Solanum anomalostemon occurs in southern Peru on rocky and clayey arid slopes at ca. 2800 m (ca. 13°30’S, 72°40’W) on either side of the Río Apurímac west of Cusco on the road to Abancay.
Soolanum anomalostemon is a species of uncertain affinities, but appears to be related to species of the Morelloid and Dulcamaroid clades (Tiina Sarkinen, pers. comm.).
Solanum anomalostemon appears to be unique in Solanum in its cordate, sharply pointed anthers with a prolonged beak-like apex, which dehisce by longitudinal slits that are only poricidal very briefly at the beginning of anthesis. Otherwise, Solanum is remarkably uniform in basic anther morphology in the ca. 1500 species. Approximately 95% of the species are divided between two groups: (1) those with oblong anthers with relatively large terminal pores and later longitudinal dehiscence to a greater or lesser extent (the non-spiny solanums), and (2) species with attenuate anthers with very small terminal anthers that do not later enlarge (the Leptostemonum and Wendlandii clades [sensu Bohs, 2005; Weese & Bohs, 2007]). In other nonspiny solanums (excluding the Wendlandii clade [sensu Bohs, 2005; Weese & Bohs, 2007]), the anthers split longitudinally with age, but the pores are distinct at the beginning of anthesis (Knapp, 2002). Throughout Solanum many different types of anther modifications occur in almost all of the monophyletic clades in the genus (Levin et al., 2006; Anderson et al., 2006). Heterandry can be present, either by the unequal growth of a single filament (e.g., S. uncinellum Lindley of the Dulcamaroid clade [sensu Bohs, 2005; Weese & Bohs, 2007], or S. turneroides Chodat of the Brevantherum clade [sensu Bohs, 2005; Weese & Bohs, 2007]), or by variously unequal anthers (e.g., S. rostratum Dunal and all but one of the other species of section Androceras (Nuttall) Marzell of the Leptostemonum clade). Members of the Pachyphylla clade (sensu Bohs, 2005; Weese & Bohs, 2007, formerly Cyphomandra Martius ex Sendtner) have unusually thickened connectives, and in the tomatoes the anthers are tightly connate and have a sterile tip that functions as a single pore (Glover et al., 2004; Peralta et al., 2008). The Argentine species S. delitescens C. V. Morton, of the Geminata clade, has ellipsoid anthers that are narrowed and apparently sterile in the lower third.
The anthers of Solanum anomalostemon are most like those of the small section Chamaesarachidium Bitter (S. chamaesarachidium, S. gilioides Rusby, and S. annuum C. V. Morton; considered part of the Morelloid clade on morphological grounds pending molecular investigation [G. Barboza, pers. comm.]). These tiny, often annual, plants of the high Andes have basally appendaged anthers, somewhat reminiscent of the cordate anther base of S. anomalostemonum. In habit and leaf morphology S. anomalostemon also resembles the species of section Chamaesarachidium: the plants are shrublets or small perennial herbs and the leaves are variously pinnatifid (Barboza, 2005). Solanum chamaesarachidium has glandular pubescence like that of S. anomalostemon, but has a marked basal connectival extension and is a much smaller, apparently annual plant (Barboza, 2005). The flowers of members of section Chamaesarachidium are usually somewhat campanulate at anthesis, as apparently are the flowers of S. anomalostemon. The seeds of S. anomalostemon are not tuberculate, as are those of all known species of section Chamaesarachidium. There are herbaceous species in the Andes of section Parasolanum A. Child (S. tripartitum Dunal and relatives) with somewhat similar leaves, but these lack the glandular hairs, and anthers are more typical of the nonspiny solanums. In molecular analyses it resolves as a species on a long branch related to the Morelloid clade (T. Sarkinen, pers. comm.).
Anderson, G. J., G. Bernardello, L. Bohs, T. Weese & A. Santos Guerra. 2006. Phylogeny and biogeography of the Canarian Solanum vespertilio and S. lidii (Solanaceae). Anales Jard. Bot. Madrid 63: 159–167.
Barboza, G. 2005. Revision of Solanum sect. Chamaesarachidium. Nordic J. Bot. 23(2): 155–168.
Bohs, L. 2005. Major clades in Solanum based on ndhF sequences. Pp. 27–49 in R. C. Keating, V. C. Hollowell & T. B. Croat (editors), A Festschrift for William G. D’Arcy: The Legacy of a Taxonomist. Monogr. Syst. Bot. Missouri Bot. Gard. 104.
Glover, B. J., S. Bunnewell & C. Martin. 2004. Convergent evolution within the genus Solanum: The specialised anther cone develops through alternative pathways. Gene 331: 1–7.
IUCN. 2001. IUCN Red List Categories and Criteria, Version 3.1. Prepared by the IUCN Species Survival Commission. IUCN, Gland, Switzerland, and Cambridge, United Kingdom.
Knapp, S. 2002. Solanum section Geminata. Flora Neotrop.84: 1–405.
Levin, R. A., N. R. Myers & L. Bohs. 2006. Phylogenetic relationships among the ‘‘spiny solanums’’ (Solanum subgenus Leptostemonum, Solanaceae). Amer. J. Bot. 93: 157–169.
Peralta, I. E., D. M. Spooner & S. Knapp. 2008. Taxonomy of tomatoes: A revision of wild tomatoes (Solanum section Lycopersicon) and their outgroup relatives in sections Juglandifolia and Lycopersicoides. Syst. Bot. Monogr. 84: 1–186.
Weese, T. & L. Bohs. 2007. A three-gene phylogeny of the genus Solanum (Solanaceae). Syst. Bot. 33: 445–463.
Solanum anomalostemon is known from only a few collections, all collected within 20 km of each other in the Río Apurímac drainage. The species had not been collected for more than half a century until its recent rediscovery in Cusco Department, on the other side of the Apurímac. The dry forests in which it occurs are not widely protected in Peru, and S. anomalostemon does not occur in or near any of the Peruvian network of protected areas (INRENA). Solanum anomalostemon can be added to the list of endemic Peruvian solanums, and using the IUCN Red List criteria (IUCN, 2001) it has been given a preliminary conservation status of Endangered (EN B1a[iii], B2a) based on its restricted distribution (extent of occurrence , 5000 km2, area of occupancy , 100 km2), low number of populations (2-3), and threatened and unprotected habitat.