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144 results for “Speciation: ecological”
Data from: Selection and genomic differentiation during ecological speciation: isolating the contributions of host association via a comparative genome scan of Neochlamisus bebbianae leaf beetles
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Data from: Thermal selection as a driver of marine ecological speciation
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Data from: Assortative flocking in crossbills and implications for ecological speciation
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Evidence for ecological processes driving speciation among endemic lizards of Madagascar
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Data from: Ecology and sexual selection: evolution of wing pigmentation in calopterygid damselflies in relation to latitude, sexual dimorphism and speciation
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Data from: Complex trait divergence contributes to environmental niche differentiation in ecological speciation of Boechera stricta
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Data from: Ecological speciation in sympatric palms: 3. genetic map reveals genomic islands underlying species divergence in Howea
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Data from: The role of ecology in allopatric speciation of darters in the Central Highlands, USA
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Data from: Ecological speciation in sympatric palms: 4. Demographic analyses support speciation of Howea in the face of high gene flow
The idea that populations must be geographically isolated (allopatric) to evolve into separate species has persisted for a long time. It is now clear that new species can also diverge despite ongoing genetic exchange, but few accepted cases of speciation in sympatry have held up when scrutinised using modern approaches. Here, we examined evidence for speciation of the Howea palms of Lord Howe Island, Australia, in light of new genomic data. We used coalescence-based demographic models combined with double digest restriction-site associated DNA sequencing of multiple individuals and provide support for previous claims by Savolainen et al. (Nature 441: 210–213, 2006) that speciation in Howea did occur in the face of gene flow.
Data from: A high frequency of allopolyploid speciation in the gymnospermous genus Ephedra and its possible association with some biological and ecological features
The origin and evolution of polyploids have been studied extensively in angiosperms and ferns but very rarely in gymnosperms. With the exception of three species of conifers, all natural polyploid species of gymnosperms belong to Ephedra, in which more than half of the species show polyploid cytotypes. Here we investigate the origin and evolution of polyploids of Ephedra distributed in the Qinghai-Tibetan Plateau (QTP) and neighboring areas. Flow cytometry (FCM) was used to measure the ploidy levels of the sampled species that are represented by multiple individuals from different populations, and then two single-copy nuclear genes (LFY and DDB2) and two chloroplast DNA fragments were used to unravel the possible origins and maternal donors of the polyploids. The results indicate that the studied polyploid species are allopolyploids, and suggest that allotetraploidy is a dominant mode of speciation in Ephedra. The high percentage of polyploids in the genus could be related to some of its biological attributes such as vegetative propagation, a relatively high rate of unreduced gamete formation, and a small genome size relative to most other gymnosperms. Significant ecological divergences between allotetraploids and their putative progenitors were detected by PCA analyses and ANOVA and Tukey's tests, with the exception of E. saxatilis. The overlap of geographical distributions and ecological niches of some diploid species could have provided opportunities for interspecific hybridization and allopolyploid speciation.
Data from: The contribution of post-copulatory mechanisms to incipient ecological speciation in sticklebacks
Ecology can play a major role in species diversification. As individuals are adapting to contrasting habitats, reproductive barriers may evolve at multiple levels. While pre-mating barriers have been extensively studied, the evolution of post-mating reproductive isolation during early stages of ecological speciation remains poorly understood. In diverging three-spined stickleback ecotypes from two lakes and two rivers, we observed differences in sperm traits between lake and river males. Interestingly, these differences did not translate into ecotype-specific gamete precedence for sympatric males in competitive in vitro fertilization experiments, potentially owing to antagonistic compensatory effects. However, we observed indirect evidence for impeded development of inter-ecotype zygotes, possibly suggesting an early stage of genetic incompatibility between ecotypes. Our results show that pre-zygotic post-copulatory mechanisms play a minor role during this first stage of ecotype divergence, but suggest that genetic incompatibilities may arise at early stages of ecological speciation.
Data from: The role of local ecology during hybridisation at the initial stages of ecological speciation in a marine snail
Hybrid zones of ecologically divergent populations are ideal systems to study the interaction between natural selection and gene flow during the initial stages of speciation. Here we perform an AFLP genome scan in parallel hybrid zones between divergent ecotypes of the marine snail Littorina saxatilis, which is considered a model case for the study of ecological speciation. RB (Ridged-Banded) and SU (Smooth-Unbanded) ecotypes are adapted to different shore levels and microhabitats, although they present a sympatric distribution at the mid-shore where they meet and mate (partially assortatively). We used shell morphology, outlier and non-outlier AFLP loci from RB, SU and hybrid specimens captured in sympatry to determine the level of phenotypic and genetic introgression. We found different levels of introgression at parallel hybrid zones and non-outlier loci showed more gene flow with greater phenotypic introgression. These results were independent from the phylogeography of the studied populations, but not from the local ecological conditions. Genetic variation at outlier loci was highly correlated with phenotypic variation. In addition, we used the relationship between genetic and phenotypic variation to estimate the heritability of morphological traits and to identify potential QTLs to be confirmed in future crosses. These results suggest that ecology (exogenous selection) plays an important role in this hybrid zone. Thus, ecologically-based divergent natural selection is responsible, simultaneously, for both ecotype divergence and hybridisation. On the other hand, genetic introgression occurs only at neutral loci (non-outliers). In the future, genome-wide studies and controlled crosses would give more valuable information about this process of speciation in the face of gene flow.
Data from: Emergence of novel fungal pathogens by ecological speciation: importance of the reduced viability of immigrants
Expanding global trade and the domestication of ecosystems have greatly accelerated the rate of emerging infectious fungal diseases, and host-shift speciation appears to be a major route for disease emergence. There is therefore an increased interest in identifying the factors that drive the evolution of reproductive isolation between populations adapting to different hosts. Here, we used genetic markers and cross-inoculations to assess the level of gene flow and investigate barriers responsible for reproductive isolation between two sympatric populations of Venturia inaequalis, the fungal pathogen causing apple scab disease, one of the fungal populations causing a recent emerging disease on resistant varieties. Our results showed the maintenance over several years of strong and stable differentiation between the two populations in the same orchards, suggesting ongoing ecological divergence following a host-shift. We identified strong selection against immigrants (i.e. host-specificity) from different host varieties as the strongest and likely most efficient barrier to gene flow between local and emerging populations. Cross-variety disease transmission events were indeed rare in the field and cross-inoculation tests confirmed high host specificity. Because the fungus mates within its host after successful infection and because pathogenicity-related loci prevent infection of non-host trees, adaptation to specific hosts may alone maintain both genetic differentiation between and adaptive allelic combinations within sympatric populations parasitizing different apple varieties, thus acting as a "magic trait". Additional intrinsic and extrinsic post-zygotic barriers might complete reproductive isolation and explain why the rare migrants and F1 hybrids detected do not lead to pervasive gene flow across years.
Data from: On the Coyne and Orr-igin of species: effects of intrinsic postzygotic isolation, ecological differentiation, X-chromosome size, and sympatry on Drosophila speciation
Coyne and Orr found that mating discrimination (premating isolation) evolves much faster between sympatric than allopatric Drosophila species pairs. Their meta-analyses established that this pattern, expected under reinforcement, is common and that Haldane's rule is ubiquitous in Drosophila species divergence. We examine three possible contributors to the reinforcement pattern: intrinsic postzygotic isolation, dichotomized as to whether hybrid males show complete inviability/sterility; host-plant divergence, as a surrogate for extrinsic postzygotic isolation; and X chromosome size, whether roughly 20% or 40% of the genome is X-linked. We focus on "young" species pairs with overlapping ranges, contrasted with allopatric pairs. Using alternative criteria for "sympatry" and tests that compare either level of prezygotic isolation in sympatry or frequency of sympatry, we find no statistically significant effects associated with X chromosome size or our coarse quantifications of intrinsic postzygotic isolation or ecological differentiation. Although sympatric speciation seems very rare in animals, the pervasiveness of the reinforcement pattern and the commonness of range overlap for close relatives indicate that speciation in Drosophila is often not purely allopatric. It remains to determine whether increased premating isolation with sympatry results from secondary contact versus parapatric speciation and what drives this pattern.
Data from: Mate choice in sticklebacks reveals that immunogenes can drive ecological speciation
Adaptation to ecologically contrasting niches can lead to the formation of new species. Theoretically, this process of ecological speciation can be driven by pleiotropic "magic traits" that genetically link natural and sexual selection. To qualify as a true magic trait, the pleiotropic function of a gene must be reflected in biologically relevant mechanisms underlying both local adaptation and mate choice. The immune genes of the major histocompatibility complex (MHC) contribute to parasite resistance and also play a major role in sexual selection. Hence, the MHC may encode a candidate magic trait. Using diverging 3-spined stickleback populations from a connected lake–river habitat, we show with mate choice experiments in a flow channel that polymorphic MHC genes probably underlie assortative mating with respect to particular habitat-adapted ecotypes, potentially resulting in reproductive isolation. By manipulating olfactory cues in controlled experiments, we show that female sticklebacks employ MHC-dependent male olfactory signals to select mates with which they can achieve a habitat-specific MHC gene structure that optimally protects their offspring against local parasites. By using MHC-based olfactory signals, females thus select individuals of their own population as mates. Our results demonstrate how mate choice and parasite resistance may be functionally linked. These findings suggest that MHC genes are pleiotropic and encode a true magic trait of biologically significant effect.
Data from: A recombination suppressor contributes to ecological speciation in Ostrinia moths
Despite unparalleled access to species' genomes in our post-genomic age, we often lack adequate biological explanations for a major hallmark of the speciation process—genetic divergence. In the presence of gene flow, chromosomal rearrangements such as inversions are thought to promote divergence and facilitate speciation by suppressing recombination. Using a combination of genetic crosses, phenotyping of a trait underlying ecological isolation, and population genetic analysis of wild populations, we set out to determine whether evidence supports a role for recombination suppressors during speciation between the Z and E strains of European corn borer moth (Ostrinia nubilalis). Our results are consistent with the presence of an inversion that has contributed to accumulation of ecologically adaptive alleles and genetic differentiation across roughly 20% of the Ostrinia sex chromosome (~4 Mb). Patterns in Ostrinia suggest that chromosomal divergence may involve two separate phases—one driving its transient origin through local adaptation and one determining its stable persistence through differential introgression. As the evolutionary rate of rearrangements in lepidopteran genomes appears to be one of the fastest among eukaryotes, structural mutations may have had a disproportionate role during adaptive divergence and speciation in Ostrinia and in other moths and butterflies.
Data from: Host-jump drives rapid and recent ecological speciation of the emergent fungal pathogen Colletotrichum kahawae
Ecological speciation through host-shift has been proposed as a major route for the appearance of novel fungal pathogens. The growing awareness of their negative impact on global economies and public health created an enormous interest in identifying the factors that are most likely to promote their emergence in nature. In this work, a combination of pathological, molecular and geographic data was used to investigate the recent emergence of the fungus Colletotrichum kahawae (Ck). Ck emerged as a specialist pathogen causing Coffee Berry Disease in Coffea arabica, due to its unparalleled adaptation of infecting green coffee berries. Contrary to current hypotheses, our results suggest that a recent host-jump underlay the speciation of Ck from a generalist group of fungi seemingly harmless to coffee berries. We posit that immigrant inviability and a predominantly asexual behavior could have been instrumental in driving speciation by creating pleiotropic interactions between local adaptation and reproductive patterns. Moreover, we estimate that Ck began its diversification at less than 2,200 yrs leaving a very short time frame since the divergence from its sibling lineage (∼5,600 yrs), during which a severe drop in Ck's effective population size occurred. This further supports a scenario of recent introduction and subsequent adaptation to C. arabica. Phylogeographic data revealed low levels of genetic polymorphism but provided the first geographically consistent population structure of Ck, inferring the Angolan population as the most ancestral and the East African populations as the most recently derived. Altogether, these results highlight the significant role of host specialization and asexuality in the emergence of fungal pathogens through ecological speciation.
Data from: Ecological speciation in dynamic landscapes
Although verbal theories of speciation consider landscape changes, ecological speciation is usually modeled in a fixed geographical arrangement. Yet landscape changes occur, at different spatio-temporal scales, due to geological, climatic or ecological processes, and these changes result in repeated divisions and reconnections of populations. We examine the effect of such landscape dynamics on speciation. We use a stochastic, sexual population model with polygenic inheritance, embedded in a landscape dynamics model (allopatry-sympatry oscillations). We show that, under stabilizing selection, allopatry easily generates diversity, but species coexistence is evolutionarily unsustainable. Allopatry produces refuges whose persistence depends on the characteristic time scales of the landscape dynamics. Under disruptive selection, assuming that sympatric speciation is impossible due to Mendelian inheritance, allopatry is necessary for ecological differentiation. The completion of reproductive isolation, by reinforcement, then requires several sympatric phases. These results demonstrate that the succession of past, current and future geographical arrangements considerably influence the speciation process.
Data from: A question of time: the land snail Murella muralis (Gastropoda: Pulmonata) reveals constrains to past ecological speciation
The lively debate about speciation currently focuses on the relative importance of factors driving population differentiation. While many studies are increasingly producing results on the importance of selection, little is known about the interaction between drift and selection. Moreover there is still little knowledge on the spatial-temporal scales at which speciation occurs, i.e. arrangement of habitat patches, abruptness of habitat transitions, climate and habitat changes interacting with selective forces. To investigate these questions, we quantified variation on a fine geographical scale analysing morphological (shell) and genetic datasets coupled with environmental data in the land snail Murella muralis, endemic to the Mediterranean island of Sicily. Analysis of a fragment of the mitochondrial DNA Cytochrome Oxidase I gene (COI) and eight nuclear microsatellite loci showed that genetic variation is highly structured at a very fine spatial scale by local palaeogeographical events and historical population dynamics. Molecular clock estimates, calibrated here specifically for Tyrrhenian land snails, provided a framework of palaeogeographical events responsible for the observed geographical variations and migration routes. Finally, we showed for the first time well documented lines of evidences of selection in the past, which explains divergence of land snail shell shapes. We suggest that time and palaeogeographical history acted as constraints in the progress along the ecological speciation continuum. Our study shows that testing for correlation among palaeogeography, morphology and genetic data on a fine geographical scale provides information fundamental for a detailed understanding of ecological speciation processes.
Data from: Speciation, ecological opportunity, and latitude
Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciation rates are currently highest in the temperate zone, and that diversification rates (speciation minus extinction) are similar between latitudes. In contrast, clades whose oldest analyzed dates precede the Eocene thermal maximum, when the extent of the tropics was much greater than today, tend to show highest speciation and diversification rates in the tropics. These findings are consistent with age and area, which is alone among hypotheses in predicting a time trend. Higher recent speciation rates in the temperate zone than the tropics suggest an additional response to high ecological opportunity associated with low species diversity. These broad patterns are compelling but provide limited insights into underlying mechanisms, arguing that studies of speciation processes along the latitudinal gradient will be vital. Using threespine stickleback in depauperate northern lakes as an example, I show how high ecological opportunity can lead to rapid speciation. The results support a role for ecological opportunity in speciation, but its importance in the evolution of the latitudinal gradient remains uncertain. I conclude that per-capita evolutionary rates are no longer higher in the tropics than the temperate zone. Nevertheless, the vast numbers of species that have already accumulated in the tropics ensure that total rate of species production remains highest there. Thus, "tropical evolutionary momentum" helps to perpetuate the steep latitudinal biodiversity gradient. 28 pages, 4 figures; Supplement EndDryadContent
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.