Folia Geobotanica 33: 353-366, 1998 THE TAXONOMIC TREATMENT OF AGAMOSPERMS IN THE GENUS LIMONIUM MILL. (PLUMBAGINACEAE) Robyn Cowan 1) Martin J. Ingrouillel) & M. Dolores Lied62) 1) Department of Biology, Birkbeck College, University of London, Malet Street, London, WCIE 7HX, England; fax +44 171 631 6246, E-mail m.ingrouille@biology.bbk.ac.uk. 2) Department of Plant Sciences, University of Oxford, South Parks Rd., Oxford, OX1 3RB, England; fax +44 1865 275074, E-mail lola.lledo@plant-sciences.oxford.ac.uk Keywords: Apomixis, Hybridisation, Taxonomic hierarchy, Species concepts Abstract: Agamospermous species account for a large proportion of the species of Limonium. Agamospermy is indicated by uneven polyploidy or aneuploidy, low pollen stainability and by the presence of monomorphic self-incompatible populations. The taxonomic treatment of agamospermous taxa varies from recognition of all of them at the same specific rank or by utilising a range of ranks in the taxonomic hierarchy. The influence of evolutionary hypotheses on taxonomic systems is considered. Molecular data provide a means of measuring the genetical relationships of taxa and establishing groups in a taxonomic hierarchy. Introduction The genus Limonium MILL. has a world-wide distribution in temperate and subtropical regions on coasts and inland on salt-steppes. The centre of diversity of the genus is the Mediterranean region. BOISSIER (1848) produced the last comprehensive systematic treatment of the genus. Subsequently, other authors (BENTHAM & HOOKER 1873--1876, PAX 1897) have followed Boissier's arrangement in general with minor changes in rank. A large part of the diversity of the genus is due to the presence of agamospermy. All agamospermous species are found in three, rather poorly differentiated, subsections of the largest section Limonium: subsect. Densiflorae, subsect. Dissitiflorae and subsect. Steirocladae, all sensu BOISSmR (B AKER 195 3). Estimates of the number of species in the genus vary from 150 (ERBEN 1979) to 350 (KUBITZrd 1993). This wide range of estimates is due to the description of new taxa, mainly microspecies from geographically restricted areas. Most of these microspecies are probably agamospermous. The detection of agamospermy In the genus Limonium, the presence of agamospermy has often been suspected but has rarely been directly tested. HJELMQVIST & GRAZI (1964) and INGROUILLE (1982) reported diplospory followed by parthenogenesis in triploid and tetraploid agamospermous species of the L. binervosum (G.E. SM.) C.E. SALMONgroup. Normal seed production was reported from isolated male-sterile populations of the L. binervosum group species. In other species of Forum: Species concept in agamic and autogamic complexes