Three subspecies of house mice of different geographic origins have reached New Zealand; M. m. domesticus (10 haplotypes), M. m. musculus (1 haplotype) both from Europe, and M. m. castaneus (3 haplotypes) from Asia. Identifying the sources of the multiple historical introductions of the house mouse is a complex issue, particularly during the peak colonisation period of 1830-1880. The early European settlers came with many bags, crates, plants, seed and livestock, which provided ample travel opportunities for stowaway rats and mice. With the assistance of volunteers, I have collected mice from various locations throughout the New Zealand region, to confirm the previously recorded haplotypes and to look for evidence of hybridisation between the colonising subspecies. Morphological characteristics traditionally used for identification of subspecies were compared with genetic characters, to establish whether the use of morphology is still a viable method of identifying subspecific distinctions between mice in New Zealand. While no M. m. musculus haplotypes were found among these samples, some mice still had the coat colouration typical of M. m. musculus. Data from mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) markers revealed some surprising results. I have found six new M. m. domesticus haplotypes, and three new M. m. castaneus haplotypes. The data have also revealed extensive hybridisation, particularly between M. m. domesticus and M. m. castaneus. The finding of the new haplotypes supports the previous assumption that there were multiple introductions of mice into New Zealand, but the finding of M. m. castaneus in inland towns and cities does not support the associated assumption that European mice were initially the only mice present in New Zealand. Rather, the wide distribution of M. m. castaneus suggests that this subspecies probably arrived during the early nineteenth century. The house mouse has long been recognised as an ideal organism for hybridisation studies, and the finding of a hybrid zone within New Zealand would provide an excellent opportunity to extend our knowledge of hybridisation and gene transfer. Previous studies found M. m. domesticus in Napier, and a M. m. musculus/M. m. castaneus hybrids in Wellington. A systematic sampling programme was undertaken between Wellington and Napier following State Highway 2 (SH2), in an attempt to locate a hybrid zone. Analysis of mtDNA and nDNA showed that, M. m. castaneus was found as far North as Dannevirke, and M. m. domesticus as far South as Featherston. There was also extensive evidence of integration of M. m. domesticus nDNA markers into mice with M. m. castaneus mtDNA. There was no clear support for a hybrid zone, but this does not mean that one has not existed in the past and that it has since been overrun by movement of mice with humans and their goods. Identification of subspecies by morphological characteristics, while used with confidence in other countries, is of little use in New Zealand. Extensive hybridisation/and or introgression between the subspecies has long since blurred any morphological distinctions the colonising mice may have had. I propose that these physical characters should be used in support of genetic analysis of the subspecies. The official classification of the New Zealand house mouse currently stands as M. m. musculus, however, data collected does not support this and it is proposed that the official classification should be changed to M. m. domesticus.
| Identifer | oai:union.ndltd.org:ADTP/238346 |
| Date | January 2008 |
| Creators | Chubb, Tanya L. A. |
| Publisher | The University of Waikato |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.waikato.ac.nz/library/research_commons/rc_about.shtml#copyright |
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