Eggplant (Solanum melongena L.): Taxonomy and Relationships 2 Sandra Knapp, Xavier Aubriot and Jaime Prohens Abstract currently recognised members of the Eggplant Solanum melongena L. (brinjal eggplant) is a clade and discuss character evolution and member of a small monophyletic group biogeography in the group in the context of (Eggplant clade) of mainly andromonoecious phylogeny. species in the large and diverse Leptoste- monum clade of Solanum (previously referred to as subgenus Leptostemonum Bitter). The 2.1 Introduction Leptostemonum clade (also known as the spiny solanums) is the most diverse mono- The brinjal eggplant (Solanum melongena L.) is phyletic group in the species-rich genus one of approximately 1300 species in the extre- Solanum and contains more than 500 species mely species-rich genus Solanum L. in the occurring on all continents except Antarctica. nightshade family Solanaceae. The family com- In this chapter, we summarise the current state prises 101 genera, including many economic and of knowledge of the taxonomy and phylogeny horticultural importance such as Nicotiana L. of Solanum, the Leptostemonum clade and (the tobaccos, see Knapp et al. 2004) and Petunia that of the monophyletic group of Old World L. (Stehmann et al. 2000). Generic diversity in taxa to which S. melongena belongs. We the family is concentrated in the Americas, provide a species list with distributions of the but there have been several instances of long-distance dispersal giving rise to genera and/or groups that are endemic to the Old World (Dupin et al. 2017). Generic limits in the family are under active investigation, and new genera S. Knapp (&) have been included (e.g. Nolana L.f. and Department of Life Sciences, Natural History Sclerophylax Miers, traditionally recognised as Museum, Cromwell Road, London SW7 5BD, UK e-mail: [email protected] separate families; see Olmstead et al. 2008) and segregated based on new understanding from X. Aubriot Laboratoire Écologie, Systématique et Évolution, molecular phylogenetics (e.g. Trompettia Dupin UMR 8079, Université & S.S.Smith; Dupin and Smith 2018). With the Paris-Sud/CNRS/AgroParisTech, Orsay, France inclusion of previously segregated genera such as J. Prohens Lycopersicon Mill., Cyphomandra Sendtn. and Instituto de Conservación y Mejora de la Normania Lowe, Solanum is resolved as strongly Agrodiversidad Valenciana, Universitat Politècnica è monophyletic and as sister to the genus Jal- de Val ncia, Camino de Vera 14, 46022 Valencia, ä Spain tomata Schltdl. (S rkinen et al. 2013). © Springer Nature Switzerland AG 2019 11 M. A. Chapman (ed.), The Eggplant Genome, Compendium of Plant Genomes, https://doi.org/10.1007/978-3-319-99208-2_2 [email protected] 12 S. Knapp et al. Solanum comprises around half of the species relationships of others are less clear (e.g. species diversity of the family and is one of only a like S. clandestinum Bohs and S. mapiriense handful of flowering plant genera with more than Bohs; see Särkinen et al. 2013). Relationships 1000 species (Frodin 2004). Not only because of between the clades are relatively stable, but a its large size, Solanum is also important for polytomy at the base of Clade 2 of Särkinen et al. containing species of great economic importance (2013) means the sister group of the largest and for humans, such as potato (S. tuberosum L.), most species-rich clade of Solanum—the tomato (S. lycopersicum L.) and of course the Leptostemonum clade or the spiny solanums—is eggplant, plus a host of minor fruit and leaf crops not yet clear (Särkinen et al. 2013). cultivated locally worldwide (see Anderson 1977; Whalen et al. 1981;Särkinen et al. 2018). Species of Solanum occur on all continents 2.2 The Leptostemonum Clade except Antarctica, in a wide variety of habitats from tropical rainforests to the driest deserts and The prickly solanums are the largest mono- have a wide range of life forms, from annual phyletic group within the genus Solanum (Bohs herbs to rainforest trees. The traditional view has 2005;Särkinen et al. 2013; Stern et al. 2011). been that the large majority of species of Sola- They were traditionally referred to as subgenus num occurred in the New World, mostly in South Leptostemonum Bitter (Bitter 1919), or as “cho- America (e.g. see D’Arcy 1972) but recent work rus subgenerum” Stellatipilum Seithe (Seithe in Africa (Vorontsova and Knapp 2016), Asia 1962), highlighting the two characters whose (Aubriot et al. 2016) and Australia and New combination defined the group—the presence of Guinea (e.g. Bean 2002, 2004, 2010, 2011, 2014, stellate trichomes and long attenuate anthers. 2016; Bean and Albrecht 2008) has revealed Neither of these is unique to the Leptostemonum hitherto poorly understood diversity in the clade. Stellate trichomes are found in the Bre- Old World, especially in the spiny solanums vantherum clade (Stern et al. 2013; Giacomin (see below). and Stehmann 2014) and attenuate anthers in two The genus was divided into two main groups small groups, S. nemorense Dunal and relatives by authors in the nineteenth and early twentieth (Bohs 2005) and the S. wendlandii clade (Clark centuries (e.g. Dunal 1852; Seithe 1962), simply et al. 2016); all of these groups are part of the described as the spiny and non-spiny solanums. polytomy at the base of Clade 2 of Särkinen et al. These broad groups were defined on the presence (2013). or absence of prickles and anther shape (see The Leptostemonum clade is strongly mono- Vorontsova and Knapp 2016 for a more com- phyletic (Stern et al. 2011) and comprises at plete discussion). Within those broad groups, current estimates some 560 accepted species Solanum was divided into a number of sections distributed on all continents except Antarctica (S. (see D’Arcy 1972, who listed many sections, Knapp, unpublished). Approximately half of subsections and series), defined largely on these occur in the New World and half in the Old macro-morphological characteristics. Phyloge- World (see Aubriot et al. 2016). Using DNA netic work using DNA sequences showed that sequence data to delimit monophyletic groups most of these sectional groupings were not within the Leptostemonum clade revealed that monophyletic (Bohs 2005); the genus can be the Old World species were a single, mono- divided into 13 major clades (Bohs 2005; phyletic clade (with a few exceptions; Levin Särkinen et al. 2013; Weese and Bohs 2007). et al. 2006; Stern et al. 2011) rather than being Some of these (e.g. the Potato clade, including related to diverse groups of New World taxa as tomatoes and their relatives and a number of had previously been thought (e.g. D’Arcy 1972; smaller groups such as section Pteroidea Dunal Whalen 1984). This large Old World group was and the Regmandra clade; see Tepe et al. 2016) derived within the spiny solanums and was sister are well-supported and monophyletic, while the to a small group of taxa that exhibit an [email protected] 2 Eggplant (Solanum melongena L.): Taxonomy and Relationships 13 amphitropical disjunct distribution between and the rest of the Old World taxa (see Fig. 2.1a North and South America (the S. elaeagnifolium for a summary of the Old World spiny solanum Cav. clade, see Knapp et al. 2017). New World relationships). Monophyletic groups first recog- species of spiny solanums could be divided into nised in the analysis of African taxa by Vor- 13 smaller monophyletic groups, some of them ontsova et al. (2013) were for the most part endemic to Brazil (e.g. Gouvêa and Stehmann upheld in an expanded analysis that included 2019) while others were more widespread across Asian and Pacific taxa (Aubriot et al. 2016), but the Americas (e.g. Whalen et al. 1981). The first relationships between groups along the backbone dichotomy in the spiny solanums is between a of the tree are still poorly resolved. Australian group of taxa from Brazil and the Caribbean (the species do not comprise a single monophyletic Gardneri, Thomasiifolium and Erythrotrichum group, but sampling of these taxa in Aubriot clades) and the rest of group (Stern et al. 2011). et al. (2016) was limited; Australian species The largest of the New World clades is the Torva diversity is very high (see below), and expanded clade with ca. 70 species of mostly Andean sampling of these taxa is a priority for under- distribution (but see below). The continued standing relationships in the Old World spiny discovery of new species of spiny solanums in solanums. Previous phylogenetic work on Aus- the Americas, particularly in Brazil (e.g. Gouvêa tralian spiny solanums has focused on small and Stehmann 2016; Gouvêa et al. 2018; groups of dioecious taxa (Martine et al. 2006, Ribero-Silva and Proença 2011), means that 2009). The endemic Malagasy spiny solanums limits and composition of New World groups are are all closely related and form a monophyletic both in active revision. group, despite their markedly divergent mor- phologies (see Vorontsova and Knapp 2016). The Eggplant clade, containing S. melongena and its 2.3 The Old World spiny solanums close relatives (Knapp et al. 2013), has been recovered as a strongly supported lineage in all Data from a number of studies using molecular analyses to date (Fig. 2.1b; see also summary in phylogenetics showed that the Old World species Aubriot et al. 2016), but with some differences in of spiny solanums formed a strongly supported circumscription (see below). That early branching monophyletic group (Aubriot et al. 2016; Levin lineages in the Old World spiny solanums are all et al. 2006; Stern et al. 2011; Vorontsova et al. Australasian, and Pacific suggests that any 2013), with the exception of a small clade of long-distance dispersal from the New World was Asian species nested within the otherwise New across what is now the Pacific Ocean and not the World Torva clade (Aubriot et al.