Revision of Ryssopterys and transfer to Stigmaphyllon (Malpighiaceae)

Abstract

Molecular evidence shows the Old World genus Ryssopterys (Malpighiaceae) nested within the New World genus Stigmaphyllon; therefore, Ryssopterys is here transferred to Stigmaphyllon as subg. Ryssopterys. The subgenera share most vegetative and fruit characters. Subgenus Stigmaphyllon comprises 92 species characterized by hermaphrodite, bilaterally symmetrical flowers. Subgenus Ryssopterys includes 21 species that appear androdioecious but are probably functionally dioecious; the flowers are either hermaphrodite but likely functionally female, owing to inaperturate pollen, or male with a rudimentary gynoecium. All species have radially symmetrical flowers in which all parts of each floral whorl are equal; they lack calyx glands as well as the stylar folioles common in subg. Stigmaphyllon, for which the genus is named. The range of subg. Ryssopterys encompasses Indonesia (except Borneo and Sumatra), New Guinea, Queensland (Australia), New Caledonia, Vanuatu, the Solomon Islands, Micronesia, Palau, and the Philippines; S. timoriense has also been recorded from Taiwan and the Ryukyu Islands. An overview of the two subgenera is given. For subg. Ryssopterys summaries of the taxonomic history and morphology, as well as descriptions, a subgeneric key and regional keys, distribution maps, and illustrations of the novelties are provided. Twelve new combinations are proposed: Stigmaphyllon subg. Ryssopterys, S. abutilifolium, S. albidum, S. angustifolium, S. australiense, S. dealbatum, S. discolor, S. grandifolium, S. gymnopodum, S. intermedium, S. taomense, S. timoriense. Ten new species are described: S. brassii, S. mackeeanum, S. mariae, S. mcphersonii, S. merrillii, S. micranthum, S. papuanum, S. pullenii, S. solomonense, S. sundaicum.