© 2014, Springer-Verlag Wien. The variation and evolutionary dynamics of the twin hairs covering the achenes of the external female florets in Filago and related genera are studied using scanning electron microscope (SEM) and a Bayesian reconstruction of ancestral character states. A molecular phylogenetic hypothesis based on sequences of ITS and ETS (nuclear ribosomal DNA) and plastid rpl32-trnL intergenic spacer regions was used as a framework to test the phylogenetic, evolutionary and taxonomic significance of this character in the study group. The phylogenetic position of three island-endemic species (F. petro-ianii, F. tyrrhenica and F. wagenitziana) is explored. Three types of twin hairs are described, which alone or combined define five different types of indumentum. The results suggest that glabrous achenes are the ancestral condition for “Filago group s.str.”, while the presence of long-clavate twin hairs on the achene represents the ancestral character state for the genus Filago. Several cases of parallelisms are detected. With regard to taxonomy, twin hairs provide additional support for the recognition of Bombycilaena and Logfia at the generic level and allow the taxonomic re-evaluation of F. lutescens subsp. atlantica and F. crocidion. Finally, the utility of a Bayesian Binary MCMC approach (using the software RASP) for evolutionary reconstruction of morphological characters is demonstrated.
- Evolution of twin hairs