Solanum americanum Mill.

from Sarkinen et al. 2018 (https://phytokeys.pensoft.net/article/21991/login.php). Solanum americanum is a diploid species that can be easily recognised by its shiny black fruits on spreading pedicels with strongly reflexed calyx lobes (to parallel with the pedicel) that are somewhat papillate abaxially. In fruit, the pedicels remain on the plant after fruits fully mature and drop off, leaving behind a distinct group of tightly clustered spreading pedicels with reflexed calyx lobes; this character is easily visible in many herbarium specimens. In flower, S. americanum has tiny, almost globose anthers 0.8-1.5 mm long borne on short filaments. It can be distinguished from S. opacum, that also has tiny anthers of the same size, in its shorter filaments relative to anther size, and in its deltate calyx lobes with rounded tips. Solanum opacum has longer filaments relative to anther size, long-triangular calyx lobes, and in fruit, the calyx lobes are appressed to the base of the berry. Three other morelloids with such small anthers can be difficult to distinguish from S. americanum, and are often confused with it in herbaria. Solanum emulans Raf. does not occur in the Old World (except sometimes in old botanical garden collections, see discussion of the typification of S. patulum and S. dillenii below; it is a species of the northeastern United States and Canada) has matte berries and longer calyx lobes. Solanum nitidibaccatum also has extremely small anthers, but can be easily distinguished by its glandular pubescence and accrescent calyx in fruit. Solanum opacum Is the third morelloid with tiny anthers and the most difficult to distinguish from S. americanum in the Old World.  Solanum americanum and S. opacum co-occur across the Pacific, and distinguishing individual specimens can be difficult, but the shiny fruits (versus matte in S. opacum) and persistent pedicels with srongly reflexed calyx lobes are good characters by which to recognise S. americanum.

In southeast Asia and China S. americanum is at least partially sympatric with S. nigrum (see discussion of S. nigrum). The species can be distinguished by anther size (0.8-1.5 mm versus ca. 2-2.5 mm) and by inflorescence morphology; S. americanum usually has few flowers that are tightly congested in the distal part of the inflorescence, while S. nigrum usually has more flowers that are more spaced out along the inflorescence rhachis, although young inflorescences of S. nigrum can appear sub-umbellate. In fruit, the srongly reflexed calyx lobes of S. americanum are distinctive, and the seeds are smaller than those of the hexaploid S. nigrum (ca. 1 mm versus ca. 2 mm long).
Solanum merrillianum was recognised as a distinct species in the Flora of China (Zhang et al. 1994), but variation described fits within the observed variation of S. americanum after studies of the species across its global range. Specimens described as S. merrillianum show branching inflorescences in some individuals with generally larger number of flowers per inflorescence than seen in S. americanum, but the larger inflorescences may be due to pre-domestication and/or selection of the species in China and Taiwan, where fruits of S. americanum are commonly eaten.

Solanum americanum exhibits the highest infraspecies genetic diversity compared to polyploids (Dehmer and Hammer 2004). Based on its distribution, molecular and crossing experiments it is believed to be the diploid parent of the two hexaploids S. nigrum and S. scabrum (Edmonds 1979a, Ganapathi and Rao 1987a, 1987b). There are a relatively few differences among the two species in SSR (Dehmer 2001), AFLP (Dehmer and Hammer 2004), RAPD (Poczai et al. 2010), ISSR and SCoT (Poczai and Hyvönen 2011), and intron-targeting markers (Poczai et al. 2014), and a number of additive bands could be counted between S. americanum and the two hexaploids indicating their parental relationships. Solanum americanum is also the putative parent of the tetraploid S. villosum (Poczai and Hyvönen 2011).

The taxonomic status and relationship of S. americanum to S. nodiflorum was studied by Manoko et al. (2007). Solanum nodiflorum has been considered as a distinct taxon by some (e.g., Henderson 1974, Heiser et al. 1979) while a synonym or infraspecific taxon of S. americanum by others (e.g., Edmonds 1971; D’Arcy 1974a, b; Symon 1981). Manoko et al. (2007) used AFLP data to study the relationship of the two taxa, but used different taxon concepts than we adopt here, in part because their examination of type specimens was limited. Based on detailed study of the voucher material used, it is clear that the taxon referred to as S. nodiflorum in Manoko et al. (2007) refers to what is considered S. americanum in this treatment, while material referred to as S. americanum represents S. nigrescens M.Martens & Galeotti, a species endemic to the New World. Such confusion is easy in this complex group when studying only a portion of species and their ranges even though type material was consulted in the original paper by Manoko et al. (2007). The taxon referred to as Solanum sp. from Brazil in Manoko et al. (2007) also refers to S. americanum as treated here, but represents morphological variation mainly observed within the New World and was hence difficult to interpret with limited sampling in previous studies. The re-examination of the study results by Manoko et al. (2007) in the light of the new identifications highlights that clear population structure can be observed within S. americanum as circumscribed here, where populations from Brazil show high genetic divergence from the rest of the World, including northern South American material.

The results described above based on AFLP markers should be tested with modern population genetic tools such as functional markers (Poczai et al. 2013) or genotyping-by-sequencing (GBS) and phylogenetic analysis. Species-level phylogenetic studies with multiple accessions of all species would also be useful in confirming the monophyly of the highly variable and widespread S. americanum in the context of other species of the Morelloid clade.
Edmonds (2012) incorrectly designated as the lectotype of S. nigrum var. patulum L. a specimen in the Dillenian herbarium at OXF. This typification is in conflict with the protologue (see McNeill et al. 2012, Art. 9.19) because the specimens themselves are not original material for this name. Linnaeus never saw Dillenius’s herbarium (Jarvis 2007), but based his name entirely on the plates from Hortus Elthamensis (Dillenius 1732). We have therefore re-lectotypified this name based on original material, and designated the specimen chosen by Edmonds as the epitype.

The identity of the species depicted in plate 355 (Dillenius 1732) has been the subject of much speculation. Thellung (1927) studied material in Dillenius’ herbarium at OXF in an attempt to come to grips with the identity of S. dillenii (see below) and made careful annotations on specimens associated with plate 355. Material stored under the plate 355 is mixed; some specimens are of the North American endemic S. emulans Raf. with 9-11 stone cells, calyx lobes appressed to the berry and matte fruit texture, and others are of S. americanum with no or up to 4 stone cells, strongly reflexed calyx lobes in fruit, and shiny mature berries. Thellung (1927) associated the name S. dillenii with the Dillenian specimens of the North American native S. emulans, but did not realise that there were two taxa involved in the material stored under plate 355. Polgár (1939) redescribed S. dillenii, confining it to his original circumscription (Polgár 1926) and equating it with S. nodiflorum and coined a new epithet, S. dillenianum Polg. for the North American material in the Dillenian herbarium that had been called S. nigrum var. dillenii by Gray (1878). We have epitypified the name S. nigrum var. patulum to conform with current usage, because in our view the plate is unambiguously of a plant of S. americanum with small flowers, black fruit and sepals that are strongly reflexed in fruit.

Solanum papilionaceum was almost certainly described from living material only. Dumont de Courset (1802: 135) cited no specimens and gave no other provenance than “Cette morelle, qui m’a été envoye en graines du Jardin. nat.”. Searches in Paris have revealed no authentic original material, so we have selected a neotype that is a specimen dated after the description that was cultivated in Paris (P00582223). The specimen matches the description, which is of a plant with small flowers in umbelliform inflorescences and fruits like “cassis” (blackcurrants).

The specimens in Zuccagni’s herbarium in Florence were consumed by fire, making the designation of a neotype for S. strictum Zucc. necessary. The specimen we have selected is dated later than the description, but is labelled as “strictum Zucc.” and is from Italy in cultivation (G00144215); it was used by Dunal in his Prodromus treatment as S. strictum (Dunal 1852).
The identity of Schultes’s (1814) name S. dillenii has a complex history. Schultes (1814) coined a replacement name because the epithet “patulum” had been used at the species rank by Persoon (1805: 223) for the Peruvian taxon now known as S. ruizii S.Knapp (see Knapp 1989, 2013). He did not realise that Roth (1800) had already recombined Linnaeus’s S. nigrum var. patulum (see above) at the specific rank, basing his description entirely on Hortus Elthamensis plate 355 (Dillenius 1732). In his protologue Schultes refers to a collection by Kitaibel from Hungary (“das ich vor mir habe” [which I have before me]), and the illustration in Hortus Elthamensis (Dillenius 1732), and describes a plant with small flowers and fruits borne on erect pedicels. Polgár (1926) examined the specimen in Kitaibel’s herbarium (“A IX Fasc. 102”) labelled “Solanum nigrum an patulum, Esse patulum affirmat Willdenow. In silvis Matrae” and equated it specimen with the American species he called S. nodiflorum Jacq. and suggested it was not native to Hungary, but rather from a botanic garden. This sheet (Herb. Kit. Fasc. IX, No. 102) in BP is a tangled mixture of two elements (see Poczai et al. 2009). One stem has small flowers in sub-umbellate inflorescences and matches the protologue description (but has no fruit) and the other stem has larger flowers in elongate racemose inflorescences and was identified by Poczai et al (2009) as S. scabrum. It is quite possible that there was considerable mix-up with the labelling of plants in Kitaibel’s herbarium; a specimen at BP (Herb. Kit. Fasc. IX, No. 101) exactly matching the small-flowered stem of Herb. Kitaibel fasc. IX, No. 102 is labelled “Solanum nigrum β patulum” in Kitaibel’s hand, and “ex horto” in another hand. It is possible that the large-flowered plants collected in Mátra (which we identify as S. nigrum) were mixed with small-flowered plants from cultivation and in distributing duplicates confusion ensued. Because Schultes (1814) cited a specimen (see McNeill et al. 2012, Art. 9.12), we have lectotypified S. dillenii with the only sheet in the Kitaibel herbarium (BP) that bears the locality cited in Schultes’s (1814) protologue, but limit our typification to the stem with small flowers only. A sheet in B-W [B-W 04364-03] of Kitaibel’s with a label in his hand “161/Solanum nigrum an patulum ?/In sylvis Hungaria” is certainly a duplicate; we cannot be sure this is the sheet Schultes had in his possession, since the locality is not exactly the same as that in the protologue and it does not have fruit. The BP sheet (fasc. IX No. 101) is also possibly a duplicate; it does have berries borne on erect pedicels. Gray (1878) used Schultes’s epithet at the infraspecific rank (as S. nigrum L. var. dillenii (Schult.) A.Gray) for plants from northeastern North America now known as S. emulans Raf.
In describing S. microspermum Dunal (1816) used an unpublished name by L’Heritier and cited a specimen and his own unpublished illustration, now held in MPU. We have selected the specimen in G-DC that comes from “herb. Thibaud” and is annotated by Dunal as the lectotype. The online catalogue at G indicates the collector of this sheet as “L’Héritier de Brutelle”.
Although the protologue of S. erythrocarpon (Meyer 1818) indicates the fruits are red (“Baccae pendulae, pisi minoris magnitudine, lutescenti-rubrae, nitidae”), the specimen in GOET (GOET003505) that represents original material for this name (here selected as the lectotype) matches S. americanum in all other respects.

D’Arcy (1974a: 735) cited as “type” a specimen in P as “Type: Herb. Rich. (P)” with a footnote stating that the sheet has two labels, one with “Isle de France” in Dunal’s hand and the other indicating it is from Herb. Richard. Since the protologue does not mention Isle de France, and Dunal had nothing to do with the description of this name, this unintentional lecotypification is in conflict with the protologue, in which the locality is “insulae Cubae”  and Richard is mentioned. We therefore supercede it and designated a specimen in P (P00370899) that matches the protologue in being from Cuba and originally from Herb. Richard as the lectotype for S. indecorum.

Sendtner (1846) described his var. aguaraquiya referring to Piso’s (1648: 55) pre-Linnaean name “Aguara-quiya” and citing un-numbered collections of Sellow and one Martius collection with a number and locality we have here selected as the lectotype. The Sellow collections associated with this name (BR [BR0000005538058], K, W [W0004136]) have large anthers and represent S. chenopodioides; they have neither numbers or localities. The specimen selected as lectotype here (Martius 1225, M-0171809) contains detail of collection locality cited in the protologue, and is hence the best material.
D’Arcy (1974a) lectotypified both S. amarantoides (Gaudichaud 552) and S. nodiflorum var. acuminatum (Vauthier 537) by stating “type” and a single herbarium, “P”. In the case of S. amarantoides two specimens are found in P; we have selected that which  has a label with Dunal’s handwriting in a second step lectotypification (P00319574). For S. nodiflorum var. acuminatum, however, D’Arcy (1974a) cited “P, ex Herb. Drake”, indicating a single specimen. Unfortunately this pecimen (P00319615) is not the duplicate of Vauthier 537 with Dunal’s label (that with the annotation from Dunal is P00315614), but must be acepted as the lectotype nevertheless.
In describing S. minutibaccatum, Bitter (1912a) cited a single Buchtien collection (Buchtien 1443), but no herbarium. We have selected the sheet in US (US00027684) as the lectotype because it is the best preserved of the duplicates we have seen.

Solanum calvum was described using “Palmer 60 p. pte.” (Bitter 1913b) with a single herbarium cited (“herb. Upsal.”). Edward Palmer began his number series again on every collecting trip (McVaugh 1956), but the collection number in question here refers to plants collected on Guadalupe Island (Baja California) in 1875. Other duplicates of Palmer 60 (another sheet at UPS, MO [MO-158569]) are part of type material of S. profundeincisum Bitter, a synonym of Solanum douglasii Dunal from Mexico and the southwestern United States, while others are of material of S. nitidibaccatum (BM001017193 and MO-158570). We exclude these as types of S. calvum, and urge caution when interpreting other duplicates of Palmer 60.

The protologue of S. nigrum var. pauciflorum (Liou 1935) cited three specimens from Hainan Island; Chen 1, Wang 2 and Lau 209, all perhaps from LU, although no herbarium was cited. We select here the more widely distributed Lau 209 with the BM sheet (BM000942311) as lectotype for this name.