Spermacoce in the Americas: small group, small flowers but great taxonomic problems

ROBERTO M. SALAS,; JAVIER E. FLORENTÍN,; STEVEN DESSEIN, ; ANDREA A. CABAÑA FADER,; STEVEN JANSSENS, ; SANDRA V. SOBRADO, ; LAILA M. MIGUEL, ; ELSA L. CABRAL

Copenhagen

Conferencia; VII International Rubiaceae and Gentianales Conference; 2017

Natural History Museum of Denmark

The genus Spermacoce belongsto tribe Spermacoceae s.l. Together with 23 other genera it Forms the monophyletic Spermacoce clade. Several genera of this Spermacoce clade are well Supported by molecular data (e.g. Mitracarpus, Richardia, Galianthe), while others areparaphyletic (e.g. Borreria and Spermacoce). The generic boundaries of Spermacoce areproblematic and currently strongly discussed. There are two concepts, the mostcomprehensive one includes other genera (Borreria and parts of Diodia), whereas the narrow one includes only the type S. tenuior, and seven closely related species. Based on ourmolecular dataset (ITS and ETS), the genus comprises American and Australian species divided into three lineages: Spermacoce s.s. (including type species), S. eryngioides group (exB. sect. Pseudodiodia),andanAustraliangroup.In the Americas, Spermacocediffersfromitsclosestrelatives in having small urceolate corolla, lobes internally pilose, stamens and stigmaincluded,and pollen grains with tectate exine,long colpi,and endocingulum. In this continent,as defined above,it comprises 35 species,of which five are new to science. There view,based on over 1900 specimens,provides nomenclatural and taxonomic discussion about the type species, the S. ocymoides complex, and the geographic distributions. Species within Spermacoce can be distinguished from each other based on calyx lobes/corolla length ratio,internal indumentum of the corolla,morphology of the ventral face of theseeds,exotesta patterns,and pollen characters such as shape,number of colpi,distribution of perforations,and supratectal elements.