Unilateral exclusion of three leaf beetle species due resource competition for oviposition sites

Resource competition is a key factor in shaping community structure. In herbivorous insects, living space occupation is likely to lead to exclusion due to resource competition with coercion of consuming poor resources. Given that eggs are immobile, their placement is critical for larval survival and development, especially in terms of optimal resource consumption, making oviposition site selection a crucial factor for females. Therefore, competition for oviposition sites may lead to exclusion if resources are scarce.

This study examined the competitive relationships among three leaf beetle species (Coleoptera: Chrysomelidae): Aspidimorpha difformis (Motschulsky), Aspidimorpha transparipennis (Motschulsky) and Laccoptera nepalensis Boheman. Competitive dynamics were assessed using field surveys, experiments and simulations.

Results revealed that habitats for both Aspidimorpha species were less than half the size of L. nepalensis habitats. Additionally, both Aspidimorpha species avoided oviposition on leaves with the oothecae of other species, with A. difformis showing a reduction of up to 70% in ootheca number. Simulation results indicated that only A. difformis , which experienced oviposition site reductions due to other species, faced certain extinction under conditions mimicking natural habitats.

Our findings suggest that A. difformis experiences unilateral exclusion due to resource competition for oviposition sites, as observed in the field. Thus, based on our findings, even free‐living herbivorous insects can be excluded due to interference competition during their immobile stage, such as eggs.