Spatial genetic structure of the sea sandwort (Honckenya peploides) on Surtsey: an immigrant's journey

[摘要] Sea sandwort (Honckenya peploides) was one of the first plants to successfully colonize andreproduce on the volcanic island Surtsey, formed in 1963 off the southerncoast of Iceland. Using amplified fragment length polymorphic (AFLP) markers,we examined levels of genetic variation and differentiation amongpopulations of H. peploides on Surtsey in relation to populations on the nearby islandHeimaey and from the southern coast of Iceland. Selected populations fromDenmark and Greenland were used for comparison. In addition, we testedwhether the effects of isolation by distance could be seen in the Surtseypopulations. Using two primer combinations, we obtained 173 AFLP markersfrom a total of 347 plant samples. The resulting binary matrix was thenanalysed statistically. The main results include the following: (i) Surtsey hadthe highest proportion of polymorphic markers as well as a comparativelyhigh genetic diversity (55.5% proportion of polymorphic loci, PLP; 0.1974 H_E) and Denmark the lowest(31.8% PLP; 0.132 H_E), indicating rapid expansion during an earlystage of population establishment on Surtsey and/or multiple origins ofimmigrants; (ii) the total genetic differentiation (F_ST) among Surtsey(0.0714) and Heimaey (0.055) populations was less than half of that foundamong the mainland populations in Iceland (0.1747), indicating substantialgene flow on the islands; (iii) most of the genetic variation (79%, p < 0.001) was found within localities, possibly due to theoutcrossing and subdioecious nature of the species; (iv) a significant geneticdistance was found within Surtsey, among sites, and this appeared tocorrelate with the age of plant colonization; and (v) the genetic structureanalysis indicated multiple colonization episodes on Surtsey, whereby H. peploides mostlikely immigrated from the nearby island of Heimaey and directly from thesouthern coast of Iceland.

[学科分类] 地球化学与岩石