The convoluted evolutionary history of the capped-golden langur lineage (Cercopithecidae: Colobinae) – concatenation versus coalescent analyses

Evolutionary studies have traditionally relied on concatenation based methods to reconstruct relationships from multiple markers. However, due to limitations of concatenation analyses, recent studies have proposed coalescent based methods to address evolutionary questions. Results from these methods tend to diverge from each other under situations where there is incomplete lineage sorting or hybridization. Here we used concatenation as well as multispecies coalescent (MSC) methods to understand the evolutionary origin of capped and golden langur (CG) lineage. Previous molecular studies have retrieved conflicting phylogenies, with mitochondrial tree grouping CG lineage with a largely Indian genus Semnopithecus, while nuclear markers support their affinities 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. 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 MSC methods were incongruent with the above result, suggesting presence of incomplete lineage sorting (ILS)/hybridisation. Furthermore, CG lineage is morphologically intermediate between Semnopithecus and Trachypithecus . Based on this evidence, we argue that CG lineage evolved through hybridisation between Semnopithecus and Trachypithecus . Finally, we reason that both concatenation as well as coalescent methods should be used in conjunction for better understanding of various evolutionary hypotheses.