Identity of an endangered grasshopper (Acrididae: Brachaspis): Taxonomy, molecules and conservation

Abstract

Brachaspis robustus is an endangered grasshopper endemic to South Island, New Zealand. It is both rare and localised; occupying low altitude floodplain terraces and braided riverbeds of the Mackenzie Basin. This is in stark contrast to the two other species in this genus (B. nivalis and B. collinus) which occupy montane habitats. Mitochondrial and nuclear sequence data were employed to explore genetic diversity and phylogenetic relationships of populations of Brachaspis with a view to establishing the status of B. robustus. Molecular evidence indicates that Brachaspis probably radiated during the Pliocene and that divisions within the genus relate more to spatial distribution developed during the Pleistocene than to ecology. The mitochondrial (Cytochrome oxidase I) and nuclear (ITS) sequence data indicate that Brachaspis nivalis is divided into northern and southern populations. The northern clade is further subdivided geographically. The southern clade comprises alpine populations of B. nivalis and includes the lowland B. robustus. Additionally, it is observed that some morphological features previously thought to be specific to B. robustus also occur in members of the southern B. nivalis clade. It is suggested that the taxon B. robustus should include all of the southern Brachaspis populations. But it is argued that the absence of genetic evidence distinguishing the endangered population does not preclude it from conservation effort. A combination of morphological and habitat peculiarities indicate that the survival of B. robustus (sensu lato) is important to the maintenance of diversity.