A new, disjunct species of Bahiana (Euphorbiaceae-Acalyphoideae): Phytogeographic connections between the seasonally dry tropical forests of Peru and Brazil, and a review of spinescence in the family

Bahiana is expanded from 1 to 2 species with the description of B.
occidentalis K. Wurdack, sp. nov. as a new endemic of the seasonally dry
tropical forests (SDTFs) of Peru. The disjunct distribution of Bahiana
with populations of B. occidentalis on opposite sides of the Andes in
northwestern Peru (Tumbes, San Martín) and B. pyriformis in eastern Brazil
(Bahia) adds to the phytogeographic links among the widely scattered New
World SDTFs. Although B. occidentalis remains imperfectly known due to
lack of flowering collections, molecular phylogenetic results from four
loci (plastid matK, rbcL, and trnL-F; and nuclear ITS) unite the two
species as does gross vegetative morphology, notably their spinose
stipules, and androecial structure. Spinescence in Euphorbiaceae was
surveyed and found on vegetative organs in 25 genera, which mostly have
modified sharp branch tips. Among New World taxa, spines that originate
from stipule modifications only occur in Bahiana and Acidocroton, while
the intrastipular spines of Philyra are of uncertain homologies.