Chloroplast phylogeny of asplenioid ferns based on rbcL and trnL-F spacer sequences (Polypodiidae, Aspleniaceae) and its implications for biogeography

Abstract

Molecular phylogenies have been generated to investigate relationships among species and putative segregates in Asplenium, one of the largest genera in ferns. Of the ∼700 described taxa, 71 are included in a phylogenetic analysis using the chloroplast rbcL gene and trnL-F spacer. Our results support Hymenasplenium as the sister lineage to all other asplenioid ferns, and all other putative satellite genera are nested within this asplenioid clade. Instead of the classical and well-recognized separation into Old and New World clades, asplenioid ferns reveal a separation of the deeper branches into tropical and temperate clades. Temperate clades have evolved from tropical, more-basal clades and the phylogeny indicates up to six shifts between temperate and tropical preferences in the evolution of this widespread genus. Implications for speciation processes and biogeographic aspects, including the re-colonization of temperate regions after the last glacial period, are discussed and we present a phylogenetic framework from which the historical biogeography of asplenioid ferns can be inferred for Europe and North America.