Phylogenetic relationships of the durians (Bombacaceae-Durioneae or /Malvaceae/Helicteroideae/Durioneae) based on chloroplast and nuclear ribosomal DNA sequences

The circumscription and phylogenetic position of the tribe Durioneae (Bombacaceae or /Malvaceae/Helicteroideae) was investigated by supplementing a previously publishedndhF data set. The present analysis supports a narrow conception of Durioneae (excludingCamptostemon andPapuodendron) and confirms a close relationship withHelicteres, Reevesia, Ungeria, andTriplochiton (all of traditional Sterculiaceae). Phylogenetic relationships within Durioneae were inferred from a combined analysis ofndhF and ITS sequences. These data suggest thatNeesia is sister to a clade comprising all other five genera of core Durioneae, and thatCoelostegia +Kostermansia form a clade that is sister toCullenia +Boschia +Durio. Various morphological features support these relationships. However, characters usually considered diagnostic for the entirety of Durioneae, such as a densely lepidote lower leaf surface and uni- or polylocular anthers, appear to be apomorphic within this clade. Likewise, spiny fruits and large arils covering the seeds are not plesiomorphic for Durioneae, in contradiction to Corner's classic Durian Theory. The phylogeny suggests that bat- and bird-pollination evolved from beetle-pollination and that this transition was coincident with extensive androecial modification. Similarities due to convergent evolution of floral traits in relation to pollination by birds and mammals probably account for the erroneous, traditional placement of Durioneae in Bombacaceae.