Mont Mauru (Tahiti, Society Islands) and Toovii ridges (Nuku Hiva, Marquesas Islands), two natural areas of ecological interest in French Polynesia, proposed as PABITRA sites

Jean-Yves MEYER¹ & Jacques FLORENCE²

¹ Délégation à la Recherche, Ministère de la Santé et de la Recherche (Gouvernement de Polynésie française), B.P. 20981 Papeete, Tahiti (FRENCH POLYNESIA)

² Antenne IRD, Laboratoire de Phanérogamie, Muséum national d’Histoire naturelle, 16 rue Buffon, 75005 Paris (FRANCE)

SUMMARY

The two high volcanic islands of Tahiti and Nuku Hiva have the most original and richest native flora of the 118 islands of French Polynesia. Tahiti, located in the Society archipelago, is the largest and the highest island in French Polynesia with ca. 1100 km² and a summit reaching 2241 m elevation. It has the highest number of native (495 species) and endemic (224 including 107 island endemics) vascular plants, and several species belonging to the two South-eastern Polynesian endemic genera (Fitchia and Sclerotheca). Nuku Hiva, located in the Marquesas is the second largest (ca. 340 km²) and richest island in French Polynesia with a vascular flora of 254 native species, 126 of them endemic (including 46 island endemics), one monotypic endemic genus (Pelagodoxa), and species belonging to other French Polynesian endemic genera (Apetahia, Oparanthus) and to the Marquesan endemic genus Plakothira. Most of the endemic species and genera are confined to the nearly pristine montane wet forests (cloud forests and summit shrublands). In this paper we proposed to include Mont Mauru (Tahiti) and Toovii ridges (Nuku Hiva) as PABITRA sites for French Polynesia. Both natural areas - prospected several times by the two authors - are of high ecological interest and present a strong conservation value, but are threatened by human activities (mainly road construction on Toovii, hydro-electricity development on Mont Mauru), and invasion by alien plants. They are relatively accessible from sea-level up to the highest summit (1361 m for Mont Mauru, 1227 m for Toovii ridges). An ecological survey (flora and associated fauna) of Mont Mauru and its surroundings is in process by both authors and the site has been recently proposed as a protected natural area for Tahiti. A similar conservation project for Toovii ridges is planned.

I/ INTRODUCTION

The great uniqueness of French Polynesia, an Overseas Territory of France (“Territoire d’Outre Mer”), compared to the other Pacific island countries lies in: (1) its high number of islands with 118 tropical oceanic islands including 84 atolls and 34 high islands, grouped into 5 archipelagoes, namely the Austral or Tubuai Islands, the Gambier Islands, the Marquesas, the Society Islands, and the Tuamotu; (2) their high dispersion in the ocean (the size of Europe); (3) their strong geographic isolation (more than 4000 km from the nearest continent); (4) their young geological age (between 0,5 and 15 millions years old); and (5) their small land surface (a total of 3520 km²).

As a result, the number of native vascular plant species is relatively low compared to other archipelagoes or the main islands in the Pacific (ca. 910 species vs 3250 in New Caledonia, 2360 in New Zealand, 1630 in Fiji or 1140 in Hawaii), as well as the endemism rate (74% for the flowering plants, vs 89% for Hawaii, 82% for New Zealand, 80% for New Caledonia). However, if the density of endemics is considered (i.e. the number of endemic plants per surface unit), the French Polynesian islands have far more endemic flowering plants per surface unit than New Caledonia, New Zealand, Hawaii or Fiji (Table 1). In other words, there is more chance to find an endemic plant in French Polynesia than anywhere else in the Pacific islands.

Among these 118 islands, three of them can be considered as “biodiversity hot spots” in regard to their native terrestrial biota and more particularly to their flora (DAHL 1986, PAINE 1991) :

(1) Tahiti, located in the Society Islands, is the largest and the highest island in French Polynesia with a terrestrial surface of about 1100 km² and a summit reaching up to 2241 m elevation. Its native flora is the most interesting of French Polynesia with 495 native plants including 224 endemics (45% endemism, FLORENCE 1993), 107 of them strictly restricted to Tahiti (FLORENCE 1997), and with several species belonging of two South-eastern Polynesia endemic genera (2 of the 7 species of Fitchia, 5 of the 6 species of Sclerotheca);

(2) Nuku Hiva, located in the Marquesas, is the second largest (ca. 340 km²) and richest island in French Polynesia with 254 native species including 126 endemics (50% endemism), 46 of them strictly restricted to Nuku Hiva (FLORENCE & LORENCE 1997), and with one monotypic endemic genus (Pelagodoxa), species belonging to French Polynesian endemic genera (Apetahia, Oparanthus) and 2 of the 3 species of the Marquesan endemic genus Plakothira ;

(3) Rapa, located in the Austral, is the southernmost island in French Polynesia with a subtemperate climate and floristic affinities with New Zealand. It has 189 native species including 67 endemics (35% endemism, FLORENCE 1997), two island endemic genera (Apostates, Metatrophis) and species belonging to 4 other endemic genera (Apetahia, Fitchia, Haroldiella, Oparanthus) on a land surface of only 40 km².

Most of the endemic species and genera cited above are confined to the still intact montane forests (cloud-forests and sub-alpine forests). The other vegetation types (coastal forests, dry lowland forests, valley forests of low and middle elevation) have been seriously disturbed by human activities, introduced mammals (feral goats, sheep, cattle, horses and wild pigs) and alien invasive plants (ca. 375 alien plant species are naturalized on Tahiti and ca. 220 on Nuku Hiva, FLORENCE 1993).

II/ PROPOSED PABITRA SITES FOR FRENCH POLYNESIA

In this paper, two sites of high ecological interest and strong conservation value are proposed as PABITRA sites for French Polynesia and their physical and floristic characteristics are described:

Mont Mauru, located in the island of Tahiti (Society Islands) and the Toovii ridges, located in the island of Nuku Hiva (Marquesas). No PABITRA site is proposed for the island of Rapa (Australs) because of the current logistic difficulties to travel to this very remote island (no airport on the island which is only accessible by boat once every 4-7 weeks) and to conduct field-work.

The two natural sites cited above fulfill most of the selection criteria proposed by the PABITRA Initiative  (MUELLER-DOMBOIS et al. 1999):

- they have relatively intact montane forest with cloud or moss forest,

- they extend into a range of other ecosystems along a vertical transect with major stream system,

- they are relatively accessible to researchers (compared to other sites in French Polynesia),

- there is an institution that could serve as the lead agency in coordinating and facilitating the PABITRA initiative, namely the Délégation à la Recherche which is a Governmental agency,

- they have ongoing research or a body of existing data from past studies, and have been recently (the last 10 years) prospected by both authors,

- there is a scope for collaboration with local governmental and non governmental organizations (especially nature protection groups, “associations de protection de la nature”) and local communities (good support of the county mayor or island mayor) and with French and foreign research organization (especially IRD “Institut de Recherche pour le Développement”, formely known as ORSTOM, which is a French overseas research institution; and the National Tropical Botanical Garden, Hawaii).

However, several criteria proposed by the Pabitra Initiative are not respected yet, but all of them could be fulfilled in the future:

- the sites have no protected status. An official request to protect Mont Mauru as a wildlife reserve (“zone de nature sauvage”) has been recently submitted (30 March 1999) by the first author to the advising comitee in charge of the identification and protection of the natural and cultural sites in French Polynesia (“Commission des Sites et Monuments Naturels”) with a favorable answer. The same proposal is planned for the protection of the Toovii ridges.

- there is no official government support for the designation of these areas as PABITRA sites for long-term ecological research. An official letter should be sent by PABITRA leaders to the President of the Government of French Polynesia in order to have his agreement.

We also need to mention that there are few funding sources available in French Polynesia for ecological research (short- or long-term) and that human ressources are scarce in French Polynesia with the lack of a strong conservation agency and the complete absence of managers and workers in charge of protected areas (MEYER 1997). However, some solutions could be found, especially through the University of French Polynesia (“Université de Polynésie française”) where the first author is assigned since January 1999.

III/ DESCRIPTION OF THE TWO PROPOSED PABITRA SITES IN FRENCH POLYNESIA

III.1/ MONT MAURU

Preliminary data on the flora and vegetation types of Mont Mauru and surroundings gulches and crests have been obtained by both authors (MEYER & FLORENCE 1998) during three exploratory trips organized in 1997 and 1998 by M. Jacqui DROLLET, mayor of the Hitia’a o te Ra county, in collaboration with members of a Tahitian nature protection group called “Te Rau Atiati A Tau A Hiti Noa Tu” (Polynesian Union for Nature Conservation).

Location

Mount Mauru is located on the East coast of the island of Tahiti (also called the Windward coast) at latitude 17°37’46’’ South and longitude 149°22’53’’ West (D. LEQUEUX, Service de l’Urbanisme, pers. comm. 1998). Its summit reaches an elevation of 1,361 m (according to the Service de l’Urbanisme topographic map at the scale of 1:20,000). Mont Mauru is the highest western point of a large volcanic slope (“planèze”) oriented East-West. This slope is separated on the North by the Tahaute valley and on the South by the large valley of Vaiiha (also called Papeiha valley on the I.G.N. map at the scale of 1:100,000). This slope is deeply dissected by smaller valleys such as the Fara’ura or Mahateaho river, and the Fa’atautia valley which is locally well-known (by local hikers and foreign ecotourists) under the name of “la vallée des lavatubes”.

Climate

Mean annual rainfall in the vicinity of Mont Mauru, according to a recently published rainfall map of Tahiti (PASTUREL, 1993: Planche 43) is between 8,000 and 8,500 mm/yr. According to the Weather Bureau (Météo-France, Direction Inter-régionale de Polynésie française, pers. comm. 1998), the mean annual rainfall mesured at Hitia’a county at sea-level is 3,644 mm (between 1968 and 1995) and it reaches 6,467 mm/an (between 1989 et 1997) at the Fa’atautia valley located at 500 m elevation. Assuming that precipitations increase proportionally to elevation, we can reasonably assumed that the surroundings of Mont Mauru at above 1,000 m elevation receive more than 9,000 mm/year. This area may be considered as one of the wettest place in the island of Tahiti, with the peninsula of Tahiti-Iti.

Soil

According to a recently published soil map of Tahiti (JAMET, 1993: Planche 38), the soils of Mont Mauru and surrounding steep slopes are described as “sols ferralitiques” (i.-e. very acid high-iron oxisol), highly “désaturés“ (i.-e. nutrient poor) and very “ humifères“ (i.-e. humus-rich) because of the important deposit of the organic matter related to the elevation cooling (the mean average temperature in this area is between 16° and 18°C, PASTUREL, loc. cit.); the soil in gulches located lower down Mont Mauru at and above the elevation of 1,100 m are moderatly to highly “désaturés“ and “podzolisés“ (i.-e. with the formation of a thick humic horizon called podzol). Below 1,000 m elevation, on low or medium slopes, slighty to moderatly “désaturés et humifères“ soils are found (JAMET, loc. cit.).

Access

A track suitable for motor vehicles starts from the kilometer point PK 40 (according to the Service de l’Urbanisme map at the scale 1:5,000) and goes along Fa’atautia valley (this track is locally called the “routes des lavatubes”) up to the first electricitry pylon located at about 880 m elevation (according to the map 1:20,000 scale). A trail leads to the fourth pylon at about 1,080 m elevation. The 1997 and 1998 expedition members have opened for the first time a trail with machettes along the crest overhanging the Vaiiha valley up to the summit of Mont Mauru. During the June 1988 3-days trip, a base-camp has been set up at the foot of Mont Mauru, at about 1,170 m elevation, then dismantled.

Vegetation types

According to a recently published vegetation map of Tahiti (FLORENCE, 1993: Planche 54), Mont Mauru and its surroundings belong to the high elevation ombrophilous communities (“groupements ombrophiles de haute altitude”) characterized a rainfall of over 3,000 mm per year, a high hygrometry, and diurnal cloup cap. Two main montane wet-forests (or “cloud-forests”) subtypes may be distinguished: the Weinmannia parviflora-Alstonia costata forest and the Ilex anomala-Streblus anthropophagorum forest in wetter habitats, but with some variants depending on the topography (slopes, crests, gulches) and micro-climatic factors such as the abruptness, wind and light exposition, river bank, etc.).

Botanical relevés

Several short botanical relevés have been made by both authors to characterized the different variants of the plant communities in the studied site:

- Relevé N°1 made nearby the fourth electric pylon at about 1,080 m elevation: low and open disturbed shrubland with the native plants Lycopodium cernuum, Metrosideros collina and sedges Machaerina bidwillii et Gahnia schoenoides, colonized by adventive grasses such as Sacciolepis indica, Pycreus polystachyos, Paspalum conjugatum and the alien fern Pityrogramma calomelanos.

- Relevé N°2 made on a sheltered crest at about 1,200 m elevation: a closed-canopy cloud-forest with the native trees Metrosideros collina, Weinmannia parviflora, Ilex anomala, Ascarina polystachya, Myrsine ovalis, Streblus anthropophagorum and in the understory the endemic shrubs Astronidium sp., Cyrtandra vairiae and more rarely Psychotria tahitensis, and native ferns such Marattia salicina and Asplenium australasicum, the native liana Freycinetia impavida and the epiphytic Peperomia grantii.

- Relevé N°3 made on an exposed crest at about 1,210 m elevation: open forest with the native Metrosideros collina, Freycinetia impavida, Ilex anomala, Myrsine ovalis, Omalanthus nutans, Cyathea medullaris, Ascarina polystachya and in the understory the ferns Blechnum sylvaticum and Selliguea feeoides, the sedge Machaerina bidwillii, the epiphytic orchid Dendrobium involutum and epiphytic fern Oleandra sibaldii, and the parasitic Korthalsella aoraiensis.

- Relevé N°4 on an exposed crest at about 1,310 m elevation: low-statured forest with Metrosideros collina and Freycinetia impavida with in the understory the ferns Dicranopteris linearis and Gleichenia tahitensis, the epiphytic ferns Elaphoglossum samoense, Selliguea feeoides, Hymenophyllum polyanthos, Humata banksii, Oleandra sibaldii, the epiphytic orchid Dendrobium involutum, and the epiphytic lily Astelia nadeaudii.

- Relevé N°5 on the summit of Mont Mauru summit at about 1,360 m elevation: shrubland with Metrosideros collina (2 different varieties), Myrsine ovalis, Ilex anomala, Vaccinium cernuum and lower below some rare Weinmannia parviflora, Cyrtandra vairiae, Meryta mauruensis (male and female trees) and Reynoldsia verrucosa.

- Relevé N°6 in a small gulch at about 1,140 m elevation: river-bank forest with Cyathea affinis, Freycinetia impavida, Sclerotheca oreades, Coprosma cf. orohenensis and in the understory Macropiper latifolium, Cyrtandra apiculata and Elatostemma sessile and the ferns Asplenium australasicum, Blechnum vulcanicum, Blechnum patersonii, Blechnum sylvaticum, and some rare Ophiorrhiza sp.

- Relevé N°7 in a very wet gulch at about 1,050 m elevation: closed-canopy forest with Ilex anomala, Freycinetia arborea, Astronidium spp. and rare Psychotria sp. nov. and Pittosporum tahitense.

Relevant endemic taxa

Several important and healthy populations of Cyrtandra vairiae Drake (Gesneriaceae), Fitchia tahitensis Nadeaud locally named “toromeho” (Compositae) and the lobeliad Sclerotheca oreades F. Wimmer (Campanulaceae) have been observed during the field prospections in the gulches and crests surrounding Mont Mauru. These three endemic shrubs are considered to be vulnerable in French Polynesia according to the IUCN categories (FLORENCE, 1996). It is interesting to note that the “toromeho” was already known from the Hitiaa district, between 800 m and 1000 m elevation, during the last century (NADEAUD, 1873: 49).

A few populations of Psychotria tahitensis (Drake) Drake (Rubiaceae) and Cyrtandra apiculata C. Clarke (Gesnériaceae), two endemic shrubs classified as critically endangered (FLORENCE, loc. cit.) have been also noticed. Moreover, we discovered an unidentified Ophiorriza endemic species (Rubiaceae), and an endemic Psychotria species (Rubiaceae) which is new for science and has been only found by the second author on the Viriviritera’i plateau, located South-West of Mont Mauru.

Main threats: alien invasive plants and hydro-electricity development

Several Miconia calvescens DC (Mélastomataceae) trees, an alien plant legally declared “a threat for biodiversity” in French Polynesia (by a decree adopted in February 1998) were observed and destroyed lower below Mont Mauru, at about 1,100 m elevation. There are still a few reproductive trees left and hundreds of young non mature plants and seedlings which should be eradicate as soon as possible in order to avoid a catastrophic biological invasion with dramatic ecological impacts (MEYER & FLORENCE, 1996). Among the other alien invasive plants which have been declared a threat to biodiversity, we have observed the presence of the thimbleberry Rubus rosifolius J. E. Smith (Rosaceae), sometimes very abundant in the understory of wet and shady gulches located between 1,000 m and 1,200 m elevation; the molasses grass Melinis minutiflora Beauvois (Gramineae) is forming dense mats up to 900 m elevation, at the level of the third electric pylon area. The inexorable progression of the giant sensitive plant Mimosa diplotricha C. Wright ex Sauvalle (syn. M. invisa Martius ex Colla, Leguminosae) up to 800 m elevation on road sides has also been noted. It is obvious that these tracks built on the Hitia’a plateaus in the early 80’s for the hydro-electricity equipment serves as corridors for numerous alien invasive species (plants and animals).

Conclusions: a relatively intact site with high floristic richness

The Mont Mauru and its surrounding gulches and crests embrace native wet forests (or primary wet forests) still relatively intact, that is to say not or very little disturbed by human activities. By way of comparison, the Fa’atautia valley located lower below has been completely ruined by hydro-electricity equipments (water dam, power stations) with significant ecological and landscape damages. Likewise, the Vaiiha low valley is now completely invaded by the alien tree Miconia calvescens which forms dense monotypic stands and where finding a single endemic plant is a challenge (N-B : it took nearly 4 hours to find a single Cyrtandra individual in the valley during a hike with J. DROLLET in March 1997 !). This observation is strengthen by the measurement of the secondarization index (SI) which is defined by the ratio between the primary flora (native species) and the secondary flora (naturalized alien species). The SI value in the study site of Mont Mauru is 8,4 whereas in Tahiti this index falls to 2,2 because of a higher secondarization of habitats (FLORENCE, 1993).

Located at an elevation above 1,000 m and with a very high annual rainfall (> 8,000 mm/yr), Mont Mauru and its surroundings are the domain of the cloud-forests characterized by the abundance of mosses, lichens and epiphytic plants (especially filmy ferns of the family Hymenophyllaceae, and orchids) growing on branches or tree trunks. The richness and uniquess of the vegetation in this study site are reinforced by the high endemism rate of the primary flora with at least 40 endemic plants observed, that is to say 53% of endemism (Table 2). By comparison, the endemism rate for the vascular flora is 45% on the whole Tahiti island (FLORENCE, 1993). Endemism is reaching 68% on Mont Mauru if only flowering plants (Angiosperms) are considered.

The relative abundance of Fitchia tahitensis and Sclerotheca oreades which belong to two Southeastern Polynesia endemic genera and which constitute relevant taxa for the evolution of the flora in our region, and more particularly on Tahiti (2 of the 7 Fitchia species and 5 of the 6 Sclerotheca species are stricltly endemic to Tahiti, FLORENCE, 1997), as well as the species diversity of the genus Cyrtandra observed in some prospected gulches (Table 3), reinforce the scientific interest and the high conservation value of the Mont Mauru site and our proposal to include this natural area in the PABITRA project. The fact that Mont Mauru is not yet completely invaded by the aggressive Miconia calvescens is also highly significant.

III.2/ TOOVII RIDGES

Preliminary botanical data have been gathered by the second author when he was working at the Centre ORSTOM in Tahiti between 1982-1994, especially during the “Fatu Hiva Expedition” in 1988 (a collaborative scientific expedition with the Bishop Museum, the National Tropical Botanical Garden, and the Smithsonian Institution), and by the first author in June 1997 (“Henua Enana Expedition” with plant collectors Steve Perlman and Ken Wood of the National Tropical Botanical Garden) and more recently in March 1999 during a research project on Marquesan endemic sandalwoods (collaboration with the “Service du Développement Rural“, which is the French Polynesian Department of Agriculture, and “CIRAD”, a French Agronomical Research Institution). There is no recent published detailed description of this natural site (except a short paragraph on the Toovii plateau in MUELLER-DOMBOIS & FOSBERG 1998), so the following description is the first synthesis of what is currently known.

Location and description

The Toovii ridges (which includes the Pahuhituone ridges and the Tekao ridges as described on one of the oldest map of Nuku Hiva based on a manuscript sketch by G. LEBRONNEC, in ADAMSON 1936) belong to the highest and main mountain mass of the island of Nuku Hiva. These ridges were considered to be the most striking topographical feature of the island (ADAMSON op.cit.: 57). They encircle the Toovii (or Tovii) plateau on its west side, with the highest point reaching 1,227 m elevation according to the I.G.N. map at the scale of 1:50,000.

The Toovii plateau, located at about 8°53’ latitude South and 140°8’ longitude West is a central and wide volcanic basin or depression at an average altitude lying between 750 and 850 m elevation. This plateau, formely covered by a Metrosideros-Weinmannia boggy forest, has been totally converted since 1977 by the forestry section of the “Service du Développement Rural” into a monotypic plantation of the Caribbean Pine Pinus caribaea var. hondurensis (ca. 900 ha, J.-P. MALET, pers. comm. 1999) and into extensive pastures for cattle. It is now covered with a Dicranopteris linearis-Paspalum orbiculare-Metrosideros collina savanna (MUELLER-DOMBOIS & FOSBERG 1998). The inner eastern slopes of the Toovii ridges are steep and dissected by very numerous small V-shaped ravines whereas on the outer western side there are long volcanic slopes to the sea. This western volcanic slope, located in the dry leeward side of the island, has been extensively deforested and grazed by goats (first introduced to Nuku Hiva in 1804) and cattle, and now constitutes barren grounds with rapid soil erosion locally known as the “Terre Déserte“ (“fenua ataha” in Marquesan language).

Access

The Toovii ridges are accessible by a track suitable for motor vehicles built in 1979 that goes from the airport located near sea-level (ca. 50 m elevation) in the Terre Déserte to the main village of Taiohae. A new road built in 1988 crosses the Toovii ridges at a pass located at about 1,100 m elevation and goes down to the Toovii plateau than to Taiohae.

Climate and soil

According to data from the Weather Bureau (Météo-France, pers. comm. 1999), the mean annual rainfall on the Toovii plateau, at 800 m elevation (between 1975 and 1997), is 3026 mm/yr. By comparison, the precipitations measured at the airport of Terre Déserte (at about 50 m elevation) is only 1,243 mm/yr. The respective average temperature (1996-1995) are 20,5°C on Toovii plateau and 26,8°C on Terre Déserte. It can be assumed that the Toovii ridges located above 1,000 m elevation receive more than 3500 mm/year.

According to a recently published soil map of Nuku Hiva (JAMET, 1993: Planche 40), the soils of the Toovii ridges are described as “sols d’érosion andiques ferralitiques” (i.-e. very acid high-iron oxisols or andic eroded soils), very “humifères“ (i.-e. humus-rich). The highests summits have “sols ferralitiques fortement désaturés podzolisés” i.-e. very nutrient poor oxisol with a thick humic horizon.

Vegetation types and relevant endemic taxa

According to a recently published vegetation map of Nuku Hiva (FLORENCE, 1993: Planche 55), the plant communities of the Toovii ridges belong to the ombrophilous zone (“série ombrophile”). At elevations between 800 and 1,000 m elevation, two montane wet-forest subtypes may be distinguished: the Metrosideros collina-Weinmannia parviflora var. marquesana forest on drier slopes and ridges, and the Hernandia nukuhivensis-Cyathea affinis forest with Fagraea berteroana var. marquesensis in more humid valleys and gulches.

The highest slopes and summit at and above 1,000 m have cloud forests with Cheirodendron bastardianum-Ilex anomala-Metrosideros collina-Freycinetia impavida and summit wet shrubland communities dominated by Metrosideros collina-Vaccinium cereum var. adenandrum-Styphelia tameiameiae var. marquesensis (FLORENCE 1993, FLORENCE & LORENCE 1997).

Relevant Angiosperms taxa found in the Toovii ridges belongs to the most diverse lineages in the Marquesas: Psychotria (Rubiaceae, 12 spp. endemic to the Marquesas Islands), Bidens (Compositae, 9 spp.), Cyrtandra (Gesneriaceae, 8 spp.), Peperomia (Piperaceae, 7 spp.), Myrsine (Myrsinaceae, 6 spp.) and Melicope (Rutaceae, 6 spp.). Some very unusual genera for French Polynesia can also be found on that site, such as Trimenia (Trimeniaceae) with Fijian floristic affinities, Cheirodendron (Araliaceae) with Hawaiian floristic affinities.

Among impressive unique taxa growing on the Toovii ridges are Oparanthus teikiteetinii, a giant arborescent Compositae which can reach 12 m in height ; Apetahia longistigmata, a lobeliad with purple flowers found on exposed summits; Plakothira frutescens (Loasaceae) found on ravines at about 900 m elevation; the very rare Cyrtandra toviiana (Gesneriaceae) with only one known station; Claoxylon oomuense (Euphorbiaceae) restricted to the Toovii ridges; and 2 of the 3 Marquesan endemic species of Coprosma (Rubiaceae) (Table 5). A new species of Melicope (sect. Cubicarpa) has been recently discovered by field collector Steve Perlman (National Tropical Botanical Garden) on the summit of Tekao peak at about 1,000-1,500 m elevation (D. LORENCE, pers. comm. 1999).

Main threats: road constructions and alien invasive plants

The alien tree Syzygium jambos, first introduced to Nuku Hiva by Europeans in the 19th century, is starting to invade the native montane habitats of Toovii. Dense thickets have been noted in June 1997 on the road that goes from Taiohae to Toovii at about 650 m elevation and on the Toovii plateau above Aakapa Bay at about 800 m elevation. During the Marquesas sandalwoods survey conducted by the first author in May 1999, several isolated trees were found in the cloud forests at and above 1,000 m elevation. The dispersal agents of the large fleshy fruits (also called “rose-apple”) of this alien tree, legally declared a threat to biodiversity (by a decree adopted in February 1998), may be wild pigs or the rare endemic Marquesan Giant Fruitdove (Ducula galeata). We have noticed that S. jambos are commonly found nearby Fagraea berteroana (Loganiaceae) fruiting trees, one of the favorite food source for Ducula galeata, and a bird has been seen eating rose-apple fruits on the Toovii plateau (J.-F. BUTAUD, pers. comm. 1999).

Another major threat for the Toovii ridges is the aggressive Miconia calvescens (Melastomataceae): 7 plants were first found in June 1997 during the “Henua Enana Expedition”; 6 more have been destroyed at the end of year 1997, and 27 between 1998-1999 (J.-P. MALET, pers. comm. 1999), including two plants reaching 1,5 m in heigh. This Miconia isolated population is located on the roadside near the pass (Terre Déserte-Toovii) at about 1,100 m elevation. It originated undoubtedly from infected soil (contaminated by Miconia seeds) coming from Tahiti and brought back to Nuku Hiva with bulldozers and other vehicles that were used to do road constructions. A new road construction project which will cross the Toovii ridge again is unfortunately planned.

Conclusions

The Toovii ridges are certainly the most easily accessible place in the Marquesas islands with nearly pristine and species-rich montane wet forests and summit shrublands. This site has been already proposed during the last 20 years (GILLETT 1970; DAHL, 1980) to be protected as a natural preserve. A detailed ecological survey and a conservation plan is now urgently needed before futher irreversible human-disturbances and spread of alien invasive plants.

AKNOWLEDGMENTS

We would like to thank Jean-François BUTAUD (CIRAD), Didier LEQUEUX (Géomètre of the section topographie of the Service de l’Urbanisme), David LORENCE (Senior Botanist at the National Tropical Botanical Garden, Hawaii), and Jean-Pierre MALET (Chief of the forestry section of the Service du Développement Rural, Nuku Hiva) for their comments. A special thank to David LORENCE for revising the English in an early version of this paper.

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TABLE 1: A comparison of some physical and floristic characteristics between selected islands or group of islands in the Pacific Ocean

	NEW CALEDONIA (Morat 1993, Bouchet et al. 1995, Jaffre et al. 1998)	NEW ZEALAND (Sohmer 1990, Daugherty et al. 1994)	FIJI (Sohmer 1990, Given 1992)	HAWAII (Wagner 1991)	GALAPAGOS (Mauchamp et al. 1998)	FRENCH POLYNESIA (Florence 1997)
Island type	Continental	Continental	Semi-continental	Oceanic	Oceanic	Oceanic
Distance from the nearest continent		2000 km		3200 km	800 km	4000 km
Total land surface (S)	19 060 km²	269 057 km²	18 274 km²	16 887 km ²	7 900 km ²	3 521 km ²
Vascular flora	3250	2362	1628	1138	541	911
Flowering plants (number of endemics)	3063 (2448)	2066 (1693)	1302 (799)	966 (859)	434 (139)	675 (500)
Rate of endemism for the flowering plants	80%	82 %	61 %	89%	32%	74%
Density of the endemic flowering plants = End/S (log End/logS)	0.128 (0.792)	0.006 (0.595)	0.043 (0.681)	0.051 (0.694)	0.017 (0.549)	0.142 (0.954)

TABLE 2: Primary and secondary flora of Mont Mauru and its surroundings (after Meyer & Florence 1998)

STATUS	NUMBER OF SPECIES
Native (Indigenous)	46
Island endemics (Tahiti)	18
Archipelago endemics (Society islands)	16
Southeastern Polynesia endemics	6
Primary flora	76
Naturalized aliens (Polynesian introductions)	3
Naturalized aliens (European introductions)	6
Secondary flora	9
TOTAL	95

TABLE 3: Status and IUCN categories of the endemic plants collected or observed on Mont Mauru and its surroundings (after Meyer & Florence 1998)

E1 =Island endemics (Tahiti); E2 = Archipelago endemics (Society Islands); E3 =Southeastern Polynesia endemics

CR = Critical Rare; EN = Endangered; VU =Vulnérable; LR = Low Risk; LRlc = Minor Risk; DD = Data Deficient; NE = Not Evaluated

DICOTYLEDONS Status IUCN category

ARALIACEAE

Meryta mauruensis E1 DD

Reynoldsia verrucosa E2 LRlc

CAMPANULACEAE

Sclerotheca oreades E1 VU

CHLORANTHACEAE

Ascarina polystachya E2 LRlc

COMPOSITAE

Fitchia tahitensis E1 VU

CUNONIACEAE

Weinmannia parviflora E2 LRlc

ERICACEAE

Vaccinium cereum var. cereum E2 LRlc

EUPHORBIACEAE

Glochidion taitense E2 LRlc

GESNERIACEAE

Cyrtandra apiculata E2 CR

C. apiculata x C. vairiae E2

Cyrtandra nadeaudii E1 LR

Cyrtandra vairiae E1 VU

Cyrtandra cf. vescoi E1 DD

MELASTOMATACEAE

Astronidium cf. glabrum E1 LRlc

MYRSINACEAE

Myrsine ovalis var. ovalis E2 LRlc

PIPERACEAE

Peperomia grantii E2 LRlc

Peperomia hombronii E1 LRlc

PITTOSPORACEAE

Pittosporum taitense E2 LRlc

RUBIACEAE

Coprosma tahitensis E1 LRlc

Coprosma orohenensis E1 LRlc

Ophiorrhiza sp. E1

Psychotria tahitensis E1 CR

Psychotria sp. nov. E1

RUTACEAE

Melicope lucida (auriculata) E1 LRlc

URTICACEAE

Elatostema sessile E2 LRlc

Pipturus polynesicus var. polynesicus E2 LR

VISCACEAE

Korthalsella aoraiensis E1 LRlc

TABLE 3 (continuing): Status and IUCN categories of the endemic plants collected or observed on Mont Mauru and its surroundings (after Meyer & Florence 1998)

E1 =Island endemics (Tahiti); E2 = Archipelago endemics (Society islands); E3 =Southeastern Polynesia endemics

CR = Critical Rare; EN = Endangered; VU =Vulnérable; LR = Low Risk; LRlc = Minor Risk; DD = Data Deficient; NE = Not Evaluated

MONOCOTYLEDONS Status IUCN category

CYPERACEAE

Gahnia schoenoides E3 LRlc

LILIACEAE

Astelia nadeaudii E2 LRlc

ORCHIDACEAE

Bulbophyllum tahitense E2 LRlc

Dendrobium involutum E3 LR

PTERIDOPHYTES Status IUCN category

ASPLENIACEAE

Dryopteris diksonioides E2 LRlc

GLEICHENIACEAE

Gleichenia tahitensis E2 LRlc

GRAMMITIDACEAE

Calymmodon orientalis E2 LR

Ctenopteris purpurascens E3 LRlc

Grammitis subspathulata E1 LRlc

HYMENOPHYLLACEAE

Trichomanes societense E3 LRlc

Trichomanes taeniatum E3 LRlc

LOMARIOPSIDACEAE (ASPLENIACEAE)

Elaphoglossum sp. (nadeaudii) E1 LRlc

Elaphoglossum samoense E3 LRlc

LYCOPODIACEAE

Lycopodium haeckelii E1 LRlc

TABLE 4: Status of the alien plants collected or observed on Mont Mauru and its surroundings (after Meyer & Florence 1998)

A = adventices (weeds) ; N = other naturalized alien plants

1 = Polynesian introduction; 2 =European introduction

* Legally declared a threat to the biodiversity in French Polynesia

DICOTYLEDONS Status

COMPOSITAE

Adenostemma viscosum A1

MELASTOMATACEAE

Miconia calvescens N2 *

ROSACEAE

Rubus rosifolius N2 *

MONOCOTYLEDONS Status

AGAVACEAE

Cordyline fruticosa (terminalis) N1

CYPERACEAE

Pycreus polystachyos A2

GRAMINAE

Paspalum conjugatum A2

Sacciolepis indica A2

MUSACEAE

Musa troglodytarum N1

Musa x-paradisiaca N1

PTERIDOPHYTES Status

PTERIDACEAE (ADIANTACEAE)

Pityrogramma calomelanos A2

TABLE 5: Status and IUCN category of some relevant endemic flowering plants found on the Toovii ridges

E1 =Island endemics (Nuku Hiva); E2 = Archipelago endemics (Marquesas Islands)

CR = Critical Rare; EN = Endangered; VU =Vulnérable; LR = Low Risk; LRlc = Minor Risk; DD = Data Deficient; NE = Not Evaluated

Status IUCN category

APOCYNACEAE

Alstonia marquesensis E2 LR

ARALIACEAE

Cheirodendron bastardianum E2 LRlc

Reynoldsia marchionensis E2 LRlc

CAMPANULACEAE

Apetahia longistigmata E2 VU

CHLORANTHACEAE

Ascarina marquesensis E2 VU

COMPOSITAE

Bidens polycephala E2 LR

Oparanthus teikiteetinii E1 NE

CUNONIACEAE

Weinmannia parviflora var. marquesana E2 LRlc

EUPHORBIACEAE

Claoxylon oomuense E1 LR

Glochidion tooviianum E1 LR

Phyllanthus pacificus E2 LR

GESNERIACEAE

Cyrtandra nukuhivensis E2 LRlc

Cyrtandra thibaultii E1 LR

Cyrtandra toviiana E1 CR

HERNANDIACEAE

Hernandia nukuhivensis E2 LRlc

GOODENIACEAE

Scaevola subcapitata E2 LRlc

LOASACEAE

Plakothira frutescens E1 VU

LOGANIACEAE

Geniostoma hallei var. hallei E1 DD

MYRSINACEAE

Myrsine nukuhivensis E1 LRlc

ORCHIDACEAE

Habenaria marquesensis E2 DD

PIPERACEAE

Peperomia tooviiana E1 LR

RUBIACEAE

Coprosma nephelephila E1 LRlc

Coprosma reticulata E1 LRlc

Hedyotis sp. nov. E1 LRlc

Ixora ooumuensis E1 DD

Psychotria taupotini E1 LRlc

Psychotria tooviiana E1 LRlc

RUTACEAE

Melicope inopinata E1 CR

Melicope revoluta E1 LRlc

Melicope sp. nov. E1

TRIMENIACEAE

Trimenia sp. nov. E1 LRlc

SANTALACEAE

Santalum insulare var marchionense E2 VU

URTICACEAE

Pipturus henryanus E1 VU

Pipturus toovianus E1 VU