Revisiting the phylogeny of Bombacoideae (Malvaceae): Novel relationships, morphologically cohesive clades, and a new tribal classification based on multilocus phylogenetic analyses

Abstract

Bombacoideae (Malvaceae) is a clade of deciduous trees with a marked dominance in many forests, especially in the Neotropics. The historical lack of a well-resolved phylogenetic framework for Bombacoideae hinders studies in this ecologically important group. We reexamined phylogenetic relationships in this clade based on a matrix of 6465 nuclear (ETS, ITS) and plastid (matK, trnL-trnF, trnS-trnG) DNA characters. We used maximum parsimony, maximum likelihood, and Bayesian inference to infer relationships among 108 species (∼70% of the total number of known species). We analyzed the evolution of selected morphological traits: trunk or branch prickles, calyx shape, endocarp type, seed shape, and seed number per fruit, using ML reconstructions of their ancestral states to identify possible synapomorphies for major clades. Novel phylogenetic relationships emerged from our analyses, including three major lineages marked by fruit or seed traits: the winged-seed clade (Bernoullia, Gyranthera, and Huberodendron), the spongy endocarp clade (Adansonia, Aguiaria, Catostemma, Cavanillesia, and Scleronema), and the Kapok clade (Bombax, Ceiba, Eriotheca, Neobuchia, Pachira, Pseudobombax, Rhodognaphalon, and Spirotheca). The Kapok clade, the most diverse lineage of the subfamily, includes sister relationships (i) between Pseudobombax and "Pochota fendleri" a historically incertae sedis taxon, and (ii) between the Paleotropical genera Bombax and Rhodognaphalon, implying just two bombacoid dispersals to the Old World, the other one involving Adansonia. This new phylogenetic framework offers new insights and a promising avenue for further evolutionary studies. In view of this information, we present a new tribal classification of the subfamily, accompanied by an identification key.

Could coastal plants in western Amazonia be relicts of past marine incursions?

“…Our results also suggest that dispersal may have been bidirectional, i.e., some species may have evolved in Amazonia or the foothills of the Guiana Shield and dispersed towards the coasts ( Pachira ; Carvalho‐Sobrinho et al., ), while others dispersed from the present coastline towards the centre of the continent. For instance, the genus Manicaria originated in the middle Eocene c .…”

A new combination and taxonomic notes in Pseudobombax Dugand (Malvaceae)

“…Previously, phylogenetic analyses of DNA sequences were interpreted as supporting the accessions examined of these two taxa as sister groups (Carvalho-Sobrinho et al 2016: fig. 2), but we now consider P. guayasense to be a synonym of P. millei on the basis of combined morphological and molecular evidence.…”

“…A. Robyns (Carvalho-Sobrinho et al 2016: fig. 2), a widespread species in South American savannas, by its cuneate (vs. truncate) leaflets, shorter (c. 10 vs. 16–50 mm long) petiolules, and its 5-angulate (vs. circular) fruits in cross-section.…”

“…Field and herbarium studies of the Neotropical genus Pseudobombax Dugand (Malvaceae) along with previously published molecular phylogenetic studies (Carvalho-Sobrinho et al 2016) revealed that taxonomic changes are needed in the genus. Nomenclatural changes are proposed herein for taxa that will be included in a monograph of Pseudobombax for Brazil (Carvalho-Sobrinho in prep.…”

Flora da Serra do Cipó, Minas Gerais:

“…Bombacoideae engloba 160 espécies dentro de 18 gêneros, sendo distribuídos principalmente na região neotropical do globo terrestre, ocorrendo também no Paleotrópico: no continente africano, há 18 espécies nativas pertencendo aos gêneros Adansonia L., Bombax L. (utilizada em ornamentação pública no Brasil, sendo uma espécie exótica) e Rhodognaphalon (Ulbr.) Roberty (Carvalho-Sobrinho et. al., 2016).…”