Delimitation of the genus Margaritopsis (Rubiaceae) in the Asian, Australasian and Pacific region, based on molecular phylogenetic inference and morphology

Abstract

In the past, the circumscription of the large genus Psychotria (Rubiaceae) was difficult, until molecular phylogenetic studies revealed its considerable paraphyly, enabling the delimitation of its major lineages and the grouping of related genera, and most notably the separation of Psychotria and its relatives (former Psychotrieae) into two tribes: Psychotrieae and Palicoureeae. The genus Margaritopsis, which is included in Palicoureeae, encompasses 27 Neotropical species, and in previous studies these have been shown to be close relatives of a group of eight Psychotria species that occur over a large region extending from South‐East Asia to tropical South Pacific through Malesia (= the AMP region, defined as including South‐East Asia, Malesia, tropical Australia, Melanesia, Micronesia, New Caledonia and Polynesia). A molecular phylogenetic study, using one nuclear DNA region (ITS) and four plastid DNA regions (ndhF, rps16, trnH‐psbA, trnT‐F), is undertaken in order to test the placement of 17 AMP Psychotria species within Palicoureeae. The phylogenetic results show that they form a monophyletic clade (= clade G), which also includes the monotypic Fijian genus Readea and Hodgkinsonia frutescens from Australia. Clade G is embedded in a well‐supported grade with five Neotropical representatives of Margaritopsis. A morphological survey based on twenty characters, with the potential to circumscribe generic entities, shows that the monophyly of clade G is supported by a character combination that is similar to species of Neotropical Margaritopsis, confirming their inclusion in this genus. Taxonomic and nomenclatural work on these species is required to formalize nomenclatural implications. Based on the same set of morphological characters, but in absence of molecular data, 28 other Psychotria species from the AMP region were detected as likely candidates for inclusion in Margaritopsis, allowing the estimation of species richness of clade G to be a minimum of 47 species. Within clade G, five well‐supported subclades and a Readea lineage are delimited and each of these is generally supported by unique morphological features. Phylogenetic topologies reveal biogeographical patterns, including a main route of dispersal from western to eastern parts of the AMP region, with subsequent dispersals between archipelagos in the region.

Molecular phylogeography of the Society Islands (Tahiti; South Pacific) reveals departures from hotspot archipelago models

“…More genera (at least thirteen) show evidence of polyphyly or paraphyly in the Society Islands than strongly supported monophyly (four; Table ). Some of polyphyletic/paraphyletic groups are best interpreted as repeated independent colonizations of the Societies from elsewhere: these include the forest herbs Peperomia (Piperaceae; Bradley, ), the understorey shrubs Cyrtandra (Gesneriaceae; Clark et al ., ), Psychotria (Rubiaceae; Barrabé et al ., , ) and Melicope (Rutaceae; Meyer et al ., ), succineid snails (Holland & Cowie, ), Tetragnatha spiders (Gillespie, ; Gillespie et al ., ; Casquet et al ., ), Epicephala moths (leafflower moths; Hembry et al ., ) and kingfishers (the Chattering Kingfisher Todiramphus tutus and the Society Kingfisher T. veneratus ; Andersen et al ., ). Peperomia , Cyrtandra , Melicope , Epicephala , Tetragnatha and Succineidae all show evidence of the repeated colonization of the same island (Table ).…”

New Caledonia: A Hot Spot for Valuable Chemodiversity Part 3: Santalales, Caryophyllales, and Asterids

“…It encompasses more than 55 species . As mentioned above, three of them were recently separated from this genus to form the Margaritopsis genus . These three species were analyzed and it was showed that these contain alkaloids.…”

“…They concluded that alkaloid‐bearing plants seem to be restricted to the genera Guettarda , Gea , Tinadendron , Psydrax , Augusta , Coelospermum , and ‘Psychotria ’. Recently, the phylogeny of New Caledonian Psychotria species have been revised and are now separated into two genera, namely Margaritopsis and Psychotria . All species which have been investigated so far belong to Margaretopsis genus.…”

“…Psychotria is the third largest genus in New Caledonia flowering plants. It encompasses more than 55 species . As mentioned above, three of them were recently separated from this genus to form the Margaritopsis genus .…”

“…Both species are used in traditional medicine. Thus, these species were evaluated for antimycobacterial, antiprotozoal, and antiparasitic activities but did not express significant activities .…”