Genetic, phenotypic and ecological divergence with gene flow at the Isthmus of Tehuantepec: the case of the azure‐crowned hummingbird (Amazilia cyanocephala)

Abstract

Aim We test whether populations of the Mesoamerican azure‐crowned hummingbird, Amazilia cyanocephala (Trochilidae), located east and west of the Isthmus of Tehuantepec are genetically, morphologically and environmentally differentiated and examine the relative role of drift and selection in driving diversification. Location Mexico. Methods We sequenced the mitochondrial ATPase‐6 and ATPase‐8 genes and the control region of 130 individuals collected throughout the range of the species in Mexico. Population genetic methods and coalescent tests were used to reconstruct the phylogeography of the species. Morphological and niche variation between genetic groups of A. cyanocephala were assessed. Results The data revealed two genetic groups separated by the Isthmus of Tehuantepec in the late Pleistocene (49,300–75,800 years ago), with the split occurring in the presence of gene flow. Deviations from demographic equilibrium were detected for the two genetic groups, indicating more recent population expansions. Amazilia cyanocephala individuals from populations on either side of the Isthmus of Tehuantepec differed in morphology and were distributed in unique environmental space. A coalescent‐based test indicated that selection is driving the observed morphological differentiation. Main conclusions Our findings implicate the Isthmus of Tehuantepec as a permeable barrier driving recent diversification of A. cyanocephala in the presence of gene flow. The two A. cyanocephala mitochondrial DNA (mtDNA) groups corresponding with morphological and environmental niche differences, in concert with the results of a coalescent‐based test, suggest that selection has been strong enough to counteract the effects of gene flow.

Ongoing Speciation and Gene Flow between Taxonomically Challenging Trochulus Species Complex (Gastropoda: Hygromiidae)

“…This may result from incomplete sorting of microsatellite alleles into these lineages or independent evolution of the same microsatellite alleles in these species. Patterns of divergence with gene flow were observed in both invertebrate [81,82] and vertebrate species [83–85]. …”

Comparative Phylogeographic Analyses Illustrate the Complex Evolutionary History of Threatened Cloud Forests of Northern Mesoamerica

“…Similar to divergence patterns in plants, phylogeographic investigations of cloud forest bird species have identified two discrete diversification events, estimated as occurring in the Pleistocene or late Pliocene, separating populations that occur in cloud forests on either side of the Isthmus of Tehuantepec and currently isolated from one another by the intervening valley [17]–[20]. Fluctuations in cloud forests induced by climatic cycles and a late Pliocene seaway at the isthmus have been implicated in subdividing the distribution of this bird fauna spanning the isthmus [18].…”

“…The 15 taxa were also chosen because they are thought to be cloud forest endemics whose distributions span northern Mesoamerica and closely follow the highly fragmented forest; all of the birds are considered to be cloud forest residents. Some of the targeted species ecologically interact with one another; P. padifolia and M. deppeana are mainly pollinated by the hummingbird species ( C. curvipennis , A. cyanocephala , and L. amethystinus , respectively) and seeds of R. baccifera are dispersed by C. ophthalmicus [15], [19], [20]. Our a priori expectation was that such ecologically linked species might share a common biogeographic history.…”

Genetic diversity and structure of wild populations ofCarica papayain Northern Mesoamerica inferred by nuclear microsatellites and chloroplast markers

“…In Northern Mesoamerica two historical events are known to have reduced dispersal and generated a spatial structuring of genetic diversity in different species: the Isthmus of Tehuantepec (pre-Pleistocene event) and the Pleistocene glacial refugia (Bryson et al, 2011;Gutiérrez-Rodr ıguez et al, 2011;Rodr ıguez-G omez et al, 2013). The Isthmus of Tehuantepec forms a narrow piece of lowland that separates the southcentral Mexican highlands (Sierra de Ju arez and Sierra Madre del Sur) from the highlands of Chiapas (Ornelas et al, 2010).…”