Cryptic diversity in the aspidiotus nerii complex in Australia

Aspidiotus nerii Bouch (Hemiptera: Diaspididae), oleander scale, is a cosmopolitan pest that feeds on >100 families of plants. A previous study of mitochondrial DNA variation in A. nerii suggested a possible Australian origin for the species. Here, we expand upon that study to include four gene regions and multiple Australian samples. We sequenced fragments of three nuclear genes (CAD, elongation factor 1, and 28S rDNA) and one mitochondrial region (spanning parts of cytochrome oxidase I and II), for a total aligned sequence length of 2448 bp, from 22 individuals identified as A. nerii. We infer an allele genealogy for each gene region, and we interpret branches that are congruent across gene regions as indicative of species boundaries. Using this criterion, we recognize three species within our sample of A. nerii. One of these corresponds to the cosmopolitan pest species and the other two are found only in Australia. The two putative Australian species have overlapping ranges and both are found on multiple hosts. Contrary to previous suggestions, the cosmopolitan sexual and parthenogenetic lineages of A. nerii are not recognized as distinct species by both of our methods of phylogenetic reconstruction. Cryptic diversity within what seem to be single cosmopolitan armored scale insect species is a potential serious problem for plant quarantine.