Isozyme variation and recent biogeographical history of the long-lived conifer Fitzroya cupressoides

Aim Palaeoenvironmental records of Pleistocene glaciation and associated ve getation changes in Patagonia have led to the hypothesis that during the la st glacial maximum (LGM) tree species survived locally in favourable habita ts. If present populations originated from spread from only one refugium, s uch as an ice-free area of coastal Chile (Single Refugium hypothesis), we w ould expect that eastern populations would be genetically depauperate and h ighly similar to western populations. In contrast, if the ice cap was not c omplete and tree species persisted in forest patches on both slopes of the Andes (Multiple Refugia hypothesis), we would expect a greater degree of ge netic divergence between populations either on opposite sides of the Cordil lera (Cordillera Effect scenario) or towards its present-day southern distr ibutional limit where the ice sheet reached its maximum coverage (Extent-of -the-Ice scenario). Location We tested this refugia hypothesis using patterns of isozyme variat ion in populations sampled over the entire modern range of the endemic coni fer Fitzroya cupressoides (Mol.) Johnst. (Cupressaceae) in temperate South America. Methods Fresh foliage was collected from twenty-four populations and analys ed by horizontal electrophoresis on starch gels. Results Twenty-one putative loci were reliably scored and 52% were polymorp hic in at least one population. Populations from the eastern slope of the A ndes were genetically more variable than those from the western slope; the former had a greater mean number of alleles per locus, a larger total numbe r of alleles and rare alleles, and higher polymorphism. Genetic identities within western populations were greater than within eastern populations. Di scriminant analyses using allelic frequencies of different grouping schedul es of populations were non significant when testing for the Single Refugium hypothesis whereas significant results were obtained for the Multiple Refu gia hypothesis. Main conclusions Our results indicate that present Fitzroya populations are the result of spreading from at least two, but possibly more, glacial refu gia located in Coastal Chile and on the southern flanks of the Andes in Arg entina.