The evolution of thermal performance can constrain dispersal during range shifting

Organisms can cope with changing temperature under climate change by either adapting to the temperature at which they perform best and/or by dispersing to more benign locations. The evolution of a new thermal niche during range shifting is, however, expected to be strongly constrained by genetic load because spatial sorting is known to induce fast evolution of dispersal. To broaden our understanding of this interaction, we studied the joint evolution of dispersal and thermal performance curves (TPCs) of a population during range shifting by applying an individual-based spatially explicit model. Always, TPCs adapted to the local thermal conditions. Remarkably, this adaptation coincided with an evolution of dispersal at the shifting range front being equally high or lower than at the trailing edge. This optimal strategy reduces genetic load and highlights that evolutionary dynamics during range shifting change when crucial traits such as dispersal and thermal performance jointly evolve

Spatial selection and local adaptation jointly shape life-history evolution during range expansion

In the context of climate change and species invasions, range shifts increasingly gain attention because the rates at which they occur in the Anthropocene induce rapid changes in biological assemblages. During range shifts, species experience multiple selection pressures. For poleward expansions in particular, it is difficult to interpret observed evolutionary dynamics because of the joint action of evolutionary processes related to spatial selection and to adaptation toward local climatic conditions. To disentangle the effects of these two processes, we integrated stochastic modeling and data from a common garden experiment, using the spider mite Tetranychus urticae as a model species. By linking the empirical data with those derived form a highly parameterized individual-based model, we infer that both spatial selection and local adaptation contributed to the observed latitudinal life-history divergence. Spatial selection best described variation in dispersal behavior, while variation in development was best explained by adaptation to the local climate. Divergence in life-history traits in species shifting poleward could consequently be jointly determined by contemporary evolutionary dynamics resulting from adaptation to the environmental gradient and from spatial selection. The integration of modeling with common garden experiments provides a powerful tool to study the contribution of these evolutionary processes on life-history evolution during range expansion

Antipredator Behavior and Physiology Determine Lestes Species Turnover Along the Pond-Permanence Gradient

Identifying key traits that shape trade-offs that restrict species to only a subset of environmental gradients is crucial to understanding and predicting species turnover. Previous field experiments have shown that larvae of Lestes damselfly species segregate along the entire gradient of pond permanence and predator presence and that differential predation risk and life history constraints together shape their distribution. Here, we report laboratory experiments that identify key differences in behavior and physiology among species that structure their distributions along this gradient. The absence of adaptive antipredator behavioral responses against large dragonfly larvae and fish of Lestes dryas, the only species to inhabit predator-free vernal ponds that dry each year, is consistent with its high vulnerability to predation and probably the key trait that excludes it from parts of the gradient with predators. The reciprocal dominance of two other Lestes species in permanent waters dominated by either dragonflies or fish can be explained by the lack of effective antipredator behaviors against dragonflies and fish, respectively. Maximal growth rates did not differ among Lestes along the gradient. However, in the natural predator environment of vernal ponds (only conspecific cannibals), the vernal-pond Lestes had higher growth rates than the other Lestes suggesting that this excludes other Lestes from vernal ponds. Similarly, Lestes species that inhabit temporary ponds (i.e., ponds that dry intermittently every few years but not every year) had a higher growth rate than the fishless permanent-pond Lestes in the presence of the syntopic dragonfly predator. These growth differences among Lestes in predator treatments were not due to differences in food intake, but due to differences in physiology. The vernal-pond Lestes converted more assimilated food into body mass compared to the other Lestes in the presence of conspecific larvae, and the temporary-pond Lestes had a higher conversion efficiency than the fishless permanent-pond Lestes in the presence of the syntopic dragonfly predators. In contrast, reductions in growth rate within species in the presence of syntopic predators were both physiologically and behaviorally mediated. The interplay between behavior and physiology may be a common feature of the growth/predation-risk trade-off, and their joint study is therefore critical to mechanistically link phenotype, performance, and community assembly along the freshwater habitat gradient

Predators and Life Histories Shape Lestes Damselfly Assemblages Along a Freshwater Habitat Gradient

Survey data from New England showed that assemblages of Lestes damselflies are organized along the entire gradient of pond permanence and predator presence. One assemblage occupies vernal ponds lacking large dragonfly predators and fish; four are largely confined to temporary ponds that typically contain dragonfly predators; one dominates fishless permanent ponds and lakes where dragonflies are the top predators; and one dominates permanent ponds and lakes where fish are the top predators. We determined the role of life history and predation in maintaining this striking pattern by conducting a series of transplant experiments in the field and a laboratory experiment manipulating presence and absence of local predators. Life history (1) shaped the ability of species to cope with drying regime, thereby excluding temporary‐pond Lestes from vernal ponds and permanent‐water Lestes from temporary ponds, and (2) generated size differences among species due to differences in the timing of hatching. This mediated the exclusion of temporary‐pond Lestes from permanent water bodies through asymmetric intraguild predation by permanent‐water Lestes. Dragonfly predation on permanent‐water Lestes had an indirect positive effect on the survival of temporary‐pond Lestes; however, this effect apparently is too small to allow coexistence of both Lestes groups. Predation by large dragonfly larvae excluded the Lestes species of vernal ponds from temporary ponds, and differential vulnerability to large dragonfly larvae and fish shaped the reciprocal dominance of L. eurinus and L. vigilax in fishless and fish‐containing permanent water bodies, respectively. Taken together, these results show that life history constraints and predation both shape the distributions of Lestes species along the pond permanence gradient in New England. We discuss the importance of this freshwater habitat gradient in shaping local and regional species diversity

Predators and Life Histories Shape Lestes Damselfly Assemblages Along a Freshwater Habitat Gradient

Survey data from New England showed that assemblages of Lestes dam- selflies are organized along the entire gradient of pond permanence and predator presence. One assemblage occupies vernal ponds lacking large dragonfly predators and fish; four are largely confined to temporary ponds that typically contain dragonfly predators; one dom- inates fishless permanent ponds and lakes where dragonflies are the top predators; and one dominates permanent ponds and lakes where fish are the top predators. We determined the role of life history and predation in maintaining this striking pattern by conducting a series of transplant experiments in the field and a laboratory experiment manipulating presence and absence of local predators. Life history (1) shaped the ability of species to cope with drying regime, thereby excluding temporary-pond Lestes from vernal ponds and permanent- water Lestes from temporary ponds, and (2) generated size differences among species due to differences in the timing of hatching. This mediated the exclusion of temporary-pond Lestes from permanent water bodies through asymmetric intraguild predation by permanent- water Lestes. Dragonfly predation on permanent-water Lestes had an indirect positive effect on the survival of temporary-pond Lestes; however, this effect apparently is too small to allow coexistence of both Lestes groups. Predation by large dragonfly larvae excluded the Lestes species of vernal ponds from temporary ponds, and differential vulnerability to large dragonfly larvae and fish shaped the reciprocal dominance of L. eurinus and L. vigilax in fishless and fish-containing permanent water bodies, respectively. Taken together, these results show that life history constraints and predation both shape the distributions of Lestes species along the pond permanence gradient in New England. We discuss the importance of this freshwater habitat gradient in shaping local and regional species diversity

More rapid climate change promotes evolutionary rescue through selection for increased dispersal distance

Acknowledgements This research was funded by FWO projects G.0057.09 to DB and JB, and G.0610.11 to DB, JB and RS. JMJT, DB and RS are supported by the FWO Research Network EVENET.Peer reviewedPublisher PD

Antipredator behavior and physiology determine Lestes species turnover along the pond-permanence gradient.

Abstract. Identifying key traits that shape trade-offs that restrict species to only a subset of environmental gradients is crucial to understanding and predicting species turnover. Previous field experiments have shown that larvae of Lestes damselfly species segregate along the entire gradient of pond permanence and predator presence and that differential predation risk and life history constraints together shape their distribution. Here, we report laboratory experiments that identify key differences in behavior and physiology among species that structure their distributions along this gradient. The absence of adaptive antipredator behavioral responses against large dragonfly larvae and fish of Lestes dryas, the only species to inhabit predator-free vernal ponds that dry each year, is consistent with its high vulnerability to predation and probably the key trait that excludes it from parts of the gradient with predators. The reciprocal dominance of two other Lestes species in permanent waters dominated by either dragonflies or fish can be explained by the lack of effective antipredator behaviors against dragonflies and fish, respectively. Maximal growth rates did not differ among Lestes along the gradient. However, in the natural predator environment of vernal ponds (only conspecific cannibals), the vernal-pond Lestes had higher growth rates than the other Lestes suggesting that this excludes other Lestes from vernal ponds. Similarly, Lestes species that inhabit temporary ponds (i.e., ponds that dry intermittently every few years but not every year) had a higher growth rate than the fishless permanent-pond Lestes in the presence of the syntopic dragonfly predator. These growth differences among Lestes in predator treatments were not due to differences in food intake, but due to differences in physiology. The vernal-pond Lestes converted more assimilated food into body mass compared to the other Lestes in the presence of conspecific larvae, and the temporary-pond Lestes had a higher conversion efficiency than the fishless permanent-pond Lestes in the presence of the syntopic dragonfly predators. In contrast, reductions in growth rate within species in the presence of syntopic predators were both physiologically and behaviorally mediated. The interplay between behavior and physiology may be a common feature of the growth/predation-risk trade-off, and their joint study is therefore critical to mechanistically link phenotype, performance, and community assembly along the freshwater habitat gradient

Transgenerational interactions between pesticide exposure and warming in a vector mosquito

While transgenerational plasticity may buffer ectotherms to warming and pesticides separately, it remains unknown how combined exposure to warming and pesticides in the parental generation shapes the vulnerability to these stressors in the offspring. We studied the transgenerational effects of single and combined exposure to warming (4°C increase) and the pesticide chlorpyrifos on life history traits of the vector mosquito Culex pipiens. Parental exposure to a single stressor, either warming or the pesticide, had negative effects on the offspring: both parental exposure to warming and to the pesticide resulted in an overall lower offspring survival, and a delayed offspring metamorphosis. Parental exposure to a single stressor did, however, not alter the vulnerability of the offspring to the same stressor in terms of survival. Parental pesticide exposure resulted in larger offspring when the offspring experienced the same stressor as the parents. Within both the parental and offspring generations, warming made the pesticide more toxic in terms of survival. Yet, this synergism disappeared in the offspring of parents exposed to both stressors simultaneously because in this condition the pesticide was already more lethal at the lower temperature. Our results indicate that transgenerational effects will not increase the ability of this vector species to deal with pesticides in a warming world. Bifactorial transgenerational experiments are crucial to understand the combined impact of warming and pesticides across generations, hence to assess the efficacy of vector control in a warming world.status: publishe

Time Constraints Mediate Predator-Induced Plasticity in Immune Function, Condition, and Life History

The simultaneous presence of predators and a limited time for development imposes a conflict: accelerating growth under time constraints comes at the cost of higher predation risk mediated by increased foraging. The few studies that have addressed this trade-off have dealt only with life history traits such as age and size at maturity. Physiological traits have largely been ignored in studies assessing the impact of environmental stressors, and it is largely unknown whether they respond independently of life history traits. Here, we studied the simultaneous effects of time constraints, i.e., as imposed by seasonality, and predation risk on immune defense, energy storage, and life history in lestid damselflies. As predicted by theory, larvae accelerated growth and development under time constraints while the opposite occurred under predation risk. The activity of phenoloxidase, an important component of insect immunity, and investment in fat storage were reduced both under time constraints and in the presence of predators. These reductions were smaller when time constraints and predation risk were combined. This indicates that predators can induce sublethal costs linked to both life history and physiology in their prey, and that time constraints can independently reduce the impact of predator-induced changes in life history and physiology