Potential fecundity, larval development, and survival of two invasive species of &lt;i&gt;Arhopalus&lt;/i&gt; (Coleoptera: Cerambycidae) coexisting in southern South America

Monica F Nime,Romina Fachinetti,Mariano P Grilli,Laura Pedemonte

doi:10.15446/caldasia.v41n2.75352

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.

Highlights

Egg size and number are critical life-history traits in insects because the former influences offspring fitness by determining initial resources level (Fox 1994, Fox and Czesak 2000) and the latter influences overall progeny production (Fox and Czesak 2000, Kato et al 2000)
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 first larval instar or larval instar I was considered as the period of time in days from egg hatching to the first molt, the second larval instar or larval instar II was considered as the period of time in days

Summary

Introduction

Egg size and number are critical life-history traits in insects because the former influences offspring fitness by determining initial resources level (Fox 1994, Fox and Czesak 2000) and the latter influences overall progeny production (Fox and Czesak 2000, Kato et al 2000). The size and number of eggs produced by a female are known to correlate with female size and weight (Berrigan 1991, Honek 1993). Several studies have suggested that egg size and/or the number of eggs produced vary depending on maternal conditions such as body size, nutritional status, age or weight (Fox and Czesak 2000, Kojima 2015). It is argued that this trade-off is a consequence of a fixed level of resource availability that could affect the production of offspring (Smith and Fretwell 1974)

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