Maori Cultivation of Hebe Speciosa SuspectedNapuka/Titirangi (Hebe speciosa) is one of the most spectacular of New Zealand’s Hebe species. The large magenta flowers mark it out from a genus where flowers are more typically muted tones of lilac, mauve, blue or white. Napuka was made known to science in the early 1834 when Richard Cunningham was taken by Maori guides to see it at Te Arai Te Uru (Outer South Head, Hokianga Harbour, North Island). Not long after, the species reached Europe where it was one of the first hebes to be used for plant breeding within the genus. So successful has this been that many garden centres now stock cultivars and hybrids involving this species, though few actually market the true species.
In the wild Napuka has not fared well. Field surveys and analysis of herbarium specimens and literature records in 1992 confirmed that 14 populations were once spread along the west coast from Te Paki in the North Island to the Marlborough Sounds of the South Island. By 1992 seven (50%) of these had gone extinct. As of 2005, two populations, one at Mokau (with 40 plants) the other at Titirangi Bay (with 27 plants) are surviving only because of hands on management and even so the situation remains precarious. Only three northern populations, those at Te Arai Te Uru, Maunganui Bluff, and near Muriwai Beach were in anyway large, though these too are seriously threatened.
What struck researchers in 1992 was that eight populations were clearly associated with significant Maori Pa sites, tribal boundaries, and urupa (burial sites). It was wondered whether Napuka might have been deliberately planted and/or traded by Maori.
A New Zealand Department of Conservation funded study on the species has just been published by the London based Botanical Journal of the Linnean Society. That paper shows how the use of the Amplified Fragment Length Polymorphism technique (AFLP) on samples of DNA gathered from all extant Napuka populations was able to answer critical questions about this species population health, genetic variability, and whether or not populations might have been planted.
It now appears fairly conclusive that there are only three extant natural populations of Napuka, located at Te Arai Te Uru, Maunganui Bluff and Muriwai Beach. The remaining extant populations are the probable result of deliberate Maori plantings. Even more stunning is that Titirangi (Marlborough Sound) plants were the same as samples from Te Arai Te Uru (outer South Head, Hokianga Harbour), suggesting that Titirangi plants were the result of one direct movement from the Hokianga. Archaeological evidence provided a hint at the idea but DNA data appears to have clinched it. Napuka was spread by northern Maori south into the western Waikato, Taranaki and northern South Island. The research also showed that Mokau was one clone, and that genetic variability within these southern populations was virtually non-existent. Thus while coastal erosion, weeds and browsing animals remain the most serious threats affecting the species, inbreeding depression may be silently reducing the vigour of the more southerly populations of this species.
What does this mean for the conservation of Napuka? Well one view would be that future management should only involve the three “natural” populations identified by this study. However, others would argue that the southern populations, as an unambiguous example of an indigenous plant cultivated by Maori for purely aesthetic reasons should be maintained. If so then to maintain a healthy, genetically variable unit, further plants from the northern populations need to be introduced into these southerly ones to ensure their genetic fitness.
Armstrong, T.T.J.; de Lange, P.J. 2005: Conservation genetics of Hebe speciosa (Plantaginaceae) an endangered New Zealand shrub. Botanical Journal of the Linnean Society 149: 229-239.
Posted: 21 October 2005