World Congress for Middle Eastern Studies

Barcelona, July 19th – 24th 2010

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Systematics and biogeography of Senna (Leguminosae) in the Arabian Peninsula - NOT_DEFINED activity_field_Poster

· NOT_DEFINED institution: Centre for Middle Eastern Plants (CMEP)

· NOT_DEFINED organizer: Faten Filimban

· NOT_DEFINED language: English

· NOT_DEFINED description: Senna is diversity both in habit and habitat. Approximately 350 species are known of which 80% occur in the Americas. Twelve species are native to the Arabian Peninsular. Species of Senna were formerly included among the approximately 600 species of Cassia s.l. Subsequent taxonomic treatments subdivided this large genus into the smaller Cassia s. str., Chamaecrista, and Senna, and ascribed these three genera to subscribe Cassiinae. In the most recent monograph, Senna comprised approximately 260 species in the new world, which later increased to 350, mainly as a result of new nomenclatural combinations in non- American taxa. The separation of Senna from Cassia was confirmed by further taxonomic, structural, and phenetic studies. Published molecular phylogenies, comprising only 11 species of Senna, supported its monophyly (based on both molecular and morphological data). In these phylogenies, Cassiinae are included in a large clade with other subfamily Caesalpinioideae legumes (Caesalpinieae, Cassieae and subtribe Ceratoniinae) and subfamily Mimosoideae. Although a recent survey of legumes by considered Cassiinae monophyletic (as Cassieae s. str.), relationships among the three genera Cassia, Chamaecrista, and Senna remain unclear. The most recent classification of Senna relied greatly on Bentham’s (1871) taxonomic revision of Cassia, specifically of Cassia subgenus Senna. Although some researchers focused only on the American species, which represent the majority of the genus, their classification was soon adopted in subsequent treatments of Senna in other continents. Most of the old world species have a widespread distribution but Senna hookeriana is restricted to the Arabian Peninsula plus Somalia, S. holosericea is known from the Arabian Peninsula plus North Africa, Iran, India and Pakistan (acc to ILDIS) and S. socotrana is endemic to Socotra. The purpose of this project is to study the systematics, phylogenetics and biogeography of Senna in the Arabian Peninsula. The project has two major aims. The first one is to prepare a comprehensive account of the species to include their taxonomy, nomenclature, distribution and conservation status. The second major aim is to generate a molecular phylogeny of Senna building on the work of Marazzi et al., (2006). The phylogeny will be compared with current classification systems and used tot est the morphological delimitation of the species, Examine the placement of the restricted and widespread species, reveal whether the Arabian Peninsular species form a natural group, discover which, if any, morphological traits are congruent with the clades defined by the molecular phylogeny and to elucidate patterns of morphological evolution.