skip to main content

Attention:

The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Friday, November 15 until 2:00 AM ET on Saturday, November 16 due to maintenance. We apologize for the inconvenience.


Search for: All records

Creators/Authors contains: "Gehara, Marcelo"

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.

  1. Abstract

    The North American racers (Coluber constrictor) are widely distributed across the Nearctic and numerous studies have demonstrated extensive variation in morphology, ecology, and population genetic structure. Here we take an integrative approach to understand lineage diversification within this taxon by combining genomic sequence capture data, mtDNA sequence data, morphometrics, and ecological niche models. Both the genomic data and mtDNA phylogeographic analyses support five lineages distributed across the range of this species. However, demographic model selection based on these two datasets strongly conflict in both the model of divergence and estimates of timing of lineage divergence. While mtDNA and concatenated genomic data suggest a Miocene origin of these distinct groups, coalescent-based demographic models with the sequence capture data suggest lineage diversification occurred at ~33 kya in allopatry without gene flow. Using linear morphological measurements of head shape we demonstrate that lineages distributed largely east and west of the Mississippi River are distinguishable. Furthermore, ecological niche models demonstrate that lineages distributed in subtropical habitats have environmental niche space that is significantly differentiated from lineages distributed across the continent. Taken together, these results suggest that ecology is an important axis of lineage divergence within this group and that more fine-scale analyses may find even greater differentiation between the populations identified here. This abstract translated to Spanish is avaliable in the Supporting Infromation section (Este resumen traducido al español está disponible en la sección, Supporting Infromation).

     
    more » « less
    Free, publicly-accessible full text available March 20, 2025
  2. Hancock, Angela (Ed.)
    Abstract

    Geographic barriers are frequently invoked to explain genetic structuring across the landscape. However, inferences on the spatial and temporal origins of population variation have been largely limited to evolutionary neutral models, ignoring the potential role of natural selection and intrinsic genomic processes known as genomic architecture in producing heterogeneity in differentiation across the genome. To test how variation in genomic characteristics (e.g. recombination rate) impacts our ability to reconstruct general patterns of differentiation between species that cooccur across geographic barriers, we sequenced the whole genomes of multiple bird populations that are distributed across rivers in southeastern Amazonia. We found that phylogenetic relationships within species and demographic parameters varied across the genome in predictable ways. Genetic diversity was positively associated with recombination rate and negatively associated with species tree support. Gene flow was less pervasive in genomic regions of low recombination, making these windows more likely to retain patterns of population structuring that matched the species tree. We further found that approximately a third of the genome showed evidence of selective sweeps and linked selection, skewing genome-wide estimates of effective population sizes and gene flow between populations toward lower values. In sum, we showed that the effects of intrinsic genomic characteristics and selection can be disentangled from neutral processes to elucidate spatial patterns of population differentiation.

     
    more » « less
    Free, publicly-accessible full text available January 1, 2025
  3. Abstract

    Divergence dating analyses in systematics provide a framework to develop and test biogeographic hypotheses regarding speciation. However, as molecular datasets grow from multilocus to genomic, sample sizes decrease due to computational burdens, and the testing of fine-scale biogeographic hypotheses becomes difficult. In this study, we use coalescent demographic models to investigate the diversification of poorly known rice paddy snakes from Southeast Asia (Homalopsidae:Hypsiscopus), which have conflicting dates of origin based on previous studies. We use coalescent modeling to test the hypothesis thatHypsiscopusdiversified 2.5 mya during the Khorat Plateau uplift in Thailand. Additionally, we use ecological niche analyses to identify potential differences in the niche space of the two most widely distributed species in the past and present. Our results suggestHypsiscopusdiversified ~ 2.4 mya, supporting that the Khorat Plateau may have initiated the diversification of rice paddy snakes. We also find significant niche differentiation and shifts between species ofHypsiscopus, indicating that environmental differences may have sustained differentiation of this genus after the Khorat Plateau uplift. Our study expands on the diversification history of snakes in Southeast Asia, and highlights how results from smaller multilocus datasets can be useful in developing and testing biogeographic hypotheses alongside genomic datasets.

     
    more » « less
  4. null (Ed.)
  5. Abstract

    Genetic structure can be influenced by local adaptation to environmental heterogeneity and biogeographic barriers, resulting in discrete population clusters. Geographic distance among populations, however, can result in continuous clines of genetic divergence that appear as structured populations. Here, we evaluate the relevant importance of these three factors over a landscape characterized by environmental heterogeneity and the presence of a hypothesized biogeographic barrier in producing population genetic structure within 13 codistributed snake species using a genomic data set. We demonstrate that geographic distance and environmental heterogeneity across western North America contribute to population genomic divergence. Surprisingly, landscape features long thought to contribute to biogeographic barriers play little role in divergence community wide. Our results suggest that isolation by environment is the most important contributor to genomic divergence. Furthermore, we show that models of population clustering that incorporate spatial information consistently outperform nonspatial models, demonstrating the importance of considering geographic distances in population clustering. We argue that environmental and geographic distances as drivers of community‐wide divergence should be explored before assuming the role of biogeographic barriers.

     
    more » « less