The challenge of managing threatened invasive species at a continental scale.

The European Union's (EU) environmental legislation establishes common measures to prevent the entry and spread of invasive non-native species and to minimize their impacts. However, species that are native to at least one member state but non-native and potentially invasive in others (NPIS) are in limbo because they are neither legally regulated at the EU level nor in most member states. We used the Communication and Information Resource Centre for Administrations, Businesses and Citizens (CIRCABC) raw data on NPIS (317 taxa) to analyze their distribution across the EU and identify which biogeographical regions are the main sources of invasions. We additionally evaluated the conservation challenge posed by NPIS that are threatened within their native ranges. We performed a pairwise analysis summarizing the number of species that are native to a given member state but non-native to another and vice versa. Although distribution patterns of NPIS varied across taxa groups, overall, southern and central EU countries were both donors and recipients of NPIS. Eastern countries were mainly a source, and western and northern countries mostly received NPIS. Around 27% of NPIS were threatened in some of their EU native ranges, which is a challenge for conservation and management because some of them have serious negative effects on European biodiversity, but hitherto remain outside the scope of the EU regulation of invasive non-native species. This highlights an unresolved paradox because efforts to manage species as invasive conflict with efforts to protect them as threatened within the same territory.

Retos en la gestión de las especies invasoras amenazadas a escala continental Resumen La legislación ambiental de la Unión Europea (UE) establece medidas comunes para prevenir la entrada y dispersión de especies invasoras no nativas y para minimizar su impacto. Sin embargo, las especies que son nativas en al menos uno de los estados miembros, pero no nativas y potencialmente invasoras (ENPI) en los demás, están en un limbo ya que no están reguladas en la UE ni en la mayoría de los estados miembros. Usamos los datos brutos del Centro de Recursos de Información y Comunicación para las Administraciones, Empresas y Ciudadanos (CIRCABC) sobre las ENPI (317 taxones) para analizar su distribución en la UE e identificar qué regiones biogeográficas funcionan como principales orígenes de las invasiones. Además, evaluamos el reto que representan las ENPI amenazadas dentro de su distribución nativa. Realizamos un análisis por pares que resumió el número de especies nativas en un estado miembro pero no nativa en otro y viceversa. Aunque los patrones de distribución de las ENPI variaron entre los grupos taxonómicos, en general fueron los países del sur y centro de la UE quienes donaron y recibieron a las ENPI. Los países del este fueron principalmente un origen de ENPI; la mayoría de los del oeste y el norte fueron receptores. Un 27% de las ENPI están amenazadas en alguna de sus distribuciones nativas en la UE, lo que representa un reto para la conservación y la gestión porque algunas de las especies tienen efectos negativos serios sobre la biodiversidad europea, pero hasta ahora permanecen fuera del alcance de la regulación de la UE para las especies invasoras no nativas. Lo anterior resalta una paradoja sin resolver ya que los esfuerzos para manejar a las especies como invasoras entran en conflicto con los esfuerzos por protegerlas como amenazadas dentro del mismo territorio.

Escalating the conflict? Intersex genetic correlations influence adaptation to environmental change in facultatively migratory populations.

Males and females are often subject to different and even opposing selection pressures. When a given trait has a shared genetic basis between the sexes, sexual conflict (antagonism) can arise. This can result in significant individual-level fitness consequences that might also affect population performance, whilst anthropogenic environmental change can further exacerbate maladaptation in one or both sexes driven by sexual antagonism. Here, we develop a genetically explicit eco-evolutionary model using an agent-based framework to explore how a population of a facultatively migratory fish species (brown trout Salmo trutta) adapts to environmental change across a range of intersex genetic correlations for migration propensity, which influence the magnitude of sexual conflict. Our modelled focal trait represents a condition threshold governing whether individuals adopt a resident or anadromous (sea migration) tactic. Anadromy affords potential size-mediated reproductive advantages to both males and females due to improved feeding opportunities at sea, but these can be undermined by high background marine mortality and survival/growth costs imposed by marine parasites (sea lice). We show that migration tactic frequency for a given set of environmental conditions is strongly influenced by the intersex genetic correlation, such that one sex can be dragged off its optimum more than the other. When this occurred in females in our model, population productivity was substantially reduced, but eco-evolutionary outcomes were altered by allowing for sneaking behaviour in males. We discuss real-world implications of our work given that anadromous salmonids are regularly challenged by sea lice infestations, which might act synergistically with other stressors such as climate change or fishing that impact marine performance, driving populations towards residency and potentially reduced resilience.

Mechanistic simulations predict that thermal and hydrological effects of climate change on Mediterranean trout cannot be offset by adaptive behaviour, evolution, and increased food production.

Streamflow is a main driver of fish population dynamics and is projected to decrease in much of the northern hemisphere, especially in the Mediterranean region, due to climate change. However, predictions of future climate effects on cold-water freshwater fish populations have typically focused only on the ecological consequences of increasing temperatures, overlooking the concurrent and interacting effects of climate-driven changes in streamflow regimes. Here, we present simulations that contrasted the consequences of changes in thermal regime alone versus the combined effects of changes in thermal regime and streamflow for resident trout populations in distinct river types with different sensitivities to climatic change (low-altitude main river vs. high-altitude headwaters). We additionally assessed the buffering effect of increased food production that may be linked to warming. We used an eco-genetic individual-based model that integrates the behavioural and physiological effects of extrinsic environmental drivers -temperature and flow- with intrinsic dynamics -density-dependence, phenotypic plasticity and evolutionary responses - across the entire trout life cycle, with Mediterranean brown trout Salmo trutta as the model species. Our simulations indicated that: (1) Hydrological change is a critical dimension of climate change for the persistence of trout populations, in that neither river type supported viable populations under strong rates of flow change, even under scenarios of increased food production. (2) Climate-change-related environmental change most affects the largest, oldest trout via increased metabolic costs and decreased energy inputs. In both river types, populations persisted under extreme warming alone but became dominated by younger, smaller fish. (3) Density-dependent, plastic and evolutionary changes in phenology and life-history traits provide trout populations with important resilience to warming, but strong concurrent shifts in streamflow could exceed the buffering conferred by such intrinsic dynamics.

Eco-evolutionary responses to recreational fishing under different harvest regulations.

Harvesting alters demography and life histories of exploited populations, and there is mounting evidence that rapid phenotypic changes at the individual level can occur when harvest is intensive. Therefore, recreational fishing is expected to induce both ecological and rapid evolutionary changes in fish populations and consequently requires rigorous management. However, little is known about the coupled demographic and evolutionary consequences of alternative harvest regulations in managed freshwater fisheries. We used a structurally realistic individual-based model and implemented an eco-genetic approach that accounts for microevolution, phenotypic plasticity, adaptive behavior, density-dependent processes, and cryptic mortality sources (illegal harvest and hooking mortality after catch and release). We explored the consequences of a range of harvest regulations, involving different combinations of exploitation intensity and minimum and maximum-length limits, on the eco-evolutionary trajectories of a freshwater fish stock. Our 100-year simulations of size-selective harvest through recreational fishing produced negative demographic and structural changes in the simulated population, but also plastic and evolutionary responses that compensated for such changes and prevented population collapse even under intense fishing pressure and liberal harvest regulations. Fishing-induced demographic and evolutionary changes were driven by the harvest regime, and the strength of responses increased with increasing exploitation intensity and decreasing restriction in length limits. Cryptic mortality strongly amplified the impacts of harvest and might be exerting a selective pressure that opposes that of size-selective harvest. "Slot" limits on harvestable length had overall positive effects but lower than expected ability to buffer harvest impacts. Harvest regulations strongly shape the eco-evolutionary dynamics of exploited fish stocks and thus should be considered in setting management policies. Our findings suggest that plastic and evolutionary responses buffer the demographic impacts of fishing, but intense fishing pressure and liberal harvest regulations may lead to an unstructured, juvenescent population that would put the sustainability of the stock at risk. Our study also indicates that high rates of cryptic mortality may make harvest regulations based on harvest slot limits ineffective.

Cross-disciplinary links in environmental systems science: Current state and claimed needs identified in a meta-review of process models.

Terrestrial environmental systems are characterised by numerous feedback links between their different compartments. However, scientific research is organized into disciplines that focus on processes within the respective compartments rather than on interdisciplinary links. Major feedback mechanisms between compartments might therefore have been systematically overlooked so far. Without identifying these gaps, initiatives on future comprehensive environmental monitoring schemes and experimental platforms might fail. We performed a comprehensive overview of feedbacks between compartments currently represented in environmental sciences and explores to what degree missing links have already been acknowledged in the literature. We focused on process models as they can be regarded as repositories of scientific knowledge that compile findings of numerous single studies. In total, 118 simulation models from 23 model types were analysed. Missing processes linking different environmental compartments were identified based on a meta-review of 346 published reviews, model intercomparison studies, and model descriptions. Eight disciplines of environmental sciences were considered and 396 linking processes were identified and ascribed to the physical, chemical or biological domain. There were significant differences between model types and scientific disciplines regarding implemented interdisciplinary links. The most wide-spread interdisciplinary links were between physical processes in meteorology, hydrology and soil science that drive or set the boundary conditions for other processes (e.g., ecological processes). In contrast, most chemical and biological processes were restricted to links within the same compartment. Integration of multiple environmental compartments and interdisciplinary knowledge was scarce in most model types. There was a strong bias of suggested future research foci and model extensions towards reinforcing existing interdisciplinary knowledge rather than to open up new interdisciplinary pathways. No clear pattern across disciplines exists with respect to suggested future research efforts. There is no evidence that environmental research would clearly converge towards more integrated approaches or towards an overarching environmental systems theory.

Thermal carrying capacity for a thermally-sensitive species at the warmest edge of its range.

Anthropogenic environmental change is causing unprecedented rates of population extirpation and altering the setting of range limits for many species. Significant population declines may occur however before any reduction in range is observed. Determining and modelling the factors driving population size and trends is consequently critical to predict trajectories of change and future extinction risk. We tracked during 12 years 51 populations of a cold-water fish species (brown trout Salmo trutta) living along a temperature gradient at the warmest thermal edge of its range. We developed a carrying capacity model in which maximum population size is limited by physical habitat conditions and regulated through territoriality. We first tested whether population numbers were driven by carrying capacity dynamics and then targeted on establishing (1) the temperature thresholds beyond which population numbers switch from being physical habitat- to temperature-limited; and (2) the rate at which carrying capacity declines with temperature within limiting thermal ranges. Carrying capacity along with emergent density-dependent responses explained up to 76% of spatio-temporal density variability of juveniles and adults but only 50% of young-of-the-year's. By contrast, young-of-the-year trout were highly sensitive to thermal conditions, their performance declining with temperature at a higher rate than older life stages, and disruptions being triggered at lower temperature thresholds. Results suggest that limiting temperature effects were progressively stronger with increasing anthropogenic disturbance. There was however a critical threshold, matching the incipient thermal limit for survival, beyond which realized density was always below potential numbers irrespective of disturbance intensity. We additionally found a lower threshold, matching the thermal limit for feeding, beyond which even unaltered populations declined. We predict that most of our study populations may become extinct by 2100, depicting the gloomy fate of thermally-sensitive species occurring at thermal range margins under limited potential for adaptation and dispersal.