Phylogeny, ontogeny and floral evolution in Malmeeae (Annonaceae) and Trimezieae (Iridaceae)

Abstract

Angiosperms are a morphologically and distinctive group, easily recognizable by the flower, which is also one of its most important evolutionary novelties. Flower characters have been historically widely used in taxonomy, mostly for identification purposes, and recently, also for phylogenetic reconstructions and monophyletic groups delimitation. Despite this, a high level of homoplasies is commonly found within flower characters suggesting their homology should be more carefully investigated. Therefore it would be highly valuable to associate developmental studies with phylogenetic reconstructions. Furthermore, this would provide a better refinement of morphological characters used as synapomorphies. In connection with this topic, recent phylogenetic hypotheses concerning Annonaceae and Iridaceae contribute to this kind of approach. Annonaceae, mostly tribe Malmeeae, display a great number of androdioecous taxa. That means the same species present some specimens with bisexual flower while others have only male flowers. Besides rare, the androdioecy is more commonly found within herbs having dioecious ancestors. In contrast, Annonaceae comprises woody plants and hermaphroditism as the plesiomorphic condition what makes it a good model for studying androdioecy evolution within woody and hermaphrodite species. In Iridaceae, the flowers vary greatly in shape, size and ornamentation and this diversity has been historically providing important taxonomic characters. Within tribe Trimezieae, style and stigma are especially diverse and elaborate structures widely used in the group taxonomy, usually associated to other floral characters such as shape and tepal ornamentations. However, the homology of these complex characters has never been investigated and recent molecular phylogenetic analyses have showed the genera are polyphyletic indicating also these morphological characters are actually highly homoplastic. The results demonstrate the urgency of examination in greater detail these morphological features allowing a better understand of their evolution and possible role in the tribe systematics. Within this context, the diversity and relatively restricted distribution of Trimezieae, a Neotropical group centred in Brazil, makes it great a model to this kind of approach. The main goal of this study is to better understand the androdioecy evolution in Malmeeae and patterns of floral evolution in Trimezieae (Iridaceae). This will be achieved by associating ontogenetic studies of flower structures to a phylogenetic context. New taxa and molecular characters will be added to the previously existing phylogeny for Trimezieae, and sequences from chloroplast DNA genome will be used for refining Malmeeae phylogeny thus providing appropriate frameworks for these approaches. (AU)