Testing hypotheses on species delimitations and disjunctions in the liverwort Bryopteris (Jungermanniopsida : Lejeuneaceae)

Abstract

Nucleoticle sequence variation in the ITS1-5.8S-ITS2 region of nuclear ribosomal DNA and in the trnL-trnF region of chloroplast DNA from 49 specimens of Bryopteris (Lejeuneaceae) and three outgroup species was analyzed using maximum parsimony and maximum likelihood. The nrITS region exhibits high levels of nucleotide variation, whereas the trnL-trnF region is fairly similar among samples of the same species. Three major clades were found corresponding to the Neotropical species Bryopteris diffusa and Bryopteris filicina, as well as Bryopteris gaudichaudii from the Malagasy region. Morphological characters utilized in earlier studies to distinguish five microspecies within B. filicina are diffusely distributed in the molecular topologies and do not trace monophyletic lineages. The nrlTS signal suggests a separation into two biogeographically defined B. filicina clades-one mainly Andean clade and one mainly northern Neotropical clade-but these clades lack statisticat support. The two clades can possibly be explained by the hypothesis that the nrITS signal reflects a former disjunct range of B. filicina with a few subsequent dispersal events. Bryopteris gaudichaudii is resolved as sister of B. filicina; these species are in turn sister to B. diffusa. Clocklike evolution of nr1TS1 and 2 and nrITS sequence divergence estimates from the literature allow for a rough estimation of the divergence time of Bryopteris, indicating a separation of B. gaudichaudii from B. filicina in the Miocene, separation of B. diffusa in the Early Tertiary, and an emergence of Bryopteris in the Cretaceous. The African-American range of Bryopteris is not the result of vicariance but of dispersal.