TANE 28,1982 VASCULAR PLANTS OF AN UNCLASSIFIED ISLET, CAPE BRETT PENINSULA, NORTHERN NEW ZEALAND by E.K. Cameron Department of Botany, University of Auckland, Private Bag, Auckland SUMMARY

Seventy indigenous and 2 adventive vascular plants taxa are recorded for the "unmodified" islet. Its botanical value exceeds its small size because of the modification of the adjacent Cape Brett Peninsula and nearby islands.

INTRODUCTION

The islet is situated only a few metres off the northern coastline of Cape Brett Peninsula (Fig. 1). This steep beehive-shaped greywacke islet, less than two hectares in area, supports an excellent cover of indigenous vegetation compared with the adjacent goat (Copra hircus) browsed mainland. Approximately thirty minutes was spent on the islet during a four day botanical survey of Cape Brett Peninsula carried out for the Department of Lands and Survey, Auckland, in June 1980 (Cameron 1980). Time permitted only a single south-west to north-east traverse, returning to the starting point via the north-west littoral.

PLANT COMMUNITIES

For ease of description four plant associations (Fig. 2) are recognised although it must be remembered that these are by no means distinct as they grade into one another.

Area 1: Coastal Rock. The amount of coastal rock on the islet is proportional to the degree of wave exposure and thus the north-eastern side of the islet has the greatest amount of exposed rock. Plants such as Asplenium flaccidum ssp. haurakiense, Samolus repens and the shore lobelia (Lobelia anceps) are frequently found growing in cracks and crevices. Others found here include the N.Z. ice plant (Disphyma australe), glasswort (Salicornia australis) shore groundsel (Senecio lautus), Scirpus nodosus and at the upper level Rhagodia triandra.

Area 2: Prostrate Vegetation. The steep (c.50°) exposed northern slopes are carpeted with prostrate shrubs; kowhai (Sophora microphylla),

213 Piercy I 0

214 Melicytus novae-zelandiae and taupata (Coprosma repens) all less than half a metre in height. Underneath and growing through this mat is the twining Muehlenbeckia complexa and the 'succulent' pepper, Peperomia urvilleana. Associated with these plants are; the N.Z. iceplant; the renga lily (Arthropodium cirratum); coastal snow tussock (Chionochloa bromoides) and small ferns (Cheilanthes spp.)

Area 3: Shrub development. Found at a similar level to Area 2, on the islet, but less exposed. This increase in shelter has allowed shrub development up to 2-3 m in height. Close to Area 2 ngaio (Myoporum laetum), coastal maire (Nestegis apetala) and kowhai are common; with Melicytus novae-zelandiae fringing the rock-shrub interface. On the south-western side coastal maire is abundant with spreading branches and attaining 2-3 m in height. Karaka (Corynocarpus laevigatas), Coprosma macrocarpa, houpara (Pseudopanax lessonii) and mahoe (Melicytus ramiflorus) are common; tawapou (Planchonella novo- zelandica) is present and the N.Z. jasmine (Parsonsia sp.) tangles through this mixed canopy. Ferns (Asplenium oblongifolium, Phymatodes diversifolium, Doodia media, Polystichum richardii) renga lily and Peperomia urvilleana are common on the loose, steep rocky ground. By the rock-shrub interface, karo (Pittosporum crassifolium) N.Z. flax (Phormium tenax) and coastal snow tussock grow.

Fig. 2. Four plant communities of the islet; Cape Brett Peninsula in the background.

Area 4: Tree development. The islet is crowned with a small forest 5-6 m tall and is comprised of coastal maire, kohekohe (Dysoxylum spectabile), mapou (Myrsine australis) and tawaroa (Beilschmiedia sp.) Pohutukawa

215 (Metrosideros excelsa) and kanuka (Leptospermum ericoides) emerge through this canopy to about 12 m in height. Hangehange (Geniostoma ligustrifolium), rangiora (Brachyglottis repanda) and Coprosma macrocarpa are common shrubs. The ground here is fairly level, less rocky, and the reasonable soil layer supports several ferns (Adiantum cunninghamii, Asplenium oblongifolium), Gahnia lacera and Astelia banksii.

ANNOTATED SPECIES LIST

Seventy-two taxa of vascular plants were recorded on the islet (Table 1). During the survey no conscious attempt was made to record all the adventive plants, making this group under-recorded. But it should be noted that the adventive plants were small and insignificant compared with the indigenous vegetation. Synonyms or references are given for the lesser-known name changes, * denotes adventive species. Table 1. Vascular flora of unclassified islet according to plant groups and indigenous o adventive status.

Group Indigenous Adventive Totals

Ferns 11 . 11 Dicots 45 1 46 Monocots 14 1 15 TOTALS 70 2 72

FILICOPSIDA Polypodiaceae Phymatodes diversifolium Hound's tongue. Abundant terrest rially in shaded sites throughout. Pyrrosia serpens Rupestral by the coast and epiphytic on pohutukawa. Aspleniaceae Asplenium flaccidum subsp. (Brownsey 1977). Occasional on ban haurakiense coastal rock. A. oblongifolium Col. Huruhuru whenua. Common, shaded (A. lucidum) sites throughout. Blechnaceae Doodia media Abundant, especially on the western. sides; shaded sites. Dryopteridaceae Polystichum richardii Frequent on the upper western side Adiantaceae Adiantum cunninghamii Maidenhair. Local, by the top of th< islet. A. hispidulum Rosy maidenhair. Occasional shaded sites. Cheilanthes distans Local, on bare rock between prostrate plants, north-eastern side. Growing by C. sieberi. C. sieberi As for C. distans. Pellaea rotundifolia Local open site near the top of the islet, AKU 11573.

216 Dicotyledones Beilschmiedia sp. Tawaroa (large-leaved tawa). Several trees (5-6 m tall) near summit. Clematis parviflora Clematis. Climbing through shrubs on the south-western side. Peperomia urvilleana Frequent on the shaded rocky slopes throughout. Melicytus novae-zelandiae (Green 1970). Prostrate and common on the steep, exposed north-eastern rock; more upright but less frequent on the less exposed north-western side. M. ramiflorus Mahoe. Occasional in the shrub canopy on the south-western side. Disphyma australe N.Z. iceplant; horokaka. Common on the coastal rock, especially on the northern side. Tetragonia trigyna N.Z. spinach. Local, north-eastern side by prostrate shrubs. Muehlenbeckia australis Single, climbing vine near summit. M. complexa Wire vine. Sprawling mats on steep north-eastern side. Rhagodia triandra Occasional sprawling, rock-shrub interface. Salicomia australis Glasswort. Occasional on coastal rocks. Colli trie he muelleri Local, damp mud near summit. Knightia excelsa Rewarewa. Occasional near summit. Pittosporum crassifolium Karo. Occasional 1-2 m tall, rock- shrub interface, south-western side. Occasional, rock-shrub interface, P. umbellatum south-western side and taller plants (5-6 m) near summit. Kanuka. Common at summit, Leptospermum ericoides individual trees reaching about 12 m tall. Pohutukawa. Only present near Metrosideros excelsa summit, emergent to 12 m tall, 60 cm DBH. M. peforata Occasional, near summit as a small liane. Hoheria populnea Houhere; lacebark. Rare, near summit. Sophora microphylla Kowhai. Common and prostrate on the steep north-eastern side. Corynocarpus laevigatus Kohekohe. Occasional, near summit, 5-6 m tall. Pseudopanax arboreus (Philipson 1965). Whauwhaupaku. Occasional, shrub association, south• western side. P. crassifolius x lessonii Two noticed near the summit P. lessonii Houpara. Common from the rock- shrub interface to about halfway up

217 the mid-face on the south-west* side. Epacridaceae Cyathodes juniperina Mingimingi. Rare, near summit. Sapotaceae Planchonella novo-zelandica Tawapou. Occasional from the n> shrub interface to about halfway the mid-face on the south-west* side, 2-3 m tall. Myrsinaceae Myrsine australis Mapou. Common; from small plant the rock-shrub interface on the soul western side to 5-6 m tall trees near the summit. Oleaceae Nestegis apetala Coastal maire. Frequent, low a spreading on the south-western roc shrub interface, becoming taller a: more erect proceeding up the mi face; attaining 6 m tall and 60 c DBH near the summit. It is absent i the north-eastern side. N. lanceolata White maire. Rare, only near sum mi Loganiaceae Geniostoma ligustrifolium Hangehange. Common understorey near summit. Apocynaceae Parsonsia sp. Kaihua. Climbing through the shrub association on the south-western mi face. Rubiaceae Coprosma arborea A single tree about 5 m tall net summit. C. macrocarpa Karamu. Abundant shrub forming i places the main vegetation cove especially near the sea on the wester side; present also in the underscore near the summit. C. repens Taupata. Common and prostrate o the exposed north-eastern side. Compositae Brachyglottis repanda Rangiora. Frequent in the under storey near the summit, 1-2 m tall. Gnaphalium audax (Drury 1972) Occasional, in ope sites. Hypochoeris radicata* Catsear. Several plants, open site between low vegetation. Olearia furfuracea Akepiro. Occasional; 1-2 m tall shrub on the south-western side near ti rock-shrub interface. Senecio kirkii A single 1.5 m plant with very wide leaves observed by the rock-shrub interface on the south-western side. S. lautus Shore groundsel. Frequent on coastal rock. Primulaceae Samolus repens Common on coastal rock, growing closer to the sea than any other vascular plant. Lobeliaceae Lobelia anceps Shore lobelia. Occasional, coastal rock. Convolvulaceae Dichondra repens Mercury Bay weed. Present among; the prostrate cover on the north eastern side.

218 Gesneriaceae Rhabdothamnus solandri Waiuatua. Rare, near summit. Myoporaceae Myoporum laetum Ngaio. Occasional, a few plants observed by the northern rock-shrub interface, 2-3 m tall.

Monocotyledones Liliaceae Arthropodium cirratum Renga lily. Common on the north• eastern coastal rock. Frequent on the steeper slopes underneath the shrub canopy. Astelia banksii Wharawhara. Common from the rock- shrub interface to the steep mid-face, especially on the western side. Occasionally by summit. Collospermum hastatum Occasional epiphytic near summit. Phormium tenax N.Z. flax. Frequent at the rock-shrub interface on the south-western side; also scattered plants below this interface. Orchidaceae Acianthus fornicatus Occasional near summit var. sinclairii Cyperaceae Carex breviculmis Among the prostrate vegetation on the north-eastern side. C. lambertiana Occasional western side, protected sites. Gahnia lacera Frequent near summit. Scirpus nodosus Common, bare coastal rock, especially on the south-western side. Gramineae Chionochloa bromoides Coastal snow tussock. This attractive hanging grass is common on steep coastal rock. Dichelachne crinita Long-hair plume grass. Occasional, open sites. AKU 11571. Oplismenus imbecillis Beneath the prostrate vegetation, north-eastern side. Pea anceps Occasional north-eastern side. Rytidosperma sp. (Connor and Edgar 1979). Danthonia. Frequent amongst low vegetation, north-eastern side. Sporobolus africanus* Rats tail. Frequent, exposed open sites.

MAMMALS

Faecal pellets found on the islet were identified by Dr J.L. Craig as opossum (Trichosurus vulpecula) and rat (Rattus sp.), probably R. rattus (too large for R. exulans). Opossum browsing was not obvious on the islets vegetation. How opossums reached here is a mystery, but on such a small island their extermination should not be difficult. Feral goat numbers on the adjacent mainland were very high and in places shrubs are almost absent from the forests.

219 DISCUSSION

Because the vegetation of Cape Brett Peninsula, and most of the adjacent islands is so modified the few remaining unmodified islands hold the key for interpreting this region's vegetation. Although the described islet is very small, it has a valuable scientific attraction due to its "unmodified" flora. Coastal maire and Melicytus novae-zelandiae are prevalent on the islet, but infrequent to rare on the adjacent mainland. This situation perhaps indicates that both these plants were once common on Cape Brett Peninsula. However, they have now been markedly reduced because of either browsing, or burning, or Maori habitation, or a combination of all three. A survey of the larger Piercy Island (Fig. 1), off the end of Cape Brett Peninsula, would supply a valuable insight into the pre-Maori vegetation of this region, as this island also has unmodified vegetation.

ACKNOWLEDGEMENTS

Mr John Gardiner (Chief Ranger, Bay of Islands, Maritime and Historic Park) for providing boat transport and accommodation during the four day survey of Cape Brett Peninsula. Bill Carlin who spotted the islet, after a heavy swell had made a landing on Piercy Island impossible. Mr A.E. Esler for several plant identifications. Dr J.E. Braggins for reading manuscript and suggesting improvements.

REFERENCES

Brownsey, P.J. 1977: A taxonomic revision of the New Zealand species of Asplenium, New Zealand Journal of Botany 15 (1): 39-86. Cameron, E.K. 1980: Botanical features of Cape Brett Peninsula. Unpublished report, file No. 20/548/1, Department of Lands & Survey, Auckland. Connor, H.E. & Edgar, E. 1979: Rytidosperma Steudel in New Zealand. New Zealand Journal of Botany 17:311-337. Drury, D.G. 1972: The cluster and solitary-headed cudweeds native to New Zealand. New Zealand Journal of Botany 10(1): 112-179. Green, P.S. 1970: Notes relating to the floras of Norfolk and Lord Howe Islands. Journal of the Arnold Arboretum 51:204-220. Philipson, W.R. 1965: The New Zealand genera of the Araliaceae. New Zealand Journal of Botany 3:333-341.

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