Systematics Section / ASPT
Koehler, Samantha , Singer, Rodrigo , Williams, N. H. , Whitten, W. M. , do Amaral, Maria do Carmo .
Phylogeny and systematics of the brazilian ‘Maxillaria madida’ alliance (Maxillariinae: Orchidaceae): a group got the shrinks.
The ‘Maxillaria madida’ alliance comprises a group of orchids of the subtribe Maxillariinae with predominantly Southeastern Brazilian distribution. These plants are characterized by the presence of coriaceous to fleshy leaves, short inflorescences and purple to tan-yellowish rewardless flowers with a conspicuous shiny spot on the lip midlobe. Although the group is easily recognizable, species delimitation within this alliance can be very challenging due to the overlapping of many floral and vegetative characters, especially leaf shape and lip morphology. The main goals of this study were (1) to define species limits based on molecular and morphological studies; (2) to infer the phylogenetic relationships within the ‘M. madida’ alliance; and (3) to identify morphological synapomorphies supporting clades. Our final goal is to present a complete taxonomic revision for this group. Sequence data from nuclear (ITS1-2) and chloroplast DNA (trnL-F and matK) suggests the ‘M. madida’ alliance comprises a monophyletic group. Both molecular and morphological results indicate that a much smaller number of species should be recognized (about 9 of the 22 described). Many of the species are highly polymorphic and the most conspicuous morphological characters, such as leaf number and shape, appeared homoplastic when mapped onto molecular trees. Therefore, previous classifications proposed for the ‘M. madida’ alliance are not satisfactory. Additional data from leaf anatomy and floral fragrances are currently being gathered in order to complement macro-morphological studies and to help clarifying species delimitation. The morphological homogeneity and the overlapping geographical distribution of several species may indicate recent speciation events. For this reason, a study of the phylogeography of populations of the M. acicularis-M. madida species complex is currently being developed in order to help understand diversification patterns within these Southeastern Brazilian orchids.
1 - University of Florida, Department of Natural History, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
2 - Universidade Estadual de Campinas, Departamento de Botanica, Caixa Postal 6109, Campinas, Sao Paulo, 13083 970, Brazil
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 10:15 AM