Biogeography and comparative phylogeography of freshwater snails of India

Abstract

Distribution of flora and fauna is shaped by both current and historical processes. In my thesis I concentrated on how the historical component of the governing processes have dictated the current distribution of biota. The history of a lineage is intricately linked to and is moulded by the history of the place it occurs in. Hence, I made an attempt to investigate the course of two families of freshwater snails distributed in the Indian subcontinent with respect to the paleogeology and paleoclimate of the subcontinent. In the first chapter, I gave a brief overview of the discipline of historical biogeography and the plate tectonic and climatic histories of the Indian subcontinent. I also introduced my model systems: Ampullariidae and Viviparidae. Indian biota has affinities to many different biogeographic regions- a legacy of its current position and its plate tectonic history. Hence, the first step in order to trace the history of a group is to understand its biogeographic origin. In the second chapter, I aimed to uncover the historical biogeography of the pan-tropical freshwater snail family Ampullariidae with respect to the plate tectonic history of the Indian subcontinent. I tested three hypotheses regarding the time and route of colonization - colonization when India was a part of Gondwanaland, colonization after Indian plate’s separation from Madagascar and northwards drift, and colonization after the Indian plate collided with Asia. I employed phylogenetics, molecular dating and ancestral range estimation analysis to address this question. I came to the conclusion that Pila colonized India from Africa after India collided with Asia following a ‘Eurasian route’.