title: A new delimitation of the Afro-Eurasian plant genus Althenia to include its Australasian relative, Lepilaena (Potamogetonaceae) - Evidence from DNA and morphological data.
abstract: Althenia (Potamogetonaceae) is an aquatic plant genus disjunctly distributed in the southern- (South Africa's Cape Floristic Region: CFR) and northern- (Mediterranean Eurasia) hemispheres. This genus and its Australasian relative, Lepilaena, share similar floral characters yet have been treated as different genera or sections of Althenia sensu lato (s.l.) due to the isolated geographic distribution as well as the differences in sex expression, stamen construction, and stigma morphology. The diagnostic characters, however, need reevaluation over the boundaries between the entities. Here we tested the taxonomic delimitation between the entities, assessed synapomorphies for evolutionary lineages, and inferred biogeographic history in a phylogenetic framework. Our results indicated that Lepilaena was resolved as non-monophyletic in both plastid DNA and nuclear PhyC trees and Althenia was nested within it. As Althenia has nomenclatural priority, we propose a new delimitation to recognize Althenia s.l., which can be diagnosed by the female flowers with 3-segmented perianths and male flowers with perianths. The previously used diagnostic characters are either autapomorphies or synapomorphies for small lineages within Althenia s.l., and evolutionary transitions to sessile female flowers and narrow leaves characterize larger clades. Biogeographic analyses suggested a Miocene origin of Althenia s.l. in Australasia and indicated at least one inter- and one intra-specific inter-continental dispersal events among Australasia, Mediterranean Eurasia, and CFR need to be hypothesized to explain the current distribution patterns.
authors.affiliation: School of Biological Sciences, University of Canterbury, Christchurch 8020, New Zealand. Electronic address: yu.ito@xtbg.ac.cn.
authors.forename: Yu
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Tsukuba Botanical Garden, National Museum of Nature and Science, Tsukuba 305-0005, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Vegetal Biology and Ecology, Faculty of Pharmacy, University of Seville, Seville E-41012, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: García-Murillo
authors.affiliation: Department of Biological Sciences, University of Cape Town, Rondebosch 7701, South Africa.
authors.forename: A Muthama
authors.initials: AM
authors.lastname: Muasya
mesh_terms: D001208:Asia; D044362:Australasia; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D005060:Europe; D019083:Mediterranean Region; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D031821:Potamogetonaceae / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013019:South Africa
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant
keywords: Ancestral state reconstruction; Biogeography; Disjunct distribution; Molecular dating; Monocots; Taxonomy