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

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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.. 2016). The Atlantic (see Dupin et al. 2017). Fijian S. repandum Forst. and Asian S. lasio- Both Vorontsova et al. (2013) and Aubriot carpum Dunal that have long been recognised as et al. (2016) recovered a large grade that has been members of the largely New World Lasiocarpum called the “Anguivi grade”; relationships in this clade (Whalen et al. 1981) were recovered in that group are not well-defined (Fig. 2.1a). Members position in all molecular analyses. The many of this grade include the scarlet eggplant S. species of New World solanums that are thought aethiopicum L. and its progenitor S. anguivi to have been introduced to the Old World (e.g. Lam. The widespread Asian species S. violaceum S. elaeagnifolium, S. sisymbrifolium Lam., Ortega (often synonymised with S. anguivi and S. viarum Dunal; see Vorontsova and Knapp often called S. indicum L., a name suppressed 2016) are all members of New World clades. [nom. utique rej.] under the International Code Relationships amongst the Old World spiny of Nomenclature for algae, fungi and plants, solanums show an initial split between a group of Turland et al. 2018) is morphologically similar to species whose distributions are centred on Aus- S. anguivi, but is part of a monophyletic and tralia and New Guinea extending into the Pacific strongly supported group with four other Asian (the Sahul-Pacific clade of Aubriot et al. 2016) species that is sister to the Eggplant clade.

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[email protected] 2 Eggplant (Solanum melongena L.): Taxonomy and Relationships 15 b Fig. 2.1 Outline phylograms to illustrate relationships Blue branches indicate Australia/New Guinea/Pacific, discussed in the text. Unless otherwise noted with asterisk green African/Middle East/Tropical Asia and yellow (*), all nodes are well-supported; for support values see New World species distributions. b Relationships of the the original publications. a The major clades of Old eggplant (Solanum melongena) and its relatives in the World spiny solanums (modified from Aubriot et al. Eggplant clade (modified from Aubriot et al. 2018) 2016) with representative fruits to illustrate diversity.

Aubriot et al. (2016) suggest this represents an Australia has been recognised as a secondary instance of dispersal from Africa to Asia, since centre for Solanum diversity by many previous this large Asian lineage is nested within an authors (Symon 1981; Bohs 2005). Using a variety otherwise almost exclusively African group. of diversification analysis methods and a PASTIS Within the Anguivi grade, the Macaronesian tree corrected for taxon sampling, Echeverria- endemics S. lidii Sunding and S. vespertilio Londoño et al. (2018) showed that contrary to Aiton were recovered in all analyses as sister expectation, the Old World clade of spiny sola- taxa, but with unresolved broader relationships. nums exhibited the fastest diversification rate in Some Indian and south-eastern Asian species are Solanum, despite its lower numbers of species as nested in otherwise African groups (i.e. S. pub- compared to the New World clades. Based on the escens Willd. in the Giganteum clade and S. dated phylogeny published by Särkinen et al. trilobatum L. with S. usaramense Dammer as (2013), this explosive diversification in the Old sister to the Gboma eggplant, S. macrocarpon L.; World, and more specifically in Australia, occur- see Fig. 3 in Aubriot et al. 2016, but see below). red after the Miocene (ca. 10 Mya) when aridifi- Species diversity in the Old World spiny cation and spread of dry woodlands and deserts in solanums is not evenly distributed geographi- the interior of Australia began. They hypothesised cally. Vorontsova and Knapp (2016) recognised a long-distance dispersal event ca. 6 Mya, fol- 76 native African species (including Madagascar; lowed by a rapid invasion of new niches being there are also 10 introduced taxa, all from the opened up by the expansion of dry forest habitat New World), Aubriot et al. (2016) recognised 56 types. Future analysis of the relationships of native species in Asia (including New Guinea, Australian spiny solanums in the light of these with taxa described in Bean (2016) this number findings will certainly help explain patterns of will certainly increase), and McClelland (2012) expansion and diversification in the region. suggested there were ca. 30 species occurring in Australian solanums also share a number of the Pacific region. Other areas have much smaller drought resistance features that will be of interest numbers of taxa. The maximum species diversity to eggplant breeders in future. in the Old World spiny solanums occurs in Australia + New Guinea, with ca. 175 species described (see Symon 1981, 1985) many of these 2.4 The Eggplant Clade relatively recently (Barrett 2013; Bean 2002, 2004, 2010, 2011, 2016; Bean and Albrecht The eggplant and its wild relatives have been the 2008; Martine et al. 2006, 2009, 2016a, b). Most subject of considerable taxonomic confusion and of these endemic Australian species have narrow controversy (e.g. Deb 1989; Lester and Hazan distributions (e.g. S. watneyi Martine & Frawley 1990, 1991; Meyer et al. 2012; Samuels 1996, from a small area in north-western Northern 2010, 2012, 2013a, b, 2016) and for much of the Territory or S. zoeae R.L.Barrett from a very late twentieth century, only two species (S. mel- restricted locality in the Kimberley); some have ongena and S. incanum) were recognised (e.g. long been recognised as distinct, but others are Daunay and Hazra 2012), each with several completely new discoveries. forms or races (see Knapp et al. 2013). In part, The New World has been presumed to be the this has been due to their morphological simi- primary diversification “hotspot” for the genus larity, and the propensity of extremely closely because the species diversity is higher there, but related taxa to interbreed when in sympatry

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Table 2.1 Species currently recognised as members of the Eggplant clade (Aubriot et al. 2018). For distribution maps and detailed descriptions of African species, see Vorontsova and Knapp (2016) Species Distribution Breeding system Chromosome number Solanum agnewiorum Kenya Andromonoecious Not known Voronts. Solanum aureitomentosum Malawi to South Africa Andromonoecious Not known Bitter Solanum campylacanthum Widespread throughout eastern Africa; Kenya Andromonoecious n =24 Hochst. ex A.Rich. to South Africa Solanum cerasiferum Dunal Sub-Saharan Africa; Senegal to Kenya Andromonoecious Not known Solanum incanum L. North-eastern Africa to Pakistan Andromonoecious n =12 Solanum insanum L. India and China, east to the Philippines (also Andromonoecious n =12 on Madagascar) Solanum lanzae Stork & Eastern Africa Rift valley; Ethiopia to Hermaphroditic Not known Tanzania Solanum lichensteinii Willd. South Africa to Angola, Tanzania and Andromonoecious Not known Democratic Republic of the Congo Solanum linnaeanum Hepper South Africa (populations in northern Africa Andromonoecious n =12 & P.M.-L.Jaeger perhaps introduced) Solanum melongena L. Cultivated Andromonoecious n =12 Solanum rigidum Lam. Cape Verde Islands Andromonoecious Not known Solanum umtuma Voronts. Eastern South Africa Andromonoecious Not known & S.Knapp Solanum usambarense Bitter Tanzania and Kenya; centred on Usambara Hermaphroditic Not known & Dammer Mountains

(Davidar et al. 2015; Hurtado et al. 2012; Mutegi S. agnewiorum Voronts. belonged to this et al. 2015). Detailed taxonomic work on the monophyletic Eggplant clade—a surprising spiny solanums of the Old World (Ranil et al. result given its small fruit and weak andromo- 2017; Vorontsova and Knapp 2016), coupled noecy (see Vorontsova and Knapp 2016). The with phylogenetic work more generally (Aubriot inclusion of more species from Africa and et al. 2016; Vorontsova et al. 2013), has resulted Southeast Asia (Aubriot et al. 2016) revealed that in the recognition of thirteen species in the “core” two additional African species with hermaphro- Eggplant clade (Table 2.1; Fig. 2.1b). ditic flowers and small fruit were members of the Weese and Bohs (2010) used germplasm monophyletic Eggplant clade (S. lanzae J.-P. materials and taxon circumscriptions of Lester Lebrun & Stork and S. usambarense Bitter & and Hasan (1991) to test the hypothesis of step- Dammer). Both these studies used a combination wise migration from Africa to Asia for the origin of plastid and nuclear molecular markers, and of S. melongena. Their results supported this and although the circumscription of the Eggplant showed that another African species, S. lin- clade improved, relationships within it remained naeanum Hepper & P.M-L.Jaeger, was a mem- poorly resolved (see Fig. 2.1b). ber of the group. Vorontsova et al. (2013) The African taxa in Table 2.1 were recog- expanded the data set by including many African nised in previous taxonomic treatments as sec- taxa and still recovered a monophyletic Eggplant tion melongena Bitter and defined by their clade, but with little internal resolution. Their possession of an andromonoecious breeding data showed that the narrow Kenyan endemic system (e.g. Bitter 1923), but it is clear from

[email protected] 2 Eggplant (Solanum melongena L.): Taxonomy and Relationships 17 recent phylogenetic work that both andromo- S. lanzae and S. usambarense;affinities within noecious and hermaphroditic species belong to this small group are not well-resolved. The next the monophyletic Eggplant clade. Andromo- branching lineage is composed of the eggplant noecy is a derived breeding system where a (S. melongena) and its wild progenitor (S. insa- single or a few flowers in an inflorescence are num). This lineage is sister to a monophyletic hermaphroditic, and the rest of the flowers are group that includes all remaining species of the staminate and functionally male (Whalen and Eggplant clade and is composed of two sister Costich 1986). This breeding system is common clades: (1) a “Southern African” group with four in the Leptostemonum clade (see Miller and species from southern Africa (S. aureitomento- Diggle 2003, 2007) and is thought to have sum Bitter, S. lichtensteinii Willd., S. linnaeanum originated multiple times in Solanum more gen- and S. umtuma Voronts. & S.Knapp) and (2) a erally (Whalen and Costich 1986). Andromo- “Widespread” group, which includes three noecy is correlated with larger fruit size in species with very large distribution ranges Solanum (Miller and Diggle 2007) and is one of (S. campylacanthum Hochst. ex A.Rich., the characters that has been important in the S. cerasiferum Dunal and S. incanum) and the domestication of the brinjal eggplant (Daunay Cape Verde islands endemic S. rigidum Lam. and Janick 2007; Wang et al. 2008). None of the (Aubriot et al. 2018). This new phylogeny con- hermaphroditic taxa newly recognised as mem- firms taxonomic composition and phylogenetic bers of the Eggplant clade has been grown in structure of the Eggplant clade as found by cultivation, and both are relatively narrowly Aubriot et al. (2016), but with the addition of distributed in eastern Africa as is S. agnewiorum Solanum rigidum and much improved resolution (see Vorontsova and Knapp 2016). and support, especially amongst the African taxa Aubriot et al. (2018) used whole plastome sister to the eggplant and its wild progenitor. sequences to resolve relationships within the These results suggest that the lineage from Eggplant clade; they also tested species-level cir- which the brinjal eggplant arose evolved after a cumscription to further refine species boundaries single dispersal to Asia from Africa, but that the and definitions. They found that the widespread great diversity of eggplant wild relatives arose polymorphic species as currently circumscribed after that split, and in Africa itself. Biogeo- (e.g. Knapp et al. 2013; Meyer et al. 2012; Ranil graphic analysis showed that the origin of the et al. 2017; Vorontsova and Knapp 2016) were Eggplant clade lies in north-eastern Africa and monophyletic; a single accession of S. incanum the Middle East, with spread both south from Burkina Faso in the easternmost part of the (“Widespread” and “Southern African” groups) species range did not group with the rest and was and east (S. insanum + S. melongena). Aubriot the exception. This accession may be of hybrid et al. (2018) suggest that the tropical Asian lin- origin and needs further investigation. Phyloge- eage of S. insanum did not proceed from a netic reconstruction using whole plastome stepwise expansion through the Middle East, as sequences confirmed the monophyly of the Egg- previously thought (Lester and Hasan 1991) but plant clade including the three hermaphroditic instead from an early dispersal from Africa, species identified as members by Vorontsova et al. unrelated to the southwards spread of African (2013) and Aubriot et al. (2016). Sister to the species. Eggplant clade is a lineage of two African Several African eggplant wild relatives are (S. polhillii Voronts. and S. supinum Dunal) and widespread (e.g. S. campylacanthum), but others, one tropical Asian species (S. trilobatum). particularly those recently identified as members Whole plastome sequences improved resolu- of the Eggplant clade (e.g. S. agnewiorum, tion of relationships within the Eggplant clade S. lanzae, S. usambaraense), have more restric- (Aubriot et al. 2018, see summary phylogram in ted distributions and are of some conservation Fig. 2.1b). The first branching lineage comprises concern (Syfert et al. 2016). Programmes to the three hermaphroditic species: S. agnewiorum, collect and conserve germplasm of these taxa

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(Dempewolf et al. 2014) are focusing on these relationships of S. macrocarpon and its wild African species. Future collecting and preserva- progenitor S. dasyphyllum within the Anguivi tion of wild relative germplasm should also grade. sample across the range of widespread taxa like The scarlet eggplant S. aethiopicum L. is S. campylacanthum and S. incanum; their distri- widely cultivated across Africa for leaves and bution has been suggested to have been influ- fruit, with several fruit types recognised as dis- enced by the migration patterns of large tinct cultivar groups (Lester and Niakan 1986). mammalian herbivores like elephants and impala Solanum aethiopicum has been taken up in cul- (Aubriot et al. 2018). Recent and ongoing range tivation much further afield than has S. macro- contraction of large mammalian seed dispersers carpon; it is commonly cultivated in Asia and could ultimately contribute to population isola- Brazil, where it is known as “gilo” and is usually tion, genetic differentiation and ultimately eaten green (belying its English common name). speciation. The relationship between the African wild spe- cies S. anguivi and the scarlet eggplant is well established, but previous work considered S. 2.5 Other Cultivated Eggplant anguivi to be closely related to morphologically Species similar species such as S. violaceum and S. usambarense (see Vorontsova and Knapp Although we have concentrated here on the 2016). Phylogenetic analysis has shown, how- taxonomy and relationships of the brinjal egg- ever, that despite morphological similarity, these plant S. melongena, two other spiny solanum taxa are not particularly closely related (Aubriot species that are members of the Old World clade et al. 2016). Solanum usambarense is well sup- are cultivated and merit brief discussion here and ported as being a member of the Eggplant clade; are described in more detail in Chaps. 10 and 11. S. violaceum and relatives (S. deflexicarpum C.Y. The Gboma eggplant (S. macrocarpon) is locally Wu & S.C.Huang of south-western China, and cultivated in Africa (Bukenya 1992; Bukenya S. hovei Dunal and S. multiflorum Roth of and Carasco 1999) and is derived from the wild southern India) are sister to the Eggplant clade species S. dasyphyllum Schumach. & Thonn. In (Aubriot et al. 2016; but see Aubriot et al. 2018 all phylogenetic studies to date, these two taxa for an alternative position of S. violaceum). are sisters (Aubriot et al. 2016; Vorontsova et al. Solanum anguivi is a member of the poorly 2013) and members of the poorly resolved resolved Anguivi grade, along with similar Anguivi grade. Aubriot et al. (2016) recovered S. S. aldabrense C.H.Wright (endemic to the Sey- trilobatum and S. usamarense Dammer as sister chelles) and S. platacanthum Dunal of the Mid- to S. macrocarpon + S. dasyphyllum—a sur- dle East (see Aubriot et al. 2016). It is clear that prising result considering that these two taxa are several dispersals from Africa to Asia have scrambling vines with hermaphroditic breeding occurred in this group, and resolving relation- system, and the eggplants are robust, erect ships and biogeography of the Anguivi grade andromonoecious shrubs. The relationship will greatly aid in identification of wild relatives between S. trilobatum and S. usaramense (not for use in improvement of the scarlet eggplant. sampled in Aubriot et al. 2018) is strong but it seems now clear that these two species are not actually related to S. macrocarpon (very low 2.6 Conclusions and Prospects support in Aubriot et al. 2016), but rather to for Future Understanding S. supinum Dunal and S. polhillii (possibly also including S. nigriviolaceum Bitter but that spe- Recent in-depth taxonomic work using thousands cies was not sampled in Aubriot et al. 2018). of herbarium specimens has clarified species Further work with additional taxa and molecular identities and boundaries in Old World spiny markers will be necessary to recover the solanums (Vorontsova and Knapp 2016;

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X. Aubriot and S. Knapp, in prep.) and coupled Note Complete taxonomic descriptions for all with phylogenetic studies using a variety of species mentioned in this chapter can be found in molecular markers, eggplant relationships are the works cited, but also on the website Solana- now better resolved and robustly supported ceae Source (www.solanaceaesource.org). (Aubriot et al. 2018). Several areas for future taxonomic and phylogenetic study remain to be Acknowledgements We thank Mark Chapman for explored and better resolved in order to have a inviting us to write this chapter; our understanding of eggplant taxonomy and relationships has been based on more complete understanding of diversity, bio- the foundational work done by the late Richard N. Lester geography and evolutionary history in the (Birmingham) whose generosity with materials and ideas recently evolved and explosively radiating Old was inspirational and who is much missed; funding for — World spiny solanums. work on spiny solanums came from many sources the US National Science Foundation (NSF) through the Planetary Biodiversity Initiative (PBI) grant “PBI Sola- 1. Chromosome numbers are known for very num—a worldwide perspective” (DEB-0316614) to SK; few of these species; cytological investiga- the Natural History Museum’s Natural Resources and tions will greatly aid prioritisation of wild Hazards Initiative; travel for herbarium visits was financed by the SYNTHESYS Project (http://www. relatives for use in breeding programmes. synthesys.info/) financed by European Community 2. Genetic diversity across the range of wide- Research Infrastructure Actions under the FP6 and FP7 spread taxa such as S. campylacanthum “Structuring the European Research Area” Programme, remains to be investigated with population and the Special Funds of the Natural History Museum. genetics tools (as has been done for S. mel- ongena by Cericola et al. 2013; see also Literature Cited Chaps. 10–12). 3. Relationships of the highly diverse Australian Anderson GJ (1977) The variation and evolution of species are poorly understood, both within the selected species of Solanum section Basarthrum continent and to groups in Asia and Africa. (Solanaceae) II. Brittonia 29:116–128 4. While the wild progenitors of S. aethiopicum Aubriot X, Singh P, Knapp S (2016) Tropical Asian and S. macrocarpon are well documented, the species show the Old World clade of “spiny solanums” (the Leptostemonum Clade: Solanaceae) wider relationships of these cultivated taxa to is not monophyletic. Bot J Linn Soc 180:1–27 members of the Anguivi grade are a priority; Aubriot X, Knapp S, Syfert MM, Poczai P, Buerki S this will require new molecular markers (2018) Shedding new light on the origin and spread of and increased taxonomic and geographic the brinjal eggplant (Solanum melongena L.) and its wild relatives. Am J Bot 105: 1175-1187 sampling. Barrett RL (2013) Solanum zoeae (Solanaceae), a new 5. In-depth studies of morphological and molec- species of bush tomato from the North Kimberley, ular variation in landraces of the cultivated Western Australia. Nuytsia 23:5–21, http://florabase. eggplant (S. melongena) and its wild progen- dpaw.wa.gov.au/science/nuytsia/655.pdf Bean AR (2002) New prostrate species in Solanum subg. itor (S. insanum) across their geographical Leptostemonum (Dunal) Bitter from eastern Australia. ranges will certainly reveal pathways for Austrobaileya 6:247–252 domestication (e.g. Meyer et al. 2014, 2015) Bean AR (2004) The taxonomy and ecology of Solanum and new characters for crop improvement. subg. Leptostemonum (Dunal) Bitter (Solanaceae) in Queensland and far north-eastern New South Wales, Australia. Austrobaileya 6:639–816 New genomic tools will certainly improve our Bean AR (2010) Two new species of Solanum L. ability to discover new molecular markers and (Solanaceae) from central Queensland. Austrobaileya ways of looking at relationships, but as ongoing 8:165–170 Bean AR (2011) New and reinstated species of the taxonomic work has shown, improving taxon Solanum ellipticum R.Br. (Solanaceae) species sampling both in terms of species and populations group. Austrobaileya 8:412–430 is equally important. The combination of the two Bean AR (2014) Four new Queensland species of will yield much fruit in the years to come. Solanum L. allied to S. ellipticum R.Br. (Solanaceae). Austrobaileya 9:216–228

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