Impact of Climate Change on Evolution: A Case Study of Mahseer Species from Central India.

The ‘Mahseer’ are fishes of genus Tor, Neolissocheilus and Naziritor of  family Cyprinidae, distributed from Iran to Vietnam in Asia and are important due to their high economic significance. In central India, three species of genus Tor are found and are considered as rare and threatened. Conservation strategy based on evolutionary systematics and ecology may generate high success rate in species conservation. The study explores the climatic change and its impact on evolution of Mahseer, that inclueds historical as well as recent overview of geographical, geological modifications of the region with molecular dating of Mahseer species with focuse on divergence of species due to various factors. Climate of central India during 18 Ma to 10-11 Ma, was tropical and water level was much higher in comparison to late Miocene and early Pliocene where regression of tropical zone was formed. Establishment of dry zone/savannas climate is dated (1.6 Ma) that resulted in shrinking of aquatic habitat, fragmentation and concentration of aquatic organisms, was formed at certain points. This trigered natural selection in fish species for, its survival and reproduce successfully in adverse conditions, in a population over successive generations and hence lead to the formation of new species. The divergence time frame of Mahseer species through molecular dating of mtDNA estimation (9.2 Ma to 1.8 Ma) come within the climatic change of the central India. The central India has also experienced multiple cycles of dry and wet climatic conditions during epoch Quaternary to recent 1800 years ago and resulted in fluctuation in water level of water bodies in the region. The study showed that geological change and climatic shift in the past had left significant impact on Mahseer divergence. Further detailed study is recommended in paleobiology and biogeography to get clear picture of effect of climatic conditions and geological events on evolution of Mahseer species in India.