Reproductive Ecology and Impact of the Invasive Praying Mantis Miomantis caffra

Abstract

This thesis concerns the two species of praying mantis in New Zealand, the introduced Miomantis caffra and native Orthodera novaezealandiae. The aims of this research are to: 1) predict the potential future distribution of M. caffra in New Zealand and to test the modelling procedure used for this purpose, 2) examine the influence of relatedness and body mass on the rate of cannibalism in juvenile M. caffra and 3) assess the potential for impact of M. caffra upon O. novaezealandiae. The first of these goals was approached using the computerised species distribution modelling package Maxent, as well as a field test of M. caffra ootheca viability in the South Island. The second was examined by captive observation of M. caffra nymphs in groups with differing body mass and relatedness. Y-maze experiments were used to assess the possibility of heterospecific attraction and mating observations were carried out to quantify copulatory cannibalism and examine the possibility of interspecific impact. Modelling results suggest that M. caffra will be able to colonise much of the eastern half of the South Island and assessment of Maxent indicates that it is robust to low levels of input data, supporting its usefulness as a tool for predicting the spread of invasive species. The test of oothecae indicate that these are resilient to most of the winter conditions which the New Zealand environment presents and consequently should be able to facilitate the widespread dispersal of M. caffra. It was found that juvenile M. caffra do not show kin-biased discrimination in their cannibalism, although this was influenced by size heterogeneity. The males of O. novaezealandiae are attracted to heterospecific females, more so in fact than conspecifics, a behaviour which exposes them to the risk of copulatory predation from M. caffra, which was found to be commonplace. This identifies a possible mechanism for the purported displacement of O. novaezealandiae by M. caffra and suggests that M. caffra is a threat to O. novaezealandiae, possibly responsible for the widespread decline of the former in New Zealand and likely to cause further loss of O. novaezealandiae abundance in the future.