Comparison of resource consumption, fecundity, and developmental parameters of three Calystegia (Solanales, Convolvulaceae)-feeding leaf beetle species (Coleoptera: Chrysomelidae: Cassidinae) to identify coexistence conditions

Abstract

Differences in life-history traits, such as fertility, resource consumption, and developmental parameters, can determine the advantage among competing species. A previous study of three leaf beetles with overlapping host ranges and active season—Laccoptera nepalensis Boheman (Coleoptera: Chrysomelidae: Cassidinae), Aspidimorpha difformis (Motschulsky) (Coleoptera: Chrysomelidae: Cassidinae), and Aspidimorpha transparipennis (Motschulsky) (Coleoptera: Chrysomelidae: Cassidinae)—revealed that L. nepalensis competitively excluded A. difformis due to resource competition under rearing conditions, but A. difformis still habited in the fields. Conversely, reared A. transparipennis and L. nepalensis did not compete, but A. transparipennis was rare in the field. Thus, this study aimed to clarify whether differences in life-history traits among the three phylogenetically-related leaf beetles influence the outcome of competition and competitiveness. Specifically, resource consumption, fertility, and developmental parameters of three leaf beetle species were measured experimentally, and their seasonal occurrence was predicted. Resource consumption and fecundity were the lowest in A. transparipennis and A. difformis, respectively; they were the highest in L. nepalensis. Additionally, predicted seasonal occurrence was mismatched between the two Aspidimorpha species and the coexisting L. nepalensis. These results suggest that the two Aspidimorpha species can avoid co-occurrence with L. nepalensis, which carries the risk of resource depletion through temporal niche partitioning. However, because the annual generation of L. nepalensis and A. transparipennis was more than one, any shift in their seasonal occurrence could lead to resource depletion for A. transparipennis. This study underscores the importance of discussing the processes and results of interspecific competition based on differences in life-history traits.