Melicope is a genus of about 240 species of shrubs and trees in the family Rutaceae, occurring from the Hawaiian Islands across the Pacific Ocean to tropical Asia, Australia and New Zealand. Plants in the genus Melicope have simple or trifoliate leaves arranged in opposite pairs, flowers arranged in panicles, with four sepals, four petals and four or eight stamens and fruit composed of up to four follicles.

Description

Plants in the genus Melicope have simple or trifoliate leaves arranged in opposite pairs, or sometimes whorled.The flowers are arranged in panicles and are bisexual or sometimes with functionally male- or female-only flowers. The flowers have four sepals, four petals and four or eight stamens. There are four, sometimes five, carpels fused at the base with fused styles, the stigma similar to the tip of the style. The fruit is composed of up to four follicles fused at the base, each with one or two seeds.

Taxonomy

The genus Melicope was first formally described in 1775 by Johann Reinhold Forster and his son Georg Forster in their book Characteres Generum Plantarum and the first species they described (the type species) was Melicope ternata. The generic name Melicope is derived from Greek words μελι (meli), meaning "honey," and κοπη (kope), meaning "a division," referring to the glands at the base of the ovary. The 2009 Takhtajan system placed the genus in the subfamily Rutoideae, tribe Zanthoxyleae. A 2021 subfamily classification of the Rutaceae, based both on a new and previous molecular phylogenetic studies, places Melicope (with an expanded circumscription) in the subfamily Zanthoxyloideae, stating that the evidence does not yet support classification to tribal level. Evidence from 2007 onwards showed that with its traditional circumscription, Melicope was not monophyletic. The previously separated genus Platydesma of four species is nested within the genus Melicope and is sister to all Hawaiian Melicope species. And while Melicope species are usually dioecious (individual plants only bear either male or female flowers), the flowers of the former Platydesma are hermaphroditic, suggesting a rare evolutionary reversion away from dioecy in Platydesma. Molecular phylogenetic analyses also suggest that the genera Comptonella, Dutaillyea, Picrella, and possibly Dutailliopsis, all from New Caledonia, might also be nested in Melicope, although they are accepted in the 2021 classification, as is the temperate Asian genus Tetradium, which has sometimes been merged into Melicope (possibly including the tropical Euodia).

Ecology

Melicopes are foodplants for various animals, mainly invertebrates. Caterpillars of the Ulysses butterfly (Papilio ulysses) are fond of M. elleryana. Caterpillars of Thyrocopa moths have been found on M. clusiifolia. The larvae of some belid weevils from the genus Proterhinus also feed on Melicope although they prefer unhealthy, dying or dead specimens. The plants of some species may not be safe for humans. The nectar of wharangi (M. ternata) is known to yield toxic honey that may kill whoever eats it.

Conservation

Several of the Hawaiian species are listed as "endangered" by the Government of the United States of America, due to habitat loss and competition from invasive non-native plants. A few species are already extinct.

Species list

The following is a list of species accepted by Plants of the World Online as of July 2020: