LICHENS FROM THE MOTUROA ISLAND GROUP

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1 TANE 23, 1977 LICHENS FROM THE MOTUROA ISLAND GROUP by Glenys C. Hayward* and A.E. Wright *35A Marin Road, Onehunga, Auckland 6 ("Department of Botany, University of Auckland, Private Bag, Auckland SUMMARY A reduced lichen flora (twenty-one species from fifteen genera) is recorded for the Moturoa Islands. The plants were found in three habitat groups: on bark in coastal scrub, on sandy soil in developing heath and on coastal rocks. The reduced numbers and lack of diversity reflect the harsh coastal environment of these islands. INTRODUCTION The lichens recorded here were collected by A.E.W. on the Auckland University Field Club scientific camp to the Moturoa Islands in May, The collection was later sent to G.C.H. for identification and discussion. The collection from Whale Island can be regarded as fairly complete, but on the smaller islands collection time was limited. Most lichens from the study are held in the collection of G.C.H. with duplicates deposited by A.E.W. in the Herbarium of the Auckland Institute and Museum. HABITAT DESCRIPTIONS The Moturoa Island Group (latitude 34 37'S, longitude 'E) lies off Karikari Peninsula, Northland, New Zealand (Fig. 1). The Group comprises five main islands (Green, Moturoa, Rocky, Sugarloaf and Whale Islands) ranging from less than one hectare to twelve hectares in area, and several off-lying stacks. All are exposed and frequently covered with salt spray. The physiography and history of the islands are described by Wright (1977a) and the higher plant vegetation by Wright (1977b). The lichens were collected from three main substrates: rock, bark and sandy soil. Rock Hard rock surfaces suitable for lichen colonisation were confined mainly to the coast. Lichens grew only on in situ rockfaces the few cobble beaches in the group being unstable for colonisation. The gently shelving rock flats along the southeastern coast of Whale Island, especially where freshwater seeps through, supported a prolific growth of lichens. 31

2 t J Fig. 1. Map showing distribution and location of the Moturoa Islands, Northland, New Zealand.

3 Bark The two main species forming the coastal scrub were Hymenanthera novaezelandiae and taupata (Coprosma repens). These formed the dominant vegetation on all islands except Whale Island where they were confined to scattered patches. Of the two species Hymenanthera bark was the more favoured substrate for lichen colonisation, probably because it grew on the island summits and was therefore less prone to salt spray. In the scrub, lichen growth was confined to the damper, more shaded areas, especially on Green and Moturoa Islands. In contrast the taupata grew on the coastal areas and near the main petrel landing points. Most plants were severely defoliated. In addition the taupata bark was scaly and frequently shed, providing a poor substrate for colonisation. Sandy Soil This substrate was confined to a small area on the summit of Whale Island, where scattered shrubs of manuka (Leptospermum scoparium) provided suitable conditions for a small number of species. SPECIES LIST Key to Distribution Symbols: Island A = G = M - R S = w = all islands Green Island Moturoa Island Rocky Island Sugarloaf Island Whale Island Habitat 1= Intertidal 2= Maritime 3= Scrub 4= Manuka heath CLASS ASCOMYCETES Substrate r = rock s = soil t = treebark ORDER LECANORALES Suborder Lecanorineae Cladoniaceae Cladia aggregata (Sw.) NyL W4s Cladonia coniocraea (Florke) Spreng. W4s C. nemoxyna (Ach.) Nyl. W4s Cladonia sp. W4s Lecideaceae Lecidea spp. R2r,W2r Parmeliaceae "Parmelia (Xanthoparmelia) isidiigera (Mull. Arg.) Gyeln." (see Hayward et al. 1976) A2r Parmotrema reticulatum (Tayl.) Choisy A2r,W3t3r Xanthoparmelia furcata (Mull. Arg.) Hale W2r X. scabrosa (Tayl.) Hale S2r Xanthoparmelia sp. W2r Usnea sp. G3t,W3t Ramalinaceae Ramalina ecklonii (Spreng.) Mey.+Flot. A2r R. c.f. farinacea (L.) Ach. S3t Suborder Lichinineae Lichinaceae Lichina sp. Air Suborder Teloschistineae Teloschistaceae Xanthoria parietina (L.) Th.Fr. A2r,A3t Suborder Physciineae 33

4 Physciaceae Buellia stellulata (Tayl.) Mudd. W2r Dirinaria picta (Sw.) Clem.+Schaer. S3t Heterodermia pseudospeciosa (Kurok.) Culb. A2r,G3t,M3t Suborder Pertusariineae Pertusariaceae Pertusaria sp. W2r ORDER ARTHONIALES Opegraphaceae Opegrapha agelaeoides Nyl. M3t DISCUSSION Lichen diversity on the Moturoa Islands is poor and directly reflects the range of available habitats and their lack of variety. Rock Even though this substrate had the most diverse lichen flora found on the islands, the number of species recorded is fewer than in similar habitats elsewhere. The foliose species Xanthoma parietina, Heterodermia pseudospeciosa and the four species of Xanthoparmelia are all common "weed" species of northern New Zealand coastal rocks. The zonation patterns of these foliose lichens, the crustose species Pertusaria sp., Lecidea spp., and Buellia stellulata and the erect Lichina sp., conform broadly to those described by Hayward and Hayward (1974a, 1974b). Bark The species recorded on bark (Parmotrema reticulatum, Usnea sp., Ramalina c.f. farinacea, Dirinaria picta and Heterodermia pseudospeciosa) are all hardy lichens with subdued thallus colours; either mineral grey or light yellow green. The specimens of Xanthoria parietina on bark were also grey-green, rather than the brilliant yellow of the maritime saxicolous specimens, (X. parietina var. parietina f. chlorina of Murray 1960, but see also Hill and Woolhouse 1966) reflecting the low light intensity and poor environment for lichens under this petrel scrub. The lack of damper forest habitats found on larger islands results in the absence of common epiphytic species such as Pseudocyphellaria spp., Sticta spp., Menegazzia circumsorediata, Megalospora spp., Catillaria spp., and Collema spp. Most of the larger Pannariaceae and Parmeliaceae are also missing (c.f. Hayward etal 1976). Soil Under manuka heath the ground-dwelling Cladoniaceae are usually very diverse but on Whale Island the manuka heath is not suitable for lichens. Apart from a few scattered bushes the stands are dense impenetrable hedges 3-3.5m high, with poor light penetration. Under this cover lichens were not found. Those in this habitat, three species of Cladonia and Cladia aggregata, were on the fringe of the heath where the broken canopy allowed a higher light intensity. Older manuka heath on the nearby mainland exhibited the usual range of Cladonia and Cladia. Despite the presence of a clay bank on Whale Island, Baeomyces found. was not 34

5 Although the lichens recorded here have all been collected from northern offshore islands before, the highly reduced flora is an indication of the narrow habitat range and exposure of these small islands. The lichens found indicate that the Moturoa Islands present the harshest habitats yet studied on A.U.F.C. scientific trips. ACKNOWLEDGEMENTS Thanks are due to Dr Mason E. Hale, Smithsonian Institution, for checking identifications and for valuable advice and discussion, and to Dr Bruce W. Hayward for critically reading the manuscript. REFERENCES Hayward, B.W. & Hayward, G.C. 1974a: Botany of Shoe Island and the Slipper Island Group - Coromandel Peninsula. Part III. Lichens. Tane 20: Hayward, B.W. & Hayward, G.C. 1974b: Lichen Flora of the Kawerua Area. Tane 20: Hayward, G.C; Hayward, B.W. & Galloway, D.J. 1976: Lichens of Great Mercury Island. Tane 22: Hill, D.J. & Woolhouse, H.W. 1966: Aspects of the Autecology of Xanthoria parietina agg. Lichenologist 3(2): Murray, J. 1960: Studies of New Zealand Lichens. II. The Teloschistaceae. Transactions of the Royal Society of New Zealand 88(2): Wright, A.E. 1977a: Auckland University Field Club Scientific Camp to the Moturoa Island Group, May Introduction and Acknowledgements. Tane 23 (this issue). Wright, A.E. 1977b: The Flora and Vegetation of the Moturoa Island Group. Tane 23 (this issue). 35

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