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

FRACAS PABLO; ARRIETA RAMIRO; BUKOWSKI BELÉN; CAMPAGNA LEONARDO; LAVINIA OBLANCA PABLO DAMIÁN; LLAMBÍAS PAULO; TUBARO PABLO LUIS; LIJTMAER DARÍO A.

London

Congreso; AOS & SCO-SOC Ornithological 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 ourunderstanding of speciation. The House Wren (Troglodytes aedon) is the most widelydistributed passerine in the Americas, including multiple lineages that differ in mitochondrialand nuclear DNA, as well as morphology and behavior. Two deeply divergent lineages comeinto contact in central Argentina and previous studies have found geographically restrictedgene flow between them. Nonetheless, they have remained divergent and without significantlevels of introgression outside the area of contact, suggesting the presence of reproductiveisolation mechanisms. Assortative mating between individuals of the same lineage wouldindicate the existence of prezygotic isolation mechanisms, whereas a high proportion ofmixed-breeding couples would suggest that postzygotic isolation mechanisms might bepreventing more widespread gene flow. To address this we captured, banded and bled 76adult wrens (38 couples) and their offspring (220 nestlings) in Uspallata, a location inMendoza province within the area of contact. To evaluate the presence of assortativemating, we assigned each adult to its lineage by sequencing its COI gene and identified theproportion of couples which members belonged to different lineages. We also analyzed nestsuccess, the proportion of hatched eggs, and the sex ratios of the nestlings to check forpost-zygotic reproductive isolation. This is being complemented with the analysis ofcoloration and vocalizations as putative prezygotic reproductive isolation mechanisms.