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Abstract
We analyzed the pollen grains of 11 species within the subfamily Bombacoideae. The pollen grains were acetolyzed, after which they were analyzed and photographed under light microscopy. Unacetolyzed pollen grains were analyzed and photomicrographed under scanning electron microscopy. We studied pollen characters such as shape, size, exine ornamentation and aperture type. The species were separated by a pollen key, which considers the presence or absence of "calotte" in the pollen grains. This attribute separated Ceiba and Eriotheca from the other genera. Some species are differentiated by specific characters: in Bombacopsis glabra and B. stenopetala, the sexine is rugulate or "vermiculate" with isolated pilate elements; in B. calophylla, the pollen grains are sinu-aperturate; Ceiba speciosa show atypical, duplicolumellate sexine; C. erianthos is the only species with 5-colporate pollen grains and a pentagonal amb; in Pachira aquatica the reticulum has muri with spiculaspinulose muri ("reticulum cristate"). The variation in the pollen morphology confirms the eurypalynous status of the genera studied here.
Highlights
The order Malvales comprises approximately 10 families, 338 genera and 6005 species, with distribution primarily in tropical regions (APG II 2003).Phylogenetic studies on Malvaceae sensu lato (Bayer et al 1999) have identified nine clades, corresponding to the following subfamilies: Bombacoideae, Brownlowioideae, Byttnerioideae, Dombeyoideae, Grewioideae, Helicteroideae, Malvoideae, Sterculioideae, and Tilioideae
Due to the taxonomic importance of the Malvaceae family and the need for studies to corroborate the circumscription of the group, which remains uncertain, this study aimed to characterize the pollen morphology of the Bombacoideae species occurring in the state of Rio de Janeiro, which are distributed predominantly in areas of restinga and Atlantic Forest, in order to support taxonomic studies of the group
Some species are differentiated by particular characters: in Bombacopsis glabra and B. stenopetala, the sexine is rugulate or vermiculate; Ceiba speciosa has an atypical duplicolumellate sexine; in Pachira aquatica the reticulum has muri with spinules (“reticulum cristate”)
Summary
The order Malvales comprises approximately 10 families, 338 genera and 6005 species, with distribution primarily in tropical regions (APG II 2003).Phylogenetic studies on Malvaceae sensu lato (Bayer et al 1999) have identified nine clades, corresponding to the following subfamilies: Bombacoideae, Brownlowioideae, Byttnerioideae, Dombeyoideae, Grewioideae, Helicteroideae, Malvoideae, Sterculioideae, and Tilioideae. The importance of palynology in the taxonomic classification of families and subfamilies has been demonstrated in various studies that used pollen data to reassess the groups; the study conducted by Saba (2007) is the one that best covers the species of Brazil, in terms of numbers and details. Similar studies include those conducted by Robyns (1963), Tsukada (1964), Palacios-Chávez (1966), Robyns (1971), Robyns & Nilsson (1975, 1981), Nilsson & Robyns (1974, 1986), Perveen et al (2004), and Perveen & Qaiser (2007).
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