Biology, host specificity and DNA barcoding of cryptic Eueupithecia species (Lepidoptera: Geometridae), and implications for biological control of Parkinsonia aculeata (Fabaceae) in Australia

Abstract

Parkinsonia aculeata L. (Fabaceae: Caesalpinioideae), native to the Americas, is a designated Weed of National Significance in Australia. The leaf-feeding geometrid moth species, Eueupithecia cisplatensis Prout (Lepidoptera: Geometridae), was identified as a potential biological control agent of P. aculeata following native range surveys in Argentina. After importation into quarantine for host specificity assessment, this species was identified as a cryptic species complex of two morphologically similar species. The new species, Eueupithecia vollonoides Hausmann (Lepidoptera: Geometridae), was subsequently described. The biology and host range of both moth species were examined to determine their suitability as biological control agents. Host specificity was evaluated in the native range, by surveying insects found on closely related plant species, and in the laboratory, by no-choice larval development tests. Native range surveys and laboratory assays revealed a high level of specificity to P. aculeata by both Eueupithecia species. Of the 71 plant species from the Fabaceae family that were tested, E. cisplatensis completed development on only one non-target species, Parkinsonia praecox. This plant species is not present in Australia, and no Eueupithecia species were found to use P. praecox in the field in its native range. Hence, the risk of non-target effects if these species were to be released in Australia was considered to be low. One mitochondrial (COI) gene region and two nuclear (28S and CAD) gene regions were tested for their ability to differentiate between the two cryptic species. COI haplotypes from E. cisplatensis and E. vollonoides belong to two divergent haplotype groups and can reliably distinguish either species from the other. Some 28S and CAD gene haplotypes are shared at low frequencies, perhaps because of rare or historical hybridisation or incomplete lineage sorting, thus cannot reliably discriminate between the species. This pattern of mito-nuclear discordance requires further elucidation using population genetics studies to determine its biological significance. Based on the results of host specificity tests, E. cisplatensis and E. vollonoides were approved for release in Australia in May 2013 and May 2014, respectively.