Phylogenetic relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as inferred from plastid DNA sequences

Abstract

Previous molecular phylogenetic analyses have revealed that elements of the former families Malvaceae sensu stricto and Bombacaceae together form a well-supported clade that has been named Malvatheca. Within Malvatheca, two major lineages have been observed; one, Bombacoideae, corresponds approximately to the palmate-leaved Bombacaceae, and the other, Malvoideae, includes the traditional Malvaceae (the mallows or Eumalvoideae). However, the composition of these two groups and their relationships to other elements of Malvatheca remain a source of uncertainty. Sequence data from two plastid regions, ndhF and trnK/matK, from 34 exemplars of Malvatheca and six outgroups were analyzed. Parsimony, likelihood, and Bayesian analyses of the sequence data provided a well-resolved phylogeny except that relationships among five lineages at the base of Malvatheca are poorly resolved. Nonetheless, a 6-bp insertion in matK suggests that Fremontodendreae is sister to the remainder of Malvatheca. Our results suggest that the Malvoideae originated in the Neotropics and that a mangrove taxon dispersed across the Pacific from South America to Australasia and later radiated out of Australasia to give rise to the ca. 1700 living species of Eumalvoideae. Local clock analyses imply that the plastid genome underwent accelerated molecular evolution coincident with the dispersal out of the Americas and again with the radiation into the three major clades of Eumalvoideae.

Morphological cladistic analysis of Pseudobombax Dugand (Malvaceae, Bombacoideae) and allied genera

“…(one), Ceiba (two), Eriotheca (three) and Pachira (one). The placement of Cavanillesia is not well established, although Baum et al (2004) considered that it should be included in Bombacoideae, but this assumption was not tested.…”

“…The outgroup, based on Baum et al (2004), comprised (i) Scleronema Benth., supported as part of a sister group of the Adansonieae; (ii) Matisia, a representative of Matisieae formerly included in "Bombacaceae" and supported in a basal position in the Malvoideae; and (iii) Ochroma Sw., which is long × width ratios in order to minimize the subjectivity present in morphological terminology. Two analyses were performed considering unordered and ordered characters (10 multistate characters that express progression series).…”

“…Cronquist 1981). However, phylogenetic studies based on morphological (Judd & Manchester 1997) and molecular data , Baum et al 2004 did not support the monophyly of Sterculiaceae, Tiliaceae and Bombacaceae, which are now classified into an expanded Malvaceae , Nyffeler et al 2005. Most of the traditional genera of "Bombacaceae" appears in a clade now classified as subfamily Bombacoideae, sister to subfamily Malvoideae.…”

“…and Quararibea Aubl.) were resolved as part of subfamily Malvoideae (Baum et al 2004, Nyffeler et al 2005.…”

“…Moreover, the distinction between Pachira and Bombacopsis has been questioned and they were treated as congeneric by Alverson (1994), Alverson & Steyermark (1997) and Fernández-Alonso (1998). Baum et al (2004) and Nyffeler et al (2005) supported the monophyly of the Adansonieae, although only four genera were sampled in each analysis: Adansonia L. (two species), Bombax (two), Ceiba Mill. (two) and Pachira (one).…”