Phylogeny, chronology, and phylogeography in Australasian Hypnodendraceae

The Hypnodendrales form the sister group to all other pleurcarpous mosses in the superorder Hypnanae. Many species are closely associated with the cool temperate rainforests of Australasia, while others are widespread in higher altitude wet forests across tropical South-East Asia. Several of the Malesian entities are taxonomically ambiguous, having been variously treated as species complexes or as single very variable species. Here we use dated phylogenies to examine the timing of diversification of major clades within the Hypnodendrales, test the hypothesis that widespread, taxonomically problematic species have diversified relatively recently in South-East Asia from within clades of southern temperate origin, and address taxonomic questions within Hypnodendron. A chronogram with broad taxonomic sampling is constructed, followed by a second dated phylogeny with dense sampling from Hypnodendron vitiense, a representative morphologically variable species found throughout Eastern Australia and South-East Asia. The crown group Hypnodendrales are found to have originated in the mid-Cretaceous, although they share a Most Recent Common Ancestor (MRCA) with the other Hypnanae in the late Jurassic. Extant members of Hypnodendron share a MRCA ±28 Mya, a little before the start of the collision of Australia with the Sunda plate that initiated the Australasian–Malesian floristic interchange. Within H. vitiense, there is strong phylogenetic structure consistent with the diversification and isolation of populations in South-East Asia within the last 10 Mya. The New Zealand endemic H. marginatum is found to be derived from within an Australasian clade of H. vitiense, this in turn being distinct from a South-East Asian/tropical Australian H. vitiense clade. Our results suggest that the phylogeography of this prominent group of mosses closely mirrors that of the rainforest ecosystems of which they are a part.