The genetic variation between individuals of a species determines its ability to respond to environmental change. It can be shaped by the biological traits of a species and the geography of where it occurs. Arthropods, which have some of the highest values of genetic diversity among animals, remain poorly represented in genetic diversity studies. Analysing publicly available data, we found that centipedes have some of the highest values of genetic diversity among arthropods, which may be due to their deep evolutionary history and low dispersal ability. The variation in genetic diversity is shaped by body size, parental care (traits), geographic distance and latitude (geography), showing convergence with well-studied taxa. Our study encourages research on poorly studied species, unique in their traits and evolutionary history, to test the generality of macroecological patterns.

Mapping large-scale patterns in species diversity can help us understand the evolutionary processes shaping them and identify regions of conservation importance. We documented spatial patterns of diversity in centipedes of the Western Ghats biodiversity hotspot using information on their evolutionary relationships and modelled distribution patterns. Echoing patterns seen in plants and vertebrates, diversity decreases from the more historically and climatically stable southern mountains to seasonal northern sites impacted by past geological events. The southern Western Ghats harbour older centipede lineages, but are similar with the northern plateaus in holding geographically unique species. While the southern Western Ghats may have been a refuge for centipede lineages over evolutionary time, the northern hills likely harbour unique species adapted to a harsh environment.

I was also involved with another study on diversity patterns of woody plants in the Western Ghats led by Abhishek Gopal, a graduate student from the CCMB Hyderabad. He showed that the southern Western Ghats hold a large number of both young and old plant lineages with northern sites harbouring a subset of these – a pattern consistent through evolutionary time. It is likely that the plants in the southern mountains have remained associated with its environment and complex terrain, and persisted in time due to its geological and climatic stability.

The Indian subcontinent is placed in a dynamic oceanographic setting, where coastal currents reverse direction between the two monsoonal seasons in a year. Circulation patterns can show variation within a season from a week to over a month, and even across years. This influences the dispersal of oceanic larvae produced by marine invertebrates, shaping their patterns of gene flow and biogeography. We identified the spatial scale of connectivity in the Indian coastline by modelling larval dispersal using ocean flow data across different release times, monsoon seasons and years. We found that only a small fraction of larvae are retained and transported between coastal areas, with greater connectivity when larvae dispersed over 20 days. Despite differences in connectivity with release time and season, we consistently identified four well-connected regions coinciding with known genetic and biogeographic breaks, which can spawn future research and inform management and conservation efforts. This work was done in collaboration with Dr. Katell Guizien at the  Observatoire Océanologique de Banyuls, CNRS-Sorbonne Université, France and Prof. P. N. Vinayachandran's group at Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore.

The ocean is often thought to be continuous and homogenous, but in fact is a mosaic of environments influencing where organisms live and how they evolve. Along the Indian coastline, periwinkle snails in mangroves and rocky shores show range discontinuities despite their broader distribution in the Indo-Pacific. Since these snails disperse over several weeks using oceanic larvae, we tested if environmental differences were limiting their distribution. Using species distribution models we found that salinity, tidal range and geomorphology are correlated with distribution patterns of ten periwinkle species. Larvae or adult snails may be influenced by differences in freshwater discharge between basins, and the seasonal formation of a high salinity water mass in the northern Arabian Sea. Tides can interact with local geomorphology to influence emersion time and hence desiccation, which is a strong environmental filter in the intertidal zone.

Dispersal over several generations shapes population genetic structure, which is influenced by the interaction of geography and environment with species traits. Using a community of eight periwinkle species varying in their dispersal potential and habitat requirements, we hypothesised that greater genetic connectivity corresponds to a longer larval duration and more widespread habitats. Surprisingly, we found that most species did not show genetic structure but all of them showed signs of recent population expansion. This is possible if their larval duration is sufficient to ensure widespread connectivity, or that population divergence has not been established since recent expansion. Two species with wide environmental tolerance and distribution showed genetic differences along the coastline that could be driven by environmental differences or oceanographic barriers.

At the start of my PhD, I explored questions related to connectivity of green turtles – ecosystem engineers dependent on seagrass habitats in the Lakshadweep islands. My field surveys across islands funded by Chester Zoo suggested that green turtle densities were associated with seagrasses that they feed on, which vary in their density and composition between and within islands. A longer perspective from subsequent field surveys by other researchers added more support that green turtle densities are related to seagrass resources, which also may drive their movement between islands. The synthesis of several years of field surveys in the Lakshadweep islands was led by Nupur Kale, a researcher from Wildlife Conservation Society, India.