Does divergence with gene flow and between microenvironments explain the evolution of species of the Genus Limnoctites (Furnariidae)?

CABANNE, GUSTAVO S.; RODRÍGUEZ-CAJARVILLE, MARÍA J.; LIMA-REZENDE, CASSIA A.; GARCÍA, NATALIA C.; CAMPAGNA, LEONARDO; CARBONI, MARTÍN; BARREIRA, ANA S.; LIJTMAER, DARÍO A.; TUBARO, PABLO L.; FERRETTI, VALENTINA; CARDONI, DANIEL A.; ISACCH, JUAN P.; FRACASSI, NATALIA

Gramado

Congreso; Second Ornithological Congress of the Americas; 2023

Association of Field Ornithologists, Sociedade Brasileira de Ornitologia y Aves Argentinas

Natural selection on characters of ecological importance drives divergence with gene flow and counteracts the homogenizing effect of gene flow. We studied genomic divergence of the two sister species [Limnoctites rectirostris] and [L. sulphuriferus] and evaluated the hypothesis of their speciation with gene flow. These birds are endemic to grasslands of the Pampean region and the southern mountains of Brazil, and although they are mostly sympatric, they are not syntopic (occupy different grassland types). Therefore, these species could have evolved in sympatry and by adaptation to different habitats, in which case one would predict to find high to moderate gene flow between them, recent divergence, and non-neutral morphological divergence (Pst) comparable to genomic divergence (Fst). We evaluated genomic divergence (n=61 samples) with ddRAD markers (catalog of 31,063 loci of 140 bp, 4402 loci shared by 80% of samples). We found strong genetic isolation (Fst 95%CI: 0.63-0.65), low migration (M0.9) between species. Although differentiation of markers linked to the Z chromosome (Fst 95%CI: 0.64-0.73) was slightly greater than that of autosomes, results suggested that fixed markers are autosomal. The Pst - Fst comparisons suggested that bill length was under divergent natural selection between species, while tarsus length was under balancing selection. The results supported the action of divergent natural selection in the evolution between species; however, this could have occurred after an initial divergence in allopatry. Our next step is to evaluate morphological predictions by only studying neutral loci.