The reproductive biology of Oxyops vitiosa Pascoe, 1870 (Colepotera: Curculionidae), a biological control agent of the invasive tree Melaleuca quinquenervia (Myrtaceae)

Abstract

The invasive tree Melaleuca quinquenervia (Cavanilles) Blake (Myrtaceae) is widely distributed throughout peninsular Florida, U.S.A. and poses a threat to species diversity in the wetland systems of the Florida Everglades. Biological control research targeting the weed resulted in the introduction of Oxyops vitiosa Pascoe, 1870 to Florida. Approximately three years following its release, adult weevils were collected over 12 consecutive months across six study sites, resulting in a 52:48 F:M sex ratio that did not vary among sites or over time. All female weevils were dissected and their reproductive anatomy was investigated, particularly in relation to the fluctuation of host plant suitability. The continuum of reproductive development was divided into three distinct stages: nulliparous, parous, or degenerative. The general anatomy of each stage is described. In contrast to other systems, fat body abundance provided little insight into the weevil's reproductive status, as 99.5% of all females possessed fat bodies that filled >2/3 of the abdominal cavity. Nulliparous weevils possessed the softest elytra and were lighter in color, parous weevils had the hardest and darkest elytra, while females with degenerative reproductive systems were intermediate to the other two reproductive classes. The proportion of parous O. vitiosa females in a population was strongly influenced by resource availability, as the number of actively ovipositing females increased concomitantly with increasing suitable foliage in the host's canopy.