The degree of plasticity an individual expresses when moving into a new environment is likely to influence the probability of colonization and potential for subsequent evolution. Yet few empirical examples exist where the ancestral and derived conditions suggest a role for plasticity in adaptive genetic divergence of populations. Here we explore the genetic and plastic components of shoaling behaviour in two pairs of populations of Poecilia reticulata (Trinidadian guppies). We contrast shoaling behaviour of guppies derived from high‐ and low‐predation populations from two separate drainages by measuring the shoaling response of second generation laboratory‐reared individuals in the presence and absence of predator induced alarm pheromones. We find persistent differences in mean shoaling cohesion that suggest a genetic basis; when measured under the same conditions high‐predation guppies form more cohesive shoals than low‐predation guppies. Both high and low‐predation guppies also exhibit plasticity in the response to alarm pheromones, by forming tighter, more cohesive shoals. These patterns suggest a conserved capacity for adaptive behavioural plasticity when moving between variable predation communities that are consistent with models of genetic accommodation.

Temperature extremes are predicted to increase in frequency, intensity and duration under global warming and are believed to significantly affect community composition and functioning. However, the effect of extreme climatic events on communities remains difficult to predict, especially because species can show dissimilar responses to abiotic changes, which may affect the outcome of species interactions. To anticipate community responses we need knowledge on within and among species variation in stress tolerance. We exposed a soil arthropod community to experimental heat waves in the field and measured heat tolerance of species of different trophic levels from heated and control plots. We measured the critical thermal maximum (CTmax) of individuals to estimate inter- and intraspecific variation in heat tolerance in this community, and how this was affected by experimental heat waves. We found interspecific variation in heat tolerance, with the most abundant prey species, the springtail Isotoma riparia, being more sensitive to high temperatures than its predators (various spider species). Moreover, intraspecific variation in CTmax was substantial, suggesting that individuals within a single species were unequally affected by heat extremes. However, heat tolerance of species did not increase after being exposed to an experimental heat wave. We conclude that interspecific variation in tolerance traits potentially causes trophic mismatches during extreme events, but that intraspecific variation could lessen these effects by enabling partial survival of populations. Therefore, ecophysiological traits can provide a better understanding of abiotic effects on communities, not only within taxonomic or functional groups, but also when comparing different trophic levels.Electronic supplementary materialThe online version of this article (10.1007/s00442-017-4032-z) contains supplementary material, which is available to authorized users.

<p>Salinizing surface water is a large problem worldwide. In many areas agriculture is dependent on surface water irrigation, but there is an increasing fresh water scarcity. Due to natural and anthropogenic processes the salt concentration of surface water has risen and this problem is predicted to increase in the future. Prioritizing on when fresh water is needed and when brackish or salt water could be possible is therefor necessary. However, this holds not only for agricultural systems, but also for natural areas which are currently overlooked. In deltaic areas – such as The Netherlands – sea water is flowing further inland via rivers during summer. In addition to this, in the hinterland, artificial drainage of low-lying polders leads to a salt groundwater surplus that is discharged into rivers and surface water reservoirs. These processes lead to salinization and could potentially affect plant biodiversity and ecosystem functioning in surface water fed ecosystems, wetlands, and riparian zones. One of such a surface water fed ecosystems is an abandoned turf extraction site ‘De Botshol’ in The Netherlands. Floating root mats have developed from peat baulks into the open water of old turf ponds. These mats can harbor a great deal of protected terrestrial, typically glycophyte (i.e. optimally encountering < 300 mg Cl.l-1), plant species related to a floating fen habitat. Currently the surface water quality of Botshol is brackish and this provided us with an opportunity to follow the local salt route through space and time. Surface water salt concentrations fluctuated slightly between winter-spring: 1400 mg Cl.l-1 and summer-autumn: 1900 mg Cl.l-1 and we linked this to root zone processes and the plant community. We used a pore water extraction setup using micro- and macrorhizons placed at 30 – 60 – 200 cm from the edge of a floating root mat. Along this transect we measured at 10 – 25 – 50 – 70 cm depth. Via this setup we were able to find that the root zone salt concentrations fluctuated with surface water concentration, however there was a substantially lower salt concentration in the soil layer. Root zone concentrations still reached above 500 mg Cl.l-1 and this might explain differences in community composition in comparison with a fresh floating fen ecosystem (e.g. ‘Nieuwkoopse Plassen’, The Netherlands). We present this work to empirically link hydrology and ecology in relation to surface water salinization, but also to practically inform water boards and nature managers to understand possibilities and limitations of surface water salinization in relation to fen restoration and protection.</p>