Using population genetics to assess the dispersal patterns of the New Zealand mayfly Coloburiscus humeralis in a landscape context.
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Mayfly species, such as Coloburiscus humeralis, are an important organism in freshwater ecosystems. As well as often being crucial intermediary links in food webs, mayfly nymphs provide a number of vital in stream functions that contribute to ecosystem health. The threat to stream invertebrate populations from habitat destruction as well as chemical and nutrient additions from agricultural land use has had considerable attention in New Zealand. However, less has been done on the potential barriers to dispersal that may negatively affect the health of stream insect populations. The goal of this study was to use AFLP techniques to measure the genetic structure of populations between streams and across catchments, and thereby to better understand the dispersal of this species across the landscape. I sampled populations in 10 forested streams, ranging from populations separated by <2km to 780 km. I found that in the Arthur’s Pass study area, populations of C. humeralis had high levels of genetic divergence even between the closest streams in the study (ΦPT = 0.065, p = 0.011). In order to identify the landscape features that either constrain or assist mayfly dispersal, I employed a resistance modelling technique based on electrical circuit theory to simulate how particular landscape factors contribute to the observed genetic structure. My resistance modelling results suggest that open areas provide barriers to dispersal while gene-flow was more likely to occur when streams are separated by connected native forest.