Morphological evolution of eupolypod II ferns

Patterns of evolution of fern morphology have long puzzled biologists. Sundue and Rothfels analyse the morphological evolution in the eupolypod II ferns, a clade that comprises approximately a third of extant fern species. Their results indicate that the historic difficulties in classifying these ferns have been due to a combination of evolutionary stasis, with disparate groups appearing to be closely related due to shared ancestral morphologies, and evolutionary convergence, with the repeated evolution of similar features. They find a general congruence of morphological and molecular data and present a revised understanding of sorus evolution. In addition, a chromosome base number of x = 41 is determined to be ancestral for eupolypods, with the eupolypods II characterized by subsequent repeated genome size reductions.