Conservation genetics and population history of Betula nana, Vaccinium uliginosum, and Campanula rotundifolia in the Arctic Archipelago of Svalbard

Plant species defined as strongly thermophilous in Svalbard are rare and may be threatened by extinction due to suppressed sexual reproduction, small population sizes, genetic depauperation, and human activity. We examined isozyme diversity in three of these species-Betula nana, Vaccinium uliginosum, and Campanula rotundifolia-in Svalbard. Twenty-five to 60 ramets from each of two to three (sub)populations of each species were analyzed for eight enzyme systems. In B. nana, genetic diversity was low within sampling plots (D:0.00-0.49) and intermediate within populations (mean D=0. 70, mean H-ep=0.119). Genetic diversity at the species level (H-es) was 0.141, and the differentiation among populations (F-ST=0.193) was higher than the average for other species with similar life traits. In V. uliginosum, no variation was observed within plots, and genetic diversity within populations was low (mean D=0.29, mean H-ep=0.082). Genetic diversity at the species level was also low (H-es=0.152), and the differentiation among populations (F-ST=0.493) was much higher than in most other species studied. The only Svalbard population of C. rotundifolia has 2n=34 and is traditionally considered as diploid, but the observed enzyme banding patterns suggest polyploidy. In this species, genotypic diversity was low within plots (D: 0.00-0.33), intermediate within subpopulations (mean D=0.74), and all multilocus phenotypes were local. The present populations of all three species in Svalbard are probably fragmented relics of larger populations in the postglacial warm period. On the basis of the observed distribution of genetic diversity and population sizes, we propose to conserve all Svalbard populations of V. uliginosum and C. rotundifolia, and at least one population of B. nana.