Of certain categories of red seaweeds R. M. Laing wrote in 1939: ‘Our ignorance of distribution is such that in most cases we are quite unable to give the exact range of any particular species.’ Though this is still all too true an attempt was made in 1947 to delimit marine algal provinces and a map showing suggested boundaries was published (Moore, 1949). Only a brief text accompanied the map and little of the evidence on which it was based was presented for possible alternative interpretation. Since 1947 there has been much activity in all fields related to New Zealand marine biology, including spectacular advances in physical oceanography which should ultimately contribute towards the understanding of patterns of distribution. Nevertheless there remain many miles of coastline, for example from Cape Runaway to Cape Palliser, where page 19

Fig. 1 : Records of some predominantly northern seaweeds, with mangrove for comparison. White maps, green algae; black maps, brown algae; stippled maps, red algae. Solid symbols, growing plants; outline symbols, drift plants. Upward arrow indicates Kermadec Islands, horizontal arrow Chatham Islands and downward arrow Auckland and/or Campbell Islands.

only the most sketchy sort of sampling has been made. The maps show how rewarding closer investigation of certain critical areas could be.

To supplement and confirm published records the following collections have been examined: Auckland Institute and Museum herbarium, including that of L. M. Cranwell; Dominion Museum, including Travers specimens from Chatham Islands and many contributed by W. R. B. Oliver; the Exsiccata of 350 numbers distributed by V. W. Lindauer and portions of his extensive herbarium; portions of the R. M. Laing herbarium; the ‘Cape Expedition’ collection from Auckland and Campbell Islands in the care of the Botany Division, D.S.I.R.; the herbarium of Botany Division including, amongst others, extensive collections presented by W. A. Scarfe from Dunedin and Wellington; by R. Gilpin from Chatham Island; by page 20 J. H. Sorenson from Kermadec Island; by M. Hodgkins from Tauranga; by H. H. Allan from the 1946 New Golden Hind expedition to Fiordland. My own notes and specimens cover sections of most parts of the coast except Westland and the more distant island groups. Many useful records were contributed by N. M. Adams who also gave much-appreciated help with the tedious business of cataloguing.

From these varied sources some 200 species of apparently restricted distribution were listed, with deliberate bias towards plants of the more exposed habitats with which I personally am more familiar. Some promising examples had to be ignored because of uncertainty about taxonomic status. Not only are many small plants still very inadequately known but many large red weeds cannot be surely placed as to family, let alone to genus or species. The extremely carefully prepared and quite widely distributed sets of V. W. Lindauer's specimens provide an indispensable standard of reference even though, as he predicted, examination of these specimens by overseas specialists is showing that certain of his determinations require revision. It is still likely that, in spite of the comprehensive lists published for the Dunedin District by Naylor (1954a) and for Hauraki Gulf by Dellow (1955), no part of the coast, however small, is covered by a complete species catalogue.

Distribution records of some thirty species are indicated on maps (Figs. 1 and 2) prepared by Nancy M. Adams, those of mangrove being included for comparison. These algae are all plants of open or rocky coasts, all are large enough to be easily seen and recognised, and most are abundant and ecologically important where they occur. It is mainly, though not exclusively, on the basis of such plants that the provincial boundaries shown in Figure 3 were drawn, but it is likely that minor constituents of the vegetation will also be affected by factors that cause a number of the more conspicuous species to appear or drop out over a short distance. Plants of estuarine waters are hardly considered but if the boundaries are valid that group should show parallel contrasts. The records of a

Fig. 2 : Suggested marine algal provinces. Reprinted from Trans. Roy. Soc. N.Z. 77(5), 1949, p. 188.

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Fig. 2 : Records of some predominantly southern seaweeds. For explanation see Fig. 1.

number of rather obscure local endemic species fit the same scheme, but these records are obviously concentrated round the centres of most active collecting and cannot be given too much weight. Several of them suggest a purely west coast element in the flora (e.g. Euptilota mooreana) and this may well be confirmed when the rich red growths of such places as Mitimiti, north of Hokianga, and Paturau River mouth. N.W. Nelson, are fully analysed.

The bull kelps of the genus Durvillea are not shown on a map but are worth mentioning. These very large plants are not easily overlooked but just because of their size they have often escaped critical examination. As late as 1954 D. caepestipes was recognised on Chatham Islands where it is abundant, though not otherwise known in the New Zealand region (Naylor, 1954b). D. willana was described page 22 only recently (Lindauer, 1949) though its solid fronds and secondary stipes easily distinguish it from its constant companion. D. antarctica, which has spongy fronds and simple stipe. It is still an open question whether D. willana grows on any of the subantarctic islands, where it would be expected since it is widespread round the South Island and occurs in Stewart Island; it is not known from Cook Strait but flourishes on the east coast at least for some miles north of Castlepoint. D. antarctica is a ‘wide’, growing on the roughest coasts from Campbell Island to the Three Kings and perhaps on the Kermadecs: on the east coast north of Hawkes Bay the few places suitable for this vigorous species are rather inaccessible but it definitely grows at Mahia Peninsula, off Anaura Bay, at Cape Runaway, on the northern tip of Great Barrier Island and on the Poor Knights. Considering only the species chosen for listing, at least ten from Kermadec Province, including several belonging to semi-tropical genera, do not reach New Zealand proper; forty or more come only from what is shown as Auckland Province; some twenty northern ones drop out about or north of Cook Strait while nearly thirty southern species do not extend beyond the line marked as the northern boundary of the Central Province. At least a dozen species are not known north of the Forsterian Province and there one otherwise very common weed (Carpophyllum maschalocarpum) is apparently lacking. The Rossian Province has a longish list of endemic species (several of the larger plants needing critical re-examination) and at least seven very common mainland plants have not been recorded — Carpophyllum maschalocarpum, Ecklonia radiata, Euzoniella incisa, Glossophora kunthii. Hormosira banksii, Splachnidium rugosum and Zonaria angustata. Chatham Province has a mixture of northern and southern plants, and has at least two large and well-authenticated brown weeds not known in New Zealand itself; no records have been published for many genera that one would expect to be plentiful, though some of them are represented in herbaria, and a check-list is urgently needed. There is certainly much in the Chathams that is common also in the Cook Strait area as with molluscs (Dell. 1960) and echinoderms (Fell, 1960).

Of some twenty genera reputedly endemic to New Zealand none are recorded from the Kermadec Province. About one-third are widely distributed round the coast, some extending to the Chatham and/or the Rossian Province. Four are definitely southern — the brown Marginariella with two large and well-known species, and three reds, each with one delicate sublittoral species quite fully represented in collections (Laingia, Marionella, Dasyptilon). The monotypic red Rhizopogonia is scarcely known beyond the shores of Cook Strait where it is locally abundant. The other endemic genera are represented by small, obscure or rare plants, including Perisporochnus from Three Kings.

Concerning extra-New Zealand relationships it will only be noted that among the species that do not extend north of the latitude of East Cape (37° 40' S.) the following are often quoted as illustrating south circum-polar distribution: Adenocystis utricularis, Ballia scoparia, Chaetomorpha darwinii, Chaetangium fastigiatum, Desmarestia firma, Halopteris funicularis, Macrocystis pyrifera, Phycodrys quercifolia, Schizoseris davisii, Scytothamnus fasciculatus. Other circum-polar species such as Ballia callitricha and Durvillea antarctica are not so restricted in New Zealand.

It is not proposed to discuss possible reasons for the distributions outlined. The object is rather to present these records in the hope that they will be checked and amplified by future collectors for comparison with occurrences of animals of various groups that live amongst these algae. Correlation with some physical factors may follow later.

References

Dell, R. K., 1960. Chatham Island Marine Mollusca based upon the Collections of the Chatham Island Expedition, 1954. N.Z. D.S.I.R. Bull, 139, 141-67.

Dellow, U. V., 1955. Marine Algal Ecology of the Hauraki Gulf, New Zealand. Trans. Roy. Soc. N.Z. 83, 1-91.

Fell, H. B., 1960. Archibenthal and Littoral Echinoderms of the Chatham Islands. N.Z. D.S.I.R. Bull. 139, 55-75.

Laing, R. M., 1939. New Zealand Seaweeds — Reference List No. II. Trans. Roy. Soc. N.Z. 69,134-64.

Lindauer, V. W., 1949. Notes on Marine Algae of New Zealand. I. Pac. Sci. 3, 340-52.

Moore, L. B., 1949. The Marine Algal Provinces of New Zealand. Trans. Roy. Soc. N.Z. 77 (5), 187-9.

Naylor, M., 1954a. A Check List of the Marine Algae of the Dunedin District. Trans. Roy. Soc. N.Z. 82, 645-63.

—— 1954b. Occurrence of Durvillea caepestipes on Chatham Island. Nature 173, 1099-1100.