Genome divergence across the Indo-Burman arc: a tale of two peacocks

Exaggerated traits of the peacock are attributed to sexual selection. Yet, the two species of Asian peacock are conspicuously different in their plumage colouration and level of sexual dichromatism. Our integrative comparative study of bird calls, morphological differences and genomic divergence between the Indian blue peafowl and the green peafowl suggests a strong role of habitat differences in shaping species-specific changes. We estimate a recent (1-3 MYA) split of these species in the Pliocene or early Pleistocene, followed by intermittent periods of gene flow. Despite the relatively recent split, the high levels of genomic differentiation (F ST ∼ 0.6) mirror the divergence in morphological traits. Several genes involved in body patterning and colouration have accumulated protein-coding differences between the peacock species. Our estimates suggest genetic diversity in the widespread Indian peafowl (θ w ∼ 0.0015) is comparable but slightly higher than in the endangered green peafowl (θ w ∼ 0.0012). The ratio of genetic diversity on the Z chromosome to the autosomes (Z/A) is consistent with a polygynous mating system in the Indian peafowl compared to monogamy in the green peafowl. The Asian peacock species continue to provide exciting new insights into speciation and mating system evolution in the post-genomic era.