The species‐rich, paleotropical genus Memecylon (Melastomataceae): Molecular phylogenetics and revised infrageneric classification of the African species

Abstract

The internal and external transcribed spacers of nuclear ribosomal DNA were sequenced in 167 samples of Memecylon s.str. and 22 outgroup samples of Lijndenia, Mouriri, Spathandra, Votomita, and Warneckea. Maximum‐likelihood analyses of ETS, ITS1, 5.8S and ITS2 alignments yielded tree topologies that are not significantly incongruent, with one exception involving the Tanzanian sample Luke 9741. Monophyly of Memecylon s.str. is strongly supported in the separate ETS and the combined ETS + ITS1 + 5.8S + ITS2 analyses. Also supported in all analyses except 5.8S is a sister‐group relationship between a small species‐group from western and central Africa (Memecylon subg. Mouririoidea, ovary 4‐loculed) and the remaining taxa (M. subg. Memecylon, ovary unilocular). In the combined analysis, internal branches at the base of M. subg. Memecylon are short and weakly supported, yet within this large subgenus one finds a series of monophyletic groups representing different parts of the widespread paleotropical distribution (one group in western and central Africa; two separate groups in East Africa, one of these extending to southern Africa and disjunctly to western and northern Madagascar; one species‐rich group occurring exclusively on Madagascar and the neighboring Comoro and Mascarene islands; and three distinct groups in Indo‐Malesia, one of these also including the Seychelles endemic M. elaeagni). Within the western and central African clade, M. sect. Polyanthema sensu Jacques‐Félix is paraphyletic with respect to M. sect. Afzeliana, and at the morphological level it seems to be a group defined by symplesiomorphies (ovary unilocular, fruit globose). Three East African species (M. fragrans, M. greenwayi, M. semseii) are returned to Memecylon s.str. after being erroneously transferred to Lijndenia by Borhidi. The Madagascan endemic M. mocquerysii is no longer considered a taxonomic synonym of the distantly related, Tanzanian M. cogniauxii. In addition to elevating M. sect. Mouririoidea to subgeneric rank, the following changes are proposed in the infrageneric classification of African Memecylon: (1) the circumscription of sect. Polyanthema is narrowed to comprise only the members of the “M. polyanthemos complex” sensu Jacques‐Félix; (2) Engler's sections Tenuipedunculata, Cauliflora, and Obtusifolia are re‐instated with emended descriptions (in the case of sect. Cauliflora with an expanded circumscription); (3) seven new sections, Buxifolia, Diluviana, Felixiocylon, Germainiocylon, Magnifoliata, Montana, and Sitacylon, are described; (4) the purported occurrence of M. sect. Pseudonaxiandra in East Africa is rejected. A key is provided to the two subgenera and twelve sections currently recognized in African Memecylon. Further study is needed toward a sectional classification of Indo‐Malesian Memecylon, and for revision of the seven Madagascan sections recognized by Jacques‐Félix.

Revised treatment of Mozambican Memecylon (Melastomataceae—Olisbeoideae), with descriptions of four new species in M. section Buxifolia

“…In accordance with recent morphological and molecular findings (Jacques-Félix 1978, Bremer 1982, Stone 2006, 2014, Stone and Andreasen 2010, it is now circumscribed to exclude the monospecific western and central African genus Spathandra Guill. & Perr.…”

“…Mona, sp. nov.) than they are to typical M. natalense sampled further to the south in KwaZulu-Natal (Stone 2014. In the present study, we have found that the Gaza and Kosi Bay populations share the features of calyx-lobes with scarious margin and anther connectives yellow in color, which clearly sets them apart from M. natalense in which the calyx-lobes remain subcoriaceous throughout and green (sometimes suffused with dark purple) and the anther connectives are white.…”

“…Buxifolia is a monophyletic group with an overall range from East Africa (Kenya and Tanzania) southwards to the eastern part of South Africa and disjunctly in western and northern Madagascar (Stone 2014). It is diagnosed by the combination of branchlets with successive nodes alternating between normal leaves and reduced, often inflorescence-bearing bracts, white petals with corolla rounded to apiculate in bud, and anther connectives bearing a dorsal oil-gland.…”

“…Buxifolia has included ten species (Stone 2014). In South Africa there are two species, M. bachmannii Engler (1921: 768) and M. natalense, according to recent treatments (Coates Palgrave 2002, Germishuizen et al 2006, Boon 2010.…”

Lijndenia udzungwarum (Melastomataceae–Olisbeoideae): a new, endemic species from the Udzungwa Mountains of southern Tanzania

“…In Borhidi's (1993) treatment there were seven Lijndenia species reported for East Africa, but his six new combinations in this genus were made without analysis of taxonomic characters, and five of these species have since been returned to Warneckea Gilg (1904: 100) or to Memecylon Linnaeus (1753: 349) sensu stricto (cf. Stone & Andreasen 2010, Stone 2014.…”