Oral Paper

         Systematics

Morphology and placement of perennating organs play an important role in generic delimitation in subtribe Malaxidinae

Presenting Author
Pankaj Kumar
Description
Malaxidinae is a small subtribe of family Orchidaceae containing 14 genera that are accepted currently. However, this subtribe has a very complicated taxonomy and the taxonomic delimitations of its genera has remained unclear after multiple attempts by many experts from time to time. most of the genera do show homoplasty along a range of morphological features, however, they also show some distinct characters which adds to the confusion. A few attempts have been made in past where functional traits of species were plotted against the phylogenetic tree obtained using combined ITS and matK sequences. One such study attempted to classify this group on the basis of species’ habit (epiphytic/terrestrial), leaf morphology (shape- linear/rounded; foldings- plicate/conduplicate/compressed/unifacial) and leaf number (1, 2, >2). However, the monophylly in Liparis (contains both epiphytic and terrestrial members and leaves can be conduplicate (linear/rounded) or plicate) and Malaxis (leaves can be both plicate or conduplicate-rounded) could not be achieved. Another attempt utilized growth habit (terrestrial/epiphytic), habitat (grassland/forest) and morphology of leaves (conduplicate/plicate/duplicate) to resolve the taxonomy. However, the monophyly was not achieved in Liparis (can be both epiphytic or terrestrial, may occur in both grassland and forest habitats; contains plicate, conduplicate and duplicate leaves) and Malaxis (occurs in both grassland and forest habitats; contains both plicate and conduplicate leaves) in this study either. Current study emphasized the use of additional ecological, vegetative and floral characters, along with the previously used characters. Analysis of 25 morphological characters based on UPGMA generated a dendrogram, which was cross-referenced against the phylogenetic tree obtained using the combined sequences of nrITS and matK regions. While growth habit, perennating organ structure (homoblastic/heteroblastic), placement of perennating organ (above ground/below ground), leaf texture (leathery/soft) and number of leaves were able to resolve the monophyly among terrestrial members of Crepidium clade, epiphytic and terrestrial members of Liparis still remained polyphyletic. The remaining set of floral characters were able to segregate genera within the terrestrial Crepidium clade further as per current taxonomic delimitations.