Genetic patterns at fine spatial scales - complex findings in a complex landscape

Abstract

Landscape genetics describes spatial genetic patterns, and overlays these onto a habitat matrix. Observed patterns are then interpreted from the viewpoint of the individual organism and how different organisms move and interact within their habitat. Previous phylogeographic studies performed on Marion Island taxa placed great emphasis on the role that heterogeneous environments play in shaping island-wide patterns. However, the investigation of genetic diversity at fine spatial scales may be a better approach for conservation biology. Using the springtail, Cryptopygus antarcticus travei from Marion Island, we explored genetic structure across a 350 m transect and interpreted our results in light of the factors driving small-scale spatial evolution in this model organism. Our results for 390 individuals from 22 sampling sites revealed the presence of two genetic lineages whose contact zone coincides with a landscape ridge. This contact zone does not manifest as a clean break, but rather a complex pattern of clustering, with sampling sites on either side of the ridge showing alternating lineage membership. Individuals within each site were not admixed but, uniformly belonged to the same lineage, and the level of inbreeding was consistent with what is expected for sexually reproducing organisms. High genetic diversity reflects a large effective population size, consistent with the high census population size reported for the species. An explanation for the complex lineage patterns observed could be micro-habitat preferences and/or a fitness funnel driven by local adaptations. The complexity of our genetic structure at a fine scale indicates that this species may be influenced by climatic change, evident from proposed local adaptations. This complexity may bring about far-reaching implications to evaluate their response to environmental change, specifically with regards to climate. Hence, springtails may serve as proxies for monitoring global climate change due to their unique role as major herbivores on a sea-locked landscape. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.