title: Isolation with asymmetric gene flow during the nonsynchronous divergence of dry forest birds.
abstract: Dry forest bird communities in South America are often fragmented by intervening mountains and rainforests, generating high local endemism. The historical assembly of dry forest communities likely results from dynamic processes linked to numerous population histories among codistributed species. Nevertheless, species may diversify in the same way through time if landscape and environmental features, or species ecologies, similarly structure populations. Here we tested whether six co-distributed taxon pairs that occur in the dry forests of the Tumbes and Marañón Valley of northwestern South America show concordant patterns and modes of diversification. We employed a genome reduction technique, double-digest restriction site-associated DNA sequencing, and obtained 4407-7186 genomewide SNPs. We estimated demographic history in each taxon pair and inferred that all pairs had the same best-fit demographic model: isolation with asymmetric gene flow from the Tumbes into the Marañón Valley, suggesting a common diversification mode. Overall, we also observed congruence in effective population size (Ne) patterns where ancestral Newere 2.9-11.0× larger than present-day Marañón Valley populations and 0.3-2.0× larger than Tumbesian populations. Present-day Marañón Valley Newas smaller than Tumbes. In contrast, we found simultaneous population isolation due to a single event to be unlikely as taxon pairs diverged over an extended period of time (0.1-2.9 Ma) with multiple nonoverlapping divergence periods. Our results show that even when populations of codistributed species asynchronously diverge, the mode of their differentiation can remain conserved over millions of years. Divergence by allopatric isolation due to barrier formation does not explain the mode of differentiation between these two bird assemblages; rather, migration of individuals occurred before and after geographic isolation.
authors.affiliation: Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611-7800, USA.|Museum of Natural Science, Louisiana State University, 119 Foster Hall, Baton Rouge, LA, 70803, USA.
authors.forename: Jessica A
authors.identifier: http://orcid.org/0000-0002-6702-3675
authors.initials: JA
authors.lastname: Oswald
authors.affiliation: Subprogram in Ecology, Evolution and Behavior, The Graduate Center of the City University of New York, New York, NY, 10016, USA.
authors.forename: Isaac
authors.initials: I
authors.lastname: Overcast
authors.affiliation: Department of Ornithology, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Mauck
authors.affiliation: Department of Ornithology, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024, USA.|Department of Biology and Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Andersen
authors.affiliation: Department of Ornithology, American Museum of Natural History, Central Park West at 79th Street, New York, NY, 10024, USA.
authors.forename: Brian Tilston
authors.initials: BT
authors.lastname: Smith
mesh_terms: D000818:Animals; D001717:Birds / Q000145:classification*; D065928:Forests; D051456:Gene Flow; D014644:Genetic Variation; D010802:Phylogeny; D058974:Phylogeography; D020641:Polymorphism, Single Nucleotide; D017422:Sequence Analysis, DNA; D013020:South America
keywords: South America; coalescent; model selection; neotropical; phylogeography; speciation with gene flow