Biochemical Characterization of Wiseana (Viette) Moths and Caterpillars (Lepidoptera: Hepialidae), and Its Implications For Pest Management

Abstract

Reliable systematics is the basis for meaningful interpretation of biological and ecological data. However, the systematics of porina moths and caterpillars (genus Wiseana) has been anything but reliable. Before the present study, Wiseana research was attempted under the assumption that only one species caused damage to New Zealand pastures. Recently, that assumption has been challenged. Therefore, in this thesis both moth and caterpillar stages were examined using the techniques of allozyme electrophoresis and discriminant function analysis to (1) develop a reliable Wiseana taxonomy, (2) learn how many Wiseana species cause damage to New Zealand pastures and (3) examine the implications that may arise if more than one species is found to be responsible for pasture damage. Analysis of allozyme variation at 26 loci among the moths revealed seven genetically distinct species: W. cervinata (Walker); W. copularis (Meyrick); W. fuliginea (Butler); W. jocosa (Meyrick); W. mimica (Philpott); W. signata (Walker); and W. umbraculata (Guenée). Each species was characterised by fixed differences at the loci Acp-1, Gp-2, Me-1, 6pg-1 and Pep-1. One species (W. cervinata) showed clinal variation with latitude at two allozyme loci (Got-1 and Nad-1). An electrophoretic key was produced to identify adults of each Wiseana species. Discriminant function analysis of the moths revealed that males of each species are morphologically differentiated, but that only W. mimica and W. umbraculata females are distinguishable. Classification functions were developed to identify males and some female moths of each Wiseana species. A morphological key was produced to help field workers identify adults of each Wiseana species. Allozyme variation at 29 loci among the caterpillars revealed that five species (W. cervinata, W. copularis, W. jocosa, W. signata and W. umbraculata) could be clearly differentiated by fixed differences at the loci Acp-2, Me-1, 6pg-1, Pep-1 and Pep-5. The species W. fuliginea and W. mimica could also be identified, but were only separable from each other by fixed differences at the locus Pgm-1 and by frequency differences at the locus Gpi-1. The clinal variation observed within W. cervinata moths was confirmed in the caterpillars. An electrophoretic key was produced to distinguish caterpillars of each Wiseana species. Discriminant function analysis of metric characters showed that it is possible to distinguish species of Wiseana caterpillars. Phylogenetic analysis of the electrophoretic data produced many reconstructions of the Wiseana phylogeny. Nevertheless, three reconstructions produced using Dioxycanus oreas as the outgroup were most consistent with the data. The consensus tree of these phylogenies placed W. cervinata, W. jocosa, W. fuliginea and W. mimica within the same clade. This is consistent with the known ecology and morphology of those species. W. signata and W. umbraculata were placed in separate clades. However, earlier analyses and the morphological data indicate that they could be placed together within a single clade. The historical relationships between each species suggest that most species originated from the southern South Island. Analysis of field-collected caterpillars indicated that at least three species (W. cervinata, W. copularis and W. fuliginea) are responsible for pasture damage throughout New Zealand. For management purposes, these species plus the northern and southern forms of W. cervinata were considered separate entities. Dispersal of these species may have been aided by the development of improved pasture and by livestock movement. Where more than one species is responsible for pasture damage (1) the timing of control applications may become critical, (2) tolerance, resistance or behavioural differences between the species could affect chemical controls, and (3) biological controls may also be affected. Species untested against a particular control could react differently to those previously tested. Consequently, differences in species compositions may account for contrasts in the efficacy of diflubenzuron in field trials held in South Otago and in Hamilton. Because it is now possible to identify field-collected Wiseana caterpillars, efforts should be made to identify all species when testing new methods of Wiseana pest control.