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Data from: Physical and ecological isolation contribute to maintain genetic differentiation between fire salamander subspecies
<p>Landscape features shape patterns of gene flow among populations, ultimately determining where taxa lay along the continuum between panmixia to complete reproductive isolation. Gene flow can be restricted leading to population differentiation in two non-exclusive ways: "physical isolation", in which geographic distance in combination with the landscape features restricts movement of individuals promoting genetic drift, and "ecological isolation", in which adaptive mechanisms constrain gene flow between different environments via divergent natural selection. In central Iberia, two fire salamander subspecies occur in parapatry across elevation gradients along the Iberian Central System mountains, while in adjacent Mountains of Toledo Region only one of them occurs. By integrating population and landscape genetic analyses, we show a ubiquitous role of physical isolation between and within mountain ranges, with unsuitable landscapes increasing differentiation between populations. However, across the Iberian Central System, we found strong support for a significant contribution of ecological isolation, with low genetic differentiation in environmentally homogeneous areas, but high differentiation across sharp transitions in precipitation seasonality. These patterns are consistent with a significant contribution of ecological isolation in restricting gene flow among subspecies. Overall, our results suggest that ecological divergence contributes to reduce genetic admixture, creating an opportunity for lineages to follow distinct evolutionary trajectories.</p>
Data from: Strong natural selection on juveniles maintains a narrow adult hybrid zone in a broadcast spawner
Natural selection can maintain and help form species across different habitats, even when dispersal is high. Selection against inferior migrants (immigrant inviability) acts when locally adapted populations suffer high mortality on dispersal to unsuitable habitats. Habitat-specific populations undergoing divergent selection via immigrant inviability should thus show (1) a change in the ratio of adapted to nonadapted individuals among age/size classes and (2) a cline (defined by the environmental gradient) as selection counterbalances migration. Here we examine the frequencies of two depth-segregated lineages in juveniles and adults of a Caribbean octocoral, Eunicea flexuosa. Distributions of the two lineages in both shallow and deep environments were more distinct when inferred from adults than juveniles. Despite broad larval dispersal, we also found an extremely narrow hybrid zone (<100 m), with coincident clines for molecular and morphological characters of the host coral and its algal symbiont. Effective dispersal estimates derived from the hybrid zone are remarkably small (<20 m) for a broadcast spawner. The large selection coefficient against mismatched genotypes derived from cohort data is consistent with that from field transplant experiments. Narrow hybrid zones and limited effective dispersal may be a common outcome of long periods of postsettlement, prereproductive selection across steep ecological gradients. Strong diversifying selection provides a mechanism to explain the prevalence of depth-segregated sibling species in the sea.
Data from: Does genetic variation maintained by environmental heterogeneity facilitate adaptation to novel selection?
Environmental heterogeneity helps maintain genetic variation in fitness. Therefore, one might predict that populations living in heterogeneous environments have higher adaptive potential than populations living in homogeneous environments. Such a prediction could be useful in guiding conservation priorities without requiring detailed genetic studies. However, this prediction will be true only if the additional genetic variation maintained by environmental heterogeneity can be used to respond to novel selection. Here we examine the effect of environmental heterogeneity on future adaptability using replicated experimental Drosophila melanogaster populations that had previously evolved for ∼100 generations under one of four selective regimes: constant salt-enriched larvae medium, constant cadmium-enriched larvae medium, and two heterogeneous regimes that vary either temporally or spatially between the two media. Replicates of these experimental populations were subjected to a novel heat stress while being maintained in their original larval diet selection regimes. Adaptation to increased temperature was measured with respect to female productivity and male siring success after ∼20 generations. For female productivity, there was evidence of adaptation overall and heterogeneous populations had a larger adaptive response than homogeneous populations. There was less evidence of adaptation overall for male siring success and no support for faster adaptation in heterogeneous populations.
Data from: Pollen flow in fragmented landscapes maintains genetic diversity following stand-replacing disturbance in a neotropical pioneer tree, Vochysia ferruginea Mart.
In forests with gap disturbance regimes, pioneer tree regeneration is typically abundant following stand-replacing disturbances, whether natural or anthropogenic. Differences in pioneer tree density linked to disturbance regime can influence pollinator behaviour and impact on mating patterns and genetic diversity of pioneer populations. Such mating pattern shifts can manifest as higher selfing rates and lower pollen diversity in old growth forest populations. In secondary forest, where more closely related pollen donors occur, an increase in biparental inbreeding is a potential problem. Here, we investigate the consequences of secondary forest colonisation on the mating patterns and genetic diversity of open-pollinated progeny arrays for the long-lived, self-compatible pioneer tree, Vochysia ferruginea, at two Costa Rican sites. Five microsatellite loci were screened across adult and seed cohorts from old growth forest with lower density, secondary forest with higher density, and isolated individual trees in pasture. Progeny from both old growth and secondary forest contexts were predominantly outcrossed (tm=1.00) and experienced low levels of biparental inbreeding (tm−ts=0.00–0.04). In contrast to predictions, our results indicated that the mating patterns of V. ferruginea are relatively robust to density differences between old growth and secondary forest stands. In addition, we observed that pollen-mediated gene flow possibly maintained the genetic diversity of open-pollinated progeny arrays in stands of secondary forest adults. As part of a natural resource management strategy, we suggest that primary forest remnants should be prioritised for conservation to promote restoration of genetic diversity during forest regeneration.
Environmental stress maintains trioecy in nematode worms
Sex is determined by chromosomes in mammals but it can be influenced by the environment in many worms, crustaceans and vertebrates. Despite this, there is little understanding of the relationship between ecology and the evolution of sexual systems. The nematode Auanema freiburgensis has a unique sex determination system in which individuals carrying one X chromosome develop into males while XX individuals develop into females in stress-free environments and self-fertile hermaphrodites in stressful environments. Theory predicts that trioecious populations with coexisting males, females and hermaphrodites should be unstable intermediates in evolutionary transitions between mating systems. In this article we study a mathematical model of reproductive evolution based on the unique life history and sex determination of A. freiburgensis. We develop the model in two scenarios, one where the relative production of hermaphrodites and females is entirely dependent on the environment and one based on empirical measurements of a population that displays incomplete, 'leaky' environmental dependence. In the first scenario environmental conditions can push the population along an evolutionary continuum and result in the stable maintenance of multiple reproductive systems. The second 'leaky' scenario results in the maintenance of three sexes for all environmental conditions. Theoretical investigations of reproductive system transitions have focused on the evolutionary costs and benefits of sex. Here, we show that the flexible sex determination system of A. freiburgensis may contribute to population-level resilience in the microscopic nematode's patchy, ephemeral natural habitat. Our results demonstrate that life history, ecology and environment may play defining roles in the evolution of sexual systems.
Data from: Maintained functional diversity in benthic communities in spite of diverging functional identities
Ecological studies based on time-series often investigate community changes centered on species abundance or biomass but rarely expose the consequential functional aspects underlying such changes. Functional diversity measures have proven to be more accurate predictors for ecosystem functioning than traditional taxonomic approaches and hence gained much attention. There are only limited studies available that analyse the functional implications behind decadal changes of entire communities. We studied zoobenthic communities of two habitats, sheltered and exposed, of a coastal system subject to contrasting changes in community composition over the past four decades. Besides eutrophication and climate-related impacts, the system has been invaded by a non-native polycheate Marenzelleria spp., adding altered functional properties to the communities. The functional dispersion (FDis) metric was used as a measure for comparing the functional diversity of the contrasting habitats, with special focus on the role of Marenzelleria for the entire communities. We highlight changes in the functional identity of the communities, expressed as community-weighted means of trait expression (CWM), using multivariate techniques, and investigate the relationship between taxonomic and functional changes. Despite contrasting community developments in the two habitats, with characteristics traditionally suggesting different environmental quality, we found that the FDis in both habitats remained similar and increased with the introduction of Marenzelleria. Although showing maintained functional diversity across time and space, the functional identity (CWM) of communities changed irrespective of taxonomical differences. Examples include inter alia alterations in palatability proxies, feeding position and sediment transportation types, indicating changed functionality of zoobenthos in coastal systems. We show, when focussing on qualitative functional changes of communities, it is important to evaluate the underlying functional identity, and not only rely on measures of the diversity of functions per se, as the quality indication of expressed functional traits can be concealed when using multi-functionality approaches.
Data from: Maintaining genetic diversity and population panmixia through dispersal and not gene flow in a holocyclic heteroecious aphid species
Heteroecious holocyclic aphids exhibit both sexual and asexual reproduction and alternate among primary and secondary hosts. Most of these aphids can feed on several related hosts, and invasions to new habitats may limit the number of suitable hosts. For example, the aphid specialist Aphis glycines survives only on the primary host buckthorn (Rhamnus spp.) and the secondary host soybean (Glycine max) in North America where it is invasive. Owing to this specialization and sparse primary host distribution, host colonization events could be localized and involve founder effects, impacting genetic diversity, population structure and adaptation. We characterized changes in the genetic diversity and structure across time among A. glycines populations. Populations were sampled from secondary hosts twice in the same geographical location: once after secondary colonization (early season), and again immediately before primary host colonization (late season). We tested for evidence of founder effects and genetic isolation in early season populations, and whether or not late-season dispersal restored genetic diversity and reduced fragmentation. A total of 24 single-nucleotide polymorphisms and 6 microsatellites were used for population genetic statistics. We found significantly lower levels of genotypic diversity and more genetic isolation among early season collections, indicating secondary host colonization occurred locally and involved founder effects. Pairwise FST decreased from 0.046 to 0.017 in early and late collections, respectively, and while genetic relatedness significantly decreased with geographical distance in early season collections, no spatial structure was observed in late-season collections. Thus, late-season dispersal counteracts the secondary host colonization through homogenization and increases genetic diversity before primary host colonization.
Negative frequency-dependent selection maintains coexisting genotypes during fluctuating selection
Natural environments are rarely static; rather selection can fluctuate on time scales ranging from hours to centuries. However, it is unclear how adaptation to fluctuating environments differs from adaptation to constant environments at the genetic level. For bacteria, one key axis of environmental variation is selection for planktonic or biofilm modes of growth. We conducted an evolution experiment with <i>Burkholderia cenocepacia</i>, comparing the evolutionary dynamics of populations evolving under constant selection for either biofilm formation or planktonic growth with populations in which selection fluctuated between the two environments on a weekly basis. Populations evolved in the fluctuating environment shared many of the same genetic targets of selection as those evolved in constant biofilm selection, but were genetically distinct from the constant planktonic populations. In the fluctuating environment, mutations in the biofilm-regulating genes wspA and rpfR rose to high frequency in all replicate populations. A mutation in wspA first rose rapidly and nearly fixed during the initial biofilm phase but was subsequently displaced by a collection of rpfR mutants upon the shift to the planktonic phase. The wspA and rpfR genotypes coexisted via negative frequency-dependent selection around an equilibrium frequency that shifted between the environments. The maintenance of coexisting genotypes in the fluctuating environment was unexpected. Under temporally fluctuating environments coexistence of two genotypes is only predicted under a narrow range of conditions, but the frequency-dependent interactions we observed provide a mechanism that can increase the likelihood of coexistence in fluctuating environments.
Data from: Frost maintains forests and grasslands as alternate states in a montane tropical forest-grassland mosaic; but alien tree invasion and warming can disrupt this balance
1. Forest-grassland mosaics, with abrupt boundaries between the two vegetation types, occur across the globe. Fire and herbivory are widely considered primary drivers that maintain these mosaics by limiting tree establishment in grasslands, while edaphic factors and frosts are generally considered to be secondary factors that reinforce these effects. However, the relative importance of these drivers likely varies across systems. In particular, although frost is known to occur in many montane tropical mosaics, experimental evidence for its role as a driving factor is limited. 2. We used replicated in-situ transplant and warming experiments to examine the role of microclimate (frost and freezing temperatures) and soil in influencing germination and seedling survival of both native forest trees and alien invasive Acacia trees in grasslands of a tropical montane forest-grassland mosaic in the Western Ghats of southern India. 3. Seed germination of both native and alien tree species was higher in grasslands regard-less of soil type, indicating that germination was not the limiting stage to tree establishment. However, irrespective of soil type, native seedlings in grasslands incurred high mortality fol-lowing winter frosts and freezing temperatures relative to native seedlings in adjoining forests where freezing temperatures did not occur. Seedling survival through the tropical winter was thus a primary limitation to native tree establishment in grasslands. In contrast, alien Acacia seedlings in grasslands incurred much lower levels of winter mortality. Experimental night-time warming in grasslands significantly enhanced over-winter survival of all tree seedlings, but increases in recruitment were much greater for alien Acacia than for native tree seedlings. 4. Synthesis: Our results provide evidence for a primary role for frost and freezing temperatures in limiting tree establishment in grasslands of this tropical forest-grassland mosaic. Future increases in temperature are likely to release trees from this limitation and favour tree expansion into grasslands, with rates of expansion of non-native Acacia likely to be much greater than that of native trees. We suggest that studies of frost limitation to plant establishment are needed across a range of tropical ecosystems to re-evaluate the general importance of frost as a driver of vegetation transitions in the tropics.
Data from: Genetic divergence with ongoing gene flow is maintained by the use of different hosts in phytophagous ladybird beetles genus Henosepilachna
Adaptation to different environments can promote population divergence via natural selection even in the presence of gene flow–a phenomenon that typically occurs during ecological speciation. To elucidate how natural selection promotes and maintains population divergence during speciation, we investigated the population genetic structure, degree of gene flow and heterogeneous genomic divergence in three closely related Japanese phytophagous ladybird beetles: Henosepilachna pustulosa, H. niponica and H. yasutomii. These species act as a generalist, a wild thistle (Cirsium spp.) specialist and a blue cohosh (Caulophyllum robustum) specialist, respectively, and their ranges differ accordingly. The two specialist species widely co-occur but are reproductively isolated solely due to their high specialisation to a particular host plant. Genome-wide amplified fragment-length polymorphism (AFLP) markers and mitochondrial cytochrome c oxidase subunit I (COI) gene sequences demonstrated obvious genome-wide divergence associated with both geographic distance and ecological divergence. However, a hybridisation assessment for both AFLP loci and the mitochondrial sequences revealed a certain degree of unidirectional gene flow between the two sympatric specialist species. Principal coordinates analysis (PCoA) based on all of the variable AFLP loci demonstrated that there are genetic similarities between populations from adjacent localities irrespective of the species (i.e. host range). However, a further comparative genome scan identified a few fractions of loci representing approximately 1% of all loci as different-host associated outliers. These results suggest that these three species had a complex origin, which could be obscured by current gene flow, and that ecological divergence can be maintained with only a small fraction of the genome is related to different host use even when there is a certain degree of gene flow between sympatric species pairs.
Data from: The return of the frogs: the importance of habitat refugia in maintaining diversity during a disease outbreak
Recent decades have seen the emergence and spread of numerous infectious diseases, often with severe negative consequences for wildlife populations. Nevertheless, many populations survive the initial outbreaks, and even undergo recoveries. Unfortunately, the long-term effects of these outbreaks on host population genetics are poorly understood; to increase this understanding, we examined the population genetics of two species of rainforest frogs (Litoria nannotis and Litoria serrata) that have largely recovered from a chytridiomycosis outbreak at two national parks in the Wet Tropics of northern Australia. At the wetter, northern park there was little evidence of decreased genetic diversity in either species, and all of the sampled sites had high minor allele frequencies (mean MAF = 0.230–0.235), high heterozygosity (0.318–0.325), and few monomorphic markers (1.4–4.0%); however, some recovered L. nannotis populations had low Ne values (59.3–683.8) compared to populations that did not decline during the outbreak (1537.4–1756.5). At the drier, southern park, both species exhibited lower diversity (mean MAF = 0.084–0.180; heterozygosity = 0.126–0.257; monomorphic markers = 3.7–43.5%; Ne = 18.4–676.1). The diversity patterns in this park matched habitat patterns, with both species having higher diversity levels and fewer closely related individuals at sites with higher quality habitat. These patterns were more pronounced for L. nannotis, which has lower dispersal rates than L. serrata. These results suggest that refugia with high quality habitat are important for retaining genetic diversity during disease outbreaks, and that gene flow following disease outbreaks is important for restabilising diversity in populations where it was reduced.
Drosophila carboxypeptidase D (SILVER) is a key enzyme in neuropeptide processing required to maintain locomotor activity levels and survival rate
<p>Neuropeptides are processed from larger preproproteins by a dedicated set of enzymes. The molecular and biochemical mechanisms underlying preproprotein processing and the functional importance of processing enzymes are well‐characterised in mammals, but little studied outside this group. In contrast to mammals, Drosophila melanogaster lacks a gene for carboxypeptidase E (CPE), a key enzyme for mammalian peptide processing. By combining peptidomics and neurogenetics, we addressed the role of carboxypeptidase D (dCPD) in global neuropeptide processing and selected peptide‐regulated behaviours in Drosophila. We found that a deficiency in dCPD results in C‐terminally extended peptides across the peptidome, suggesting that dCPD took over CPE function in the fruit fly. dCPD is widely expressed throughout the nervous system, including peptidergic neurons in the mushroom body and neuroendocrine cells expressing adipokinetic hormone. Conditional hypomorphic mutation in the dCPD‐encoding gene silver in the larva causes lethality, and leads to deficits in starvation‐induced hyperactivity and appetitive gustatory preference, as well as to reduced viability and activity levels in adults. A phylogenomic analysis suggests that loss of CPE is not common to insects, but only occurred in Hymenoptera and Diptera. Our results show that dCPD is a key enzyme for neuropeptide processing and peptide‐regulated behaviour in Drosophila. dCPD thus appears as a suitable target to genetically shut down total neuropeptide production in peptidergic neurons. The persistent occurrence of CPD in insect genomes may point to important further CPD functions beyond neuropeptide processing which cannot be fulfilled by CPE.</p>
Data from: Can ecosystem functioning be maintained despite climate-driven shifts in species composition? Insights from novel marine forests
1. Climate change is driving a redistribution of species and reconfiguration of ecological communities at a global scale. Persistent warming in many regions has caused species to extend their geographical ranges into new habitats, with thermally-tolerant species often becoming competitively dominant over species with colder affinities. Although these climate-driven changes in species abundance and diversity are well documented, their ecosystem-level implications are poorly understood, and resolving whether reconfigured communities can maintain fundamental ecosystem functions represents a pressing challenge in an increasingly warmer world. 2. Here, we investigated how climate-driven substitutions of foundation species influence processes associated with carbon and nutrient cycling (biomass production, detritus flow, herbivory, decomposition) by comparing two habitat-forming kelp species with contrasting thermal affinities. We examined the wider consequences of the observed (and predicted) emergence of novel marine forests in the NE Atlantic, which are expected to become more dominated by range-expanding, warm-temperate kelps. 3. Warm-temperate kelps both accumulated and released 80% more biomass than the cold-temperate species despite being taxonomically closely-related and morphologically similar. Furthermore, the warm-temperate species accumulated biomass and released detritus year-round, whereas the cold-temperate species did so during short, discrete periods. The warm-temperate kelps supported higher densities of invertebrate grazers and were a preferred food source. Finally, their detritus decomposed 6.5 times faster, despite supporting comparable numbers of detritivores. Overall, our results indicate an important shift in the cycling of organic matter in kelp forests along parts of the NE Atlantic coastline following climate-driven expansion of a warm-affinity kelp, with novel forests supplying large amounts of temporally-continuous—yet highly labile—organic matter. 4. Synthesis. Collectively, our results show that, like species invasions, climate-driven range expansions and consequent shifts in the identity of dominant species can modify a wide range of important ecosystem processes. However, alterations in overall ecosystem functioning may be relatively limited where foundation species share similar ecological and functional traits.
Data from: C4 savanna grasses fail to maintain assimilation in drying soil under low CO2 compared with C3 trees despite lower leaf water demand
1) C4 photosynthesis evolved when grasses migrated out of contracting forests under a declining atmospheric CO2 concentration ([CO2]a) and drying climate around 30 million years ago. C4 grasses are hypothesised to benefit from improved plant–water relations in open habitats like savannas, giving advantages over C3 plants under low [CO2]a. But experimental evidence in a low CO2 environment is limited and comparisons with C3 trees are needed to understand savanna vegetation patterns. 2) To test whether stomatal conductance (gS) and CO2 assimilation (A) are maintained in drier soil for C4 grasses than C3 trees, particularly under low [CO2]a, we investigated photosynthesis and plant–water relations of three C3 tree and three C4 grass species grown at 800, 400 or 200 ppm [CO2]a over moderate wetting–drying cycles. 3) C4 grasses had a lower soil–to–leaf water potential gradient than C3 trees, especially at 200 ppm [CO2]a, indicating reduced leaf water demand relative to supply. Yet the dependence of gS and A on predawn leaf water potential (a measure of soil water availability) was greater for the C4 grasses than trees, particularly under low [CO2]a. 4) Our findings establish that gS and A are not maintained in drier soil for C4 grasses compared with C3 trees, suggesting that this mechanism was not prevailing in the expansion of C4–dominated grasslands under low [CO2]a. This inherent susceptibility to sudden decreases in soil water availability justifies why C4 grasses have not evolved a resistant xylem allowing operation under drought, but instead shut down below a water potential threshold and rapidly recover. We point to this capacity to respond to transient water availability as a key overlooked driver of C4 grass success under low [CO2]a.
Data from: Maintaining their genetic distance: little evidence for introgression between widely hybridising species of Geum with contrasting mating systems
Within the plant kingdom many genera contain sister lineages with contrasting outcrossing and inbreeding mating systems that are known to hybridise. The evolutionary fate of these sister lineages is likely to be influenced by the extent to which they exchange genes. We measured gene flow between outcrossing Geum rivale and selfing G. urbanum, sister species that hybridise in contemporary populations. We generated and used a draft genome of G. urbanum to develop dd-RAD data scorable in both species. Coalescent analysis of RAD data from allopatric populations indicated that the species diverged 2-3 Mya, and that historical gene flow between them was extremely low (1 migrant every 25 generations). Comparison of genetic divergence between species in sympatry and allopatry, together with an analysis of allele frequencies in potential parental and hybrid populations, provided no evidence of contemporary introgression in sympatric populations. Cluster and species specific marker analyses revealed that, apart from four early generation hybrids, individuals in sympatric populations fell into two genetically distinct groups that corresponded exactly to their morphological species classification with maximum individual admixture estimates of only 1 -3%. However, we did observe joint segregation of four putatively introgressed SNPs across two scaffolds in the G. urbanum population that was associated with significant morphological variation, interpreted as tentative evidence for rare, recent interspecific gene flow. Overall, our results indicate that despite the presence of hybrids in contemporary populations, genetic exchange between G. rivale and G. urbanum has been extremely limited throughout their evolutionary history.
Data from: Maintaining a wild phenotype in a conservation hatchery program for Chinook salmon: the effect of managed breeding on early male maturation
In many salmonid species, age and size of maturation is plastic and influenced by the interaction between genetic and environmental factors. Hatchery reared salmon often mature at an earlier age and smaller size than wild fish. Modern salmon conservation efforts have focused on managing the level of gene flow between hatchery and natural origin fish to minimize potential genotypic and phenotypic change. In salmonids, maturation probability is dependent on exceeding a genetically set threshold in growth rate and energetic status (and by association body size) referred to as the probabalisitic maturation reaction norm (PMRN). Over fourteen years, we monitored the frequency of age-2 precocious male maturation (common term: minijack rate) and the PMRN of a natural founder (FNDR), integrated natural-hatchery (INT), and segregated hatchery (SEG) broodlines of spring Chinook salmon, Oncorhynchus tshawytscha. The average minijack rate (± SEM) of the FNDR, INT and SEG broodlines was 48.2 ± 5.2%, 41.9 ± 3.6% and 30.9 ± 4.7%, respectively. Additionally, the PMRN WP50 (predicted weight at 50% maturation) of the SEG broodline was significantly greater (20.5 g) than that of the FNDR/INT broodline (18.2 g). We also conducted a common garden experiment exploring the effects of less than one [INT (0-1)], one [SEG (1)] or two [SEG (2)] generations of hatchery culture on the minijack rate and PMRN WP50 . Growth was not significantly different among broodlines, but minijack rates were significantly lower following two consecutive generations of hatchery culture: [INT (0-1): 68.3 ± 1.7%], [SEG (1): 70.3 ± 1.8%] and [SEG (2): 58.6 ± 0.4%] and the PMRN WP50 was significantly higher by 6.1 g after two generations of SEG culture. These results indicate that managed gene flow reduces phenotypic divergence, but may serve to maintain potentially undesirable high minijack rates in salmon conservation hatchery programs.
Data from: Strong selection against hybrids maintains a narrow contact zone between morphologically cryptic lineages in a rainforest lizard
Phenotypically cryptic lineages comprise an important yet understudied part of biodiversity; in particular, we have much to learn about how these lineages are formed and maintained. To better understand the evolutionary significance of such lineages, we studied a hybrid zone between two morphologically-cryptic phylogeographic lineages in the rainforest lizard, Lampropholis coggeri. Analyzing a multilocus genetic dataset through cline inference, individual-based methods and population measures of disequilibrium and using simulations to explore our genetic results in context of theoretical expectations, we inferred the processes maintaining this hybrid zone. We find that these lineages meet in a hybrid zone that is narrow (~400 m) relative to inferred dispersal rate. Further, the hybrid zone exhibits substantial genetic disequilibrium and sharply coincident and largely concordant clines. Based on our knowledge about the region's biogeography, the species' natural history, and our simulation results, we suggest that strong selection against hybrids structures this system. As all clines show a relatively narrow range of introgression, we posit that this hybrid zone might not yet be in equilibrium. Nonetheless, our results clearly show that phylogeographic lineages can evolve substantial reproductive isolation without concomitant morphological diversification, suggesting that such lineages can constitute a significant component of evolutionary diversity.
Maintaining genetic integrity with high promiscuity: Frequent hybridization with low introgression in multiple hybrid zones of Melocactus(Cactaceae)
<p>Hybridization and introgression between species in contact/hybrid zones provide important insight into the genetic and ecological mechanisms of speciation. Cactaceae represents the most important radiation of true succulent angiosperms in the New World. This diversification continues to date, with species experiencing few intrinsic barriers to gene flow and the frequent occurrence of natural hybridization. Here, we used RAD-Seq single-nucleotide polymorphism (SNP) data to investigate the genetic architecture of hybridization in four hybrid zones hosting Melocactus concinnus and four congeneric species (M. ernestii, M. glaucescens, M. paucispinus, and M. zehntneri). Our results revealed that M. concinnusis highly promiscuous in sympatric areas and hybridizes with various species distributed in Morro do Chapéu (Diamantina Plateau, Bahia), eastern Brazil. However, the contemporary genomic introgression among the investigated species is very low (c. 2–5%), confirming that even in the face of hybridization, Melocactus species maintain their genetic integrity. The genomic cline approach showed a large fraction of loci deviating from a model of neutral introgression, where most of the loci are consistent with selection favoring parental genotypes. Our results suggest the occurrence of weak premating but strong <br> postmating reproductive isolation in the analyzed cactus species. Furthermore, as most of the Melocactus species are restricted in distribution, hybridization might negatively affect their integrity if hybrids replace the parental species.</p>
Data from: Reciprocity and the tragedies of maintaining and providing the commons
Social cooperation often requires collectively beneficial but individually costly restraint to maintain a public good, or it needs costly generosity to create one. Status quo effects predict that maintaining a public good is easier than providing a new one. Here, we show experimentally and with simulations that even under identical incentives, low levels of cooperation (the 'tragedy of the commons') are systematically more likely in maintenance than provision. Across three series of experiments, we find that strong and weak positive reciprocity, known to be fundamental tendencies underpinning human cooperation, are substantially diminished under maintenance compared with provision. As we show in a fourth experiment, the opposite holds for negative reciprocity ('punishment'). Our findings suggest that incentives to avoid the 'tragedy of the commons' need to contend with dilemma-specific reciprocity.
Data from: The role of predators in maintaining the geographic organization of aposematic signals
Selective predation of aposematic signals is expected to promote phenotypic uniformity. But while uniform within a population, numerous species display impressive variations in warning signals among adjacent populations. Predators from different localities learning to avoid distinct signals while performing intense selection on others are thus expected to maintain such a geographic organization. We tested this assumption by placing clay frog models, representing distinct color morphs of the Peruvian poison-dart frog Ranitomeya imitator and a non conspicuous frog, reciprocally between adjacent localities. In each locality, avian predators were able to discriminate between warning signals; the adjacent exotic morph suffered up to four times more attacks than the local one and two times more than the non conspicuous phenotype. Moreover, predation attempts on the exotic morph quickly decreased to almost nil, suggesting rapid learning. This experiment offers direct evidence for the existence of different predator communities performing localized homogenizing selection on distinct aposematic signals.
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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.