Vacant yet invasible niches in forest community assembly

Functional traits of exotic submerged macrophytes mediate diversity-invasibility relationship in freshwater communities under eutrophication

Plant diversity may respond differently in terms of whether it can drive plant invasions in freshwater ecosystem. Linkages and interactions between diversity and invasibility have not been clearly resolved, and it is unclear how nutrient enrichment (e.g., eutrophication) will affect this relationship. As a key predictor of plant growth, the ability of functional traits to mediate trade-offs in the diversity-invasibility relationship is unknown. Here, we conducted a series of experiments to determine the role of exotic plant functional traits in the diversity-invasibility relationship of submerged macrophyte communities under eutrophication. We selected common native and exotic submerged macrophytes in the subtropics to construct different diverse submerged macrophyte communities to simulate invasion. Meanwhile, to test the adaptability and importance of functional traits, we experimentally verified the differences in functional traits between exotic and native species. Our results showed a positive correlation between native plant diversity and community invasibility. Moreover, the invader's performance was predominantly determined by functional traits of exotic species, such as plant biomass and tissue nutrients, which were significantly altered by species diversity. Furthermore, our results suggested that functional traits contribute significantly more to the invasiveness of exotic submerged macrophytes than the other factors to which they are subjected. Plant functional traits can mediate the diversity-invasibility relationship because of the higher intrinsic dominance of exotic submerged macrophyte species. In summary, our study revealed diversity-invasibility relationship in submerged macrophyte communities and highlighted functional traits as key drivers of invasion of high-risk exotic submerged macrophyte species. Although previous studies have elucidated the importance of functional trait studies for plant invasions, our study provides the only current evidence demonstrating the important role of invaders' functional traits in mediating the diversity-invasibility relationship. This novel perspective offers valuable insights into the management and control of invasive aquatic plants.

Big boned: How fat storage and other adaptations influenced large theropod foraging ecology

Dinosaur foraging ecology has been the subject of scientific interest for decades, yet much of what we understand about it remains hypothetical. We wrote an agent-based model (ABM) to simulate meat energy sources present in dinosaur environments, including carcasses of giant sauropods, along with living, huntable prey. Theropod dinosaurs modeled in this environment (specifically allosauroids, and more particularly, Allosaurus Marsh, 1877) were instantiated with heritable traits favorable to either hunting success or scavenging success. If hunter phenotypes were more reproductively successful, their traits were propagated into the population through their offspring, resulting in predator specialists. If selective pressure favored scavenger phenotypes, the population would evolve to acquire most of their calories from carrion. Data generated from this model strongly suggest that theropods in sauropod-dominated systems evolved to detect carcasses, consume and store large quantities of fat, and dominate carcass sites. Broadly speaking, selective forces did not favor predatory adaptations, because sauropod carrion resource pools, as we modeled them, were too profitable for prey-based resource pools to be significant. This is the first research to test selective pressure patterns in dinosaurs, and the first to estimate theropod mass based on metabolic constraints.

Functionally distinct tree species support long-term productivity in extreme environments

Despite evidence of a positive effect of functional diversity on ecosystem productivity, the importance of functionally distinct species (i.e. species that display an original combination of traits) is poorly understood. To investigate how distinct species affect ecosystem productivity, we used a forest-gap model to simulate realistic temperate forest successions along an environmental gradient and measured ecosystem productivity at the end of the successional trajectories. We performed 10 560 simulations with different sets and numbers of species, bearing either distinct or indistinct functional traits, and compared them to random assemblages, to mimic the consequences of a regional loss of species. Long-term ecosystem productivity dropped when distinct species were lost first from the regional pool of species, under the harshest environmental conditions. On the contrary, productivity was more dependent on ordinary species in milder environments. Our findings show that species functional distinctiveness, integrating multiple trait dimensions, can capture species-specific effects on ecosystem productivity. In a context of an environmentally changing world, they highlight the need to investigate the role of distinct species in sustaining ecosystem processes, particularly in extreme environmental conditions.

The dimensionality and structure of species trait spaces

Trait-based ecology aims to understand the processes that generate the overarching diversity of organismal traits and their influence on ecosystem functioning. Achieving this goal requires simplifying this complexity in synthetic axes defining a trait space and to cluster species based on their traits while identifying those with unique combinations of traits. However, so far, we know little about the dimensionality, the robustness to trait omission and the structure of these trait spaces. Here, we propose a unified framework and a synthesis across 30 trait datasets representing a broad variety of taxa, ecosystems and spatial scales to show that a common trade-off between trait space quality and operationality appears between three and six dimensions. The robustness to trait omission is generally low but highly variable among datasets. We also highlight invariant scaling relationships, whatever organismal complexity, between the number of clusters, the number of species in the dominant cluster and the number of unique species with total species richness. When species richness increases, the number of unique species saturates, whereas species tend to disproportionately pack in the richest cluster. Based on these results, we propose some rules of thumb to build species trait spaces and estimate subsequent functional diversity indices.