pearson history and geography tests westward expansion

It extends 2500 kms in length from west to east and its width varies between 350 km in the west and 150 km in the east. The Himalayan range is a globally recognised biodiversity hotspot with high levels of endemism and a complex geography, topography and climate. In the latter case, species may undergo range expansion and exponential population growth after the end of the glacial period. Repeated periods of glaciation, especially in higher latitudes, resulted in range expansion-in the case of species adapted to cold climate and range contraction-in the species adapted to warm climate. Quaternary glaciation periods, such as the last glacial maximum (LGM), substantially influenced how genetic variation is spatially distributed in many species across the globe. Apart from the geographical barriers, Climatic fluctuations are also known to have an impact on the population genetic structure and demography. In primates, these studies of riverine barrier effect have mostly been confined to Amazonian and African taxa, with only a handful of studies in Asian primates. The effects of rivers as barriers have been studied in many taxa of plants, amphibians, reptiles, mammals and birds. The ability of a river to act as a barrier depends on various physical attributes of the river such as the size, the amount of discharge and speed of the water flow further the dispersal ability, ecology and body size of the organism also plays an important role.

Wallace noted that many south American primate species are separated by large rivers in the Amazon basin, and that different species of primates are restricted to opposite banks of the river and never cross it. Rivers are considered as long-term barriers to gene flow and therefore plays an important role in speciation and divergence. can prevent gene flow, and over time create population genetic structures. Geographical barriers such as mountain ranges and rivers environmental barriers and certain behavioural aspects of the taxa such as philopatry, dispersal ability, etc. Further, the post LGM expansion could have had confounding effect on Himalayan langur population structure in both Nepal Himalaya and IHR.Īccumulation of genetic variation across different populations of a species could be attributed to changes in geography and climate via a combined effect of genetic drift, gene flow and selection. The current genetic diversity and distribution of Himalayan langurs in the Nepal Himalaya has been shaped by river barriers, whereas the rivers in the IHR had relatively less time to act as a strong genetic barrier after the recent colonisation event. The palaeodistribution modelling showed that the extent of suitable habitat shifted from low elevation central Nepal, and adjoining parts of north India, during LGM to the western Himalaya at present. Analysis of demographic history showed that the effective population size of the Himalayan langurs decreased at the onset of last glacial maximum (LGM) and started increasing post LGM. Our statistical phylogeography analysis using diyABC supported the model of east to west colonisation of these langurs with founder event during colonisation. Samples from the Nepal Himalaya showed geographically structured haplotypes corresponding to different river barriers, whereas samples from IHR showed star-like topology with no structure. Phylogenetic analysis showed a low divergent western clade nested within high divergent group of eastern lineages and in the network analysis we identified 22 haplotypes over the entire distribution range of the Himalayan langurs. Our dataset contained 144 sequences from the IHR as well as the Nepal Himalaya. We used the mitochondrial Cytochrome- b (Cyt- b, 746 bp) region combined with multiple phylogeographic analyses and palaeodistribution modelling.

Therefore, here we revisit the questions addressed in the previous study with a near complete sampling from the IHR, along with the samples from the Nepal Himalaya. However, this study did not include the samples from the Indian Himalayan region (IHR). A recent study examined the effect of these historical events on the genetic diversity of the Himalayan langurs in Nepal Himalaya. However, very little is known regarding how this heterogenous landscape has moulded the distribution of Himalayan fauna. The Himalayas show a huge variation in topography and climatic conditions across its entire range, and have experienced major climatic fluctuations in the past. Contemporary species distribution, genetic diversity and evolutionary history in many taxa are shaped by both historical and current climate as well as topography.

Pearson history and geography tests westward expansion