Some Ecological Aspects of Natural Hybridism in New Zealand Plants.

By H. H. Allan, Botany Division, D.S.I.R., Wellington.

In the primitive vegetation hybrids are especially noticeable as ecotones and in relatively open communities. Man's occupance has not only greatly modified the primitive vegetation, but also brought into being new communities. Bare areas and intermediate habitats have greatly favoured the coming together of different species in a genus and given opportunity for the occurrence of large populations containing numerous hybrid forms. The subsequent history of such hybrid swarms needs continuous and close attention. Examples were given showing the varied forms the resultant hybridism had taken, including the occurrence of hybrids between naturalized and indigenous species. There is clear evidence that long isolation is not necessarily productive of sterility barriers. References were made to similar findings by workers in America and to the techniques developed by analyzing populations.

A more general account of recent work on wild hybrids is to be published in the Botanical Review.