Molecular phylogenetics of the Dissochaeta alliance (Melastomataceae): Redefining tribe Dissochaeteae

Abstract

The Dissochaeta alliance (= subtribe Dissochaetinae) is a group of woody climbing taxa within tribe Dissochaeteae (Melastomataceae) and comprises 90 species mainly distributed in Southeast Asia. The circumscription of the alliance and its genera has been problematic when based on only morphological characters. With a broad sampling of relevant taxa, this study aims at a natural circumscription of and revised generic delimitation within this alliance. A molecular phylogeny based on two nuclear (nrETS, nrITS) and four chloroplast (ndhF, psbK‐psbL, rbcL, rpl16) markers confirmed the non‐monophyly of Dissochaeteae s.l. Taxa traditionally placed in Dissochaeteae are found in three lineages in distant positions within Melastomataceae. The Medinilla alliance is resolved within Sonerileae + Oxysporeae, while the monophyletic Dinophora/Ochthocharis lineage forms a polytomy with Marcetieae, Melastomateae, Microlicieae, and Rhexieae; and the well‐supported Dissochaeta alliance is sister to Cambessedesieae. Based on the molecular results, Dissochaeteae is redefined to exclude the Medinilla alliance and Dinophora/Ochthocharis. It consists of six successively branching major clades, which we treat as six genera, Pseudodissochaeta, Creochiton, Dalenia (Dissochaeta sect. Dalenia), Diplectria (Dissochaeta sect. Diplectria), Macrolenes and Dissochaeta s.str. To avoid a paraphyletic Dissochaeta, Dalenia and Diplectria are resurrected, Macrolenes is expanded to include the Dissochaeta rostrata complex, and a narrowly circumscribed Dissochaeta s.str. is adopted. A re‐investigation of morphological characters based on herbarium material provides support of newly defined taxa. Two sections for Macrolenes are newly proposed, and two sections of Dissochaeta s.str. are maintained. Important morphological traits such as habit and floral characters are discussed to show the morphological support for each delimited genus and the establishment of a new classification of the tribe.

Historical biogeography of the Southeast Asian and Malesian tribe Dissochaeteae (Melastomataceae)

“…2.1 Taxon sampling, DNA sequencing, and sequence alignment A total of 58 accessions from 42 accepted and two undescribed species in the tribe Dissochaeteae were sampled, which is the same set as used for the phylogeny analysis of the group by Kartonegoro et al (2021). Forty-four species (out of c. 90) and one variety of the tribe represent Creochiton (12 spp.…”

“…The tribe Dissochaeteae (Melastomataceae) comprises 6 genera and c. 90 species of shrubs, which inhabit the tropical lowland and lower to mid-montane rainforests in Southeast Asia, stretching across E Bhutan, NE India, Myanmar, Southern China, Indochina, Thailand and throughout the Malesian Region (Kartonegoro et al, 2021). The center of diversity of the group in Southeast Asia is in west Malesia (Malay Peninsula, Sumatra, Borneo) with more than 75% of all species (Maxwell, 1984;Kartonegoro et al, 2018Kartonegoro et al, , 2019Kartonegoro et al, , 2020.…”

“…The center of diversity of the group in Southeast Asia is in west Malesia (Malay Peninsula, Sumatra, Borneo) with more than 75% of all species (Maxwell, 1984;Kartonegoro et al, 2018Kartonegoro et al, , 2019Kartonegoro et al, , 2020. Morphologically, the tribe contains shrubs with an erect habit (Pseudodissochaeta M.P.Nayar, 5 species), epiphytes or climbers (Creochiton Blume, 12 species), and woody scramblers or climbers (Dalenia Korth., 9 species; Diplectria (Blume) Rchb., 7 species; Dissochaeta Blume, 30 species; Macrolenes Naudin, 27 species) (Kartonegoro et al, 2021). Other typical characters of this group are the swollen nodes with distinct interpetiolar lines or growth, thyrsoid inflorescences, 4-merous diplostemonous flowers with iso-or dimorphic stamens, and fleshy berries as fruits (Kartonegoro et al, 2021).…”

“…Morphologically, the tribe contains shrubs with an erect habit (Pseudodissochaeta M.P.Nayar, 5 species), epiphytes or climbers (Creochiton Blume, 12 species), and woody scramblers or climbers (Dalenia Korth., 9 species; Diplectria (Blume) Rchb., 7 species; Dissochaeta Blume, 30 species; Macrolenes Naudin, 27 species) (Kartonegoro et al, 2021). Other typical characters of this group are the swollen nodes with distinct interpetiolar lines or growth, thyrsoid inflorescences, 4-merous diplostemonous flowers with iso-or dimorphic stamens, and fleshy berries as fruits (Kartonegoro et al, 2021). The fruits of the species in the Dissochaeteae are likely dispersed by birds or small mammals, like in other Melastomataceae taxa with berries (Renner, 2004b), but observations are lacking.…”

“…The fruits of the species in the Dissochaeteae are likely dispersed by birds or small mammals, like in other Melastomataceae taxa with berries (Renner, 2004b), but observations are lacking. Recent molecular phylogenetic studies revealed the monophyly of the tribe Dissochaeteae, from which some genera are excluded as they are part of the Medinilla alliance, closely related to the Sonerileae (Zeng et al, 2016;Zhou et al, 2019;Kartonegoro et al, 2021).…”