Niche model and genetics show opposite responses to glaciations in Patagonian trees with contrasting cold tolerances

T. KITZBERGER; C. P. SOUTO; M. ARBETMAN; P. MATHIASEN ; A.C. PREMOLI

San Carlos de Bariloche

Congreso; VI Southern Connection Congress; 2010

Environmental change produces multiple effects on species generating complex reshuffling of novel combinations. Projection of modern-trained ecological niche models (ENMs) onto past environmental conditions allows retrodicting distribution of species and pinpoint possible refugia. In addition, spatial patterns of genetic variation allow reconstructing persistence/migration based on the imprints left by past genetic bottlenecks occurred during range shifts. We present ENM-genetic studies of Nothofagus pumilio and Austrocedrus chilensis, two species with contrasting cold tolerances. ENM models show that LGM suitability of A. chilensis was high in a northerly area in Chile (c. 36°-38°S) while areas with current presence were largely unsuitable. Unique alleles and allelic diversity are highest in Chilean populations, decreasing sharply across the Andes and steadily southwards. In contrast, N. pumilio shows multiple areas that remained suitable during LGM throughout its current distribution (35-55°S). No large-scale trends in spatial genetic variation are evident but instead it is related to local movements of ice sheets. All this suggests highly different patterns of persistence/migration in these two species: A. chilensis having suffered isolation in a northerly refugium followed by long-distance eastward (transandean) and southward migration; N. pumilio having persisted locally in ice-free margins followed by short-distance recolonization onto deglaciated areas.