Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher.
Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?
Some links on this page may take you to non-federal websites. Their policies may differ from this site.
-
more » « less
Abstract Although the impact of Pleistocene glacial cycles on the diversification of the tropical biota was once dismissed, increasing evidence suggests that Pleistocene climatic fluctuations greatly affected the distribution and population divergence of tropical organisms. Landscape genomic analyses coupled with paleoclimatic distribution models provide a powerful way to understand the consequences of past climate changes on the present‐day tropical biota. Using genome‐wide SNP data and mitochondrial DNA, combined with projections of the species distribution across the late Quaternary until the present, we evaluate the effect of paleoclimatic shifts on the genetic structure and population differentiation of
Hypsiboas lundii , a treefrog endemic to the South American Cerrado savanna. Our results show a recent and strong genetic divergence inH. lundii across the Cerrado landscape, yielding four genetic clusters that do not seem congruent with any current physical barrier to gene flow. Isolation by distance (IBD) explains some of the population differentiation, but we also find strong support for past climate changes promoting range shifts and structuring populations even in the presence of IBD. Post‐Pleistocene population persistence in four main areas of historical stable climate in the Cerrado seems to have played a major role establishing the present genetic structure of this treefrog. This pattern is consistent with a model of reduced gene flow in areas with high climatic instability promoting isolation of populations, defined here as “isolation by instability,” highlighting the effects of Pleistocene climatic fluctuations structuring populations in tropical savannas. -
more » « less
Abstract Aim Present Amazonian diversity patterns can result from many different mechanisms and, consequently, the factors contributing to divergence across regions and/or taxa may differ. Nevertheless, the river‐barrier hypothesis is still widely invoked as a causal process in divergence of Amazonian species. Here we use model‐based phylogeographic analyses to test the extent to which major Amazonian rivers act similarly as barriers across time and space in two broadly distributed Amazonian taxa.
Local Amazon rain forest.
Taxon The lizard
Gonatodes humeralis (Sphaerodactylidae) and the tree frogDendropsophus leucophyllatus (Hylidae).Methods We obtained RADseq data for samples distributed across main river barriers, representing main Areas of Endemism previously proposed for the region. We conduct model‐based phylogeographic and genetic differentiation analyses across each population pair.
Results Measures of genetic differentiation (based on
FST calculated from genomic data) show that all rivers are associated with significant genetic differentiation. Parameters estimated under investigated divergence models showed that divergence times for populations separated by each of the 11 bordering rivers were all fairly recent. The degree of differentiation consistently varied between taxa and among rivers, which is not an artifact of any corresponding difference in the genetic diversities of the respective taxa, or to amounts of migration based on analyses of the site‐frequency spectrum.Main conclusions Taken together, our results support a dispersal (rather than vicariance) history, without strong evidence of congruence between these species and rivers. However, once a species crossed a river, populations separated by each and every river have remained isolated—in this sense, rivers act similarly as barriers to any further gene flow. This result suggests differing degrees of persistence and gives rise to the seeming contradiction that the divergence process indeed varies across time, space and species, even though major Amazonian rivers have acted as secondary barriers to gene flow in the focal taxa.
-
more » « less
Abstract Aim We combine phylogenetic and point locality data from selected lineages of the Atlantic Forest flora and fauna to compare spatial patterns of biodiversity sustained by the current configuration of forest remnants to a scenario of complete forest preservation. We then ask the question how much biodiversity is likely lost, already? Specifically, we assess how habitat loss likely impacted the climatic spaces occupied by the local species, the inferred composition of local communities and the spatial distribution of phylogenetic diversity and endemism.
Location Atlantic Forest, Brazil.
Methods Using carefully curated point localities, phylogenetic data and parameterized models of species distributions, we generate maps of phylogenetic diversity, phylogenetic endemism and phylogenetic turnover for the entire Atlantic Forest. We map patterns of clade‐specific diversity under complete preservation of forest and then incorporate present‐day deforestation patterns to provide a more realistic scenario.
Results Instead of a singular pattern, three different reoccurring syndromes described the flora and fauna of the Atlantic Forest. These patterns emerged irrespectively of clade age and life history traits. General turnover patterns were highly consistent with previous analyses of species composition and panbiogeographical studies. Deforestation has altered the availability of climatic spaces in the Atlantic Forest, its biological communities and the distribution of evolutionary lineages in space. However, approximately 60% of the pre‐Columbian climatic space persists in forest remnants, and today's biological communities are estimated to be 45% similar to pre‐deforestation times.
Main conclusions The Atlantic Forest has been reduced to 8% of its once largely continuous range. However, the disproportionately large amounts of climate, community and lineage diversity that persist in remnants provide hope and support for conservation efforts that combine species occurrence and phylogenetic data. Inclusion of evolutionary thinking into strategic approaches to restoring Brazilian ecosystems could further conservation effectiveness by incorporating the adaptive potential of local assemblages in the face of further environmental shifts.
