The Tubuai tropical moist forests is a

tropical and subtropical moist broadleaf forests Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forest, is a subtropical and tropical forest habitat type defined by the World Wide Fund for Nature (WWF). Description TSMF is generally found in la ...

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

French Polynesia French Polynesia ( ; ; ) is an overseas collectivity of France and its sole #Governance, overseas country. It comprises 121 geographically dispersed islands and atolls stretching over more than in the Pacific Ocean, South Pacific Ocean. The t ...

. It covers the

Austral Islands The Austral Islands ( officially ''Archipel des Australes;'' ) are the southernmost group of islands in French Polynesia, an overseas country of France, overseas country of the France, French Republic in the Oceania, South Pacific. Geographicall ...

Geography

The Austral islands include two island groups, the Tubuai Group and the Bass Islands. The Tubuai Group (22–23º S, 147–152º W) includes the four inhabited islands of Rimatara, Rurutu, Tubuai, and

Raivavae Raivavae (Tahitian language, Tahitian: ''Ra‘ivāvae'' International Phonetic Alphabet, /ra.ʔi.va:va.e/) is one of the Austral Islands in French Polynesia. Its total land area including offshore islets is . At the 2022 census, it had a populati ...

, along with the uninhabited Îles Maria atoll. The Bass Islands (27º 35' S, 144º W) include inhabited Rapa island (or Rapa Iti) and the uninhabited Marotiri or Bass Rocks to the southeast. Tubuai is the largest of the Austral islands at 44 km². The total land area of the ecoregion is 142 km².Meyer, Jean-Yves (2004). "Threat of Invasive Alien Plants to Native Flora and Forest Vegetation of Eastern Polynesia". ''Pacific Science'', July 2004 The islands are volcanic in origin, formed as the Pacific Plate moved west-northwest over a geologic hotspot. The inhabited islands have volcanic rocks at the center of the island, with rings of coralline limestone, known as makatea, in the coastal lowlands. Makatea was created when the islands were uplifted to expose ancient coral reefs, and often forms rough and uncultivable terrain. Tubuai has two central peaks which rise above 400 meters, and are surrounded and separated by makatea at lower elevations. Rurutu Island has volcanic hills at the center of the island, with Manureva reaching 385 meters elevation. The island was geologically uplifted, creating a continuous makatea rim along the shore that reaches 50 to 60 meters high. Rimatara Island also has a makatea rim, with low and weathered central volcanic hills. Maria is a low coral atoll. Raivavae is an heavily eroded extinct volcano with a central peak (Hiro, 438 meters), with makatea outcrops along the shore, and surrounded by a lagoon and encircling barrier reef. Rapa is an ancient crescent-shaped volcanic caldera. Its highest point is Perau at 633 meters, which is also the highest peak in the ecoregion. Marotiri consists of very young, steep volcanic crags with no fringing reef.

Flora

The natural vegetation includes lowland forest and montane rain forests. There are about 185 native species of flowering plants in the Tubuai group, of which 28, or 15%, are endemic. 20% of Rimatara's plants are endemic. Rapa has 189 vascular plant species, of which 67, or 35%, are endemic. Rapa's forests also include typical Oceanian genera like ''

Metrosideros ''Metrosideros'' is a genus of approximately 60 trees, shrubs, and vines in the family Myrtaceae, mostly found in the Pacific region. Most of the tree forms are small, but some are exceptionally large, the New Zealand species in particular. The ...

, Fitchia, Bidens'', and '' Sclerotheca'', as well as genera with New Zealand affinities like '' Hebe,

Olearia ''Olearia'', most commonly known as daisy-bush, is a genus of flowering plants belonging to the family Asteraceae, the largest of the flowering plant families in the world. Olearia are found in Australia, New Guinea and New Zealand. The genus i ...

, Haloragis'', and '' Corokia''. Montane forests on Tubuai include the trees '' Metrosideros collina, Aleurites moluccanus, Celastrus vitiensis,

Myrsine ''Myrsine'' is a genus of flowering plants in the family Primulaceae. It was formerly placed in the family Myrsinaceae before this was merged into the Primulaceae. It is found nearly worldwide, primarily in tropical and subtropical areas. It co ...

'' spp., '' Ixora'' spp., ''

Psychotria ''Psychotria'' is a large genus of flowering plants in the coffee family Rubiaceae, with over 1,600 species. The genus has a pantropical distribution and members of the genus are small understorey trees in tropical forests. Some species are endan ...

'' spp., '' Cantium barbatum'', and '' Charpentiera australis'', along with the tree fern '' Sphaeropteris medullaris'' and the large fern ''

Angiopteris ''Angiopteris'' is a genus of huge evergreen ferns from the family Marattiaceae, found throughout the paleotropics from Madagascar to the South Pacific islands. Species of smaller stature with elongate synangia and creeping rhizomes are someti ...

''.

Endemic flora

Plants endemic to Rapa Iti include the

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s '' Meryta choristantha, Corokia colleneettei, Astelia rapensis, Apostates rapae, Bidens meyeri, Fitchia rapensis, Oparanthus coriaceus, Oparanthus intermedius, Oparanthus rapensis, Sclerotheca margaretae, Gymnosporia pertinax, Pterophylla rapensis, Carex rapaensis, Cyperus rapaensis, Leptecophylla rapae, Vaccinium rapae, Acalypha rapensis, Claoxylon collenettei, Sophora rapaensis Trichomanes calyculatum, Trichomanes truncatum, Angiopteris rapensis, Ceodes coronata, Ceodes rapaensis, Pandanus rapensis, Glochidion longfieldiae, Glochidion rapaense, Pittosporum luteum, Pittosporum maireaui, Pittosporum perahuense, Pittosporum purpureum, Pittosporum rapense, Pittosporum takauele, Callitriche insularis, Plantago rapensis, Plantago rupicola, Veronica rapensis, Lysimachia rapensis, Myrsine rapensis, Coprosma cookei'', ''Coprosma rapensis'' var. ''rapensis'', '' Ixora stokesii, Kadua rapensis, Psychotria rapensis, Melicope balgooyi, Exocarpos psilotiformis'', ''Santalum insulare'' var. ''margaretae'', '' Allophylus rapensis, Myoporum rapense, Metatrophis margaretae, Pilea australis'', and '' Pilea occulta''.Endemic plants of the Tubuai Islands
Checklist builder, World Checklist of Vascular Plants (WCVP). Retrieved 12 November 2023. Ferns endemic to Rapa Iti include ''Asplenium quaylei'' var. ''rapense'', '' Athyrium tenuipaleatum, Cyathea stokesii, Diplazium fosbergii, Diplazium rapense, Thelypteris diversisora, Thelypteris margaretae, Thelypteris stokesii, Ctenitis rapensis, Adiantum glabrum, Elaphoglossum meyeri, Elaphoglossum rapense'', ''Lepisorus mucronatus'' var. ''durus'', '' Polystichum rapense'', and '' Polystichum stokesii''. '' Acalypha raivavensis, Sophora raivavaeensis,

Pittosporum raivavaeense ''Pittosporum raivavaeense'' is a species of plant in the Pittosporaceae family. It is a tree endemic to the island of Raivavae, in the Tubuai Islands of French Polynesia.''Pteris tripartita'' var. ''raivavensis'', '' Ixora raivavaensis, Psychotria raivavaensis'', ''Santalum insulare'' var. ''raivavense'', '' Myoporum stokesii, Pilea sykesii'', and ''Procris pedunculata'' var. ''stokesii'' are endemic to Raivavae. '' Cyrtandra elizabethae'' is endemic to Rurutu. '' Bidens saint-johniana'' is endemic to Marotiri. '' Myoporum rimatarense'' is endemic to Rimatara. '' Macaranga raivavaeensis'' is native to Raivavae and Rimatara. ''

Serianthes rurutensis ''Serianthes rurutensis'' is a species of flowering plant in the family Fabaceae. It is a tree endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country o ...

'' is endemic to Rurutu and Raivavae. '' Glochidion raivavense'' is endemic to Raivavae, Rurutu, and Tubuai. '' Polystichum australium'' is endemic to Raivavae and Tubuai.

Fauna

The ecoregion has two endemic birds. The Rimatara reed warbler (''Acrocephalus rimatarae'') is limited to Rimatara, but is locally abundant. The Rapa fruit-dove (''Ptilonopus huttoni''), is found only in 3 km² of mid- to high-elevation forest fragments on Rapa. Kuhl's lorikeet (''Vini kuhli'') once ranged across the Cook Islands and French Polynesia, but is now found only Rimatara, and on three islands in

Kiribati Kiribati, officially the Republic of Kiribati, is an island country in the Micronesia subregion of Oceania in the central Pacific Ocean. Its permanent population is over 119,000 as of the 2020 census, and more than half live on Tarawa. The st ...

where it was introduced by humans. The introduced

Brown rat The brown rat (''Rattus norvegicus''), also known as the common rat, street rat, sewer rat, wharf rat, Hanover rat, Norway rat and Norwegian rat, is a widespread species of common rat. One of the largest Muroidea, muroids, it is a brown or grey ...

(''Rattus norvegicus'') preys on the bird's eggs and chicks.

Conservation and threats

The lowland forests on the main high islands have mostly been destroyed by conversion to agriculture, anthropogenic fires, and uncontrolled grazing by introduced goats, pigs, cattle, and horses. Outside cultivated areas, secondary vegetation includes thickets of '' Hibiscus tiliaceus'' with introduced orange trees and common guava (''Psidium guajava''), '' Dicranopteris linearis'' fernlands, and grasslands. The lowland atoll forests of the uninhabited Maria Islands are relatively intact. Montane forests have also been reduced and degraded, but some relatively inaccessible or uncultivable areas remain intact. Many exotic plants are naturalized, and some are considered invasive. On Tubuai '' Falcataria falcata, Furcraea foetida, Hedychium flavescens,

Lantana camara ''Lantana camara'' (common lantana) is a species of flowering plant in the verbena family (Verbenaceae), native to the American tropics. It is a very adaptable species, which can inhabit a wide variety of ecosystems; once it has been introduced i ...

Leucaena leucocephala ''Leucaena leucocephala'' is a small fast-growing Mimosoideae, mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala) and is now naturalized throughout the tropics including parts of Asia. Common names inclu ...

Melia azedarach ''Melia azedarach'', commonly known as the chinaberry tree, pride of India, bead-tree, Cape lilac, syringa berrytree, Persian lilac, Indian lilac, or white cedar, is a species of deciduous tree in the mahogany family (biology), family, Meliace ...

, Merremia peltata,

Psidium guajava ''Psidium guajava'', the common guava, yellow guava, lemon guava, or apple guava is an evergreen shrub or small tree native to the Caribbean, Central America and South America. It is easily pollinator, pollinated by insects; when cultivated, it ...

'', and '' Syzygium cumini'' are naturalized, and '' Melinis minutiflora, Paspalum conjugatum, Psidium cattleianum,

Rubus rosifolius ''Rubus rosifolius'', (sometimes spelled ''Rubus rosaefolius''), also known as roseleaf bramble, Mauritius raspberry, thimbleberry, Vanuatu raspberry and bramble of the Cape is a prickly subshrub native to rainforest and tall open forest of the H ...

, Stachytarpheta urticifolia, Syzygium jambos'', and '' Tecoma stans'' are considered invasive. ''Psidium cattleianum'' or Chinese guava covers many mountain ridges on Tubuai, the former habitat of ''Charpentiera australis'' and other native species. On Rapa ''Hedychium flavescens'' and ''Melia azedarach'' are considered invasive.

s (''Rattus norvegicus'') were introduced to some of the islands by humans, and have decimated some of the local birds, including Kuhl's lorikeet. Rat control is important to the lorikeet's conservation on Rimatara.

External links

References

{{reflist Austral Islands Ecoregions of French Polynesia Oceanian ecoregions Tropical and subtropical moist broadleaf forests