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

Resource competition is a key factor in shaping community structure.
However, exclusion due to resource competition likely occurs only in
immobile herbivorous insects such as scale insects, because free-living
insects mitigate competition by moving to alternative 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,
Aspidimorpha transparipennis, and Laccoptera nepalensis. 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 0% of
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 condition of
mortality. Our findings suggest that even free-living herbivorous insect
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.