Molecular Phylogenetics and the Evolution of Morphological Complexity in Aytoniaceae (Marchantiophyta).

Aytoniaceae are one of the largest families of complex thalloid liverworts (Marchantiopsida), consisting of about 70 species, with most species being distributed in temperate areas. However, the phylogeny and evolution of the morphological character of Aytoniaceae are still poorly understood. Here, we employed two chloroplast loci, specifically, L and L-F, along with a 26S nuclear ribosomal sequence to reconstruct the phylogeny and track the morphological evolution of Aytoniaceae. Our results reveal that Aytoniaceae are monophyletic, and five monophyletic clades were recovered (i.e., -, , , - and ). was divided into five clades (i.e., , subg. , subg. , subg. and subg. ), except for which is the sister of . Bayesian molecular clock dating indicates that the five primary clades within Aytoniaceae underwent divergence events in the Cretaceous period. differentiated during the early Upper Cretaceous (c. 84.2 Ma), and originated from the late Lower Cretaceous (c. 143.0 Ma). The ancestral Aytoniaceae plant is reconstructed as the absence of a pseudoperianth, lacking equatorial apertures, and having both male and female reproductive organs on the main thallus. At present, consists of two species known in Asia and America with the new transfer of to A new subgenus, subg. , is proposed.