Patterns of isozyme variation as indicators of biogeographic history in Pilgerodendron uviferum (D. Don) Florín.

PREMOLI, ANDREA SOUTO, CINTIA ROVERE, ADRIANA ALLNUT, TEO Y NEWTON, ADRIAN

Diversity and Distribution

Blackwell Science Ltd.

Lugar: Oxford, UK; Año: 2002 p. 57 - 66

·         Abstract: The effects that Pleistocene glaciations had on the genetic characteristics of the austral most conifer of the world Pilgerodendron uviferum, were analysed under the hypothesis that persisted locally in ice-free areas in temperate South America.  These areas were probably more abundant at the northern range of the species given that ice fields were larger in southern Patagonia.  As a result, it was expected a decrease in genetic variation with latitude.  In addition, if long-distance dispersal occurred from surviving populations, it was predicted an increase in among-population genetic divergence with the distance to probable glacial refugia. The pollen record suggests a glacial refugium for Pilgerodendron in southern Chile at c. 42°S but no other information is available from the rest of the species´range. The relationship between location and within-population variability indices of twenty Pilgerodendron populations was studied by multiple regression analysis.  The degree of genetic differentiation with geographic distance between all population pairs was investigated by Mantel tests.  Results indicated that Pilgerodendron populations are highly monomorphic probably reflecting past population bottlenecks and reduced gene flow.  Southern most populations tend to be the least genetically variable and thus they were more affected by glacial activity than northern ones.  The presence of centres of genetic diversity along the species’ range together with the lack of significant correlation between genetic and geographic distances may indicate that Pilgerodendron did not advance southward after the last glaciation from a unique northern refugium, but it spread from several surviving populations in ice-free areas in Patagonia instead. Conservation considerations in Pilgerodendron include the inclusion of populations currently outside any conservation unit that are genetically distinct which in addition occur in areas with severe antropogenic disturbances.  Also long-term monitoring is needed to investigate the consequences that the complete absence of polymorphism has, if any, on the persistence of some populations.