Tropical Asian species show that the Old World clade of ‘spiny solanums’ (SolanumsubgenusLeptostemonum pro parte: Solanaceae) is not monophyletic

Abstract

The tropical Asian taxa of the species-rich genus Solanum (Solanaceae) have been less well studied than their highly diverse New World relatives. Most of these tropical Asian species, including the cultivated brinjal eggplant/aubergine and its wild progenitor, are part of the largest monophyletic Solanum lineage, the 'spiny solanums' (subgenus Leptostemonum or the Leptostemonum clade). Here we present the first phylogenetic analysis of spiny solanums that includes broad sampling of the tropical Asian species, with 42 of the 56 currently recognized species represented. Two nuclear and three plastid regions [internal transcribed spacer (ITS), waxy, ndhF-rpL32, trnS-trnG and trnT-trnF] were amplified and used to reconstruct phylogenetic relationships using maximum likelihood and Bayesian methods. Our analyses show that Old World spiny solanums do not resolve in a single clade, but are part of three unrelated lineages, suggesting at least three independent introductions from the New World. We identify and describe several monophyletic groups in Old World solanums that have not been previously recognized. Some of these lineages are coherent in terms of morphology and geography, whereas others show considerable morphological variation and enigmatic distribution patterns. Tropical Asia occupies a key position in the biogeography of Old World spiny solanums, with tropical Asian taxa resolved as the closest relatives of diverse groups of species from Australia and Africa.

A revision of the “African Non-Spiny” Clade of Solanum L. (Solanum sections Afrosolanum Bitter, Benderianum Bitter, Lemurisolanum Bitter, Lyciosolanum Bitter, Macronesiotes Bitter, and Quadrangulare Bitter: Solanaceae)

“…The large size of Solanum and its poorly understood infrageneric structure has meant that Solanum taxonomy has proceeded in a piecemeal fashion until relatively recently and the genus has acquired a reputation of being intractable. A project funded by the United States National Science Foundation’s Planetary Biodiversity Inventory (PBI) program begun in 2004 has sought to accelerate species-level taxonomic work across the genus and has resulted in a series of monographic and phylogenetic treatments from both Old and New Worlds (e.g., Tepe and Bohs 2011; Stern et al 2013; Knapp 2013; Clark et al 2015; Wahlert et al 2015; Aubriot et al 2016; Vorontsova and Knapp 2016). An electronic monographic treatment of the entire genus is begin made available online in the web resource Solanaceae Source (http://www.solanaceaesource.org).…”

Confirming the identity of two enigmatic “spiny solanums” (Solanum subgenus Leptostemonum, Solanaceae) collected by Jean-Baptiste Leschenault in Java

“…Solanum graciliflorum can be distinguished from both of them by its much sparser indumentum, stout, deltate stem prickles (rather than slender and awl-shaped), and tiny, delicate flowers (hence the species epithet) that are clustered in dense, many-flowered inflorescences. Molecular data show that Solanum cyanocarphium and Solanum graciliflorum are not closely related; Solanum graciliflorum is nested within the Sahul-Pacific clade while Solanum cyanocarphium is an unresolved species of uncertain affinities (see Aubriot et al 2016). …”

“…Recent molecular phylogenetic analysis of tropical Asian spiny solanums incorporating representatives of sections Dunaliana and Graciliflorum (including Solanum dunalianum Gaudich. and Solanum graciliflorum ) showed Solanum graciliflorum to be sister to the Philippine endemic Solanum lianoides Elmer (Aubriot et al 2016). Both species are prickly vines, but Solanum lianoides differs from Solanum graciliflorum by its denser leaf indumentum, entire leaves and larger flowers.…”

“…In the course of preparing a monographic revision of the spiny solanums from tropical Asia (see Aubriot et al 2016 for discussion of the Old World clade of subgenus Leptostemonum Bitter), we were unable to find the type material for two spiny solanums from Java. Solanum graciliflorum Dunal and Solanum poka Dunal were first described by Michel-Félix Dunal in 1814 as part of the supplement of Lamarck’s Encyclopédie Méthodique edited by Jean Poiret.…”

A sticky and heavily armed new species of Solanum (Solanum subg. Leptostemonum, Solanaceae) from eastern Brazil

“…The ‘spiny solanums’, as the group is informally named, comprises two major groups: the Old World lineage, which is particularly diversified in Australia, eastern Africa (incl. Madagascar) and tropical Asia and the highly diverse New World grade, that includes some Torva and Lasiocarpa clade representatives native to both the New and Old Worlds (Stern et al 2011; Vorontsova et al 2013; Aubriot et al 2016). …”