The major Australian cool temperate rainforest tree Nothofagus cunninghamii withstood Pleistocene glacial aridity within multiple regions: evidence from the chloroplast

Abstract

 Glacial aridity of the Pleistocene was inhospitable for the cool temperate rainforest tree Nothofagus cunninghamii over most of its current range in southeastern Australia, particularly in eastern Tasmania. A chloroplast DNA phylogeographic study was undertaken to investigate whether this species was likely to have survived in situ or conforms to a dispersal model of postglacial recovery.  Twenty-three chloroplast haplotypes were identified by PCR-RFLP and direct sequencing of 2164 base pairs from 213 N. cunninghamii individuals collected in a range-wide survey. Fine-scale haplotype distribution was investigated using PCR-RFLP in eastern Tasmania.  Deep chloroplast divergence occurred in N. cunninghamii. The single haplotype of the sister species, N. moorei, was nested among N. cunninghamii haplotypes. The distribution of N. cunninghamii haplotypes supports: multiple glacial refugia in coastal and inland western Tasmania, the centre of haplotype diversity; glacial survival in the central highlands of Victoria, corroborating pollen data; and the long-term occupation of eastern Tasmania because of the presence of a unique deeply diverged chloroplast lineage.  N. cunninghamii withstood glacial aridity within multiple regions in apparently non-equable climates. This finding contributes to a growing understanding of how the resilience of temperate species during glacial periods has shaped modern biota.