A revision of the “spiny solanums” of Tropical Asia (Solanum, the Leptostemonum Clade, Solanaceae)

Abstract

The Leptostemonum Clade, or the “spiny solanums”, is the most species-rich monophyletic clade of the large cosmopolitan genus Solanum (Solanaceae) and represents almost half the species diversity of the genus. Species diversity in the clade is highest in the Americas, but significant clusters of endemic taxa occur in the Eastern Hemisphere. We present here a taxonomic revision of the 51 species of spiny solanums occurring in tropical Asia (excluding the island of New Guinea, and the lowlands of Nepal and Bhutan). Three species are described as new: Solanum kachinense X.Aubriot & S.Knapp, sp. nov. from northern Myanmar, S. peikuoense S.S.Ying, sp. nov. from Taiwan, and S. sulawesi X.Aubriot & S.Knapp, sp. nov. from northern Sulawesi, Indonesia. Of the spiny solanums occurring in the region, 38 are native and 13 are introduced from the Americas or Africa, either as adventive weeds or as cultivated plants. Phylogenetic resolution amongst these taxa is still a work in progress, so we have chosen to treat these taxa in a geographical context to aid with identification and further taxon discovery. For the native species we provide complete nomenclatural details for all recognised species and their synonyms, complete descriptions, distributions including maps, common names and uses, and preliminary conservation assessments. For the introduced taxa that have been treated in detail elsewhere we provide details of types, synonyms based on tropical Asian material, general distributions, and common names for the region. We provide lecto- or neotypifications for 67 names; 63 for native and 4 for introduced taxa. All taxa are discussed and compared to similar species; keys are provided for all taxa. We illustrate all native species with herbarium and field photographs and introduced species with field photographs only. All specimens examined for this treatment are included in Suppl. materials 1–3 as searchable files.

Morphological trait evolution inSolanum(Solanaceae): Evolutionary lability of key taxonomic characters

“…5B,C), supporting the view that prickles have originated from the stellate trichome type. The common origin of stellate trichomes and prickles can be observed in some Leptostemonum species (e.g., S. barbisetum Nees, S. myoxotrichum Baker and S. schumannianum Dammer, all within the EHS clade) where stellate trichomes on young stems develop lignified stalks and become prickle‐like with an apical stellate trichome (Vorontsova & Knapp, 2016; Aubriot & Knapp, 2022). Previous studies have proposed glandular trichomes to be involved in prickle development (Pandey & al., 2018) but these hypotheses remain unsupported based on our findings and other studies (Zhang & al., 2021).…”

“…Our study is inspired by the dynamic research community working on Solanum continuously generating new knowledge on morphological and genotypic diversity as well as unravelling the molecular mechanisms that control the genotype‐phenotype interactions across the genus. More than 100 new species have been described in Solanum over the past 10 years (e.g., Tepe & Bohs, 2009; Bean, 2014; Giacomin & Stehmann, 2014; Stern & al., 2014; Knapp & al., 2015, 2020; Särkinen & al., 2015a,b,c; Bean, 2016a,b; Martine & al., 2016; Särkinen & Knapp, 2016; Knapp & Särkinen, 2018; Gouvêa & Stehmann, 2019; Aubriot & Knapp, 2022), revealing new traits and trait combinations. This, coupled with the densely sampled molecular phylogeny, provides an ideal opportunity to study the origin and evolution of major vegetative and reproductive traits in this agronomically important genus, and to assess/confirm diagnostic traits for Solanum clades using a formal analysis with standardised terminology.…”

Morphological trait evolution inSolanum(Solanaceae): evolutionary lability of key taxonomic characters

“…5B-C), supporting the view that prickles have originated from stellate trichome type. The common origin of stellate trichomes and prickles can be observed in some Leptostemonum species (e.g., S. barbisetum Nees, S. myoxotrichum Baker and S. schumannianum Dammer, all within the EHS clade) where stellate trichomes on young stems develop lignified stalks and become prickle-like with an apical stellate trichome (Vorontsova & Knapp 2016; Aubriot & Knapp, 2022). Previous studies have proposed glandular trichomes to be involved in prickle development (Pandey & al., 2018) but these hypotheses remain unsupported based on our findings and other studies (Zhang & al., 2021).…”

“…Our study is inspired by the dynamic research community working on Solanum continuously generating new knowledge on morphological and genotypic diversity as well as unravelling the molecular mechanisms that control the genotype-phenotype interactions across the genus. More than 100 new species have been described in Solanum over the past 10 years (e.g., Tepe & al., 2012; Bean, 2014; Giacomin & Stehmann, 2014; Stern & al., 2014; Knapp & al., 2015; Särkinen & al., 2015a, b, c; Bean, 2016a, b; Martine & al., 2016; Särkinen & Knapp, 2016; Knapp & Särkinen, 2018; Gouvêa & Stehmann, 2019; Knapp & al., 2020; Aubriot & Knapp, 2022), revealing new traits and trait combinations. This, coupled with the densely sampled molecular phylogeny, provides an ideal opportunity to study the origin and evolution of major vegetative and reproductive traits in this agronomically important genus, and to assess/confirm diagnostic traits for Solanum clades using a formal analysis with standardised terminology.…”

A revision of Lycianthes (Solanaceae) in Australia, New Guinea, and the Pacific

“…3); they are simple (unbranched, consisting of a single row of cells; e.g., L. kaernbachii, L. moszkowskii), branched like deer-antlers (with long branches that are spread apart; e.g., L. biflora, L. cladotrichota) or tightly branched (with the branches closely spaced and congested; e.g., L. bitteriana, L. dendropilosa). These tightly dendritic trichomes were termed "tannenbaumartig" (Christmas-tree type) by Seithe (1962), to differentiate them from echinoid trichomes (see Vorontsova and Knapp 2016;Aubriot and Knapp 2022) that are derived from stellate trichomes and usually have a much shorter central axis. Lycianthes kaernbachii occasionally has a few forked (furcate, with two branches only and "Y"-shaped) trichomes mixed in with more numerous simple trichomes on the stems.…”