Potential fecundity, larval development, and survival of two invasive species of Arhopalus (Coleoptera: Cerambycidae) coexisting in southern South America

Abstract

Biological invasions are one of the main threats to forest health. Although Arhopalus rusticus and Arhopalus syriacus (Cerambycidae) are alien species in South America, the ecology of these invasive species is not well studied. Here, we examined the effect of the female size on potential fecundity, size and number of mature eggs in ovaries, in both insect species. We also compared egg morphometric characteristics, larval measurements, larval development and survival between these two species. We found a positive relationship between the female size and the number of eggs in their ovaries but no relationship between the female size and egg morphometric characteristics in each of these two species. The females of A. rusticus were significantly larger and had bigger eggs than those of A. syriacus, but no significant difference was observed in the number of eggs between them. Larval body length and head capsule exuviae width were larger in A. rusticus than in A. syriacus. Arhopalus rusticus had the highest larval survival rate, but A. syriacus had the shortest larval period. Thus, female and egg size, as well as larval size and survivorship are competitive advantages to A. rusticus. However, A. syriacus has a similar number of eggs to A. rusticus and faster larval development; these could be key features to explain the coexistence of these two species.