New Hebe Recognised From Western Northland
When Hebe perbella was formally named in 1998 it was noted that the species was typically associated with basalt rock and associated soils within cloud forest and/or steep sided canyons and waterfalls from Ahipara south to the Waima Forest (de Lange 1998). However, an extreme southerly outlier of this species, a population found at Maungaraho Rock, near Tokatoka although included in the H. perbella was considered anomalous because these plants grew on andesitic rock in exposed situations prone to summer drought. Maungaraho plants also differed from H. perbella in their less highly coloured flowers, with broader subacute rather than acute corolla lobes, slightly longer corolla tube, typically shorter and broader leaves, and smaller overall growth habit. At the time H. perbella was described these plants were included within that species because they were more similar to it than to any other hebe then known (de Lange 1998; de Lange & Rolfe 2008).Subsequently Maungaraho plants were included in an investigation of the hebe flavonoids, the results of which (see Mitchell et al. 2007) had greatly influenced the taxonomic decisions reached in the recent hebe monograph by Bayly & Kellow (2006). In their paper, Mitchell et al. (2007) showed that Maungaraho plants had nothing in common with Hebe perbella. Nevertheless, Bayly & Kellow (2006) who had access to this flavonoid data included Maungaraho plants with H. perbella, and further suggested that H. perbella was probably conspecific with the Te Paki endemic H. adamsii.
In the latest issue of the New Zealand Journal of Botany (December 46(4) (2008)) de Lange & Rolfe (2008) treat the Maungaraho Rock hebe as a new species, H. saxicola de Lange. Their paper explores the morphological relationships between H. adamsii and H. perbella, and conclude that both are distinct species differing in many respects from each other, not least of which is the chromosomal difference between them (H. adamsii is tetraploid (2n = 80) and H. perbella diploid (2n – 40) and the presence of a leaf bud sinus in H. adamsii and its absence in H. perbella. Further the published flavonoid analysis of Mitchell et al. (2007) showed no obvious relationship between H. adamsii and H. perbella. The authors chose to recognise and formally describe H. saxicola as distinct from H. perbella because of its distinctive flavonoid profile, floral, fruit and vegetative differences and its ecology. A new description of H. perbella is also provided by de Lange & Rolfe (2008) to remove those characters present in the original description of that species (see de Lange 1998) and now restricted to H. saxicola.
The new hebe though reasonably common in its sole known habitat has declined from several more accessible sites on the rock since it was first discovered there in 1990. The species is threatened by a range of weeds, the most serious of which is pampas grass (Cortaderia selloana). Several of the key sites on the rock are also vulnerable to rock climbers who have marked climbing routes up the rock through these habitats.
References
Bayly, M.; Kellow, A. 2006. An illustrated guide to New Zealand hebes. Wellington, Te Papa Press. 388 p.
de Lange, P.J. 1998. Hebe perbella (Scrophulariaceae)—a new and threatened species from western Northland, North Island, New Zealand. New Zealand Journal of Botany 36: 399–406.
de Lange, P.J.; Rolfe, J.R. 2008: Hebe saxicola (Plantaginaceae) – a new threatened species from western Northland, North Island, New Zealand. New Zealand Journal of Botany 46: 531-545.
Mitchell, K.A.; Kellow, A.V.; Bayly, M.J.; Markham, K.R.; Brownsey, P.J.; Garnock-Jones, P.J. 2007. Composition and distribution of leaf flavonoids in Hebe and Leonohebe (Plantaginaceae) in New Zealand—2. “Apertae”, “Occulsae”, and “Grandiflorae”. New Zealand Journal of Botany 45: 329–392.
Posted: 13/12/2008