Phylogeny, character evolution and biogeography of the genus Sclerophylax (Solanaceae)

Abstract

The genus Sclerophylax (Atropina clade, Solanaceae) has 14 species recognized to date, all except two endemic to Argentina. To clarify its phylogenetic relationships, molecular sequence data from the trnL-trnF and the rpl32F-trnL intergenic spacer regions, the waxy gene and the ITS region were employed in maximum likelihood and Bayesian inference analyses. Divergence times were estimated for the combined dataset using secondary calibrations. Ancestral distribution areas were reconstructed by Bayesian binary analyses and seven morphological traits (one continuous, six discrete) were traced. Sclerophylax is monophyletic and its sister clade is Lycium + Nolana. Sclerophylax is divided into S. sect. Caducifructus (1 sp.) and the monophyletic sect. Sclerophylax (11 spp.). Sclerophylax sect. Sclerophylax includes five well-supported clades that are also supported by morphological synapomorphies; circumscription of some species remains uncertain, probably as a result of rapid diversifications, but four lineages are recognized by a combination of morphological traits. The ancestor of Sclerophylax was an annual, procumbent/decumbent plant with rhomboidal leaves and sessile, persistent, 2–3-seeded fruits. The most variable traits were leaf shape and life form, while flower size was shown to be highly informative in diagnosing clades within Sclerophylax. The area of origin for Sclerophylax was the Prepuna biogeographical province, from which it has spread in recent geological times. A total of 12 species are recognized in Sclerophylax, with an updated synonymy, lectotypifications, and re-circumscriptions provided.