title: Morphology informed by phylogeny reveals unexpected patterns of species differentiation in the aquatic moss Rhynchostegium riparioides s.l.
abstract: Bryophyte floras typically exhibit extremely low levels of endemism. The interpretation, that this might reflect taxonomic shortcomings, is tested here for the Macaronesian flora, using the moss species complex of Rhynchostegium riparioides as a model. The deep polyphyly of R. riparioides across its distribution range reveals active differentiation that better corresponds to geographic than morphological differences. Morphometric analyses are, in fact, blurred by a size gradient that accounts for 80% of the variation observed among gametophytic traits. The lack of endemic diversification observed in R. riparioides in Macaronesia weakens the idea that the low rates of endemism observed in the Macaronesian bryophyte flora might solely be explained by taxonomic shortcomings. To the reverse, the striking polyphyly of North American and European lineages of R. riparioides suggests that the similarity between the floras of these continents has been over-emphasized. Discriminant analyses point to the existence of morphological discontinuities among the lineages resolved by the molecular phylogeny. The global rate of error associated to species identification based on morphology (0.23) indicates, however, that intergradation of shape and size characters among species in the group challenges their identification.
authors.affiliation: Institut de Botanique, Université de Liège, B22 Sart Tilman, B-4000 Liège 1, Belgium. vhutsemekers@ulg.ac.be
authors.forename: Virginie
authors.initials: V
authors.lastname: Hutsemékers
authors.forename: Cristiana C
authors.initials: CC
authors.lastname: Vieira
authors.forename: Rosa María
authors.initials: RM
authors.lastname: Ros
authors.forename: Sanna
authors.initials: S
authors.lastname: Huttunen
authors.forename: Alain
authors.initials: A
authors.lastname: Vanderpoorten
mesh_terms: D059001:Aquatic Organisms; D001208:Asia; D005075:Biological Evolution; D044002:Bryophyta / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics*; D004275:DNA, Ribosomal / Q000235:genetics*; D005060:Europe; D049810:Genetic Speciation; D014644:Genetic Variation; D008390:Markov Chains; D009010:Monte Carlo Method; D009656:North America; D010802:Phylogeny; D058974:Phylogeography; D013045:Species Specificity
chemical_list: D004275:DNA, Ribosomal