An overview on studies of species complexes in Solanaceae

Solanaceae comprises many species complexes, taxonomically challenging lineages that require specialized effort to be reliably delimited, and thus develop a reasoned hypothesis at the species level. To obtain an overview of aspects that permeate species complexes studies in Solanaceae, we collected and summarized details of selected works, resulting in 83 published articles comprising nine genera. Solanum, the most studied genus, spans all explored biogeographic realms, characterized by taxonomic complexity related to its long history of domestication. Capsicum is a unique case due to the adoption of complexes as an indicator of gene pool, while Petunia can potentially serve as a model for the use of species complexes to improve evolutionary knowledge given their phylogeographic studies. The Neotropical region concentrates the majority of research and presents the highest number of genera studied. Morphometrics is the main applied approach probably due to its low cost, followed by population genetics, reproductive biology, phylogeny, and others. Most studies do not present taxonomic decisions or apply integrated methods. We encourage studies with some neglected genera that may have hidden species complexes; a major effort to resolve the Solanum nigrum complex; and the use of effective, less applied fields of study such as ecology and palynology.