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

SHEELA P. TURBEK; REBECCA SAFRAN; MELANIE BROWNE; ADRIAN S. DI GIACOMO; CECILIA KOPUCHIAN; LEONARDO CAMPAGNA

Conferencia; The Gordon Research Conference on Speciation; 2019

Recent advances in high throughput genomic sequencing technology are enabling finerresolution of the degree of genomic divergence between taxa previously classified on thebasis of phenotypic traits. An emerging pattern revealed by these studies is that speciescan exhibit marked differences in appearance despite little genomic differentiation.However, we lack an understanding of the reproductive barriers maintaining phenotypicdifferences among genetically similar populations that would improve our ability tointerpret these intriguing genomic patterns. The southern capuchino seedeaters (genusSporophila) constitute a highly sympatric avian radiation characterized by littleecological 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 sympatricspecies and examine the importance of mate choice in the maintenance of phenotypicdifferences. In addition, we analyzed the paternity of 39 nestlings through ddRAD todetermine whether patterns of social pairing reflect patterns of extra-pair mating. Wedetect an extremely low level of background differentiation (genome-wide F ST = 0.007)between S. iberaensis and S. hypoxantha that is punctuated by three regions of elevateddivergence that coincide with genes involved in the melanogenesis pathway. Despite thedegree of genomic homogeneity, the two species appear to mate assortatively withrespect to both social and extra-pair mates. Ongoing analyses are evaluating the specificmechanisms that allow the species to mate assortatively while breeding side by side in theIberá wetlands of Argentina.