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Postzygotic isolation drives genomic speciation between highly cryptic Hypocnemis antbirds from Amazonia
Author(s) -
Cronemberger Áurea A.,
Aleixo Alexandre,
Mikkelsen Else K.,
Weir Jason T.
Publication year - 2020
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.14103
Subject(s) - biology , hybrid zone , reproductive isolation , introgression , species complex , evolutionary biology , cline (biology) , genetic algorithm , incipient speciation , sympatric speciation , amazon rainforest , hybrid , allopatric speciation , genetics , phylogenetic tree , ecology , genetic variation , gene flow , gene , population , botany , demography , sociology
How species evolve reproductive isolation in the species‐rich Amazon basin is poorly understood in vertebrates. Here, we sequenced a reference genome and used a genome‐wide sample of SNPs to analyze a hybrid zone between two highly cryptic species of Hypocnemis warbling‐antbirds—the Rondonia warbling‐antbird ( H. ochrogyna ) and Spix's warbling‐antbird ( H. striata )—in a headwater region of southern Amazonia. We found that both species commonly hybridize, producing F 1 s and a variety of backcrosses with each species but we detected only one F 2 ‐like hybrid. Patterns of heterozygosity, hybrid index, and interchromosomal linkage disequilibrium in hybrid populations closely match expectations under strong postzygotic isolation. Hybrid zone width (15.4 km) was much narrower than expected (211 km) indicating strong selection against hybrids. A remarkably high degree of concordance in cline centers and widths across loci, and a lack of reduced interspecific F st between populations close to versus far from the contact zone, suggest that genetic incompatibilities have rendered most of the genome immune to introgression. These results support intrinsic postzygotic isolation as a driver of speciation in a moderately young cryptic species pair from the Amazon and suggest that species richness of the Amazon may be grossly underestimated.