Solanumplastisexum, an enigmatic new bush tomato from the Australian Monsoon Tropics exhibiting breeding system fluidity.

Peter Jobson,Jason T Cantley,Heather B Wetreich,Angela J Mcdonnell,Christopher T Martine

doi:10.3897/phytokeys.124.33526

Abstract

A bush tomato that has evaded classification by solanologists for decades has been identified and is described as a new species belonging to the Australian “Solanumdioicum group” of the Ord Victoria Plain biogeographic region in the monsoon tropics of the Northern Territory. Although now recognised to be andromonoecious, S.plastisexum Martine & McDonnell, sp. nov. exhibits multiple reproductive phenotypes, with solitary perfect flowers, a few staminate flowers or with cymes composed of a basal hermaphrodite and an extended rachis of several to many staminate flowers. When in fruit, the distal rachis may abcise and drop. A member of SolanumsubgenusLeptostemonum, Solanumplastisexum is allied to the S.eburneum Symon species group. Morphometric analyses presented here reveal that S.plastisexum differs statistically from all of its closest relatives including S.eburneum, S.diversiflorum F. Meull., S.jobsonii Martine, J.Cantley & L.M.Lacey, S.succosum A.R.Bean & Albr. and S.watneyi Martine & Frawley in both reproductive and vegetative characters. We present evidence supporting the recognition of S.plastisexum as a distinctive entity, a description of the species, representative photographs, a map showing the distribution of members of the S.eburneum species group and a key to the andromonoecious Solanum species of the Northern Territory of Australia. This new species is apparently labile in its reproductive expression, lending to its epithet, and is a model for the sort of sexual fluidity that is present throughout the plant kingdom.

Highlights

As one of the most species-rich angiosperm genera (Frodin 2004), Solanum L. is fast growing, with more than 90 species described within the last decade alone (e.g. Gouvêa et al 2019; Gouvêa et al 2018; Agra 2008; Stehmann and Moreira 2016)
The spiny solanums appear to have arrived in Australia some time in the last 5–10 million years (Särkinen et al 2013) and have continued to radiate throughout the continent with a large portion of the currently known species diversity occurring in the upper third of the continent known as the Australian Monsoon Tropics (AMT) (Bean 2004)
We describe Solanum plastisexum Martine & McDonnell, sp. nov., a new species restricted to a small area in the central region of the Northern Territory of Australia that has confounded field botanists since at least the early 1970s

Summary

Introduction

As one of the most species-rich angiosperm genera (Frodin 2004), Solanum L. is fast growing, with more than 90 species described within the last decade alone (e.g. Gouvêa et al 2019; Gouvêa et al 2018; Agra 2008; Stehmann and Moreira 2016). The spiny solanums appear to have arrived in Australia some time in the last 5–10 million years (Särkinen et al 2013) and have continued to radiate throughout the continent with a large portion of the currently known species diversity occurring in the upper third of the continent known as the Australian Monsoon Tropics (AMT) (Bean 2004) While this radiation is reflected in diverse plant morphologies (e.g. foliage, armature, trichomes/indument, growth form, seasonal habit), the most interesting variety in form may be related to reproductive biology (Symon 1970; Symon 1979a; Symon 1979b; Symon, 1981; Anderson and Symon 1988; Anderson and Symon 1989; Martine and Anderson 2007). Our research team has recently been interested in the evolution of the andromonoecious taxa and, through field and populationlevel genomic study (in prep), has recognised a new species that is evolutionarily and morphologically distinctive

Methods

Results

Conclusion