A global plastid phylogeny uncovers extensive cryptic speciation in the fern genus Hymenasplenium (Aspleniaceae).

The fern genus Hymenasplenium (Aspleniaceae) is one of the two genera in the family. It is generally recognized among modern pteridologists. However, its infrageneric relationships and species diversity have been unclear and controversial. The molecular studies so far have had small taxon and character sampling. In the present study, DNA sequences of six plastid markers of 158 accessions representing ca. 40 out of ca. 50 known species of Hymenasplenium, and 16 species of Asplenium were used to infer a phylogeny with maximum likelihood, Bayesian inference, and maximum parsimony approaches. Our major results include: (1) Hymenasplenium as currently defined is strongly supported as monophyletic; (2) three major clades representing early splits in Hymenasplenium are identified, with the Old World species being strongly supported as monophyletic; it is ambiguous if the New World species are monophyletic; (3) extensive cryptic speciation in the Old World is discovered demonstrating the complexity of evolution of the genus; and (4) six strongly or moderately supported subclades in the Old World clade are revealed, differing from one another in molecular, morphological, and geographical features.

Landform and lithospheric development contribute to the assembly of mountain floras in China.

Although it is well documented that mountains tend to exhibit high biodiversity, how geological processes affect the assemblage of montane floras is a matter of ongoing research. Here, we explore landform-specific differences among montane floras based on a dataset comprising 17,576 angiosperm species representing 140 Chinese mountain floras, which we define as the collection of all angiosperm species growing on a specific mountain. Our results show that igneous bedrock (granitic and karst-granitic landforms) is correlated with higher species richness and phylogenetic overdispersion, while the opposite is true for sedimentary bedrock (karst, Danxia, and desert landforms), which is correlated with phylogenetic clustering. Furthermore, we show that landform type was the primary determinant of the assembly of evolutionarily older species within floras, while climate was a greater determinant for younger species. Our study indicates that landform type not only affects montane species richness, but also contributes to the composition of montane floras. To explain the assembly and differentiation of mountain floras, we propose the 'floristic geo-lithology hypothesis', which highlights the role of bedrock and landform processes in montane floristic assembly and provides insights for future research on speciation, migration, and biodiversity in montane regions.