Biology

Dr.Jahnavi Joshi
Newton International Fellow, Natural History Museum, London

Abstract:

Understanding the causal processes that have generated the stunning biodiversity in tropical forests has been fundamental to ecological and evolutionary research. In the last two decades, the advent of molecular techniques has allowed a systematic examination of
both evolutionary and contemporary ecological processes driving diversity patterns.

In this talk, I will explore the role of the geographical, geological and ecological processes on biogeography and diversification among two arthropod groups (centipedes and butterflies) at different spatial scales, tropical forests of the Western Ghats in peninsular India and
South and Southeast Asia. To this end, I have integrated multiple lines of evidence, including DNA sequences, morphological traits, and data from geology, climate, and ecology, finding that geographic and geo-climatic processes have played an important role in diversification in both centipedes and butterflies. While some of the molecularly-delineated centipede species did not exhibit morphological divergence, they occupied distinct climatic niches across the Western Ghats, suggesting ecological speciation. Butterflies exhibited a large morphological variation in wing patterns and mimicry which are thought to be involved in ecological adaptation. However, there was no significant effect of wing pattern diversity, and mimicry detected on diversification rates, indicating that geographic factors played an important role in their diversification. These two case studies highlight the need to assess multiple ecological and evolutionary axes when examining diversification patterns and processes. I will follow this by demonstrating the use of molecular phylogenies and biogeography to understand community assembly of species, which has traditionally been studied from under an ecological lens. I will demonstrate that evolutionary history, biogeographic isolation, and stochastic colonisation influence assembly of mimetic butterfly communities.

Towards the end, I will talk about my future research, where I plan to focus on exploring processes that influence extant diversity patterns using multiple invertebrate taxa that vary across evolutionary and ecological gradients. Currently, such multi-taxa and
multi-disciplinary studies are lacking in India and are limited to few studies in tropical forests of South America and Madagascar. I hope insights from these studies will contribute towards our understanding to broader questions in evolutionary biology such as: How did tropical
biodiversity originate and how is it maintained? Why are the tropics so species rich? Also, I hope to contribute substantially towards understanding arthropod evolution and systematics in one of the most biodiverse and less explored regions in the world.