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

CABANNE, GUSTAVO S.; RODRIGUEZ-CAJARVILLE, MARIA JOSE; LIMA-REZENDE, CÁSSIA A.; GARCÍA, NATALIA C.; CAMPAGNA, LEONARDO; CARBONI, MARTÍN; BARREIRA, ANA S.; LIJTMAER, DARÍO A.; TUBARO, PABLO L.; FERRETTI, VALENTINA; CARDONI, AUGUSTO; ISAACH, JUAN P.

Congreso; II Ornithologial Congress of the Americas; 2023

Natural selection on ecologically important characters drives divergence with gene flow, which is considered a rare speciation process in birds. We studied genomic and morphological divergence of the two sister species Limnoctites rectirostris and L. sulphuriferus and evaluated the hypothesis of their speciation with gene flow. These birds are Pampas grasslands endemics, and despite being mostly sympatric, they are not syntopic because occupy different grassland types. Therefore, these species could have evolved in sympatry, by adaptation to different grasslands, where we predicted to find between them high to moderate gene flow, recent divergence, and non-neutral morphological divergence (Pst), as compared to genomic divergence (Fst). We studied genomic markers (n=61 samples, 31063 ddRAD loci of 140 bp, 4402 loci shared by 80% of samples), 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 higher than that of autosomes, the results suggested that fixed markers are autosomals. The Pst-Fst comparisons suggested that bill length was under divergent natural selection between species, that tarsus length was under balancing selection, and that bill width and height, as well as wing length, diverged by chance. The results supported the action of divergent natural selection in the evolution of these species; however, because genomic divergence is high, it is not clear if it occurred in sympatry or after an initial allopatry.