Borsch T. Ortuño Limarino T. & Nee M. H.: Phylogenetics of the neotropical liana genus Pedersenia (Amaranthaceae: Gomphrenoideae) and discovery of a new species from Bolivia based on molecules and morphology. — Willdenowia 41: 5–14. — Online ISSN 1868-6397; © 2011 BGBM Berlin-Dahlem. doi:10.3372/wi.41.41101 (available via http://dx.doi.org/)\r\n\r\nThe monophyletic genus Pedersenia comprises eleven species in the Neotropics one of which P. volubilis is here described as new to science being an endemic of mixed semi-deciduous Bolivian-Tucuman Interandean lower subhumid forest at mid elevations of the Department of Santa Cruz Bolivia. Among the liana species of Pedersenia it differs by twining stems synflorescences constituted by terminal stems of several metres and small lanceolate leaves. It is also characterised by two synapomorphic substitutions in the matK CDS. Sequence data of trnK/matK show considerable divergence between morphologically very similar liana species of tropical evergreen broad-leaved forests from different geographical regions. The phylogeny suggests the only self-sustaining tree-like species from the dry inter-Andean valleys to be derived from lianas. Allopatric speciation fostered by the ecological and geographical differentiation of the forest communities may have led to morphologically cryptic species underscoring the need for an integrated morpho-molecular revision of the genus Pedersenia.