Phylogeny of the Neotropical tribe Jacarandeae (Bignoniaceae)

The tribe Jacarandeae includes Jacaranda (49 species) and Digomphia (3 species), two genera of trees and woody shrubs with Neotropical distribution. Jacarandeae is sister to the rest of the Bignoniaceae, but not much is known about interspecific and intergeneric relationships within this group.

We reconstructed the phylogeny of Jacarandeae using chloroplast (ndhF, rpl32-trnL, trnL-F) and nuclear (ETS, PPR62) markers. Evolutionary relationships within Jacarandeae were inferred using Bayesian, Maximum Likelihood, and species tree approaches. The resulting phylogenetic framework was used as the basis to interpret the evolution of key morphological character states (i.e., stamen and calyx traits) and revise the infra-generic classification of the group.

Jacaranda and Digomphia belong to a well-supported clade, with Digomphia nested within Jacaranda. We propose the necessary taxonomic changes to recognize monophyletic taxa, including a broadly circumscribed Jacaranda divided into four sections: (1) Jacaranda sect. Nematopogon, species previously included in Digomphia and united by divided staminode apices and spathaceous calyces; (2) Jacaranda sect. Copaia, species with monothecal anthers and cupular calyces; (3) Jacaranda sect. Jacaranda, species with monothecal anthers and campanulate calyces; and (4) Jacaranda sect. Dilobos, species with dithecal anthers and cupular calyces, and including more than half of the species of the genus, all restricted to Brazil.

As circumscribed here, Jacarandeae includes only a broadly defined Jacaranda divided into four sections. Each section is defined by a unique combination of anther and calyx morphologies.