Phylogeny of Marsdenieae (Apocynaceae, Asclepiadoideae) based on chloroplast and nuclear loci, with a conspectus of the genera

Abstract

A densely sampled molecular phylogeny of the pantropical, predominantly forest‐dwelling tribe Marsdenieae (Apocynaceae) is presented, including almost a quarter of the ca. 740 species. Sampling focused on resolving the circumscription of Marsdenia, which ranges from Marsdenia sensu Bullock with less than 10 Asian species closely related to the type, M. tinctoria, to Marsdenia sensu Forster, with ca. 300 species distributed throughout the range of the tribe, encompassing the genera Cionura, Dregea, Gongronema, Gymnema, Leichhardtia, Stephanotis, and Wattakaka as synonyms. All analyses resolve two well‐supported clades: an Asia‐Pacific Clade that includes the large epiphytic Dischidia‐Hoya alliance and a number of Marsdenia species, among them the type M. tinctoria, and a Cosmopolitan Clade that includes most of the rest of Marsdenieae with several moderately to well‐supported subclades that span the entire geographic range of Marsdenieae. The position of two small genera, Rhyssolobium (southern Africa) and Sicyocarpus (Madagascar), is ambiguous. Given this topology, a monophyletic Marsdenia s.l. would subsume all species of Marsdenieae. Instead, we propose a classification that maintains Dischidia and Hoya as distinct genera. We revise generic circumscriptions, reducing Marsdenia s.str. to a small clade of Asian species. Two new genera, Gongreos gen. nov. and Gongronemopsis gen. nov., are described, with two and nine species, respectively. A total of twenty‐six new combinations, one new name, and six new synonyms are proposed. Three neotypes and eleven lectotypes are selected, and one 2nd step lectotypification is carried out. Diagnostic morphological characters for identified clades are discussed. Biogeographic analysis retrieves tropical Asia as most likely ancestral area for Marsdenieae, with widespread tropical Asia‐Africa almost equally likely. The first‐branching lineages in both major clades are tropical Asian; the Asia‐Pacific Clade comprises a sizeable radiation in the Pacific area, with two dispersals from Australia to New Caledonia. The Cosmopolitan Clade comprises several genera (Gongronemopsis, Gymnema, Stephanotis, Telosma) widespread in Africa and tropical Asia, and some also in Madagascar, and the New World genus Ruehssia.

In defense of Apocynaceae: inference on evolution of pyrrolizidine alkaloids from evolution of an enzyme in their biosynthetic pathway, homospermidine synthase

“…4,S3). Exceptions include tribes and genera whose monophyly has not been consistently supported in previous phylogenetic analyses (Odontadenieae, Nerieae, Marsdenia) (Livshultz, et al 2007;Fishbein, et al 2018;Espírito Santo, et al 2019;Liede-Schumann, et al 2022) , genera with expanded species sampling relative to previous analyses (Wrightia in the Wrightieae DHS-like 2 clade), and the position of Eucorymbia alba (Malouetieae) as sister to Amphineurion marginatum (100 BS HSS-like clade, 98 BS DHSlike clade) in the Apocyneae. These are the first published sequences from the monotypic Eucorymbia and this placement likely reflects its phylogeny.…”

Comparative wood anatomy and origin of woodiness in subfamilies Secamonoideae and Asclepiadoideae (Apocynaceae)

“…(2018), the presence of woody species in both Marsdenieae and Ceropegieae could be the result of a retention of the ancestrally woody condition, considering that most Marsdenieae and the oldest subtribes of Ceropegieae (Heterostemminae, Leptadeniinae) have at least a woody base as opposed to the few woody species nested within the predominantly herbaceous Asclepiadeae. It is, however, clear that both tribes underwent a general shift from woodiness towards herbaceousness (Meve & al., 2017; Liede‐Schumann & al., 2022). Apart from species of Marsdenieae and Ceropegieae that probably retained ancestral woodiness, we estimate the presence of 168 derived woody species in Asclepiadoideae (suppl.…”

A new threatened New Caledonian Leichhardtia (Apocynaceae, Asclepiadoideae, Marsdenieae) species discovered from a TV programme and social media

“…The recently published Marsdenieae phylogeny (Liede-Schumann et al 2022) was used to assess the phylogenetic position of the new species. Together with 17 other, previously not analyzed Leichhardtia specimens from New Caledonia, the same partial sequences as in Liede-Schumann et al (2022) (trnT-L, trnL-F and psbA-trnH intergenic spacers, trnL intron and rps16 intron for chloroplast DNA, (rDNA); the entire Internal Transcribed Spacer (ITS), including 5.8S of ribosomal DNA, and the nuclear markers At2g06530a and At2g34620b) were obtained following the procedures detailed there.…”

“…(1810: 460) (Meve et al 2017(Meve et al , 2018Gâteblé et al 2019) and the publication of the flora account in December 2020 (Liede-Schumann et al 2020) where all Marsdenia species were transferred to Leichhardtia R. Br. (1849: 81) according to the results of a detailed phylogeny of Marsdenieae (Liede-Schumann et al, 2022), we were thus hoping that the work had been done. But this was disregarding the extreme floristic diversity of the New Caledonian biome where one new tracheophyte endemic species is described each month on average (Gâteblé et al 2018).…”