Cladistic analysis of some taxa in Malvaceae s.l. “Core Malvales” based on anatomical characteristics

Abstract

Malvaceae s.l. “Core Malvales” which in their broad circumscription include members of four traditional families; Malvaceae s.s., Bombacaceae, Sterculiaceae and Tiliaceae. The aim of the present study is to evaluate the use of stem, petiole and lamina anatomical characters in analyzing the phylogenetic relationships among 39 studied taxa from Malvaceae s.l. in addition to one representative of Elaeocarpaceae as outgroup through the parsimony analysis using upgraded WinClada and TNT cladistics programs. The anatomy in cross section of stem, petiole and lamina of the 40 studied taxa of Core Malvales were examined by light microscope and photos were taken. The different anatomical characters are discussed and revealed that certain synapomorphic diagnostic characters has great taxonomic values which in turn used for analyzing the phylogenetic relationships between the studied taxa. These characters viz. (petiole outline and vascular system, cuticle thickness, diverse shapes of secondary phloem fibers, presence and types of crystals and trichomes, gossypol gland, resin ducts, tanniferous cells, star-shaped idioblasts, vessels size and distribution, anomalous xylem structure, extrafloral nectaries, ...). Our results of the phylogenetic analysis conducted from the cladogram (rooted tree) based on 44 anatomical characters and 111 character states strongly support the monophyly of family Malvaceae s.s. while, the other three families are para- or polyphyletic. It shows, also the graduation of the taxa under study in relation to the outgroup; from Tiliaceae and Sterculiaceae directly attached to the tree (ancestor) while taxa from Bombacaceae and Malvaceae are far away from the root of the tree with little deviation. This indicates that Tiliaceae is the most primitive family followed by Sterculiaceae, Bombacaceae ending recently by the most advanced family Malvaceae. Our results agree to some extent with APG IV classification in transferring Elaeocarpaceae to order Oxalidales instead of Malvales also agree with other worker in transferring Gossypium and Lagunaria in family Sterculiaceae while transferring Dombeya to family Tiliaceae. For more accurate assignment of Malvaceae s.l. still more studies on a large number of taxa are needed.