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382 results for “Adaptive radiation”
Data from: Distribution models and a dated phylogeny for Chilean Oxalis species reveal occupation of new habitats by different lineages, not rapid adaptive radiation
Among the World's most challenging environments for plant life is the Atacama Desert, an arid zone extending over 1300 km and from sea level to 2000/3000 m along the southwestern Andean foothills. Plants there and in the adjacent Mediterranean zone exhibit striking adaptations, and we here use a species-rich such group to address the question whether adaptations arose in parallel, at different times, or simultaneously. Answering this type of question has been a major concern of evolutionary biology over the past few years, with a growing consensus that lineages tend to be conservative in their vegetative traits and niche requirements. Combined nuclear and chloroplast DNA sequences for 112 species of Oxalidales (4900 aligned nucleotides) yielded a fossil-calibrated phylogeny that includes 43 of the 54 species of Oxalis occurring in Chile. Distribution models (SDMs) for these species that included precipitation, temperature, fog and/or vegetation types and the phylogeny were used to reconstruct ancestral habitat preferences, relying on likelihood and Bayesian techniques. Since uneven collecting can reduce the power of SDMs, we used a background sample from 1224 Chilean Oxalis collections to correct models for collecting effort. Models with just 10 of 19 bioclim parameters did as well as more parameter-rich models. Results reveal that the Oxalis flora of Chile consists of seven distant lineages that originated at different times prior to the last Andean uplift pulse and some of which had features pre-adapting them to seasonally arid or xeric conditions. The Mediterranean core zone, south of the Atacama, offered an ecological refuge for insufficiently arid-adapted species and harbors a mix of ancient and young groups. There is no evidence of rapid adaptive radiation.
Data from: Convergence across a continent: adaptive diversification in a recent radiation of Australian lizards
Recent radiations are important to evolutionary biologists, because they provide an opportunity to study the mechanisms that link micro- and macroevolution. The role of ecological speciation during adaptive radiation has been intensively studied, but radiations can arise from a diversity of evolutionary processes; in particular, on large continental landmasses where allopatric speciation might frequently precede ecological differentiation. It is therefore important to establish a phylogenetic and ecological framework for recent continental-scale radiations that are species-rich and ecologically diverse. Here, we use a genomic (approx. 1 200 loci, exon capture) approach to fit branch lengths on a summary-coalescent species tree and generate a time-calibrated phylogeny for a recent and ecologically diverse radiation of Australian scincid lizards; the genus Cryptoblepharus. We then combine the phylogeny with a comprehensive phenotypic dataset for over 800 individuals across the 26 species, and use comparative methods to test whether habitat specialization can explain current patterns of phenotypic variation in ecologically relevant traits. We find significant differences in morphology between species that occur in distinct environments and convergence in ecomorphology with repeated habitat shifts across the continent. These results suggest that isolated analogous habitats have provided parallel ecological opportunity and have repeatedly promoted adaptive diversification. By contrast, speciation processes within the same habitat have resulted in distinct lineages with relatively limited morphological variation. Overall, our study illustrates how alternative diversification processes might have jointly stimulated species proliferation across the continent and generated a remarkably diverse group of Australian lizards.
Data from: Discovery of a giant chameleon-like lizard (Anolis) on Hispaniola and its significance to understanding replicated adaptive radiations
We report a new chameleon-like Anolis species from Hispaniola that is ecomorphologically similar to congeners found only on Cuba. Lizards from both clades possess short limbs and a short tail and utilize relatively narrow perches, leading us to recognize a novel example of ecomorphological matching among islands in the well-known Greater Antillean anole radiation. This discovery supports the hypothesis that the assembly of island faunas can be substantially deterministic and highlights the continued potential for basic discovery to reveal new insights in well-studied groups. Restricted to a threatened band of midelevation transitional forest near the border of the Dominican Republic and Haiti, this new species appears to be highly endangered.
Data from: Herbivory promotes dental disparification and macroevolutionary dynamics in grunters (Teleostei: Terapontidae), a freshwater adaptive radiation
Trophic shifts into new adaptive zones have played major (although often conflicting) roles in reshaping the evolutionary trajectories of many lineages. We analyze data on diet, tooth, and oral morphology and relate these traits to phenotypic disparification and lineage diversification rates across the ecologically diverse Terapontidae, a family of Australasian fishes. In contrast to carnivores and most omnivores, which have retained relatively simple, ancestral caniniform tooth shapes, herbivorous terapontids appear to have evolved a variety of novel tooth shapes at significantly faster rates to meet the demands of plant-based diets. The evolution of herbivory prompted major disparification, significantly expanding the terapontid adaptive phenotypic continuum into an entirely novel functional morphospace. There was minimal support for our hypothesis of faster overall rates of integrated tooth shape, spacing, and jaw biomechanical evolution in herbivorous terapontids in their entirety, compared with other trophic strategies. There was, however, considerable support for accelerated disparification within a diverse freshwater clade containing a range of specialized freshwater herbivores. While the evolutionary transition to herbivorous diets has played a central role in terapontid phenotypic diversification by pushing herbivores toward novel fitness peaks, there was little support for herbivory driving significantly higher lineage diversification compared with background rates across the family.
Data from: Evolution of genetic variance during adaptive radiation
Genetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonisation of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits, and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation.
Data from: Iterative adaptive radiations of fossil canids show no evidence for diversity-dependent trait evolution
A long-standing hypothesis in adaptive radiation theory is that ecological opportunity constrains rates of phenotypic evolution, generating a burst of morphological disparity early in clade history. Empirical support for the early burst model is rare in comparative data, however. One possible reason for this lack of support is that most phylogenetic tests have focused on extant clades, neglecting information from fossil taxa. Here, I test for the expected signature of adaptive radiation using the outstanding 40-My fossil record of North American canids. Models implying time- and diversity-dependent rates of morphological evolution are strongly rejected for two ecologically important traits, body size and grinding area of the molar teeth. Instead, Ornstein–Uhlenbeck processes implying repeated, and sometimes rapid, attraction to distinct dietary adaptive peaks receive substantial support. Diversity-dependent rates of morphological evolution seem uncommon in clades, such as canids, that exhibit a pattern of replicated adaptive radiation. Instead, these clades might best be thought of as deterministic radiations in constrained Simpsonian subzones of a major adaptive zone. Support for adaptive peak models may be diagnostic of subzonal radiations. It remains to be seen whether early burst or ecological opportunity models can explain broader adaptive radiations, such as the evolution of higher taxa.
Data from: Identification of the notothenioid sister lineage illuminates the biogeographic history of an Antarctic adaptive radiation
Background: Antarctic notothenioids are an impressive adaptive radiation. While they share recent common ancestry with several species-depauperate lineages that exhibit a relictual distribution in areas peripheral to the Southern Ocean, an understanding of their evolutionary origins and biogeographic history is limited as the sister lineage of notothenioids remains unidentified. The phylogenetic placement of notothenioids among major lineages of perciform fishes, which include sculpins, rockfishes, sticklebacks, eelpouts, scorpionfishes, perches, groupers and soapfishes, remains unresolved. We investigate the phylogenetic position of notothenioids using DNA sequences of 10 protein coding nuclear genes sampled from more than 650 percomorph species. The biogeographic history of notothenioids is reconstructed using a maximum likelihood method that integrates phylogenetic relationships, estimated divergence times, geographic distributions and paleogeographic history. Results: Percophis brasiliensis is resolved, with strong node support, as the notothenioid sister lineage. The species is endemic to the subtropical and temperate Atlantic coast of southern South America. Biogeographic reconstructions imply the initial diversification of notothenioids involved the western portion of the East Gondwanan Weddellian Province. The geographic disjunctions among the major lineages of notothenioids show biogeographic and temporal correspondence with the fragmentation of East Gondwana. Conclusions: The phylogenetic resolution of Percophis requires a change in the classification of percomorph fishes and provides evidence for a western Weddellian origin of notothenioids. The biogeographic reconstruction highlights the importance of the geographic and climatic isolation of Antarctica in driving the radiation of cold-adapted notothenioids.
Data from: Are the radiations of temperate lineages in tropical alpine ecosystems pre-adapted?
Aim: Tropical mountains around the world harbour an extraordinarily rich pool of plant species and are hotspots of biodiversity. Climatically, they can be zoned into montane climates at mid-altitudes and tropical alpine climates above the tree line. Around half of the tropical alpine species belong to plant lineages with a temperate ancestry, although these regions are often geographically distant. We test the hypothesis that these temperate lineages are pre-adapted to the tropical alpine climate. Location: New World, with a focus on tropical alpine Andes. Time period: Miocene to present. Major taxa studied: Flowering plants. Methods: We build multidimensional environmental models representing the full space of New World climates. We quantify the environmental similarity between the tropical alpine ecosystem and those of potential source areas, while correcting for regional differences by kernel density smoothers. Based on spatial observations of the genus Hypericum (St John's Wort), we quantify niche overlap and test for niche conservatism following intercontinental dispersal using density-weighted nonparametric tests. A dated species tree, biogeographical estimation, multi-optima Ornstein–Uhlenbeck models and model selection approaches are used to test for niche shifts during establishment in the tropical alpine Andes. Results: The tropical alpine ecosystem is isolated by its climate from adjacent regions and is climatically similar to temperate lowland biomes of both hemispheres. Niche conservatism is evident in the study group, except in the tropical alpine lineage that is characterized by niche expansion and shifts in temperature optima. Main conclusions: Our results reject the pre-adaptation hypothesis and instead suggest pronounced niche evolution during colonization of tropical alpine ecosystems. Establishment involved substantial niche shifts, mainly in temperature-related variables, and resulted in a tremendous proliferation of species in the newly invaded tropical alpine ecosystem.
Data from: Ecological and evolutionary determinants for the adaptive radiation of the Madagascan vangas
Adaptive radiation is the rapid diversification of a single lineage into many species that inhabit a variety of environments or use a variety of resources and differ in traits required to exploit these. Why some lineages undergo adaptive radiation is not well-understood, but filling unoccupied ecological space appears to be a common feature. We construct a complete, dated, species-level phylogeny of the endemic Vangidae of Madagascar. This passerine bird radiation represents a classic, but poorly known, avian adaptive radiation. Our results reveal an initial rapid increase in evolutionary lineages and diversification in morphospace after colonizing Madagascar in the late Oligocene some 25 Mya. A subsequent key innovation involving unique bill morphology was associated with a second increase in diversification rates about 10 Mya. The volume of morphospace occupied by contemporary Madagascan vangas is in many aspects as large (shape variation)—or even larger (size variation)—as that of other better-known avian adaptive radiations, including the much younger Galapagos Darwin's finches and Hawaiian honeycreepers. Morphological space bears a close relationship to diet, substrate use, and foraging movements, and thus our results demonstrate the great extent of the evolutionary diversification of the Madagascan vangas.
Data from: Intraspecific adaptive radiation: competition, ecological opportunity, and phenotypic diversification within species
Intraspecific variation in resource-use traits can have profound ecological and evolutionary implications. Among the most striking examples are resource polymorphisms, where alternative morphs that utilize different resources evolve within a population. An underappreciated aspect of their evolution is that the same conditions that favor resource polymorphism—competition and ecological opportunity—might foster additional rounds of diversification within already existing morphs. We examined these issues in spadefoot toad tadpoles that develop into either a generalist 'omnivore' or a specialist 'carnivore' morph. Specifically, we assessed the morphological diversity of tadpoles from natural ponds and experimentally induced carnivores reared on alternative diets. We also surveyed natural ponds to determine if the strength of intramorph competition and the diversity and abundance of dietary resources (measures of ecological opportunity) influenced the diversity of within-morph variation. We found that five omnivore and four carnivore types were present in natural ponds; alternative diets led to shape differences, some of which mirrored variation in the wild; and both competition and ecological opportunity were associated with enhanced morphological diversity in natural ponds. Such fine-scale intraspecific variation might represent an underappreciated form of biodiversity and might constitute a crucible of evolutionary innovation and diversification.
Data from: Diversity and disparity through time in the adaptive radiation of Antarctic notothenioid fishes
According to theory, adaptive radiation is triggered by ecological opportunity that can arise through the colonization of new habitats, the extinction of antagonists or the origin of key innovations. In the course of an adaptive radiation, diversification and morphological evolution are expected to slow down after an initial phase of rapid adaptation to vacant ecological niches, followed by speciation. Such 'early bursts' of diversification are thought to occur because niche space becomes increasingly filled over time. The diversification of Antarctic notothenioid fishes into over 120 species has become one of the prime examples of adaptive radiation in the marine realm and has likely been triggered by an evolutionary key innovation in the form of the emergence of antifreeze glycoproteins. Here, we test, using a novel time-calibrated phylogeny of 49 species and five traits that characterize notothenioid body size and shape as well as buoyancy adaptations and habitat preferences, whether the notothenioid adaptive radiation is compatible with an early burst scenario. Extensive Bayesian model comparison shows that phylogenetic age estimates are highly dependent on model choice and that models with unlinked gene trees are generally better supported and result in younger age estimates. We find strong evidence for elevated diversification rates in Antarctic notothenioids compared to outgroups, yet no sign of rate heterogeneity in the course of the radiation, except that the notothenioid family Artedidraconidae appears to show secondarily elevated diversification rates. We further observe an early burst in trophic morphology, suggesting that the notothenioid radiation proceeds in stages similar to other prominent examples of adaptive radiation.
Data from: Rapid Pliocene adaptive radiation of modern kangaroos
Differentiating between ancient and younger, more rapidly evolved clades is important for determining paleoenvironmental drivers of diversification. Australia possesses many aridity-adapted lineages, the origins of which have been closely linked to late Miocene continental aridification. Using dental macrowear and molar crown height measurements, spanning the past 25 million years, we show that the most iconic Australian terrestrial mammals, "true" kangaroos (Macropodini), adaptively radiated in response to mid-Pliocene grassland expansion rather than Miocene aridity. In contrast, low-crowned, short-faced kangaroos radiated into predominantly browsing niches as the late Cenozoic became more arid, contradicting the view that this was an interval of global browser decline. Our results implicate warm-to-cool climatic oscillations as a trigger for adaptive radiation and refute arguments attributing Pleistocene megafaunal extinction to aridity-forced dietary change.
Data from: Novel trophic niches drive variable progress toward ecological speciation within an adaptive radiation of pupfishes
Adaptive radiation is recognized by a rapid burst of phenotypic, ecological, and species diversification. However, it is unknown whether different species within an adaptive radiation evolve reproductive isolation at different rates. We compared patterns of genetic differentiation among nascent species within an adaptive radiation of Cyprinodon pupfishes using genotyping by sequencing. Similar to classic adaptive radiations, this clade exhibits rapid morphological diversification rates and two species are novel trophic specialists, a scale-eater and hard-shelled prey specialist (durophage), yet the radiation is less than 10,000 years old. Both specialists and an abundant generalist species all coexist in the benthic zone of lakes on San Salvador Island, Bahamas. Based on 13,912 single-nucleotide polymorphisms (SNPs), we found consistent differences in genetic differentiation between each specialist species and the generalist across seven lakes. The scale-eater showed the greatest genetic differentiation and clustered by species across lakes, whereas durophage populations often clustered with sympatric generalist populations, consistent with parallel speciation across lakes. However, we found strong evidence of admixture between durophage populations in different lakes, supporting a single origin of this species and genome-wide introgression with sympatric generalist populations. We conclude that the scale-eater is further along the speciation-with-gene-flow continuum than the durophage and suggest that different adaptive landscapes underlying these two niche environments drive variable progress toward speciation within the same habitat. Our previous measurements of fitness surfaces in these lakes support this conclusion: the scale-eating fitness peak may be more distant than the durophage peak on the complex adaptive landscape driving adaptive radiation.
Data from: Spatial storage effect promotes biodiversity during adaptive radiation
Many ecological communities are enormously diverse. Variation in environmental conditions over time and space provides opportunities for temporal and spatial storage effects to operate, potentially promoting species coexistence and biodiversity. While several studies have provided empirical evidence supporting the significance of the temporal storage effect for coexistence, empirical tests of the role of the spatial storage effect are rare. In particular, we know little about how the spatial storage effect contributes to biodiversity over evolutionary timescales. Here, we report the first experimental study on the role of the spatial storage effect in the maintenance of biodiversity in evolving metacommunities, using the bacterium Pseudomonas fluorescens SBW25 as a laboratory model of adaptive radiation. We found that intercommunity spatial heterogeneity promoted phenotypic diversity of P. fluorescens in the presence of dispersal among local communities, by allowing the spatial storage effect to operate. Mechanistically, greater niche differences among P. fluorescens phenotypes arose in metacommunities with intercommunity spatial heterogeneity, facilitating negative frequency-dependent selection, and thus, the coexistence among P. fluorescens phenotypes. These results highlight the importance of the spatial storage effect for biodiversity over evolutionary timescales.
Local adaptation of a parasite to solar radiation impacts disease transmission potential, spore yield, and host fecundity
<p>Environmentally transmitted parasites spend time in the abiotic environment, where they are subjected to a variety of stressors. Understanding how they face this challenge is essential if we are to understand how host-parasite interactions may vary across environmental gradients. We used a zooplankton-bacteria host-parasite system where availability of sunlight (solar radiation) influences disease dynamics to look for evidence of parasite local adaptation to sunlight exposure. We also examined how variation in sunlight tolerance among parasite strains impacted host reproduction. Parasite strains collected from clearer lakes (with greater sunlight penetration) were most tolerant of the negative impacts of sunlight exposure, suggesting local adaptation to sunlight conditions. This adaptation came with both a cost and a benefit for parasites: parasite strains from clearer lakes produced relatively fewer transmission stages (spores) but these strains were more infective. After experimental sunlight exposure, the most sunlight-tolerant parasite strains reduced host fecundity just as much as spores that were never exposed to sunlight. Sunlight availability varies greatly among lakes around the world. Our results suggest that the selective pressure sunlight exposure exerts on parasites may impact both parasite and host fitness, potentially driving variation in disease epidemics and host population dynamics across sunlight availability gradients. </p>
Data from: When are adaptive radiations replicated in areas? Ecological opportunity and unexceptional diversification in West Indian dipsadine snakes (Colubridae: Alsophiini)
AIM: We examine diversification in Caribbean alsophiine snakes and hypothesize that, given ecological opportunity presented by colonizing the West Indies, alsophiines should show the signature of an early burst of diversification and associated low-within clade ecological and morphological disparification. We also test if changes in morphology or ecology are associated with changes in diversification rate, as trait-dependent diversification is hypothesized to affect historical inferences of diversification and disparification. Finally, as replicated radiations are found across the West Indies in the anoles, we test for significant differences in ecological and morphological assemblages and rates among the major island groups. LOCATION: The West Indies. METHODS: A time-calibrated phylogeny produced from six genes using relaxed clock methods in BEAST was constructed to examine ancestral area using LAGRANGE. Maximum body size and ecological niche were scored for all species in the phylogeny, and comparative phylogenetic methods in R using GEIGER, LASER, APE and our own code were used to examine diversification through time, disparification and trait-dependent diversification from this dated phylogeny. RESULTS: The pattern of species diversification did not differ significantly from the Yule model of diversification. Morphology and ecology fit a Brownian and white noise model of diversification, respectively. Although not significantly different, morphological disparification was lower than the Brownian null model, whereas ecological disparification was significantly greater than the null. Trait-dependent diversification analyses suggested that the constant null models provided the best fit to these data. There was no significant signal of rate variation among the major island groups for size, but moderate evidence for niche. MAIN CONCLUSIONS: Although ecological opportunity was similarly present for alsophiines as it was for anoles, the snakes fail to show an early burst of speciation. Potential reasons for this include the young age of the group, and staggered diversification due to waiting times between island colonization. In turn, ecological and morphological disparity do not necessarily follow predictable patterns related to species diversification. Thus, the presence of ecological opportunity alone is not necessarily sufficient to trigger replicated adaptive radiations in areas.
Figure 1 in Adaptive Radiation in Socially Advanced Stem-Group Ants from the Cretaceous
Figure 1. Social Assemblages of Cretaceous Worker Ants (A–F) Top: photomicrograph of entire piece of JZC Bu1814, with detailed views of its six workers of Gerontoformica spiralis. The 0 to 180 axis was used to measure orientations of the ants. Bottom: JZC Bu116 sections A and B, containing 12 worker ants (labeled A–L). Bottom left: photomicrographs of entire piece with two sections fitting together as in the original resin flow. Bottom right: CT scans, with 10 of the 11 Gerontoformica spiralis workers in orange and one Haidomyrmex zigrasi Barden and Grimaldi in blue (one G. spiralis worker, labeled B, was not recovered by X-ray imaging); red arrows indicate orientation of body axis. The large insect is a roach. See also Figure S1.
Figure 4 in Adaptive Radiation in Socially Advanced Stem-Group Ants from the Cretaceous
Figure 4. PCA Plot of Exemplar Living and Cretaceous Ant Workers and Assemblage of Mouthpart Diversity in Cretaceous Stem-Group Ants Top: generated by PCA analysis (PC1 96% and PC2 3% of variance) of four body proportions of 107 living species in 96 genera and 19 Cretaceous species in five genera. For data and analyses see Supplemental Information. Gray and black lines circumscribe living and Cretaceous morphospace, respectively. Body shapes and sizes of six living and extinct exemplar species are presented to same scale, with the exception of the minute ants Carebara and Zigrasimecia (which are greatly enlarged). Bottom: a summary of diversity and homology among Cretaceous stem-group ant mouthparts. Note that not all structures are preserved in known specimens of Sphecomyrma freyi, S. mesaki, and Myanmyrma gracilis, and, therefore, some components are missing. See also Figures S2 and S3.
Figure 2 in Adaptive Radiation in Socially Advanced Stem-Group Ants from the Cretaceous
Figure 2. Workers of Two Species of Gerontoformica in Burmese Amber, G. tendir and G. spiralis, Captured while Fighting Specimen JZC Bu1646. (A) Photomicrograph of entire specimens. (B) Photomicrographic detail of interaction. (C) Illustration of anterior portion of specimens, clarifying positions of appendages.
Passively Adaptive Radiative Switch for Thermoregulation in Buildings
<p>Data and codes for the journal article "Passively Adaptive Radiative Switch for Thermoregulation in Buildings" in <em>Device. </em>DOI: 10.1016/j.device.2023.100186</p> <p>Version v2 added the CAD file (Data S1.STEP).</p>
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