Subject: Links between coleopteran and plant diversity in agricultural landscapes
Dates:  January 8, 2024 – December 31, 2025
CBGP manager: C. Meynard

Concurrence of plant and coleopteran diversity and abundance may be related to two, non-mutually exclusive, mechanisms: (1) the same environmental conditions (e.g. low-intensity agricultural practices, diverse landscape) favour both a high diversity of insects and plants; and (2) insects depend directly on plants as food, shelter or habitat.

We can therefore predict a direct effect of the environment on coleopteran insects (agro-environmental-driven effects) and an indirect effect via the effect of the environment on plants along with the direct effect of plants on coleopterans. To test this hypothesis we will develop path models (based on structural equation modelling, Shipley 2000) that will allow identifying the extent to which agricultural practices and other environmental variables influence coleopteran diversity directly (agro-environmental-driven effects) or indirectly, through their influence on the diversity of the flora (plant-driven effect).

We will test different path models in which we will vary the way the diversity of the flora is calculated (including taxonomic diversity and/or functional diversity). Finally, to understand how agro-environmental or plant-driven factors organise the community of species interactions, we will create potential plant-coleopteran interaction networks from the compositional data and information on beetle diets recovered from the literature. These will be bipartite (plant-herbivore) or tripartite (plant-herbivore-predator) networks with body size (i.e. larger insects tend to consume smaller species) used as the primary factor in defining trophic predator-prey relationships. We will create unweighted (binary) networks (bipartite) from different replicate sites along the intensification gradients and derive network properties that relate to the size and structure (e.g. connectance, linkage density, generality) of the assemblage. This work will provide a better understanding of the α‐diversity patterns in coleopterans of field margins by disentangling the effect of environmental gradients (including management practices) and landscape from the local effect of the structure and diversity of plant community. Each of the two approaches can be the subject of an article in a high-ranking scientific journal.