Hebe and Related Genera

New Zealand has perhaps 100 species of Hebe and there are only three species elsewhere. Two of these in southern South America are shared with New Zealand (H. elliptica, H. salicifolia) and the third is Hebe rapensis on Rapa Island in French Polynesia. The related but generally less woody Parahebe is also represented in eastern Australia and New Guinea and Chionohebe, probably derived from Parahebe, is a genus of small, high alpine cushion plants of which two of the New Zealand species extend to south-eastern Australia. Veronica, from which Raven¹⁴⁸ would consider the Hebe alliance to have been derived, is a mostly north temperate, herbaceous to slightly woody genus. It seems reduced and specialised and so is unlikely to have been ancestral to the woody hebes, some of which may become small trees with trunks sometimes 30 cm in diameter. There are differences too between the basic chromosome numbers of Veronica and the Hebe alliance which do not suggest a close relationship. There are indeed a few true veronicas in eastern Australia but, as Wardle¹⁴⁹ comments, 'it seems … possible that the handful of Australian true veronicas derive from recent northern immigrants that are not directly related to the Hebe alliance'.

Presumably Veronica was originally derived from woody, northern hemisphere ancestors, which may have been related to and perhaps also ancestral to the Hebe alliance.

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Once again it is clear that much more research is required into a number of genera before we can attain any degree of certainty about the relative proportions of New Zealand alpines that have been derived from:

(a)	geologically recent immigrants from the northern hemisphere;
(b)	more ancient immigrants from the northern hemisphere; or
(c)	genera of southern hemisphere origins.