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opencc-zeroDec 2014View details →

Data from: The role of geography and ecology in shaping repeated patterns of morphological and genetic differentiation between European minnows (Phoxinus phoxinus) from the Pyrenees and the Alps

Neutral and selective processes can drive repeated patterns of evolution in different groups of populations experiencing similar ecological gradients. In this paper, we used a combination of nuclear and mitochondrial DNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological and genetic divergence of European minnows in two mountain ranges: the Pyrenees and the Alps. European minnows (Phoxinus phoxinus) are cyprinid fish inhabiting most freshwater bodies in Europe, including those in different mountain ranges that could act as major geographical barriers to gene flow. We explored patterns of P. phoxinus phenotypic and genetic diversification along a gradient of altitude common to the two mountain ranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation (IBA). The results indicated that populations from the Pyrenees and the Alps belong to two well differentiated, reciprocally monophyletic mtDNA lineages. Substantial genetic differentiation due to geographical isolation within and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPs markers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Also, morphology varied strongly with elevation and so did genetic differentiation to a lower extent. Despite moderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneity was found at the genetic level, suggesting that selection and population specific genetic drift act in concert to affect genetic divergence.

opencc-zeroDec 2014View details →

Data from: Causes and consequences of failed adaptation to biological invasions: the role of ecological constraints

Biological invasions are a major challenge to native communities and have the potential to exert strong selection on native populations. As a result, native taxa may adapt to the presence of invaders through increased competitive ability, increased antipredator defences or altered morphologies that may limit encounters with toxic prey. Yet, in some cases, species may fail to adapt to biological invasions. Many challenges to adaptation arise because biological invasions occur in complex species-rich communities in spatially and temporally variable environments. Here, we review these 'ecological' constraints on adaptation, focusing on the complications that arise from the need to simultaneously adapt to multiple biotic agents and from temporal and spatial variation in both selection and demography. Throughout, we illustrate cases where these constraints might be especially important in native populations faced with biological invasions. Our goal was to highlight additional complexities empiricists should consider when studying adaptation to biological invasions and to begin to identify conditions when adaptation may fail to be an effective response to invasion.

opencc-zeroDec 2014View details →

Data from: Social monogamy versus polyandry: ecological factors associated with sex-roles in two closely related birds within the same habitat

Why mainly males compete and females take a larger share in parental care remains an exciting question in evolutionary biology. Role-reversed species are of particular interest, because such exceptions′ help to test the rule. Using mating systems theory as a framework, we compared the reproductive ecology of the two most contrasting coucals with regard to sexual dimorphism and parental care: the black coucal with male-only care and the bi-parental white-browed coucal. Both species occur in the same lush habitat and face similar ecological conditions, but drastically differ in mating system and sexual dimorphism. Black coucals were migratory and occurred at high breeding densities. With females being obligatory polyandrous and almost twice as heavy as males, black coucals belong to the most extreme vertebrates with reversed sexual dimorphism. Higher variance in reproductive success in fiercely competing females suggests that sexual selection is stronger in females than males. In contrast, resident white-browed coucals bred at low densities and invariably in pairs. They were almost monomorphic and the variance in reproductive success was similar between the sexes. Black coucals were more likely to lose nests than white-browed coucals, probably facilitating female emancipation of parental care in black coucals. We propose that a combination of high food abundance, high population density, high degree of nest loss, and male bias in the adult sex ratio are ecological conditions that facilitate role reversal and polyandry in coucals and terrestrial vertebrates in general.

opencc-zeroDec 2016View details →

Data from: The role of ecology, neutral processes and antagonistic coevolution in an apparent sexual arms race

Some of the strongest examples of a sexual 'arms race' come from observations of correlated evolution in sexually antagonistic traits among populations. However, it remains unclear whether these cases truly represent sexually antagonistic coevolution; alternatively, ecological or neutral processes might also drive correlated evolution. To investigate these alternatives, we evaluated the contributions of intersex genetic correlations, ecological context, neutral genetic divergence and sexual coevolution in the correlated evolution of antagonistic traits among populations of Gerris incognitus water striders. We could not detect intersex genetic correlations for these sexually antagonistic traits. Ecological variation was related to population variation in the key female antagonistic trait (spine length, a defence against males), as well as body size. Nevertheless, population covariation between sexually antagonistic traits remained substantial and significant even after accounting for all of these processes. Our results therefore provide strong evidence for a contemporary sexual arms race.

opencc-zeroMay 2019View details →

Data from: Ecological gradients drive insect wing loss and speciation: the role of the alpine treeline

Alpine ecosystems are frequently characterised by an abundance of wing-reduced insect species, but the drivers of this biodiversity remain poorly understood. Insect wing reduction in these environments has variously been attributed to altitude, temperature, isolation, habitat stability, or decreased habitat size. We used fine-scale ecotypic and genomic analyses, along with broad-scale distributional analyses of ecotypes, to unravel the ecological drivers of wing reduction in the wing-dimorphic stonefly Zelandoperla fenestrata complex. Altitudinal transects within populations revealed dramatic wing reduction over very fine spatial scales, tightly linked to the alpine treeline. Broad biogeographic analyses confirm that the treeline has a much stronger effect on these ecotype distributions than altitude per se. Molecular analyses revealed parallel genomic divergence between vestigial-winged (high altitude) and full-winged (low altitude) ecotypes across distinct streams. These data thus highlight the role of the alpine treeline as a key driver of rapid speciation, providing a new model for ecological diversification along exposure gradients

opencc-zeroDec 2016View details →

Data from: Testing the role of mating preference in a case of incomplete ecological speciation with gene flow

Mating preference can evolve as a side effect of ecological adaptation and simultaneously contribute to speciation in certain scenarios. However, theoretical predictions have been difficult to test experimentally because there has not been any simple way to relate empirical and theoretical parameters. Recently, it has been shown that the r coefficient and other statistics can be used to estimate mating preference in wild-captured mating pairs. In the present work we use these estimators to test whether mating preference has significantly increased in a context favorable for ecological divergence. We perform the study using two groups of samples from populations of the marine gastropod Littorina saxatilis: 1) a group of bimodal populations affected by ecological divergence, and 2) a group of unimodal populations. The results show that mating preference (unlike the trait affected by the preference) does not increase when two ecotypes meet and mate in sympatry, which suggests that mating preference must be controlled by strong stabilizing natural selection, and/or limited by mating cost. This would suggest that mating preference would rarely contribute to speciation under the face of gene flow in these ecotypes.

opencc-zeroDec 2017View details →

Data from: Ecological divergence plays an important role in strong but complex reproductive isolation in campions (Silene)

New species arise through the evolution of reproductive barriers between formerly interbreeding lineages. Yet, comprehensive assessments of potential reproductive barriers, which are needed to make inferences on processes driving speciation, are only available for a limited number of systems. In this study, we estimated individual and cumulative strengths of seven prezygotic and six postzygotic reproductive barriers between the recently diverged taxa Silene dioica (L.) Clairv. and S. latifolia Poiret using both published and new data. A combination of multiple partial reproductive barriers resulted in near-complete reproductive isolation between S. dioica and S. latifolia that is consistent with earlier estimates of gene flow between the taxa. Extrinsic barriers associated with adaptive ecological divergence were most important, while intrinsic postzygotic barriers had moderate individual strength but contributed only little to total reproductive isolation. These findings are most in line with ecological divergence as driver of speciation. We further found extensive variation in extrinsic reproductive isolation, ranging from sites with strong selection against migrants and hybrids to more intermediate sites where substantial hybridization is possible. This situation may allow for or even promote heterogeneous genetic divergence.

opencc-zeroOct 2019View details →

An effective mutualism? The role of theoretical studies in ecology and evolution

Theoretical models often have fundamentally different goals than do empirical studies of the same topic. Models can test the logic of existing hypotheses, explore the plausibility of new hypotheses, provide expectations that can be tested with data, and address aspects of topics that are currently inaccessible empirically. Theoretical models are common in ecology and evolution, and are generally well-cited, but I show that many citations appearing in non-theoretical studies are general to topic and a substantial proportion are incorrect. One potential cause of this pattern is that some functions of models are rather abstract, leading to miscommunication between theoreticians and empiricists. Such misunderstandings are often triggered by simplifying, logistical assumptions that modelers make. The 2018 Vice Presidential Symposium of the American Society of Naturalists included a variety of mathematical models in ecology and evolution from across several topics. Common threads that appear in the use of the models are identified, highlighting the power of a theoretical approach and the role of the assumptions that such models make.

opencc-zeroJan 2022View details →

The roles of recombination and selection in shaping genomic divergence in an incipient ecological species complex

Speciation genomic studies have revealed that genomes of diverging lineages are shaped jointly by the actions of gene flow and selection. These evolutionary forces acting in concert with processes such as recombination and genome features such as gene density shape a mosaic landscape of divergence. We investigated the roles of recombination and gene density in shaping the patterns of differentiation and divergence between the cyclically parthenogenetic ecological sister-taxa, Daphnia pulicaria and Daphnia pulex. First, we assembled a phased chromosome-scale genome assembly using trio-binning for D. pulicaria and constructed a genetic map using an F2-intercross panel to understand sex-specific recombination rate heterogeneity. Finally, we used a ddRADseq dataset with broad geographic sampling of D. pulicaria, D. pulex, and their hybrids to understand the patterns of genome-scale divergence and demographic parameters. Our study provides the first sex-specific estimates of recombination rates for a cyclical parthenogen, and unlike other eukaryotic species, we observed male-biased heterochiasmy in D. pulicaria, which may be related to this somewhat unique breeding mode. Additionally, regions of high gene density and recombination are generally more divergent than regions of suppressed recombination. Outlier analysis indicated that divergent genomic regions are likely driven by selection on D. pulicaria, the derived lineage colonizing a novel lake habitat. Together, our study supports a scenario of selection acting on genes related to local adaptation shaping genome-wide patterns of differentiation despite high local recombination rates in this species complex. Finally, we discuss the limitations of our data in light of demographic uncertainty.

opencc-zeroJun 2022View details →

Bite force in the strictly subterranean rodent family of African mole-rats (Bathyergidae): the role of digging mode, social organisation, and ecology

Bite force is an ecologically relevant performance trait that has been measured to better understand the adaptations to diet and habitat use. Moreover, bite force is relevant in understanding reproductive success, as well as inter- and intraspecific competition. African mole-rats (Bathyergidae, Rodentia) are a unique clade of mammals that use different digging strategies, show different types of social organisation, and occur in ecologically diverse savannah habitats in Sub-Saharan Africa. Whereas previous studies have suggested these animals have exceptionally high bite forces, the ecological and other proximate and ultimate drivers of variation in bite force in the group remain unstudied. In the present study we measured in vivo bite force of 394 adult specimens from ten African mole-rat species including all genera within the family. Our results show that in African mole-rats digging mode is a major driver of variation in bite force, with chisel-tooth diggers being stronger biters than scratch-diggers. Moreover, species living in habitats characterised by low and irregular precipitation patterns and in soils with a high content of coarse particles have a higher bite force than species occupying habitats with a regular rainfall pattern and fine soil types. This suggests that bite force in bathyergids has evolved in concert with rainfall and soil characteristics of different savannah habitats, which have contributed to the successful radiation of these subterranean mammals across sub-Saharan Africa.

FIG. 4 in Going with the Flow: Testing the Role of Habitat Isolation among Three Ecologically Divergent Darter Species

FIG. 4. Reduced major axis regression plots from the isolation by distance analysis for (A) Ammocrypta beanii, (B) Etheostoma swaini, and (C) Percina nigrofasciata.

FIG. 3 in Going with the Flow: Testing the Role of Habitat Isolation among Three Ecologically Divergent Darter Species

FIG. 3. Bar plots representing estimated genetic clusters (K) and individual probability estimates of cluster assignment (Q values) from program STRUCTURE for (A) A. beanii at K ¼ 5, (B) E. swaini at K ¼ 2, and (C) P. nigrofasciata at K ¼ 4. The most likely K value was estimated using the ad hoc DK statistic (Evanno et al., 2005).

FIG. 2 in Going with the Flow: Testing the Role of Habitat Isolation among Three Ecologically Divergent Darter Species

FIG. 2. Chart showing habitat characteristics of each darter species and predicted levels of gene flow between populations based on habitat variables. FST represents population differentiation, while AR represents allelic richness. Arrows pointing up indicate an increase, arrows pointing down a decrease, and horizontal arrows indicate moderate/intermediate levels. Illustrations were designed by Elizabeth Marchio (elizabeth. marchio@gmail.com; www.lizmarchio.com).

FIG. 1 in Going with the Flow: Testing the Role of Habitat Isolation among Three Ecologically Divergent Darter Species

FIG. 1. Map of Pearl River including sampling sites for the three darter species. Ammocrypta beanii, Etheostoma swaini, and Percina nigrofasciata are represented by circles, squares, and diamonds, respectively. Map was generated using ArcGIS ArcMap 10.

FIG. 1 in Warming Strengthens the Ecological Role of Intraspecific Variation in a Predator

FIG. 1. The temperature profiles of both fish sources used in the study. ''Cool-source'' fish were taken from the artesian well and ''warm-source'' fish were taken from Keough's Hot Ditch, both in Bishop, California, USA. Daily average air temperatures are plotted from the Bishop Airport weather station, Bishop, California (Station ID GHCND:USW00023157), measured over the same period. In these geothermal systems, air temperature has little influence on water temperature.

FIG. 2 in Warming Strengthens the Ecological Role of Intraspecific Variation in a Predator

FIG. 2. (A) The mean of each logged temperature for both the warmed (black) and unwarmed (gray) treatments. (B) The difference between treatment means at each time-point, with the hatched line showing the overall mean temperature increase in the warming treatment: 2.218C.

FIG. 6 in Warming Strengthens the Ecological Role of Intraspecific Variation in a Predator

FIG. 6. Trait differences between populations at the end of the experiment. Fish population growth (A) was the number of offspring present at the end of the experiment, and total fish biomass (B) was the dry mass of all fish within a mesocosm at the end of the experiment. Means and standard errors were calculated without removing outliers (Supplemental Appendix 3; see Data Accessibility). Raw data points each reflect a mesocosm (triangles are warm-source, and circles are cool-source).

FIG. 5 in Warming Strengthens the Ecological Role of Intraspecific Variation in a Predator

FIG. 5. The absolute value of effect sizes for all responses calculated over all sampling points, separately for (A) the fish introduction effect and (B) the intraspecific variation effect.

FIG. 4 in Warming Strengthens the Ecological Role of Intraspecific Variation in a Predator

FIG. 4. Response of net primary production (A) and phosphate concentration (B) to warming and fish treatments at the final sampling point of the experiment—four weeks after fish introduction. Y-axes are plotted on the log10 scale.