Phylogeography of Dolomedes in southern New Zealand: A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science with Honours at Lincoln University

Abstract

lntrogression is an important concept to consider when determining the taxonomy, and so the phylogeny, of any given species. It can have negative consequences on both populations and species as genotypic distinctiveness is removed, along with gene complexes that were co adapted to the respective environments through breeding (Rhymer and Simberloff 1996). However, it also can provide information on the direction of mitochondrial gene flow between species and the geography of introgression. We investigated the genetic structure of mitochondrial DNA (COi) and nuclear DNA (actin SC) for variations within and among populations of two nurseryweb spider species: Dolomedes aquaticus and D. minor. Specimens were collected from intermediately disturbed braided rivers located in the south of the South Island, New Zealand. The resulting sequences were compared against morphological characteristics to identify traits, both genetically and phenotypically, that indicate past occurrences of introgression. Successful amplification was gained from the majority of specimens for COi, but only from a third for actin SC. A comparison between the morphological examination and nuclear sequences were found to be in agreement for the identification of these specimens. Several D. aquaticus haplotypes supported introgression events from D. aquaticus to D. minor indicated in previous research, while an example of an additional introgression event was uncovered. No evidence was found for introgression from D. minor to D. aquaticus, indicating that the introgression is one directional and that isolation mechanisms that may be in place to prevent such an occurrence are more successful within one species. In addition, the distribution patterns of identical haplotypes were found to provide an indication for when and where introgression took place.