Molecular phylogenetics and generic taxonomy of Blechnaceae ferns

The fern family Blechnaceae is cosmopolitan; however, the vast majority of species are placed in Blechnum, which occurs predominantly in the Southern Hemisphere. There are two areas that are particularly species-rich: the south-west Pacific (including Australasia), and Central and South America. Using chloroplast DNA sequences, we report the first comprehensive phylogenetic analysis of the Blechnaceae, including all genera widely recognised in recent treatments, and over half of the species. There is strong support for several major clades, which we characterise morphologically and geographically, and some of their interrelationships. Blechnum is confirmed as polyphyletic. Blechnum indicum and B. serrulatum are more closely related to Salpichlaena and Stenochlaena, and are segregated as a new genus, Telmatoblechnum. Alternative generic circumscriptions are discussed for the remainder of Blechnum: In the absence of morphological characters to diagnose the clades within core Blechnum, and for the sake of taxonomic stability, we advocate a broad circumscription for Blechnum. Brainea and Sadleria are retained as their relationships are not well resolved, but Doodia and Pteridoblechnum are clearly nested within the core of Blechnum and we provide four new names in Blechnum. Additionally, given the focus of our sampling, we discuss the biogeography of the south-west Pacific, where immigration has been more important in community assembly than what might be superficially inferred from patterns of endemism (with ca. 60% of species endemic to individual land areas).