropods, which may be related to their long evolutionary history and low dispersal ability. In centipedes, the negative association of body size with genetic diversity may be mediated by its influence on local abundance or the influence of ecological strategy on long-term population history. Species with maternal care had higher genetic diversity, which goes against our expectations and needs further scrutiny. Hemispheric differences in genetic diversity can be due to historic climatic stability and lower seasonality in the southern hemisphere. Overall, we find that despite the differences in mean genetic diversity among animals, similar processes related to life history strategy and biogeography shape the variation within them.

evolutionary biology↗

bioRxiv2021

Connectivity networks and delineation of distinct coastal provinces along the Indian coastline using large-scale Lagrangian transport simulations

Ocean circulation defines the scale of population connectivity in marine ecosystems, and is essential for conservation planning. We performed Lagrangian transport simulations and built connectivity networks to understand the patterns of oceanographic connectivity along the Indian coastline. In these networks, nodes are coastal polygons and the edges connecting them represent the magnitude of larval transfer between them. We assessed the variation in connectivity networks within and between two monsoonal seasons, across El Nino-Southern Oscillation (ENSO) years and for pelagic larval durations (PLD) up to 50 days. We detected well-connected communities, mapped frequent connectivity breaks and ranked coastal areas by their functional role using network centrality measures. Network characteristics did not differ based on the ENSO year, but varied based on season and PLD. Large scale connectance (entire Indian coastline) was small, ranging from 0.5% to 3.4%, and the number of cohesive coastal communities decreased from 60 (PLD <4 days) to 30 (PLD >20 days) with increasing PLD. Despite intra-seasonal variation in connectivity breaks, four disconnected provinces were consistently identified across the entire PLD range, which partially overlapped with observed genetic and biogeographic breaks along the Indian coastline. Our results support the adoption of an adaptive regional management framework guided by fine-scale analysis of connectivity within the four provinces delineated in the present study. A few sites within each province displayed notably higher centrality values than other nodes of the network, but showed variation with season and PLD, and could be targeted for national and transnational conservation and management plans.

ecology↗