Solanum colombianum

Hawkes (1990) treated Solanum colombianum as one of 40 species in Solanum sect. Petota series Conicibaccata Bitter, a group containing diploids (2n = 24), tetraploids (2n = 48), and hexaploids (2n = 72). The polyploids are mainly distributed from southern Mexico south to central Peru (one species in northern Bolivia), and the diploids from northern Peru to central Bolivia.

The species boundaries and relationships of members of series Conicibaccata have been studied using plastid DNA restriction sites (Castillo and Spooner, 1997), morphology (Castillo and Spooner, 1997; Fajardo et al., 2008), AFLPs (Jiménez et al., 2008), nuclear DNA (“waxy”) sequence data (Spooner et al., 2008), other nuclear DNA sequence data (Fajardo & Spooner 2011), and monographic studies (Hawkes, 1990; Hawkes and Hjerting, 1989; Ochoa, 1990, 1999). The plastid DNA restriction site and morphological data divide the diploids and polyploids into two clades or phenetic groups, respectively, but the morphological separation generally depends on the use of character states that sometimes overlap in range. The DNA sequence data show the polyploids to be of allopolyploid origin from the diploid members of the series and members of species outside of the series.

A monographic study in progress by Fajardo and Spooner, using the above data, and herbarium specimens, is recognizing only 17 species. All are very similar, united as a group by conical fruits, leaves with generally parallel sided morphology, and narrowly ovate to elliptical leaflets. However, some unrelated species also have conical fruits, such as the Mexican diploid species S. hintonii Correll, S. lesteri Hawkes and Hjert. and S. trifidum Correll; the Mexican hexaploid species S. iopetalum (Bitter) Hawkes; and the Bolivian species S. circaeifolium Bitter. An additional problem is that some species possess ovoid fruits that are not absolutely distinct from the conical fruits of the above species or the globose fruits more common in the majority of the members of sect. Petota.

Solanum colombianum is by far the most widely distributed and polymorphic polyploid member of the series, composed of both tetraploid cytotypes (such as the previous name S. colombianum and others), and the hexaploid cytotypes S. moscapanum, S. sucubunense and S. tundalomense. Relative to the other South American polyploids, S. colombianum may be a plesiospecies (sensu Rieseberg and Brouillet, 1994; Olmstead, 1995), with the other sympatric polyploids (S. flahaultii Bitter, S. garcia-barrigae Ochoa, and S. lobbianum Bitter) as phenetically distinctive local derivatives. Its polymorphism and possible plesiomorphic species status make it hard to define, and is best differentiated from other polyploids by lack of characters that define them. These include, for example, the lack of a seed spot found in S. longiconicum, lack of an enlarged or differently shaped terminal leaflet in comparison to lateral leaflets as in S. garcia-barrigae or S. pillahuatense, lack of densely pubescent leaves as in S. lobbianum.

Dunal (1852) described S. otites based on Linden 426 in the Boissier Herbarium at G. There are two specimens of Linden 426 at G but only one bears Dunal’s handwriting that we consider as holotype. Both of these specimens have three pairs of lateral leaflets (3-jugate) We consider duplicates of this collection at BR, FI, G, OXF and P as isotypes. Bitter (1912) redescribed S. otites as a species both 2- and 3-jugate, but described two forms (forma dizygum and forma trizygum) differing in this character. A sheet at W bears two specimens differing in 2- vs. 3-jugate leaves with his handwriting describing this variation that we consider as type material.