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Predator-prey interactions determine food web structure, energy flux, and ecosystem stability. Increasing temperatures and commercial fishing both alter body size distributions that underpin predator-prey interactions, but empirical evidence of their individual and combined effects is limited. We study how the predator to prey body mass ratio (PPMR) changes as a function of temperature and fishing effort in over 50,000 predator stomachs collected across the Northeast Atlantic over 35 years. PPMR increases with temperature, an effect that is exacerbated by greater fishing effort, driven by intraspecific decreases in prey body mass in heavily fished areas. To compensate for smaller prey (both within and across species) in warmer waters and areas of high fishing, predators target the largest prey available to them, but this is insufficient to alter the community-wide increase in PPMR. Higher PPMR is associated with weaker trophic interactions that dampen strong oscillatory dynamics but could also reduce energy transfer efficiency within ecosystems, both of which can affect ecosystem stability. These results could help underpin ecosystem-based management and sustainable fisheries by providing estimates of how future climate warming might interact with fishing to affect energy flux through marine food webs. This study shows how commercial fishing and increasing temperatures impact predator-to-prey body mass ratios (PPMR) in the Northeast Atlantic. Authors identify an increase in PPMR that may weaken ecosystem stability, giving insight for sustainable fisheries management under future climate warming.

Savanna ecosystems are dominated by two distinct plant life forms, grasses and trees, but the interactions between them are poorly understood. Here, we quantified the effects of isolated savanna trees on grass biomass as a function of distance from the base of the tree and tree height, across a precipitation gradient in the Kruger National Park, South Africa. Our results suggest that mean annual precipitation (MAP) mediates the nature of tree-grass interactions in these ecosystems, with the impact of trees on grass biomass shifting qualitatively between 550 and 737 mm MAP. Tree effects on grass biomass were facilitative in drier sites (MAP≤550 mm), with higher grass biomass observed beneath tree canopies than outside. In contrast, at the wettest site (MAP = 737 mm), grass biomass did not differ significantly beneath and outside tree canopies. Within this overall precipitation-driven pattern, tree height had positive effect on sub-canopy grass biomass at some sites, but these effects were weak and not consistent across the rainfall gradient. For a more synthetic understanding of tree-grass interactions in savannas, future studies should focus on isolating the different mechanisms by which trees influence grass biomass, both positively and negatively, and elucidate how their relative strengths change over broad environmental gradients.

Fishing gear-based landings or survey methods are often used to make assessments of species stock abundance. In order to convert catch into abundance values, estimates or assumptions are made on the catch efficiency of the gear-based method. This is the case in areas where flat oysters, Ostrea edulis , are surveyed for fisheries and conservation objectives in a range of projects across Europe. Flat oyster dredge efficiency assumptions vary widely from 5–30% in published studies and uncertainty in what is an appropriate efficiency estimate has led some survey teams to switch to Catch-per-unit-effort (CPUE), where CPUE is also of concern should catch efficiency change with shellfish density, ground type or some other unmeasured variable such as shellfish distribution. We undertook an experimental approach to estimate dredge efficiency in a standard ladder dredge used to harvest and survey adult flat oysters in the UK and Ireland. The dredge efficiency trials assessed how efficiency was influenced by oyster density (between 1 and 2.2 oysters m 2 ), distribution (clumped vs uniform) and ground types across a gradient of more hard to more soft surface sediments. Dredge efficiency was significantly affected by oyster distribution, but also density and ground hardness as well as their interactions. While a median value between 7 and 10% seems an appropriate universal ladder dredge efficiency to adopt, ground type and distribution had such an effect that local conditions may effect this considerably. Catch efficiency was negatively density-dependent, this makes CPUE methods challenging where oyster densities are likely to vary. Practitioners, regulators and researchers conducting surveys can improve CPUE approaches through standard techniques and knowledge of how catch efficiency varies as we have presented here.

Sexually selected weapons used in intra‐sexual competition for mates are among the most striking animal features, but how their evolution affects life history traits closely correlated with fitness, and hence species' evolutionary trajectories, is not well understood. Here, we selected for or against male morphs carrying a lethal weapon in a male‐dimorphic mite Sancassania berlesei, and investigated how life histories evolve in populations with high vs. low proportion of weaponized, aggressive males called fighters and non‐weaponized, non‐aggressive males called scramblers. After 25 generations of experimental evolution, females from fighter‐selected lines showed higher early‐life fecundity compared to females from lines selected for non‐aggressive scrambler males. Furthermore, both sexes matured earlier in fighter‐selected lines compared to scrambler‐selected ones. Larvae‐to‐adult survivorship was not affected by such selection treatment. Finally, we investigated whether adult survivorship under temperature stress was influenced by such selection treatment, and we found no difference between fighter‐selected and scrambler‐selected lines. Our results demonstrate that composite selection pressures resulting from the prevalence of costly intra‐sexual aggression lead to an increase in key components of fitness, with likely consequences for population dynamics. However, we found no evidence that the response to such selection affects how individuals cope with environmental challenge. Using a soil mite system with dimorphic males, that is, aggressive, weaponized fighters and benign scramblers, we experimentally selected populations for higher proportion of fighter males for 25 generations. Populations with higher proportion of fighter males evolved faster juvenile development and higher early‐life fecundity. However, this evolution did not improve the survival of fighter populations in response to heat stress.

Sexual selection is a potent evolutionary force that can enhance adaptation and reduce mutational load, while simultaneously reducing survival, or causing sexual conflict that reduces fitness of one or both sexes. Many populations face extreme, short‐term stress events like heatwaves. The combined effects of sexual and environmental selection on population demography during and after such events remain poorly understood, even though such combined effects could be crucial for the persistence of small, endangered populations under climate change. In this study, we investigated how male aggression affects survival in a population during environmental stress. This was done by manipulating the expression of an aggressive male fighter morph in small populations of the male‐dimorphic mite Sancassania berlesei, using pheromonal cues from high‐density populations. We then exposed some of these populations to recurrent periods of extreme heat and monitored survival over eight generations. We found that heat exposure reduced survival, more severely in females than in males, and survival was lower in populations with higher fighter prevalence, but there was no interaction between temperature and fighter prevalence. Furthermore, survival declined across generations, and the decline was steeper in populations with lower prevalence of fighters, leading to the loss of their initial survival advantage by the last generation. Three populations exposed to heat went extinct from the reduced fighter expression regime. Our findings imply that despite its cost to individual survival, male aggression does not exacerbate population sensitivity to heatwaves over generations. Furthermore, we demonstrate that the mortality costs of male aggression are gradually compensated over successive generations, which could be a result of a more effective purging of inbreeding depression. Thus, while the additive effect of aggression and heatwaves on survival may increase demographic risks for bottlenecked populations in the short term, sexual selection may increase the resilience of populations to prolonged bottlenecks. This study examines how male aggression influences population survival under recurrent heat stress using experimental evolution in Sancassania berlesei. We show that while sexually selected tr initially reduce individual survival, they do not increase sensitivity to heatwaves and may enhance long‐term resilience to bottlenecks possibly by facilitating the purging of inbreeding depression.

The European flat oyster, Ostrea edulis , is a habitat-forming bivalve which was historically widespread throughout Europe. Following its decline due to overfishing, pollution, sedimentation, invasive species, and disease, O. edulis and its beds are now listed as a threatened and/or declining species and habitat by OSPAR. Increasing recognition of the plight of the oyster, alongside rapidly developing restoration techniques and growing interest in marine restoration, has resulted in a recent and rapid growth in habitat restoration efforts. O. edulis seed supply is currently a major bottleneck in scaling up habitat restoration efforts in Europe. O. edulis has been cultured for centuries, however, research into its culture declined following the introduction of the Pacific oyster, Crassostrea gigas to Europe in the early 1970 s. Recent efforts to renew both hatchery and pond production of O. edulis seed for habitat restoration purposes are hampered by restoration project timelines and funding typically being short, or projects not planning appropriately for the timescales required for investment, research-and-development and delivery of oyster seed by commercial producers. Furthermore, funding for restoration is intermittent, making long-term commitments between producers and restoration practitioners difficult. Long-term, strategic investment in research and production are needed to overcome these bottlenecks and meet current ambitious restoration targets across Europe.

Phenotypic plasticity is predicted to evolve in more variable environments, conferring an advantage on individual lifetime fitness. It is less clear what the potential consequences of that plasticity will have on ecological population dynamics. Here, we use an invertebrate model system to examine the effects of environmental variation (resource availability) on the evolution of phenotypic plasticity in two life history traits—age and size at maturation—in long‐running, experimental density‐dependent environments. Specifically, we then explore the feedback from evolution of life history plasticity to subsequent ecological dynamics in novel conditions. Plasticity in both traits initially declined in all microcosm environments, but then evolved increased plasticity for age‐at‐maturation, significantly so in more environmentally variable environments. We also demonstrate how plasticity affects ecological dynamics by creating founder populations of different plastic phenotypes into new microcosms that had either familiar or novel environments. Populations originating from periodically variable environments that had evolved greatest plasticity had lowest variability in population size when introduced to novel environments than those from constant or random environments. This suggests that while plasticity may be costly it can confer benefits by reducing the likelihood that offspring will experience low survival through competitive bottlenecks in variable environments. In this study, we demonstrate how plasticity evolves in response to environmental variation and can alter population dynamics—demonstrating an eco‐evolutionary feedback loop in a complex animal moderated by plasticity in growth. Phenotypic plasticity is expected to evolve in variable environments, but the consequences this might have for population dynamics in a changing world are currently unknown. Here, we show that plasticity in life history traits can evolve which in turn modulates population dynamics in novel conditions. This evidences the potential role of plasticity in moderating eco‐evolutionary feedback loops.

Understanding the herd structure of housed dairy cows has the potential to reveal preferential interactions, detect changes in behavior indicative of illness, and optimize farm management regimes. This study investigated the structure and consistency of the proximity interaction network of a permanently housed commercial dairy herd throughout October 2014, using data collected from a wireless local positioning system. Herd-level networks were determined from sustained proximity interactions (pairs of cows continuously within three meters for 60 s or longer), and assessed for social differentiation, temporal stability, and the influence of individual-level characteristics such as lameness, parity, and days in milk. We determined the level of inter-individual variation in proximity interactions across the full barn housing, and for specific functional zones within it (feeding, non-feeding). The observed networks were highly connected and temporally varied, with significant preferential assortment, and inter-individual variation in daily interactions in the non-feeding zone. We found no clear social assortment by lameness, parity, or days in milk. Our study demonstrates the potential benefits of automated tracking technology to monitor the proximity interactions of individual animals within large, commercially relevant groups of livestock.

There are growing calls to restore populations of European native oysters (Ostrea edulis), on the premise that restored populations will support a range of ecosystem services with an emphasis placed on restored oyster habitats promoting biological diversity, however benefits associated with naturally occurring O. edulis remain unclear. We undertook biannual surveys in the Blackwater, Crouch, Roach and Colne Estuaries Marine Conservation Zone (BCRC.MCZ), a highly sedimented estuary complex in the southern North Sea, to investigate links between natural densities of O. edulis (0–4.2 m−2), the prevalence of other dominant habitat features such as non‐native slipper limpet (Crepidula fornicata), dead shell abundance and epibenthic macroinvertebrate species richness. Increased epibenthic species richness was associated with O. edulis, even at densities below the OSPAR Commission recognized definition of an oyster bed (5 oysters m−2). Our analysis predicts increased associated species richness with density of native oysters (e.g., +1.6 additional species at 1 oyster m−2 or + 2.8 species at 5 oysters m−2), but only in areas with lower density of C. fornicata. Where C. fornicata are at higher density, the potential benefits of oyster restoration for associated species were curtailed. This may explain the observed asymptotic relationship between oyster density and diversity at 1 oyster m−2. In these and other high Crepidula density areas we recommend extending native oyster habitat even at low density. This may be of particular interest to areas with the protozoan oyster parasite Bonamia ostreae, which spreads more easily in high‐density areas. These lower density thresholds should also be considered for future management decisions—closing harvests so they do not reduce density further and impair biodiversity services of the habitats. In conclusion, while C. fornicata may be a useful oyster settlement substrate, we find that it limits the potential increases in associated species gains of oyster restoration.

Rising atmospheric carbon dioxide levels are driving decreases in aquatic pH. As a result, there has been a surge in the number of studies examining the impact of acidification on aquatic fauna over the past decade. Thus far, both positive and negative impacts on the growth of fish have been reported, creating a disparity in results. Food availability and single‐generation exposure have been proposed as some of the reasons for these variable results, where unrealistically high food treatments lead to fish overcoming the energetic costs associated with acclimating to decreased pH. Likewise, exposure of fish to lower pH for only one generation may not capture the likely ecological response to acidification that wild populations might experience over two or more generations. Here we compare somatic growth rates of laboratory populations of the Trinidadian guppy (Poecilia reticulata) exposed to pH levels that represent the average and lowest levels observed in streams in its native range. Specifically, we test the role of maternal acclimation and resource availability on the response of freshwater fishes to acidification. Acidification had a negative impact on growth at more natural, low food treatments. With high food availability, fish whose mothers were acclimated to the acidified treatment showed no reduction in growth, compared to controls. Compensatory growth was observed in both control–acidified (maternal–natal environment) and acidified–control groups, where fish that did not experience intergenerational effects achieved the same size in response to acidification as those that did, after an initial period of stunted growth. These results suggest that future studies on the effects of shifting mean of aquatic pH on fishes should take account of intergenerational effects and compensatory growth, as otherwise effects of acidification may be overestimated. With concerns that decreasing marine and freshwater pH, fish development, and behavior will be negatively effected, we set out to test this in freshwater guppies and found that while stream acidification limits juvenile growth, both high resource availability and maternal exposure to acidified conditions can help fishes overcome previously observed negative effects of growth. A multi‐generation approach that considers plasticity and evolution is required to adequately assess the effects of environmental change on fishes.