The indigenous earthworms (Megascolecidae: Oligochaeta) of Lord Howe Island
Abstract
The known indigenous earthworms of Lord Howe Island are restricted to the subfamily Megascolecinae. They are assignable to six genera with ten species, Diporochaeta plutelloides sp. n., Plutellus hutchingsae sp. n., Paraplutellus insularis Jamieson, and Pericryptodrilus nanus gen. et sp. n. (Tribe Perionychini), Eastoniella gen. n. with E. howeana and E. modesta spp. n. (Tribe Dichogastrini) and Spenceriella (Austroscolex) subgen. n., with S. (A) howeana, S. (A) difficilis, S. (A) hollowayi and S. (A) saundersi spp. n., (Tribe Megascolecini). In addition to these 10 endemic species, the circummundane Amynthas diffringens Baird and the anthropochorous holarctic family Lumbricidae are recorded from the island. Diporochaeta and Spenceriella (Austroscolex) are otherwise restricted to Australia and (secondarily?) New Zealand, and Plutellus to Australia. Pericryptodrilus and Eastoniella are known only from the island but have strong Australian affinities. The earthworm fauna thus appears to be of Australian origin. Evidence for rifting of the lord Howe Rise from Eastern Australia at c.80 million years before the present is noted but it is considered unlikely that the earthworm fauna dates from that period in view of catastrophic vulcanism on the island between c.30 and 8 million years before the present. The zoogeography and evolution of the earthworms is discussed and a tentative hypothesis of origin of the predominantly Oriental genus Pheretima s.lat. from an Australian precursor of Spenceriella is advanced.
