Biodiversity and genetic patterns of Austrocedrus chilensis stands mirror fire history of drylands of Patagonia

SOUTO C.P., K. HEINEMANN, T. KITZBERGER & A.C. PREMOLI

Bariloche

Congreso; VI Southern Connection Congress; 2010

Species and genetic diversity as distinct levels of biological hierarchy are rarely analyzed concomitantly despite the recognition of their conceptual unification in biodiversity and ecological evolutionary research. In northwestern Patagonia Argentina fire has been proved to have a major influence on vegetation patterns. Austrocedrus chilensis is the dominant native conifer displaying a SW-NE gradient of increasing fragmentation. We tested the hypothesis that fire history has shaped genetic traits within populations of A. chilensis as well as the composition of vegetation matrix where they are embebed. We sampled 1853 individuals in 67 populations between 37 and 42°S lat in Argentina. We measured genetic diversity and inbreeding within populations on the basis of 12 allozyme loci, scoring accompanying species along transects. Species richness increased southwards (0.28; p= 0.02), with the opposite pattern in genetic diversity (-0.41; p= 0.0006). Inbreeding was high and positive (Fis>0.14) in northern and central-eastern populations of Austrocedrus, while non-significant inbreeding was evident in less genetic variable southern and central-western populations (Fis< 0.06). These results agree with accompanying species ordination showing differences in species composition among these two areas. Our results mirror a long pre-European history of small and frequent fires in the northeast and more recent (settlement age) extensive stand-devastating fires towards southwest.