Assortative mating despite shallow genetic divergence in a sympatric pair of finch-like birds.

BROWNE, MELANIE; CAMPAGNA, LEONARDO; SAFRAN, REBECA; KOPUCHIAN, CECILIA; TURBEK, SHEELA; ADRIAN S. DI GIACOMO

Ventura

Congreso; Speciation Gordon Research Conference; 2019

Gordon Research

Recent advances in high throughput genomic sequencing technology are enabling finer resolution of the degree of genomic divergence between taxa previously classified on the basis of phenotypic traits. An emerging pattern revealed by these studies is that species can exhibit marked differences in appearance despite little genomic differentiation. However, we lack an understanding of the reproductive barriers maintaining phenotypic differences among genetically similar populations that would improve our ability to interpret these intriguing genomic patterns. The southern capuchino seedeaters (genus Sporophila) constitute a highly sympatric avian radiation characterized by little ecological or genetic divergence despite striking differences in male song and melanin-based plumage coloration. We sequenced 37 genomes of S. iberaensis and S. hypoxantha, including 17 breeding pairs, to classify the degree of divergence between the sympatric species and examine the importance of mate choice in the maintenance of phenotypic differences. In addition, we analyzed the paternity of 39 nestlings through ddRAD to determine whether patterns of social pairing reflect patterns of extra-pair mating. We detect an extremely low level of background differentiation (genome-wide FST = 0.007) between S. iberaensis and S. hypoxantha that is punctuated by three regions of elevated divergence that coincide with genes involved in the melanogenesis pathway. Despite the degree of genomic homogeneity, the two species appear to mate assortatively with respect to both social and extra-pair mates. Ongoing analyses are evaluating the specific mechanisms that allow the species to mate assortatively while breeding side by side in the Iberá wetlands of Argentina.