Abstract
BackgroundPleistocene climatic fluctuations are known to be an engine of biotic diversification at higher latitudes, but their impact on highly diverse tropical areas such as the Andes remains less well-documented. Specifically, while periods of global cooling may have led to fragmentation and differentiation at colder latitudes, they may – at the same time – have led to connectivity among insular patches of montane tropical habitat with unknown consequences on diversification. In the present study we utilized ~5.5 kb of DNA sequence data from eight nuclear loci and one mitochondrial gene alongside diagnostic morphological and bioacoustic markers to test the effects of Pleistocene climatic fluctuations on diversification in a complex of Andean tyrant-flycatchers of the genus Elaenia.ResultsPopulation genetic and phylogenetic approaches coupled with coalescent simulations demonstrated disparate levels of gene flow between the taxon chilensis and two parapatric Elaenia taxa predominantly during the last glacial period but not thereafter, possibly on account of downward shifts of montane forest habitat linking the populations of adjacent ridges. Additionally, morphological and bioacoustic analyses revealed a distinct pattern of character displacement in coloration and vocal traits between the two sympatric taxa albiceps and pallatangae, which were characterized by a lack of gene flow.ConclusionOur study demonstrates that global periods of cooling are likely to have facilitated gene flow among Andean montane Elaenia flycatchers that are more isolated from one another during warm interglacial periods such as the present era. We also identify a hitherto overlooked case of plumage and vocal character displacement, underpinning the complexities of gene flow patterns caused by Pleistocene climate change across the Andes.
Highlights
Pleistocene climatic fluctuations are known to be an engine of biotic diversification at higher latitudes, but their impact on highly diverse tropical areas such as the Andes remains less well-documented
principal component analysis (PCA) of vocal parameters of the three Elaenia taxa revealed albiceps is vocally distinct from pallatangae and chilensis (Fig. 2), with the main differences mostly a result of parameters that quantify timbre and call quality (Additional file 2: Figure S1)
Ample bioacoustic overlap was present between the vocal traits of pallatangae and chilensis (Fig. 2), with a roughly clinal arrangement along a north-south axis mainly based on average frequency parameters (Additional file 2: Figure S1)
Summary
Pleistocene climatic fluctuations are known to be an engine of biotic diversification at higher latitudes, but their impact on highly diverse tropical areas such as the Andes remains less well-documented. One of the greatest planetary engines of environmental change driving biotic diversification over the last 2,000,000 years has been the cyclical succession of periods of global cooling, the so called ‘ice ages’ [1,2,3]. Over the Quaternary period, ice ages have regularly led to significant earth-historic change through fluctuations in temperature, sea level and extensive glaciations. Despite the wealth of research that has gone into the investigation of the effects of Pleistocene glaciations on biotic differentiation in northern temperate latitudes, much less is known about how periods of global cooling have impacted the most species-rich tropical regions of the world (for exceptions see, e.g., [9,10,11]). Earth-historic evidence for lowland rainforest contractions during glacial
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
