The impact of habitat loss on molecular signatures of coevolution between an iconic butterfly (Alcon blue) and its host plant (Marsh gentian).

Habitat loss is threatening natural communities worldwide. Small and isolated populations suffer from inbreeding and genetic drift, which jeopardize their long-term survival and adaptive capacities. However, the consequences of habitat loss for reciprocal coevolutionary interactions remain poorly studied. In this study, we investigated the effects of decreasing habitat patch size and connectivity associated with habitat loss on molecular signatures of coevolution in the Alcon blue butterfly (Phengaris alcon) and its most limited host, the marsh gentian (Gentiana pneumonanthe). Because reciprocal coevolution is characterized by negative frequency-dependent selection as a particular type of balancing selection, we investigated how signatures of balancing selection vary along a gradient of patch size and connectivity, using single nucleotide polymorphisms (SNPs). We found that signatures of coevolution were unaffected by patch characteristics in the host plants. On the other hand, more pronounced signatures of coevolution were observed in both spatially isolated and in large Alcon populations, together with pronounced spatial variation in SNPs that are putatively involved in coevolution. These findings suggest that habitat loss can facilitate coevolution in large butterfly populations through limiting swamping of locally beneficial alleles by maladaptive ones. We also found that allelic richness (Ar) of the coevolutionary SNPs is decoupled from neutral Ar in the butterfly, indicating that habitat loss has different effects on coevolutionary as compared with neutral processes. We conclude that this specialized coevolutionary system requires particular conservation interventions aiming at generating a spatial mosaic of both connected and of isolated habitat to maintain coevolutionary dynamics.

Seventh BMC ecology image competition: the winning images.

The seventh BMC Ecology competition attracted entries from talented ecologists from around the world. Together, they showcase the beauty and diversity of life on our planet as well as providing an insight into the biological interactions found in nature. This editorial celebrates the winning images as selected by the Editor of BMC Ecology and senior members of the journal's editorial board. Enjoy!

BMC ecology image competition 2018: the winning images.

The sixth BMC Ecology Image Competition received more than 145 photographs from talented ecologists around the world, showcasing the amazing biodiversity, natural beauty and biological interactions found in nature. In this editorial, we showcase the winning images, as selected by our guest judge, Professor Zhigang Jiang from the Institute of Zoology of the Chinese Academy of Sciences, with help from the journal's editorial board. Enjoy!

Genetic costructure in a meta-community under threat of habitat fragmentation.

Habitat fragmentation increasingly threatens the services provided by natural communities and ecosystem worldwide. An understanding of the eco-evolutionary processes underlying fragmentation-compromised communities in natural settings is lacking, yet critical to realistic and sustainable conservation. Through integrating the multivariate genetic, biotic and abiotic facets of a natural community module experiencing various degrees of habitat fragmentation, we provide unique insights into the processes underlying community functioning in real, natural conditions. The focal community module comprises a parasitic butterfly of conservation concern and its two obligatory host species, a plant and an ant. We show that both historical dispersal and ongoing habitat fragmentation shape population genetic diversity of the butterfly Phengaris alcon and its most limited host species (the plant Gentiana pneumonanthe). Genetic structure of each species was strongly driven by geographical structure, altitude and landscape connectivity. Strikingly, however, was the strong degree of genetic costructure among the three species that could not be explained by the spatial variables under study. This finding suggests that factors other than spatial configuration, including co-evolutionary dynamics and shared dispersal pathways, cause parallel genetic structure among interacting species. While the exact contribution of co-evolution and shared dispersal routes on the genetic variation within and among communities deserves further attention, our findings demonstrate a considerable degree of genetic parallelism in natural meta-communities. The significant effect of landscape connectivity on the genetic diversity and structure of the butterfly also suggests that habitat fragmentation may threaten the functioning of the community module on the long run.

BMC ecology image competition 2017: the winning images.

For the fifth year, BMC Ecology is proud to present the winning images from our annual image competition. The 2017 edition received entries by talented shutterbug-ecologists from across the world, showcasing research that is increasing our understanding of ecosystems worldwide and the beauty and diversity of life on our planet. In this editorial we showcase the winning images, as chosen by our Editorial Board and guest judge Chris Darimont, as well as our selection of highly commended images. Enjoy!

Evolution of a butterfly dispersal syndrome.

The existence of dispersal syndromes contrasting disperser from resident phenotypes within populations has been intensively documented across taxa. However, how such suites of phenotypic traits emerge and are maintained is largely unknown, although deciphering the processes shaping the evolution of dispersal phenotypes is a key in ecology and evolution. In this study, we created artificial populations of a butterfly, in which we controlled for individual phenotypes and measured experimentally the roles of selection and genetic constraints on the correlations between dispersal-related traits: flight performance and wing morphology. We demonstrate that (i) trait covariations are not due to genetic correlations, (ii) the effects of selection are sex-specific, and (iii) both divergent and stabilizing selection maintain specific flight performance phenotypes and wing morphologies. Interestingly, some trait combinations are also favoured, depending on sex and fitness components. Moreover, we provide evidence for the role of (dis)assortative mating in the evolution of these dispersal-related traits. Our results suggest that dispersal syndromes may have high evolutionary potential, but also that they may be easily disrupted under particular environmental conditions.

The Metatron: an experimental system to study dispersal and metaecosystems for terrestrial organisms.

Dispersal of organisms generates gene flow between populations. Identifying factors that influence dispersal will help predict how species will cope with rapid environmental change. We developed an innovative infrastructure, the Metatron, composed of 48 interconnected patches, designed for the study of terrestrial organism movement as a model for dispersal. Corridors between patches can be flexibly open or closed. Temperature, humidity and illuminance can be independently controlled within each patch. The modularity and adaptability of the Metatron provide the opportunity for robust experimental design for the study of 'meta-systems'. We describe a pilot experiment on populations of the butterfly Pieris brassicae and the lizard Zootoca vivipara in the Metatron. Both species survived and showed both disperser and resident phenotypes. The Metatron offers the opportunity to test theoretical models in spatial ecology.

BMC Ecology Image Competition 2015: the winning images.

For the third time, BMC Ecology is delighted to announce the winners of our Image Competition. This year featured entries from all over the world and showcased not only the creativity and talent of the participants, but also the exquisite beauty and diversity of our planet. We are pleased to present the winning selections of the editorial board of the journal and guest judge Dr. Ana Luz Porzecanski, as well as some highly commended images that are sure to impress.

A comparative analysis of dispersal syndromes in terrestrial and semi-terrestrial animals.

Dispersal, the behaviour ensuring gene flow, tends to covary with a number of morphological, ecological and behavioural traits. While species-specific dispersal behaviours are the product of each species' unique evolutionary history, there may be distinct interspecific patterns of covariation between dispersal and other traits ('dispersal syndromes') due to their shared evolutionary history or shared environments. Using dispersal, phylogeny and trait data for 15 terrestrial and semi-terrestrial animal Orders (> 700 species), we tested for the existence and consistency of dispersal syndromes across species. At this taxonomic scale, dispersal increased linearly with body size in omnivores, but decreased above a critical length in herbivores and carnivores. Species life history and ecology significantly influenced patterns of covariation, with higher phylogenetic signal of dispersal in aerial dispersers compared with ground dwellers and stronger evidence for dispersal syndromes in aerial dispersers and ectotherms, compared with ground dwellers and endotherms. Our results highlight the complex role of dispersal in the evolution of species life-history strategies: good dispersal ability was consistently associated with high fecundity and survival, and in aerial dispersers it was associated with early maturation. We discuss the consequences of these findings for species evolution and range shifts in response to future climate change.

Conservation genetics of a threatened butterfly: comparison of allozymes, RAPDs and microsatellites.

BACKGROUND: Addressing genetic issues in the management of fragmented wild populations of threatened species is one of the most important challenges in conservation biology. Nowadays, a diverse array of molecular methods exists to assess genetic diversity and differentiation of wild populations such as allozymes, dominant markers and co-dominant markers. However it remains worthwhile i) to compare the genetic estimates obtained using those several markers in order to ii) test their relative utility, reliability and relevance and iii) the impact of these results for the design of species-specific conservation measures. RESULTS: Following the successful isolation of 15 microsatellites loci for the cranberry fritillary butterfly, Boloria aquilonaris, we analyzed the genetic diversity and structure of eight populations located in four different landscapes, at both the regional and the landscape scales. We confront results based on microsatellites to those obtained using allozymes and RAPDs on the same samples. Genetic population analyses using different molecular markers indicate that the B. aquilonaris populations are characterized by a weak genetic variation, likely due to low effective population size and low dispersal at the regional scale. This results in inbreeding in some populations, which may have detrimental consequences on their long term viability. However, gene flow within landscape is limited but not inexistent, with some long range movements resulting in low or no isolation by distance. Spatial structuring was detected among the most isolated populations. CONCLUSIONS: The use of allozymes and RAPD are of very limited value to determine population structuring at small spatial (i.e. landscape) scales, microsatellites giving much higher estimate resolution. The use of RAPD data is also limited for evidencing inbreeding. However, coarse-grain spatial structure (i.e. regional scale), and gene flow estimates based on RAPD and microsatellites data gave congruent results. At a time with increasing development of new molecular methods and markers, dominant markers may still be worthwhile to consider in organisms for which no genomic information is available, and for which limited resources are available.

BMC Ecology image competition 2014: the winning images.

BMC Ecology showcases the winning entries from its second Ecology Image Competition. More than 300 individual images were submitted from an international array of research scientists, depicting life on every continent on earth. The journal's Editorial Board and guest judge Caspar Henderson outline why their winning selections demonstrated high levels of technical skill and aesthetic sense in depicting the science of ecology, and we also highlight a small selection of highly commended images that we simply couldn't let you miss out on.

Intra- and inter-individual variation in flight direction in a migratory butterfly co-vary with individual mobility.

Flight direction is a major component of an animal's migratory success. However, few studies have focused on variation in flight direction both between and within individuals, which is likely to be correlated with other traits implied in migration processes. We report patterns of intra- and inter-individual variation in flight direction in the large white butterfly Pieris brassicae. The presence of inter-individual variation in flight direction for individuals tested in the same conditions suggests that this trait is inherited in P. brassicae and we propose that a rapid loss of migratory skills may exist in the absence of selection for migration. The magnitude of intra-individual variation was negatively correlated to two surrogates of the potential for migration: mobility and wing length. Highly mobile and longed-winged individuals within the same family were found to fly in similar directions, whereas less mobile and short-winged individuals displayed divergent flight direction compared with the average direction of their kin. There was also a negative correlation between the variance to the mean flight direction of a family and its average mobility, but no correlation with wing length. We discuss these issues in terms of the evolution of traits potentially implied in both migration and dispersal in P. brassicae.

Population sex ratio and dispersal in experimental, two-patch metapopulations of butterflies.

1. Sex-biased dispersal, that is, the difference in dispersal between males and females, is thought to be the consequence of any divergent evolutionary responses between sexes. In anisogamous species, asymmetry in parental investment may lead to sexual conflict, which entails male-male competition (for sexual partner access), female-female competition (for feeding or egg-laying habitat patches) and/or male-female competition (antagonistic co-evolution). 2. As competition is one of the main causes of dispersal evolution, intra- and intersexual competition should have strong consequences on sex-biased dispersal. However, very few experimental studies, if any, have simultaneously addressed the effect of biased sex ratio on (i) each dispersal stage (emigration, transience, immigration), (ii) the dispersal phenotype and (iii) the colonization success of new habitat in order to fully separate the effects of varying male and female density. 3. Here, we used the Metatron, a unique experimental system composed of 48 interconnected enclosed patches dedicated to the study of dispersal in meta-ecosystems, to investigate the effect of sex ratio on dispersal in a butterfly. We created six populations with three different sex ratios in pairs of patches and recorded individual movements in these simple metapopulations. 4. Emigration was higher when the proportion of males was higher, and individuals reached the empty patch at a higher rate when the sex ratio in the departure patch was balanced. Males had a better dispersal success than females, which had a lower survival rate during dispersal and after colonization. We also showed that sex and wing size are major components of the dispersal response. 5. We did not observe sex-biased dispersal; our results thus suggest that female harassment by males and male-male competition might be more important mechanisms for the dispersal of females and males, than the search for a mating partner. Furthermore, the demonstration of a differential mortality between males and females during dispersal provides causal hypotheses of the evolution of sex-biased dispersal.

BMC Ecology image competition: the winning images.

BMC Ecology announces the winning entries in its inaugural Ecology Image Competition, open to anyone affiliated with a research institute. The competition, which received more than 200 entries from international researchers at all career levels and a wide variety of scientific disciplines, was looking for striking visual interpretations of ecological processes. In this Editorial, our academic Section Editors and guest judge Dr Yan Wong explain what they found most appealing about their chosen winning entries, and highlight a few of the outstanding images that didn't quite make it to the top prize.

Food transport in Reptilia: a comparative viewpoint.

Reptilia exploit a large diversity of food resources from plant materials to living mobile prey. They are among the first tetrapods that needed to drink to maintain their water homeostasis. Here were compare the feeding and drinking mechanisms in Reptilia through an empirical approach based on the available data to open perspectives in our understanding of the evolution of the various mechanisms determined in these Tetrapoda for exploiting solid and liquid food resources. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

How is dispersal integrated in life histories: a quantitative analysis using butterflies.

As dispersal plays a key role in gene flow among populations, its evolutionary dynamics under environmental changes is particularly important. The inter-dependency of dispersal with other life history traits may constrain dispersal evolution, and lead to the indirect selection of other traits as a by-product of this inter-dependency. Identifying the dispersal's relationships to other life-history traits will help to better understand the evolutionary dynamics of dispersal, and the consequences for species persistence and ecosystem functioning under global changes. Dispersal may be linked to other life-history traits as their respective evolutionary dynamics may be inter-dependent, or, because they are mechanistically related to each other. We identify traits that are predicted to co-vary with dispersal, and investigated the correlations that may constrain dispersal using published information on butterflies. Our quantitative analysis revealed that (1) dispersal directly correlated with demographic traits, mostly fecundity, whereas phylogenetic relationships among species had a negligible influence on this pattern, (2) gene flow and individual movements are correlated with ecological specialisation and body size, respectively and (3) routine movements only affected short-distance dispersal. Together, these results provide important insights into evolutionary dynamics under global environmental changes, and are directly applicable to biodiversity conservation.

Habitat fragmentation impacts mobility in a common and widespread woodland butterfly: do sexes respond differently?

BACKGROUND: Theory predicts a nonlinear response of dispersal evolution to habitat fragmentation. First, dispersal will be favoured in line with both decreasing area of habitat patches and increasing inter-patch distances. Next, once these inter-patch distances exceed a critical threshold, dispersal will be counter-selected, unless essential resources no longer co-occur in compact patches but are differently scattered; colonization of empty habitat patches or rescue of declining populations are then increasingly overruled by dispersal costs like mortality risks and loss of time and energy. However, to date, most empirical studies mainly document an increase of dispersal associated with habitat fragmentation. We analyzed dispersal kernels for males and females of the common, widespread woodland butterfly Pararge aegeria in highly fragmented landscape, and for males in landscapes that differed in their degree of habitat fragmentation. RESULTS: The male and female probabilities of moving were considerably lower in the highly fragmented landscapes compared to the male probability of moving in fragmented agricultural and deciduous oak woodland landscapes. We also investigated whether, and to what extent, daily dispersal distance in the highly fragmented landscape was influenced by a set of landscape variables for both males and females, including distance to the nearest woodland, area of the nearest woodland, patch area and abundance of individuals in the patch. We found that daily movement distance decreased with increasing distance to the nearest woodland in both males and females. Daily distances flown by males were related to the area of the woodland capture site, whereas no such effect was observed for females. CONCLUSION: Overall, mobility was strongly reduced in the highly fragmented landscape, and varied considerably among landscapes with different spatial resource distributions. We interpret the results relative to different cost-benefit ratios of movements in fragmented landscapes.

Selection on the wing in Heliconius butterflies.

To what extent population structure favours the establishment of new phenotypes within a species remains a fundamental question in evolutionary studies. By reducing gene flow, habitat fragmentation is a major factor shaping the genetic structuring of populations, favouring isolation of small populations in which drift may rapidly change frequencies of new variants. When these variants provide advantages to individuals, the combined effect of selection and drift can lead to rapid shifts in phenotypes. In a study published in BMC Genetics, Albuquerque de Moura et al. asked whether such a general pattern of population structure can be observed in Heliconius species, which could have strong implication in the evolution of colour pattern diversification in these butterflies. In this commentary we discuss the potential roles of these three processes (drift, selection and dispersal) on the evolution of Heliconius wing patterns in regard to the findings of a common fine-scale population structure within the co-mimetic species H. melpomene and H. erato. Indeed, a general pattern of population subdivision in the history of these two species may have provoked the major phenotypical shifts observed in their wing colour patterns. The suggestion that coupled environmental pressures (counter-selection of dispersal and selection on co-evolved traits) could be responsible for identical genetic differentiation profiles in H. erato and H. melpomene clearly merits further investigations using both detailed population genetic (including landscape genetic) and ecological studies.

Congruent Genetic and Demographic Dispersal Rates in a Natural Metapopulation at Equilibrium.

Understanding the functioning of natural metapopulations at relevant spatial and temporal scales is necessary to accurately feed both theoretical eco-evolutionary models and conservation plans. One key metric to describe the dynamics of metapopulations is dispersal rate. It can be estimated with either direct field estimates of individual movements or with indirect molecular methods, but the two approaches do not necessarily match. We present a field study in a large natural metapopulation of the butterfly Boloria eunomia in Belgium surveyed over three generations using synchronized demographic and genetic datasets with the aim to characterize its genetic structure, its dispersal dynamics, and its demographic stability. By comparing the census and effective population sizes, and the estimates of dispersal rates, we found evidence of stability at several levels: constant inter-generational ranking of population sizes without drastic historical changes, stable genetic structure and geographically-influenced dispersal movements. Interestingly, contemporary dispersal estimates matched between direct field and indirect genetic assessments. We discuss the eco-evolutionary mechanisms that could explain the described stability of the metapopulation, and suggest that destabilizing agents like inter-generational fluctuations in population sizes could be controlled by a long adaptive history of the species to its dynamic local environment. We finally propose methodological avenues to further improve the match between demographic and genetic estimates of dispersal.

Toward reliable habitat suitability and accessibility models in an era of multiple environmental stressors.

Global biodiversity declines, largely driven by climate and land-use changes, urge the development of transparent guidelines for effective conservation strategies. Species distribution modeling (SDM) is a widely used approach for predicting potential shifts in species distributions, which can in turn support ecological conservation where environmental change is expected to impact population and community dynamics. Improvements in SDM accuracy through incorporating intra- and interspecific processes have boosted the SDM field forward, but simultaneously urge harmonizing the vast array of SDM approaches into an overarching, widely adoptable, and scientifically justified SDM framework. In this review, we first discuss how climate warming and land-use change interact to govern population dynamics and species' distributions, depending on species' dispersal and evolutionary abilities. We particularly emphasize that both land-use and climate change can reduce the accessibility to suitable habitat for many species, rendering the ability of species to colonize new habitat and to exchange genetic variation a crucial yet poorly implemented component of SDM. We then unite existing methodological SDM practices that aim to increase model accuracy through accounting for multiple global change stressors, dispersal, or evolution, while shifting our focus to model feasibility. We finally propose a roadmap harmonizing model accuracy and feasibility, applicable to both common and rare species, particularly those with poor dispersal abilities. This roadmap (a) paves the way for an overarching SDM framework allowing comparison and synthesis of different SDM studies and (b) could advance SDM to a level that allows systematic integration of SDM outcomes into effective conservation plans.