An introduction to the flora of the Milne Bay Archipelago

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RESEARCH ARTICLE InTRoduCTIon
The Milne Bay Archipelago includes a series of larger islands -Goodenough, Fergusson, and Normanby (collectively called the D'Entrecasteaux Islands); the northern chain of island groups -Trobriand and Woodlark; and the south-eastern chain -the Louisiade Archipelago -which includes Misima, Rossel, and Sudest.Within the archipelago there are thousands of smaller, often unnamed, islands.The vegetation includes mangrove and coastal rainforest, lowland tropical rainforest and lower montane rainforest.Higher altitude vegetation types are confined to the D'Entrecasteaux Islands.Mt Vinevo (Goodenough Island), the highest mountain in the archipelago, reaches a height of 2 566 m (Table 1).
Several islands have extensive areas of limestone and ultramafic floras which are poorly collected.With the extension of mining activities plant species on the ultramafics are threatened with extinction.

HISToRy of BoTAnICAL ExpLoRATIon
The first European explorer to sight the d'Entrecasteaux Islands was Rear Admiral Bruny d'Entrecasteau in 1793.Early European settlement in the islands dates back to a group of missionaries who established a Catholic Mission station on Woodlark Island from 1854 -1856.There are no records of any botanical specimens being collected during this period.Captain John Moresby visited the area in 1874.
Andrew Goldie made several trips to New Guinea, the first in 1876, followed by several trips to Port Moresby and environs.In 1878 he visited Cloudy Bay and the Louisiade Archipelago.He collected around Port Moresby in 1879 and 1880.In 1882 he landed by boat on the west coasts of Fergusson and Normanby Islands.Live plants were sent to London and dried specimens to Melbourne for study by Ferdinand von Mueller (1896).George Brown collected in New Guinea from 1875 (Frodin & Gressitt 1982).
William E. Armit commanded the Argus Expedition to British Papua (Papua New Guinea) in 1883.He was acting Government Agent for Rigo and Mekeo from July 1894 to January 1895 and sub-collector of Customs at Samarai (1895 -1897).After his expedition to Mt Maneo (Dayman) from 23 March to 3 April he sailed to Port Moresby on the 'Merrie England'.Shortly after, in 1895, he returned to Goodenough Island for exploration of the mountains.The collections of Armit from Goodenough were sent to MEL for study by Ferdinand von Mueller.
The earliest official Government expeditions were made by staff under the direction of William MacGregor, Administrator of British New Guinea from 1890 -1898.During his frequent trips around the archipelago on administrative duties in the late 1890s the government officers accompanying him made small, but important collections of plants.MacGregor sent these specimens to Von Mueller for some ten years.Following the death of Von Mueller the specimens were sent to the Royal Botanic Gardens, Kew.G.R. Le Hunte followed MacGregor as Administrator of British New Guinea in 1900.Le Hunte collected in the Milne Bay Archipelago in 1899 -1902, visiting several localities including Goodenough Island (Poiana) and the southern coast of Normanby Island.The scientific results were published in the Annual Reports of British New Guinea (1890 -1898).
In 1950 Mrs. M.J. van Steenis-Kruseman listed the D'Entrecasteaux and Trobriand Islands as a priority for plant collection because of their low collecting intensity (Van Steenis-Kruseman 1950).She did not discuss the Louisiade Archipelago.This dearth of collections was partly addressed by the 4th (1953) and 5th ( 1956) Archbold Expeditions and more recently by the collecting trips reported here.The 4th (Brass 1956) and 5th Archbold Expeditions were the first major botanical expeditions that included visits to the islands of Milne Bay organised by L.J. Brass.Len Brass, the leader and also the botanical collector for the expeditions to southeast Papua New Guinea, made extensive collections on Goodenough Island and small collections from Ferguson Island during the 4th Expedition and collected on the remaining islands of the Milne Bay Archipelago during the 5th Expedition.On these expeditions Brass was joined (briefly) by John Womersley and other staff from the National Herbarium, Lae.
with 137 recorded species.Goodenough Island was next related to Normanby and Fergusson with an average of 135 species in common.These five islands had 102 species (on average) in common, Misima Island had 86 species on average in common with the previous islands.The Trobriands and Woodlark are too poorly represented in the database to show any significant relationships, but appear more closely related (30 species in common) than to any of the other island with an average of only 19 species connecting these two islands to the rest of the islands of the archipelago.
A better understanding of the interrelationships of the island floras must await more collecting and a more detailed study of the existing collections from the archipelago.

EndEMISM In THE vASCuLAR pLAnTS
So far 239 endemics have been described from the islands of the Milne Bay Archipelago (Appendix 1).Several genera show strong patterns of island speciation particularly the tree fern genus, Cyathea (Cyatheaceae), Anthorrhiza¸ Dolicholobium, Psychotria, and Hydnophytum (Rubiaceae), Freycinetia (Pandanaceae), Rhododendron and Vaccinium (Ericaceae), and Diospyros (Ebenaceae).The most diverse of the endemic genera is Myristica (Myristicaceae) with probably 9 endemic species.Syzygium (Myrtaceae) has 6 island endemics.Pandanus (Pandanaceae) has several endemic species but the status of some of the species is in doubt and they may be minor variants of more widely dispersed species.The endemic genus Rosselia requires more study as even its position in the Burseraceae has been questioned.The family Orchidaceae is very poorly represented in the database.
As the exploration of the islands intensifies we expect that the number of locally endemic species increases and the distribution patterns are extended, particularly to adjacent islands.Many undescribed species have already been collected, particularly in taxa that have not recently been revised.This includes undescribed taxa in Saurauia (Actinidiaceae) and Calamus (Aceraceae).

RELATIonSHIpS of THE fLoRA
Generally the flora of the archipelago is most closely related to the mainland of the Milne Bay Province.Several species including Livistona woodfordii Ridl.(Arecaceae) occur on the islands of the archipelago and in the Solomons.Other species occur on the Bismarck Archipelago and on the islands.Tabernae montana remota Leeuwenb.(Apocynaceae) is recorded also from Sulawesi (Middleton 2007: 388).This species is listed because of its very unusual distribution.Macaranga misimae Airy Shaw (Euphorbiaceae) is reported from 3 widely separate localities: Goodenough Island, the Eastern Highland of PNG and Biak Island in Papua.Macaranga tentaculata Airy Shaw (Euphorbiaceae) from Goodenough Island is known from a 'second' collection from the Bismarck Archipelago (Ridsdale NGF 30425) but this differs in having fruit tentacles almost glandless.Dactyliophora novae-guineae (F.M. Bailey) Danser (Loranthaceae) is disjunct to Cape York.Dendrobium atroviolaceum Rolfe (Orchidaceae) is known from two collections from South Queensland but these are probably cultivated in origins (Cribb pers. comm. 1982).

ConCLuSIonS
More collecting is urgently needed throughout the Milne Bay Archipelago to provide the basis for adequate conservation action, particularly in lowland areas threatened by the population explosion, and in the limestone and ultramafic areas with their distinctive floras.It is proposed to organize several expeditions Another major source of botanical collections in New Guinea was the work of missionaries such as Rev. C. (Copland) King and Rev. N. Cruttwell.Several of the missionaries had special training in botany because of the potential importance of local plants for medicinal purposes.The inherent botanical knowledge of the village people of the region is potentially an important source of botanical information, but has been only partly documented.Good botanical collections are rarely made to accompany such studies of traditional plant uses.Without adequate specimens much of this information on traditional plant uses is of limited use.

RECEnT ExpLoRATIon
A comprehensive inventory of the flora and vegetation of the islands started in October 2006, and so far has included several trips from the National Herbarium in Lae and by staff from the Herbarium of the University of Papua New Guinea and the Botanical Research Institute of Texas.As a background for this inventory, a list of all available plant collections from the Milne Bay Archipelago and their (preliminary) identifications was databased by the senior author.The database now includes over 6 500 collections from the Milne Bay Archipelago, mostly vascular plants, but additions from previous collectors are still being made.Nearly half the vascular plant collections are not identified to below the genus.).These data highlight the importance of future expeditions.Many local endemics have been described most based on 1-2 collections (Appendix 1).

RELATIonSHIpS BETwEEn THE ISLAnd fLoRAS
A preliminary analysis of the distribution data of species on the islands of the Milne Bay Archipelago was made.The most closely related island floras were those of Normanby and Fergusson with 180 recorded species occurring on both islands.The next two closely related islands were Sudest and Rossel to each of the islands of the Milne Bay Archipelago.A checklist of collections has been prepared for each island.These will be published separately after more detailed expeditions have been completed and additional collections identified and databased.The papers will include an historical account of the history of their botanical exploration, ecological notes, and conservation proposals,

Table 1
Geographical and plant diversity information from the major islands of the Milne Bay Archipelago.