Venation pattern and micromorphology of schizocarps of Gaya and related genera within Malveae (Malvaceae)

Abstract Few studies have reported the venation pattern and micromorphology of Malveae schizocarpic fruits. These reproductive structures are present in Gaya and other genera of the tribe and may prove useful for solving taxonomic problems and understanding phylogenetic relationships within. We analyzed the mericarp and the seeds of 13 Brazilian species of Gaya and 11 species of related genera to provide useful comparative features for their taxonomy and phylogeny. The samples were subjected to the herborization reversal procedure and followed methods of scanning electron microscopy, light microscopy and diaphanization. The studied species of Gaya were compared on a binary matrix of characters analyzed through UPGMA. Within Gaya, the mericarp constriction corresponds to the dehiscence lines, which may occur at the basal portion or ventrally. Two to three veins in contact with the columella (central structure to which the mericarps are attached) were observed in this region. At the upper ventral margin, we observed only one vein connecting with the columella. The exocarp exhibited simple, biradiate, stellate and multiradiated trichomes. Capitate glandular trichomes were also observed. Species from related genera (Briquetia, Callianthe, Herissantia and Hochreutinera) showed stellate trichomes. Glandular and tector trichomes were observed in Gaya seeds, while other genera exhibited only simple trichomes. Venation pattern and micromorphological characters of mericarps, as well as novel seed trichome types here reported support of Gaya support the delimitation of genera studied and highlight the isolated position of Gaya within Malvaeae.