No barrier to fertilisation when different sexual populations of the mānuka stick insect are crossed

Abstract

The mānuka stick insect Clitarchus hookeri (White) is facultatively parthenogenetic, but females from sexual populations that have mated with males from their own population do not produce any offspring via asexual reproduction. In contrast, females from parthenogenetic populations of C. hookeri mate with males (in captivity) but show a partial barrier to fertilisation with more than 90% of their offspring resulting from asexual reproduction post mating. Captive crossing experiments with parthenogenetic females require the mating of individuals from different populations (sexual and parthenogenetic), thus potential intraspecific differences bring a confounding element to these experiments. Experiments mating sexual females with males from different sexual populations were undertaken to determine whether offspring resulting from such a cross would be the result of sexual or parthenogenetic reproduction. Virgin females and males were collected from two sexual populations known to represent distinct genetic lineages (Waikato and Whanganui). Eleven adult females were caged with non-local males and eggs collected post-mating. Approximately equal numbers of sons and daughters hatched (168 female; 210 male) suggesting all offspring were the result of sexual reproduction. In these intraspecific crosses no barriers to fertilisation were detected, suggesting that in the absence of males the decay of some sexual trait in Phasmids can occur in fewer than 100 generations.