Abhijna Parigi's scientific contributions

The phylogenetic position of the capped and golden langur (CG) lineage has been ambiguous owing to the discordance between phylogenies from multiple molecular markers. Previous molecular studies have hypothesised that this discordance likely arises from either a hybridization event that took place between the Indian genus Semnopithecus and the Southeast Asian genus Trachypithecus or from incomplete lineage sorting (ILS). Distinguishing between hybridization and ILS is challenging and these processes can lead to serious difficulties in inferring phylogenies. In this study, we used genetic markers (nine nuclear and eight mitochondrial) in conjunction with coalescent based species tree approach and a test for hybridization using posterior predictive checking to better understand the evolutionary origin of the CG lineage. Both the concatenated nuclear as well as the mitochondrial dataset recovered congruent relationships where CG lineage was sister to Trachypithecus. However, nuclear species tree estimated using different multispecies coalescent methods suggested an opposite result, i.e. CG lineage was sister to Semnopithecus. Hybridization analysis strongly indicates gene flow between Semnopithecus and Trachypithecus that likely gave rise to the hybrid CG lineage. Further, the CG lineage is morphologically intermediate between Semnopithecus and Trachypithecus with respect to skull and body measurements. In light of the above evidences, we argue that the CG lineage needs to be elevated to a new genus of its own. Taxonomic and conservation implications of these results are also discussed.

Hybridisation and incomplete lineage sorting (ILS) are two of the many naturally occurring evolutionary processes that contribute to variability in individual gene histories. However, distinguishing between hybridisation and ILS is challenging and these processes can lead to serious difficulties in inferring phylogenies. These processes have been invoked as a possible explanation for the evolution of the endangered golden langur and its sister species, the capped langur. Previous molecular studies have retrieved conflicting phylogenies, with mitochondrial tree grouping capped and golden langur (CG) lineage with a largely Indian genus Semnopithecus while nuclear markers supporting their affiliation with a Southeast Asian genus, Trachypithecus. However, as pointed by others, the use of nuclear copies of mitochondrial DNA in the above studies might have generated the discordance. Because of this discordance, the phylogenetic position of CG lineage has been much debated in recent times. In this study, we have used nine nuclear and eight mitochondrial markers in conjunction with coalescent based species tree approach to better understand the evolutionary origin of CG lineage. Concatenated nuclear as well as the mitochondrial dataset recovered congruent relationships where CG lineage was sister to Trachypithecus. However nuclear species tree estimated using different multispecies coalescent methods were incongruent with the above result, suggesting presence of ILS/hybridisation. Furthermore, CG lineage is morphologically intermediate between Semnopithecus and Trachypithecus with respect to skull and body measurements. Based on these evidences, we argue that CG lineage evolved through hybridisation between Semnopithecus and Trachypithecus. Taxonomic and conservation implications of these results are also discussed.