Tabaroa, a new genus of Leguminosae tribe Brongniartieae from Brazil

Abstract

A new genus of Leguminosae in tribe Brongniartieae is proposed based on a new species endemic to the Caatinga of Bahia state. The new genus is named as Tabaroa L. P. Queiroz, G. P. Lewis & M. F. Wojc. and the new species as Tabaroa caatingicola L. P. Queiroz, G. P. Lewis & M. F. Wojc. A phylogenetic study of the Brongniartieae based on nuclear rDNA ITS and plastid matK sequences supports a closer relationship between Tabaroa and Harpalyce Moc. & Sesse than to the two South American genera Poecilanthe Benth. and Cyclolobium Benth., which are more similar morphologically. Optimisation of selected morphological characters on one of the most parsimonious trees indicates that the sessile ovary and the explosive pollen presentation are putative synapomorphies of the Tabaroa-Harpalyce clade. The genus Tabaroa may be diagnosed by the absence of peltate glandular trichomes; leaves imparipinnate, exstipellate and with opposite leaflets; flowers sessile, not resupinate, grouped in panicles; anthers apiculate; and fruit indehiscent. The only known species inhabits areas of arboreal caatinga on sandy soil in southwestern Bahia, near the boundaries of Dom Basilio and Livramento de Nossa Senhora municipalities.