Effects of glacial climates on floristic distribution in New Zealand 2. The role of long-distance hybridisation in disjunct distributions

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Abstract
In Part 1, it is proposed that cold-intolerant disjunct species in southern and central centres of floristic richness occur as the result of post-glacial long-distance hybridisation with resident hardier species, followed by reconstitution of the less hardy species. For this to operate, the species involved must hybridise freely, pollen must be transported over long distances, and it must retain viability. Nothofagus species meet these conditions, and their hybrids have been found several kilometres from one parent. Hybrids between three other pairs of anemophilous species have probably arisen through pollen dispersal over hundreds of kilometres. Early post-glacial conditions are likely to have been especially conducive to segregation of immigrant species from populations of fertile hybrids.