Project description:The Neotropics are one of the most biodiverse regions of the world, where environmental dynamics, climate and geology resulted in a complex diversity of fauna and flora. In such complex and heterogeneous environments, widely distributed species require deep investigation about their biogeographic history. The gray-breasted sabrewing hummingbird Campylopterus largipennis is a species complex that occurs in forest and open ecosystems of South America, including also high-altitude grasslands. It has been recently split into four distinct species distributed in Amazonia (rainforest) and Cerrado (savanna) biomes with boundaries marked by ecological barriers. Here, we investigated the evolutionary dynamics of population lineages within this neotropical taxon to elucidate its biogeographical history and current lineage diversity. We used a reduced-representation sequencing approach to perform fine-scale population genomic analyses of samples distributed throughout Amazonia and Cerrado localities, representing all four recently recognized species. We found a deep genetic structure separating species from both biomes, and a more recent divergence between species within each biome and from distinct habitats. The population dynamics through time was shown to be concordant with known vicariant events, isolation by distance, and altitudinal breaks, where the Amazon River and the Espinhaço Mountain Range worked as important barriers associated to speciation.
Project description:BackgroundMesoamerica is one of the most threatened biodiversity hotspots in the world, yet we are far from understanding the geologic history and the processes driving population divergence and speciation for most endemic taxa. In species with highly differentiated populations selective and/or neutral factors can induce rapid changes to traits involved in mate choice, promoting reproductive isolation between allopatric populations that can eventually lead to speciation. We present the results of genetic differentiation, and explore drift and selection effects in promoting acoustic and morphological divergence among populations of Campylopterus curvipennis, a lekking hummingbird with an extraordinary vocal variability across Mesoamerica.ResultsAnalyses of two mitochondrial genes and ten microsatellite loci genotyped for 160 individuals revealed the presence of three lineages with no contemporary gene flow: C. c. curvipennis, C. c. excellens, and C. c. pampa disjunctly distributed in the Sierra Madre Oriental, the Tuxtlas region and the Yucatan Peninsula, respectively. Sequence mtDNA and microsatellite data were congruent with two diversification events: an old vicariance event at the Isthmus of Tehuantepec (c. 1.4 Ma), and a more recent Pleistocene split, isolating populations in the Tuxtlas region. Hummingbirds of the excellens group were larger, and those of the pampa group had shorter bills, and lineages that have been isolated the longest shared fewer syllables and differed in spectral and temporal traits of a shared syllable. Coalescent simulations showed that fixation of song types has occurred faster than expected under neutrality but the null hypothesis that morphological divergence resulted from drift was not rejected.ConclusionsOur phylogeographic analyses uncovered the presence of three Mesoamerican wedge-tailed sabrewing lineages, which diverged at different time scales. These results highlight the importance of the Isthmus of Tehuantepec and more recent Pleistocene climatic events in driving isolation and population divergence. Coalescent analyses of the evolution of phenotypic traits suggest that selection is driving song evolution in wedge-tailed sabrewings but drift could not be rejected as a possibility for morphological divergence.