Evaluating assortative mating and reproductive isolation in a contact zone between lineages of the House Wren

PABLO FRACAS; ARRIETA, RAMIRO S.; BUKOSKY BELEN; CAMPAGNA LEO; LAVINIA PABLO; LLAMBIAS PAULO E; TUBARO PABLO; LIJMAER DARIO

London, Ontario

Congreso; AOS/SCO-SOC Joint Conference; 2023

Diversification in the presence of gene flow is far more common than traditionally believed, both in the onset of divergence and during secondary contact, a notion that has changed our understanding of speciation. The House Wren (Troglodytes aedon) is the most widely distributed passerine in the Americas, including multiple lineages that differ in mitochondrial and nuclear DNA, as well as morphology and behavior. Two deeply divergent lineages come into contact in central Argentina and previous studies have found geographically restricted gene flow between them. Nonetheless, they have remained divergent and without significant levels of introgression outside the area of contact, suggesting the presence of reproductive isolation mechanisms. Assortative mating between individuals of the same lineage would indicate the existence of pre-zygotic isolation mechanisms, whereas a high proportion of mixed-breeding couples would suggest that post-zygotic isolation mechanisms might be preventing more widespread gene flow. To address this we captured, banded and bled 76 adult wrens (38 couples) and their offspring (220 nestlings) in Uspallata, a location in Mendoza province within the area of contact. To evaluate the presence of assortative mating, we assigned each adult to its lineage by sequencing its COI gene and identified the proportion of couples which members belonged to different lineages. We also analyzed nest success, the proportion of hatched eggs, and the sex ratios of the nestlings to check for post-zygotic reproductive isolation. This is being complemented with the analysis of coloration and vocalizations as putative pre-zygotic reproductive isolation mechanisms