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175 results for “ecological divergence”
Genomics of extreme ecological specialists: multiple convergent evolution but no genetic divergence between ecotypes of Maculinea alcon butterflies
<p>Biotic interactions are often acknowledged as catalysers of genetic divergence and eventual explanation of processes driving species richness. We address the question, whether extreme ecological specialization is always associated with lineage sorting, by analysing polymorphisms in morphologically similar ecotypes of the myrmecophilous butterfly <em>Maculinea alcon</em>. The ecotypes occur in either hygric or xeric habitats, use different larval host plants and ant species, but no significant distinctive molecular traits have been revealed so far. We apply genome-wide RAD-sequencing to specimens originating from both habitats across Europe in order to get a view of the potential evolutionary processes at work. Our results confirm that genetic variation is mainly structured geographically but not ecologically — specimens from close localities are more related to each other than populations of each ecotype from distant localities. However, we found two loci for which the association with xeric versus hygric habitats is supported by segregating alleles, suggesting convergent evolution of habitat preference. Thus, ecological divergence between the forms probably does not represent an early stage of speciation, but may result from independent recurring adaptations involving few genes. We discuss the implications of these results for conservation and suggest preserving biotic interactions and main genetic clusters.</p>
Data from: Can the genomics of ecological speciation be predicted across the divergence continuum from host races to species? A case study in Rhagoletis
<p>Studies assessing the predictability of evolution typically focus on short-term adaptation within populations or the repeatability of change among lineages. A missing consideration in speciation research is to determine whether natural selection predictably transforms standing genetic variation within populations into differences between species. Here, we test whether host-related selection on diapause timing anticipates genome-wide differentiation during ecological speciation by comparing ancestral hawthorn and newly formed apple-infesting host races of <i>Rhagoletis pomonella </i>to their sibling species <i>R. mendax</i> that attacks blueberries. The responses of 57,857 single nucleotide polymorphisms in a diapause study on the hawthorn race strongly predicted the direction and magnitude of genomic divergence among the three flies at a field site in Fennville, Michigan, USA. As anticipated, the apple race and <i>R. mendax</i> show parallel changes in the frequencies of putative inversions on three chromosomes associated with the earlier fruiting times of apples and blueberries compared to hawthorns. A diapause experiment on <i>R. mendax</i> revealed compensatory mutations throughout the genome accounting for the earlier eclosion of blueberry, but not apple flies. Thus, a degree of predictability, although not complete, exists in the genomics of diapause across the ecological speciation continuum in <i>Rhagoletis</i>. The generality of this result is placed in the context of other similar systems.</p>
Data from: Gene flow, ancient polymorphism, and ecological adaptation shape the genomic landscape of divergence among Darwin's finches
Genomic comparisons of closely related species have identified "islands" of locally elevated sequence divergence. Genomic islands may contain functional variants involved in local adaptation or reproductive isolation and may therefore play an important role in the speciation process. However, genomic islands can also arise through evolutionary processes unrelated to speciation, and examination of their properties can illuminate how new species evolve. Here, we performed scans for regions of high relative divergence (FST) in 12 species pairs of Darwin's finches at different genetic distances. In each pair, we identify genomic islands that are, on average, elevated in both relative divergence (FST) and absolute divergence (dXY). This signal indicates that haplotypes within these genomic regions became isolated from each other earlier than the rest of the genome. Interestingly, similar numbers of genomic islands of elevated dXY are observed in sympatric and allopatric species pairs, suggesting that recent gene flow is not a major factor in their formation. We find that two of the most pronounced genomic islands contain the ALX1 and HMGA2 loci, which are associated with variation in beak shape and size, respectively, suggesting that they are involved in ecological adaptation. A subset of genomic island regions, including these loci, appears to represent anciently diverged haplotypes that evolved early during the radiation of Darwin's finches. Comparative genomics data indicate that these loci, and genomic islands in general, have exceptionally low recombination rates, which may play a role in their establishment.
Sensory weighting reflects changing patterns of visual investment during ecological divergence in Heliconius butterflies
<p>Integrating information across sensory modalities enables animals to orchestrate a wide range of complex behaviours. The relative importance placed on one sensory modality over another reflects the reliability of cues in a particular environment and corresponding differences in neural investment. As populations diverge across environmental gradients, the reliability of sensory cues may shift, favouring divergence in neural investment and sensory weighting. During their divergence across closed-forest and forest-edge habitats, <em>Heliconius </em>butterflies <em>H. cydno</em> and <em>H. melpomene </em>evolved distinct brain morphologies, with the former<em> </em>investing more in vision. Molecular and anatomical data suggest selection drove these changes, but their behavioural effects remain uncertain. We hypothesised that divergent investment in neuropils may alter sensory weighting during behavioural tasks. To address this, we trained individuals in an associative learning experiment using multimodal colour and odour cues. When positively rewarded stimuli were presented in conflict pairing positively trained colour with negatively trained odour, and vice-versa, <em>H. cydno</em> prioritised visual cues more strongly than <em>H. melpomene</em>. Hence, differences in sensory weighting may evolve early during divergence and are predicted by patterns of neural investment. These findings, alongside other examples, imply that differences in sensory weighting stem from sensory investment as adaptations to local sensory environments.</p>
Fig. 6. Divergence times estimated from a in Ecological and geographical speciation in Lucilia bufonivora: The evolution of amphibian obligate parasitism
Fig. 6. Divergence times estimated from a concatenated data set of per, COX1 and ITS2 sequences for the Lucilia bufornivora species group. Substitution model and relaxed clock models were unlinked for each gene. The tree was calibrated by setting the root to the node age corresponding to the split between Luciilinae and Calliphorinae subfamilies (~19 mya) as estimated by Wallman et al. (2005). Blue bars represent 95% highest posterior density (HPD) of each node age. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Data from: Gene flow, ancient polymorphism, and ecological adaptation shape the genomic landscape of divergence among Darwin's finches
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Data from: Ecological trait divergence over evolutionary time underlies the origin and maintenance of tropical spider diversity
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Data from: Can the genomics of ecological speciation be predicted across the divergence continuum from host races to species? A case study in Rhagoletis
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Weighting of sensory cues reflects changing patterns of visual investment during ecological divergence in Heliconius butterflies
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Data from: Change in sexual signalling traits outruns morphological divergence across an ecological gradient in the post‐glacial radiation of the songbird genus Junco
<p>The relative roles of natural and sexual selection in promoting evolutionary lineage divergence remains controversial and difficult to assess in natural systems. Local adaptation through natural selection is known to play a central role in promoting evolutionary divergence, yet secondary sexual traits can vary widely among species in recent radiations, suggesting that sexual selection may also be important in the early stages of speciation. Here we compare rates of divergence in ecologically relevant traits (morphology) and sexually selected signaling traits (coloration) relative to neutral structure in genome-wide molecular markers, and examine patterns of variation in sexual dichromatism to explore the roles of natural and sexual selection in the diversification of the songbird genus <i>Junco </i>(Aves: Passerellidae). Juncos include divergent lineages in Central America and several dark-eyed junco (<i>J. hyemalis</i>) lineages that diversified recently as the group recolonized North America following the last glacial maximum (c.a. 18,000 years ago). We found an accelerated rate of divergence in sexually selected characters relative to ecologically relevant traits. Moreover, sexual dichromatism measurements suggested a positive relationship between the degree of color divergence and the strength of sexual selection when controlling for neutral genetic distance. We also found a positive correlation between dichromatism and latitude, which coincides with the geographic axis of decreasing lineage age in juncos but also with a steep ecological gradient. Finally, we found significant associations between genome-wide variants linked to functional genes and proxies of both sexual and natural selection. These results suggest that the joint effects of sexual and ecological selection have played a prominent role in the junco radiation.</p>
Data from: The genomic signature of ecological divergence along the benthic-limnetic axis in allopatric and sympatric threespine stickleback
<p>The repeated occurrence of similar phenotypes in independent lineages (i.e., parallel evolution) in response to similar ecological conditions can provide compelling insights into the process of adaptive evolution. An intriguing question is to what extent repeated phenotypic changes are underlain by repeated changes at the genomic level and whether patterns of genomic divergence differ with the geographic context in which populations evolve. Here, we combine genomic, morphological and ecological datasets to investigate the genomic signatures of divergence across populations of threespine stickleback (<i>Gasterosteus aculeatus</i>) that adapted to contrasting ecological niches (benthic or limnetic) in either sympatry or allopatry. We found that genome-wide differentiation (F<sub>ST</sub>) was an order of magnitude higher and substantially more repeatable for sympatric benthic and limnetic specialists compared to allopatric populations with similar levels of ecological divergence. We identified genomic regions consistently differentiated between sympatric ecotypes that were also differentiated between or associated with benthic vs. limnetic niche in allopatric populations. These candidate regions were enriched on three chromosomes known to be involved in the benthic-limnetic divergence of threespine stickleback. Some candidate regions overlapped with QTL for body shape and trophic traits such as gill raker number, traits that strongly differ between benthic and limnetic ecotypes. In sum, our study shows that magnitude and repeatability of genomic signatures of ecological divergence in threespine stickleback highly depend on the geographic context. The identified candidate regions provide starting points to identify functionally important genes for the adaptation to benthic and limnetic niches.</p>
Data from: Correlated divergence of female and male genitalia in replicated lineages with ongoing ecological speciation
Divergence of genital traits among lineages has the potential to serve as a reproductive isolating barrier when copulation, insemination, or fertilization are inhibited by incompatibilities between female and male genitalia. Despite widespread evidence for genital trait diversity among closely related lineages and coevolution of female and male genitalia within lineages, few studies have investigated genital evolution during the early stages of speciation. We quantified genital variation in replicated population pairs of Poecilia mexicana with ongoing ecological speciation between sulfidic (H2S-containing) and nearby non-sulfidic habitats. These analyses revealed rapid and correlated divergence of female and male genitalia across evolutionarily independent population pairs exposed to divergent selection regimes. Both sexes exhibited convergent evolution of genital traits among populations inhabiting similar habitat types. Our results demonstrate that genital evolution can occur during the early stages of speciation-with-gene-flow, potentially as a result of variation in the intensity of sexual conflict among populations. Our results suggest genitalia may contribute to early stages of divergence, and challenge the generality of previously suggested mechanisms of genital evolution in poeciliids.
Data from: Genomic divergence across ecological gradients in the Central African rainforest songbird (Andropadus virens)
The little greenbul, a common rainforest passerine from sub-Saharan Africa, has been the subject of long-term evolutionary studies to understand the mechanisms leading to rainforest speciation. Previous research found morphological and behavioural divergence across rainforest–savannah transition zones (ecotones), and a pattern of divergence with gene flow suggesting divergent natural selection has contributed to adaptive divergence and ecotones could be important areas for rainforests speciation. Recent advances in genomics and environmental modelling make it possible to examine patterns of genetic divergence in a more comprehensive fashion. To assess the extent to which natural selection may drive patterns of differentiation, here we investigate patterns of genomic differentiation among populations across environmental gradients and regions. We find compelling evidence that individuals form discrete genetic clusters corresponding to distinctive environmental characteristics and habitat types. Pairwise FST between populations in different habitats is significantly higher than within habitats, and this differentiation is greater than what is expected from geographic distance alone. Moreover, we identified 140 SNPs that showed extreme differentiation among populations through a genomewide selection scan. These outliers were significantly enriched in exonic and coding regions, suggesting their functional importance. Environmental association analysis of SNP variation indicates that several environmental variables, including temperature and elevation, play important roles in driving the pattern of genomic diversification. Results lend important new genomic evidence for environmental gradients being important in population differentiation.
Data from: Functional trait plasticity diverges between sexes in African cichlids: a contribution toward ecological sexual dimorphism?
<p>Phenotypic plasticity enables development to produce multiple phenotypes in response to environmental conditions. Plasticity driven variation has been suggested to play a key role in adaptive divergence, and plasticity itself can evolve. However, the interaction of plasticity with the multiple levels involved with adaptive divergence is less understood. For example, sexual dimorphism can contribute to adaptive variation through ecological sexual dimorphism (ESD), but the contribution of plasticity to this phenomenon is unknown. Therefore, to determine the potential contribution of plasticity to ESD, we used the adaptive radiation of Malawi cichlids. Two mouthbrooding species (<em>Labeotropheus fuelleborni </em>and <em>Tropheops</em> "Red Cheek", hereafter LF and TRC respectively) with differences in foraging tactics underwent foraging experiments using benthic and limnetic treatments while accounting for sex. Plasticity in craniofacial shape and three functionally important traits were measured. Plasticity was shown, but without any sex-based differences in shape. However, for mechanical advantage traits of the mandible sex by diet interactions were found. This suggests that ESD, may be influenced by phenotypic plasticity that diverges between sexes. Given the involvement of the mandible in parental care in cichlids this may indicate that sexual divergence in plasticity may trade-off against maternal care tactics.</p>
The evolution of plasticity in brain morphology following colonization of an ecologically divergent habitat in Trinidadian guppies
<p>Natural environments are constantly changing. To survive, organisms will either need to rapidly adapt to new conditions or colonize new habitats. Colonization has been hypothesized to select for increased plasticity as well as increased brain size, though empirical tests of these effects have proven difficult to evaluate. In particular, the degree to which plasticity of brain morphology can evolve, and its subsequent ecological consequences have rarely been explored. Trinidadian guppies (<em>Poecilia reticulata</em>) are known for their repeated adaptation to ancestral high-predation (HP) and derived low-predation (LP) environments. We used this system to examine the evolution and plasticity of brain morphology. We exposed second-generation offspring of individuals collected from HP and LP sites to two different kinds of environmental treatments: predation cues and conspecific social environment. We found that guppies descended from a colonized LP habitat showed greater plasticity in brain morphology than descendants of their ancestral HP population, supporting the hypothesis that plasticity of brain morphology may increase fitness after colonization of a novel habitat. Additionally, we show sexual dimorphism in brain morphology plasticity. Overall, these results suggest the evolution of brain morphology plasticity as an important mechanism that allows for ecological diversification and colonization of novel habitats.</p>
Data from: Extensive sympatry and frequent hybridization of ecologically divergent aquatic plants on the Qinghai-Tibetan Plateau
<p><span>Hybridization has fascinated biologists in recent centuries for its evolutionary importance, especially in plants. Hybrid zones </span><span>are </span><span>commonly located in regions across environmental gradients due to more opportunities to contact and ecological heterogeneity. For aquatic taxa, intrazonal character makes broad </span><span>overlapping</span><span> regions in intermediate environments between related species. However, we have limited information on the hybridization pattern of aquatic taxa in </span><span>alpines, especially submerged macrophytes</span><span>. In this study, we aimed to test the hypotheses that niche overlap and hybridization might be extensive in related aquatic plants across an altitudinal gradient. We evaluated the niche overlap in three related species pairs on the Qinghai-Tibetan Plateau and assessed the spatial pattern of hybrid populations. Obvious niche overlap and common hybridization were revealed in all three pairs of related aquatic plants. The plateau edge and river basins were broad areas for the sympatry of divergent taxa, where a large proportion of hybrid populations occurred. Hybrids are also discretely distributed in diverse habitats on the plateau. Differences in the extent of niche overlap, genetic incompatibility and phylogeographic history might lead to variations in hybridization patterns among the three species pairs. Our results suggested that plateau </span><span>areas are</span><span> a hotspot for ecologically divergent aquatic species to contact and mate and implied that hybridization may be important for the freshwater biodiversity of highlands.</span></p>
Genomic and phenotypic divergence‐with‐gene‐flow across an ecological and elevational gradient in a neotropical bird
<p>Aim: Along with environmental gradients, some species show significant differences in morphological, ecological-related traits. Those differences are commonly related to past events of allopatry but, alternatively, could be caused by natural selection in the presence of gene flow. We aimed to explore the prevalence of the divergence-with-gene-flow model across the Chaco-Andes dry forest belt, testing competing models of evolution in a Neotropical bird.</p> <p>Location: Central Andes Mountain range and Chaco region of Argentina and Bolivia. </p> <p>Taxon: Phytotoma rutila (Aves, Cotingidae).</p> <p>Methods: We studied ddRADseq loci (4,893 SNPs) of 21 tissue samples and body size variation of 146 specimens. We evaluated population genetic structure and tested the effects of altitude and distance on genomic divergence. To evaluate allopatry and divergence-with-gene-flow, we compared the divergence on phenotypic traits (bill, tarsus, and wing measurements) versus neutral genomic variation, conducted coalescent analyses to estimate gene flow and divergence time among populations, and calculated relative (FST) versus absolute (DXY) genomic divergence.</p> <p>Results: a) there is a genomic and phenotypic differentiation in P. rutila matched the highland-lowland axis, where the altitude variation explains genomic variation; b) A larger phenotypic than neutral genomic variation was found. c) there is an asymmetric gene flow between populations; d) a pattern of relative and absolute genomic differentiation compatible with divergence-with-gene-flow.</p> <p>Main conclusions: The mechanism behind the morphological and genomic diversification along the Chaco-Andes dry forest belt in P. rutila is divergence‐with‐gene‐flow. Far more complex than we traditionally thought, diversification in South America implicates gene flow between populations and also natural selection along with the environmental gradients, as well as vicariance, contrasting with the idea of tropical speciation primarily based on allopatric models.</p> <p> </p>
Neuroanatomical shifts mirror patterns of ecological divergence in three diverse clades of mimetic butterflies
<p class="MsoNormal"><span>Microhabitat partitioning in heterogenous environments can support more diverse communities but may expose partitioned species to distinct perceptual challenges. Divergence across microhabitats could therefore lead to local adaptation to contrasting sensory conditions across small spatial scales, but this aspect of community structuring is rarely explored. Diverse communities of ithomiine butterflies provide an example where closely related species partition tropical forests, where shifts in mimetic colouration are tightly associated with shifts in habitat preference. </span><span>We test the hypothesis </span><span>that these mimetic and ecological shifts are associated with distinct patterns of sensory neural investment by comparing brain structure across 164 individuals of 16 species from three ithomiine clades. We find distinct brain morphologies between Oleriina<em> </em>and <em>Hypothyris</em>, which are mimetically homogenous and occupy a single microhabitat. Oleriina, which occur in low-light micro-habitats, invests less in visual brain regions than <em>Hypothyris</em>, with one notable exception, <em>Hyposcada anchiala, </em>the only Oleriina<em> </em>sampled to have converged on mimicry rings found in <em>Hypothyris</em>. We also find that <em>Napeogenes</em>, which has diversified into a range of mimicry rings, shows intermediate patterns of sensory investment. We identify flight height as a critical factor shaping neuroanatomical diversity, with species that fly higher in the canopy investing more in visual structures. Our work suggests that the sensory ecology of species may be impacted by, and interact with, the ways in which communities of closely related organisms are adaptively assembled.</span></p>
Data and supplementary materials from: Large genetic divergence underpins cryptic local adaptation across ecological and evolutionary gradients
<p><span>Environmentally covarying local adaptation is a form of cryptic local adaptation in which the covariance of the genetic and environmental effects on a phenotype obscures the divergence between locally adapted genotypes. Here, we systematically document the magnitude and drivers of the genetic effect (V<sub>G</sub>) for two forms of environmentally covarying local adaptation: counter- and cogradient variation. Using a hierarchical Bayesian meta-analysis, we calculated the overall effect size of V<sub>G</sub> as 1.05 and 2.13 for populations exhibiting countergradient or cogradient variation, respectively. These results indicate that the genetic contribution to phenotypic variation represents a 1.05 to 2.13 standard deviation change in trait value between the most disparate populations depending on if populations are expressing counter- or cogradient variation. We also found that while there was substantial variance among abiotic and biotic covariates, the covariates with the largest mean effects were temperature (2.41) and gamete size (2.81). Our results demonstrate the pervasiveness and large genetic effects underlying environmentally covarying local adaptation in wild populations and highlights the importance of accounting for these effects in future studies.</span></p>
Ecological divergence despite common mating sites: Genotypes and symbiotypes shed light on cryptic diversity in the black bean aphid species complex
<p>Different host plants represent ecologically dissimilar environments for phytophagous insects. The resulting divergent selection can promote the evolution of specialized host races, provided that gene flow is reduced between populations feeding on different plants. In black bean aphids belonging to the <em>Aphis fabae </em>complex, several morphologically cryptic taxa have been described based on their distinct host plant preferences. However, host choice and mate choice are largely decoupled in these insects: they are host-alternating and migrate between specific summer host plants and shared winter hosts, with mating occurring on the shared hosts. This provides a yearly opportunity for gene flow among aphids using different summer hosts, and raises the question if and to what extent the ecologically defined taxa are reproductively isolated. Here, we analyzed a geographically and temporally structured dataset of microsatellite genotypes from <em>A. fabae </em>that were mostly collected from their main winter host <em>Euonymus europaeus,</em> and additionally from another winter host and fourteen summer hosts. The data reveals multiple, strongly differentiated genetic clusters, which differ in their association with different summer and winter hosts. The clusters also differ in the frequency of infection with two heritable, facultative endosymbionts, separately hinting at reproductive isolation and divergent ecological selection. Furthermore, we found evidence for occasional hybridization among genetic clusters, with putative hybrids collected more frequently in spring than in autumn. This suggests that similar to host races in other phytophagous insects, both prezygotic and postzygotic barriers including selection against hybrids maintain genetic differentiation among <em>A. fabae </em>taxa, despite a common mating habitat.</p>
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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.
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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.
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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.