I grew up on my family’s farm north of Auckland, New Zealand, and after finishing high school in 2006 moved to Palmerston North, where I attended Massey University. Here I completed my BSc, with a double major in Zoology and Ecology, in 2009. I spent the 2009/10 summer studying the vegetation of a local coastal reserve. In 2010, I started my Honours in Ecology, under the supervision of Dr. Mary Morgan-Richards.

For my honours project, I studied Common Gecko (Woodworthia maculata) populations on the south Wellington Coast, New Zealand. These populations are found along a 13 km stretch of coast, with the geckos restricted to the narrow rocky zone, between the sea and the steep hills of the Tararua Ranges. The geckos at the northern end of this zone are almost twice the weight, and significantly longer, than those at the southern end (Fitness et al. 2012). This extreme clinal variation is thought to represent a stable hybrid zone. The aim of my study was to determine the origin and maintenance of this zone.

Six microsatellite loci were amplified and analysed, with allele frequencies calculated for each locus at each of the five study sites along the coast. One of the microsatellite loci showed clinal variation (as did mitochondrial gene 16S and nuclear loci Rag-2, identified by Fitness et al. 2012). The shape and size of leaves of a widespread shrub, Coprosma propinqua, were measured to determine local-scale climatic differences, and were found to exhibit clinal variation. Rock sizes were also measured, as a proxy for crevice size. These too showed clinal variation, with a strong and significant positive correlation between gecko size and crevice size. The results strongly suggest that the body size cline, and associated genetic clines, have arisen in situ, as a direct response to spatially varying selection pressure, resulting from a strong environmental gradient. This represents the first example of the elusive, but often theorised, evolutionary process of primary intergradation. This hybrid zone is maintained by exogenous selection, most likely variation in the geckos’ crevice habitat.

References:

Fitness J, Hitchmough RA, Morgan-Richards M. 2012. Little and large; body size and genetic clines in a New Zealand gecko (Woodworthia maculata) along a coastal transect. Ecology and Evolution. DOI: 10.1002/ece3.64

Publications:

Murphy, A.L., Fitness, J., Hitchmough, R.A., Weihong, J., Wong, C.H. & Morgan-Richards, M. Unique origins; the formation and maintenance of a coastal hybrid zone between populations of geckos (Woodworthia maculata). In Prep.

Common Gecko Woodworthia maculata