DIVERSITY & ENDEMISM
Because most of the islands of this hotspot have never been in land contact with New Guinea, their fauna and flora are a mix of recent long-distance immigrants and indigenous lineages derived from ancient Pacific-Gondwanaland species.
Thus, the hotspot contains classic examples of relatively recent adaptive radiation typical of oceanic islands, such as the white-eyes (family Zosteropidae) and monarch flycatchers (family Monarchidae), but also carries some odd colonizers from times past such as the giant prehensile-tailed skink (Corucia zebrata), whose closest living relatives are the blue-tongued skinks (genus Tiliqua) of Australia, New Guinea, and Indonesia. The East Melanesian Islands Hotspot also has affinities with Fiji (included as part of the Polynesia-Micronesia Hotspot), such as the Platymantis frogs, ancient "monkey-faced" fruit bats of the genus Pteralopex, and Nesoclopeus rails. Interestingly, while a number of species found in New Guinea also occur in this hotspot, certain groups that are prominent on mainland New Guinea are notably absent from the region. These include birds of paradise, bowerbirds, scrub-wrens, tree kangaroos, echidnas and gliders.
The isolation of many of the islands and local adaptive radiation have led to very high levels of endemism, with numerous species endemic to the hotspot and many others endemic to subsets of the hotspot or even confined to single islands.
There are an estimated 8,000 species of vascular plants in the East Melanesian Islands, about half of which are thought to be endemic to the region. The rainforests of these islands look much like those found on New Guinea, and many of the same common forest trees dominate these forests. However, a number of tree species are conspicuously absent, including the Dipterocarpaceae, which dominate in Southeast Asia and are common in a few places in New Guinea. The largest and most remarkable of the hotspot’s trees is the Kauri pine (Agathis spp.), a conifer that grows to a huge girth and is highly prized by foresters.
The avifauna of East Melanesia is compositionally more distinct from New Guinea than are the other vertebrate groups, and includes seven endemic genera. Overall, the hotspot is home to more than 360 regularly occurring bird species, more than 40 percent of which are endemic. The region encompasses six Endemic Bird Areas (EBAs), as defined by BirdLife International, including the Solomon group, which has more than 60 endemic species.
One of the hotspot's most beautiful birds, and one of the most difficult to see, is the black-faced pitta (Pitta anerythra, VU). The fearful owl (Nesasio solomonenis, VU), a Solomon Islands endemic, is the hotspot's largest nightbird. The most majestic avian flagship is Sanford's fish-eagle (Haliaeetus sanfordi, VU), which favors coastal forests, although pairs also hunt further inland and, at least on the eastern islands, appear to have entirely inland ranges where they prey largely on northern common cuscus (Phalanger orientalis) and fruit bats.
Nearly half of the region's more than 85 mammal species are endemic. The richest diversity of mammals in East Melanesia is among the bats (Chiroptera), which account for more than three-quarters of the hotspot's mammals, including three endemic genera (one of which is represented by a single species, the flower-faced bat, Anthops ornatus, VU).
The most remarkable of the bats are the flying foxes (Pteropodidae), which play an important role in pollination and seed dispersal. Of more than a dozen threatened species of pteropodid bats in the hotspot, three are highly threatened (though poorly known). The Bougainville monkey-faced bat (Pteralopex anceps, CR) was known mainly from specimens collected in the 1920s, until six bats were observed during a 1995 survey (and apparently no sign of this bat was found during fieldwork on Choiseul in 1992 or on Buka in 1997); the montane monkey-faced bat (P. pulchra, CR) is known from only a single specimen collected on Mt. Makarakomburu on Guadalcanal; and the Guadalcanal monkey-faced bat (P. atrata, CR) was last recorded in 1991.
Besides the flying foxes, the admiralty cuscus (Spilocuscus kraemeri) is the only endemic cuscus in the hotspot, being confined to the Admiralty Islands. This beautifully patterned brown, black, and white species is a popular game animal on Manus.
For the most part, the East Melanesian Islands is one typified by skinks and geckos, and the majority of the hotspot's more than 110 species of reptiles (nearly half of which are endemic) are members of the families Gekkonidae and Scincidae. The region also has six endemic genera of reptiles; five of these are each represented by a single species, including the large prehensile-tailed skink (Corucia zebrata), a lizard that lives in trees and feeds primarily on the leaves of epiphytes. It is interesting to note that both boas and pythons co-occur in this hotspot.
Not surprisingly, given its isolation, the amphibian fauna of this hotspot is somewhat impoverished. More than 40 amphibian species are recorded from this hotspot, over 90 percent of which are endemic. There are also four endemic genera of amphibians, two of which have only one species: Palmatorappia solomonis (VU), a species from the Solomon Islands that may actually represent two species, and Ceratobatrachus guentheri, found on the Solomon Islands and Bougainville and Buka islands.
The small group of freshwater fishes that inhabits the region has been little studied to date. However, work is now beginning to document the region's freshwater biota. It is estimated that there are more than 50 species of freshwater fishes in the hotspot, although only a handful are endemic, among them Stenogobius alleni, found on New Britain Island in Papua New Guinea, and Stiphodon astilbos, found in Vanuatu. Because the fishes inhabiting this hotspot are of marine origin, all freshwater fishes are capable of tolerating a wide range of saltwater concentrations.
Little is known about the invertebrate fauna of the East Melanesian Islands. Butterflies are the best-known invertebrates in the hotspot, with a few species of Ornithoptera (birdwing) butterflies, particularly O. allotae and O. victoriae – both large, prominent and spectacular species – and the blue emperor swallowtail (Papilio ulysses) found in the Bismarcks and Solomons.