An official website of the United States government
Abstract AimWe studied the niche evolution and diversification modes in transisthmianAlpheusshrimps by examining the interplay between environmental niche divergence and conservatism in allopatric sister species. In a broader perspective, the current study analysed the evolution of climatic niche and the role of the environment in species diversification ofAlpheustransisthmian shrimp. LocationAtlantic and Eastern‐Pacific oceans. TaxonAlpheusshrimps (Caridea: Alpheidae). MethodsWe assembled georeferenced occurrences for 33 species ofAlpheus(with 24 sister species) from a time‐calibrated molecular phylogeny. We modelled their ecological niches and assessed niche overlap through pairwise comparisons. Additionally, we performed phylogenetic reconstructions of the ancestral environmental niche, for each niche axis. ResultsOur results demonstrate that thermal tolerances, food availability and hydrodynamic forces were relevant environmental axes in evolutionary processes in transisthmian species ofAlpheus. Among the 528 paired comparisons, we found that most niches were divergent, including in 12 clades formed by pairs of sister species (in only two of these clades were the niches fully equivalent). Phylogenetic reconstructions of ancestral niches showed an initial niche conservatism in all axes, with divergences intensifying in the last 12 million years. Main ConclusionsWe found evidence that confirms the relevance of the environmental changes that occurred in the West Atlantic and East Pacific for niche evolution in transisthmianAlpheusspecies, as well as for the emergence of some lineages. Our findings provide evidence for different modes ofAlpheusspecies speciation in a period consistent with the closure of the Isthmus of Panama.
more »
« less
This content will become publicly available on December 1, 2026
Does Karyotype Structure Co‐Occurrence Patterns in a Chromosomally Diverse and Species‐Rich Clade of Lizards (Genus Sceloporus )?
ABSTRACT AimWe investigated the biogeographic consequences of chromosomal speciation, or structural changes in chromosome arrangement that lead to reproductive isolation, an intriguing speciation mechanism with implications for the phylogenetic and geographic distribution of species and chromosomal diversity. Location. North and Central America. Taxa. A species‐rich and chromosomally diverse clade of lizards in the genusSceloporuswhich are known to have coincident bursts of speciation and karyotype diversity, and coincident patterns of chromosomal change and branching order. Some workers have suggested that the tendency of communities ofSceloporuslizards to include species with different karyotypes is a signal of widespread chromosomal speciation, but given the high karyotypic diversity present inSceloporus, this may be due to chance rather than the effects of karyotypic speciation. MethodsWe gathered karyotypic, morphological, and biogeographic data on this chromosomally‐diverse clade in order to assess whether sympatry patterns ofSceloporusspecies are structured by karyotype. If karyotypic rearrangements contribute to the creation or maintenance of new species inSceloporus, then sympatric sister taxa should be more karyotypically diverged than allopatric sister taxa, and allopatric taxa should accumulate differences more gradually. We investigate whether species pairs with similar karyotypes are less likely to overlap geographically than expected by chance, and test whether karyotypic and geographic overlap between species pairs is related to divergence time. We pay special attention to cases of overlap between sister species. We also investigate whetherSceloporuscommunities are karyotypically overdispersed by comparing observed geographic distributions of karyotypic and phylogenetic diversity against phylogenetically‐informed modeled distributions. ResultsWe find little evidence for geographic signatures of chromosomal speciation and suggest that, while chromosomal speciation may have contributed historically to the spatial distributions ofSceloporusspecies, any geographic signature of this mode of speciation has been lost at long (> 10 Ma) temporal and broad (continental) spatial scales. Main ConclusionsThe spatial signature of chromosomal speciation is temporally restricted and the influences of other factors may have greater effects on species distributions over long time scales in this group.
more »
« less
- Award ID(s):
- 2507670
- PAR ID:
- 10679590
- Publisher / Repository:
- Wiley, Journal of Biogeography
- Date Published:
- Journal Name:
- Journal of Biogeography
- Volume:
- 52
- Issue:
- 12
- ISSN:
- 0305-0270
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Geographic isolation is the primary driver of speciation in many vertebrate lineages. This trend is exemplified by North American darters, a clade of freshwater fishes where nearly all sister species pairs are allopatric and separated by millions of years of divergence. One of the only exceptions is the Lake Waccamaw endemic Etheostoma perlongum and its riverine sister species Etheostoma maculaticeps, which have no physical barriers to gene flow. Here we show that lacustrine speciation of E. perlongum is characterized by morphological and ecological divergence likely facilitated by a large chromosomal inversion. While E. perlongum is phylogenetically nested within the geographically widespread E. maculaticeps, there is a sharp genetic and morphological break coinciding with the lake–river boundary in the Waccamaw River system. Despite recent divergence, an active hybrid zone, and ongoing gene flow, analyses using a de novo reference genome reveal a 9 Mb chromosomal inversion with elevated divergence between E. perlongum and E. maculaticeps. This region exhibits striking synteny with known inversion supergenes in two distantly related fish lineages, suggesting deep evolutionary convergence of genomic architecture. Our results illustrate that rapid, ecological speciation with gene flow is possible even in lineages where geographic isolation is the dominant mechanism of speciation.more » « less
-
Abstract Closely related species can impose strong forces of selection on one another through competition, leading to dramatic examples of phenotypic evolution. Niche partitioning can promote the use of novel resources between co-occurring species to reduce competitive overlap and thereby drive phenotypic divergence. Quantifying this potential relationship between ecology and morphology among species can reveal how opportunity and constraint interact to shape patterns of phenotypic evolution and how phenotypic diversity can facilitate co-occurrence. We explored the dynamics of ecomorphological evolution in relation to speciation and co-occurrence in Sceloporus lizards, a speciose group spanning North and Central America, where species often occur in sympatry. We collected data for 80 species and demonstrated strong relationships between multivariate morphology and ecology, finding that Sceloporus species occur in six ecological modes with associated morphologies (ecomorphs). The evolution of arboreality was a major transition that expanded morphospace, allowed for the evolution of further ecological novelty, and is associated with increased speciation rates. Across their range, Sceloporus ecomorphs are spatially overdispersed, suggesting that interspecific competition may limit the ability of similar species to coexist. By quantifying ecomorphological diversity across a diverse radiation, our results shed new light on how phenotypic variation accumulates and its implications for coexistence between closely related species.more » « less
-
Abstract PremiseAstragalus(Fabaceae), with more than 3000 species, represents a globally successful radiation of morphologically highly similar species predominant across the northern hemisphere. It has attracted attention from systematists and biogeographers, who have asked what factors might be behind the extraordinary diversity of this important arid‐adapted clade and what sets it apart from close relatives with far less species richness. MethodsHere, for the first time using extensive phylogenetic sampling, we asked whether (1)Astragalusis uniquely characterized by bursts of radiation or whether diversification instead is uniform and no different from closely related taxa. Then we tested whether the species diversity ofAstragalusis attributable specifically to its predilection for (2) cold and arid habitats, (3) particular soils, or to (4) chromosome evolution. Finally, we tested (5) whetherAstragalusoriginated in central Asia as proposed and (6) whether niche evolutionary shifts were subsequently associated with the colonization of other continents. ResultsOur results point to the importance of heterogeneity in the diversification ofAstragalus, with upshifts associated with the earliest divergences but not strongly tied to any abiotic factor or biogeographic regionalization tested here. The only potential correlate with diversification we identified was chromosome number. Biogeographic shifts have a strong association with the abiotic environment and highlight the importance of central Asia as a biogeographic gateway. ConclusionsOur investigation shows the importance of phylogenetic and evolutionary studies of logistically challenging “mega‐radiations.” Our findings reject any simple key innovation behind high diversity and underline the often nuanced, multifactorial processes leading to species‐rich clades.more » « less
-
Abstract PremiseA switch in pollinator can occur when a plant lineage enters a new habitat where the ancestral pollinator is less common, and a novel pollinator is more common. Because pollinator communities vary according to environmental tolerances and availability of resources, there may be consistent associations between pollination mode and specific regions and habitats. Such associations can be studied in lineages that have experienced multiple pollinator transitions, representing evolutionary replicates. MethodsOur study focused on a large clade ofPenstemonwildflower species in western North America, which has repeatedly evolved hummingbird‐adapted flowers from ancestral bee‐adapted flowers. For each species, we estimated geographic ranges from occurrence data and inferred environmental niches from climate, topographical, and soil data. Using a phylogenetic comparative approach, we investigated whether hummingbird‐adapted species occupy distinct geographic regions or habitats relative to bee‐adapted species. ResultsHummingbird‐adapted species occur at lower latitudes and lower elevations than bee‐adapted species, resulting in a difference in their environmental niche. Bee‐adapted species sister to hummingbird‐adapted species are also found in relatively low elevations and latitudes, similar to their hummingbird‐adapted sister species, suggesting ecogeographic shifts precede pollinator divergence. Sister species pairs—regardless of whether they differ in pollinator—show relatively little geographic range overlap. ConclusionsAdaptation to a novel pollinator may often occur in geographic and ecological isolation from ancestral populations. The ability of a given lineage to adapt to novel pollinators may critically depend on its ability to colonize regions and habitats associated with novel pollinator communities.more » « less
