BackgroundEcological constraints related to foraging are expected to affect the evolution of morphological traits relevant to food capture, manipulation and transport. Females of central-place foraging Hymenoptera vary in their food load manipulation ability. Bees and social wasps modulate the amount of food taken per foraging trip (in terms of e.g. number of pollen grains or parts of prey), while solitary wasps carry exclusively entire prey items. We hypothesized that the foraging constraints acting on females of the latter species, imposed by the upper limit to the load size they are able to transport in flight, should promote the evolution of a greater load-lifting capacity and manoeuvrability, specifically in terms of greater flight muscle to body mass ratio and lower wing loading.ResultsOur comparative study of 28 species confirms that, accounting for shared ancestry, female flight muscle ratio was significantly higher and wing loading lower in species taking entire prey compared to those that are able to modulate load size. Body mass had no effect on flight muscle ratio, though it strongly and negatively co-varied with wing loading. Across species, flight muscle ratio and wing loading were negatively correlated, suggesting coevolution of these traits.ConclusionsNatural selection has led to the coevolution of resource load manipulation ability and morphological traits affecting flying ability with additional loads in females of central-place foraging Hymenoptera. Release from load-carrying constraints related to foraging, which took place with the evolution of food load manipulation ability, has selected against the maintenance of a powerful flight apparatus. This could be the case since investment in flight muscles may have to be traded against other life-history traits, such as reproductive investment.

Aim To evaluate how the establishment risk of freshwater fish species from the aquarium trade will change under a climate change scenario forecast for the year 2050. Location North America. Methods In order to estimate changes in the magnitude of risk across geography and across different species in the aquarium pathway, we considered an integrated approach to modelling the probability of establishment, which simultaneously included proxies of propagule pressure, environmental variables, species traits and interactions between environment and traits. We then used the parameters of our model to predict how the risk of establishment will change under a scenario of climate change forecast for the year 2050. Results Our joint model performed better than submodels, suggesting that combining all components is worthwhile. The most predictive factors were precipitation, maximum temperature tolerance, maximum fish length and minimum temperature. Our joint model forecasted a 40% increase in the average risk of establishment by 2050 in the United States. In contrast to our expectations, the absolute establishment risk associated with this pathway remained very low for the entire suite of species in the aquarium trade in northern regions, such as Quebec, Canada. Instead, Florida, which has one of the highest current risks of establishment, was also forecasted to have the greatest absolute risk increase. Main conclusions Our methodology for risk assessment allows invasive species management strategies to consider entire suites of species at a time and to forecast establishment risk for each species and location. While the aquarium pathway is likely to become more important for the United States, the Quebec government should prioritize other pathways of introduction in its exotic invasive species strategy. Our approach can be extended to be applied to different sets of species pertaining to the same or different pathways.

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