Trait-matching and mass determine the functional response of herbivore communities to land use intensification

Gaëtane Le Provost, Nicolas Gross, Luca Börger, Hélène Deraison, Marilyn Roncoroni, Isabelle Badenhausser

Understanding how different organisms interact is essential to understand what drives the structure of ecological communities and how they may be affected by environmental change. One important type of interaction is a “trophic interaction” – who eats whom – and for many species the morphological attributes that determine these interactions (“trait-matching”) have been identified. For instance, we know that bird beak size is adapted to the size of the seeds they eat, or that pollinators with long tongues visit plants with deeper flowers. However, how such trait-matching between animals and their resources explains the structure of natural communities has been barely explored. This question might be particularly relevant for agricultural areas, which are subject to drastic changes globally (e.g. more intensive production methods), as the diversity of traits that help secure key resources (known as resource-acquisition traits) may inform us about the diversity of resources present in the landscape, and whether diverse animal communities can be maintained in agricultural landscapes.

In this paper, we quantified the relative contribution of trait-matching between plants and herbivores and land use intensification, operating at local and landscape scales, on the structure of ecological communities. To do so, we compiled a large dataset on the abundance and morphological/chemical attributes of plant and grasshopper species from 204 grasslands, situated in an intensively managed agricultural landscape. We considered two key functional traits of grasshopper species: (i) incisor strength, a resource-acquisition trait which strongly matches grasshopper feeding preferences; and (ii) body size, which correlates with mobility traits and may determine grasshopper dispersal abilities in fragmented landscapes.

We found that land use intensification decreased the diversity of grasshopper resource-acquisition traits and tended to select for large and mobile grasshoppers. Trait-matching between plants and grasshoppers was an important driver explaining the abundance and diversity of grasshopper communities. Diverse plant communities in old grasslands support diverse grasshopper communities, characterized by contrasting feeding preferences. Importantly, our study suggests that diversity of resource-acquisition traits in grasshoppers was also influenced by the presence of diverse habitats in the surrounding landscape. Thus, in agricultural landscapes, diverse and stable habitats are required to maintain a diversity of resources and sustain functionally diverse animal communities.

Image caption: Grasshopper in a grassland field. Photo credit: Gaëtane Le Provost.
Read the article in full here.

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