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Abstract Evolutionary transitions between marine and freshwater ecosystems have occurred repeatedly throughout the phylogenetic history of fishes. The theory of ecological opportunity predicts that lineages that colonize species-poor regions will have greater potential for phenotypic diversification than lineages invading species-rich regions. Thus, transitions between marine and freshwaters may promote phenotypic diversification in trans-marine/freshwater fish clades. We used phylogenetic comparative methods to analyze body size data in nine major fish clades that have crossed the marine/freshwater boundary. We explored how habitat transitions, ecological opportunity, and community interactions influenced patterns of phenotypic diversity. Our analyses indicated that transitions between marine and freshwater habitats did not drive body size evolution, and there are few differences in body size between marine and freshwater lineages. We found that body size disparity in freshwater lineages is not correlated with the number of independent transitions to freshwaters. We found a positive correlation between body size disparity and overall species richness of a given area, and a negative correlation between body size disparity and diversity of closely related species. Our results indicate that the diversity of incumbent freshwater species does not restrict phenotypic diversification, but the diversity of closely related taxa can limit body size diversification. Ecological opportunity arising from colonization of novel habitats does not seem to have a major effect in the trajectory of body size evolution in trans-marine/freshwater clades. Moreover, competition with closely related taxa in freshwaters has a greater effect than competition with distantly related incumbent species.
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Ecomorphology is associated with speciation and co-occurrence in Sceloporus lizards
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.
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- PAR ID:
- 10679089
- Publisher / Repository:
- Royal Society Publishing
- Date Published:
- Journal Name:
- Proceedings of the Royal Society B Biological Sciences
- Volume:
- 292
- Issue:
- 2060
- ISSN:
- 1471-2954
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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
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Abstract It remains unclear how variation in the intensity of sperm competition shapes phenotypic and molecular evolution across clades. Mice and rats in the subfamily Murinae are a rapid radiation exhibiting incredible diversity in sperm morphology and production. We combined phenotypic and genomic data to perform phylogenetic comparisons of male reproductive traits and genes across 78 murine species. We identified several shifts towards smaller relative testes mass (RTM), presumably reflecting reduced sperm competition. Several sperm traits were associated with RTM, suggesting that mating system evolution selects for convergent suites of traits related to sperm competitive ability. We predicted that sperm competition would also drive more rapid molecular divergence in species with large testes. Contrary to this, we found that many spermatogenesis genes evolved more rapidly in species with smaller RTM due to relaxed purifying selection. While some reproductive genes evolved rapidly under recurrent positive selection, relaxed selection played a greater role in underlying rapid evolution in small testes species. Our work demonstrates that postcopulatory sexual selection can impose strong purifying selection shaping the evolution of male reproduction and that broad patterns of molecular evolution may help identify genes that contribute to male fertility.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1098/rspb.2025.1305
