Incipient speciation in a neotropical Gesneriaceae: Columnea kucyniakii is nested within C. strigosa

Abstract

Speciation is an ongoing process. Many recognized species are fully divergent from each other and their ancestors, whereas others are in earlier stages in the diversification process. Such incipient speciation may create patterns when one or a few populations are phenotypically distinct, but lack genomic level coalescence from each other or from their ancestral species. As a result, such progenitor-derivative species pairs are likely to lack reciprocal monophyly or generate paraphyletic ancestral species. Here we examine phylogenetic patterns in the Columnea strigosa (Gesneriaceae) complex to evaluate whether populations that have been named C. kucyniakii are reciprocally monophyletic with C. strigosa, its presumed ancestral species. Molecular phylogenetic results do not support reciprocal monophyly of the two species, implying that incipient speciation is occurring within the C. strigosa complex. We hereby recommend that C. kucyniakii be recognized at the specific rank despite the fact that it creates a paraphyletic C. strigosa. These findings bear importance in taxonomic decisions about paraphyletic taxa and recognizing evolutionary and morphologically distinct lineages.