Восточно-азиатская – восточно-североамериканская дизъюнкция в видовом комплексе Onoclea sensibilis: викариантность или перипатрия?

Abstract

Disjunction between East Asian and eastern North American plants has been recognized since the time of Darwin. Although there is considerable evidence for congruent vicariance associated with late Neogene/Quaternary cooling among angiosperms, similar studies among specific fern families (e.g., Osmundaceae Martinov) have appeared incongruous with this pattern. Pteridologists continue to debate whether long-distance dispersal of wind-blown spores could have produced intercontinental disjunctions among ferns. To date, however, state-of-the-art historical biogeographical approaches have not been applied to this problem. In this investigation, multiple chloroplast gene (rbcL, atpA, atpB, and matK) sequences for ferns in the family Onocleaceae Pic. Serm. are drawn from GenBank, including those from the recently sequenced chloroplast genome of the East Asian fern O. sensibilis L. var. interrupta Maxim., and used to create molecular phylogenies using Bayesian (BEAUTi and BEAST) techniques. Using contemporary approaches for relaxed molecular clock divergence time estimation with fossil calibration, divergence time estimates for East Asian and eastern North American populations in the Onoclea sensibilis species complex are consistently reconstructed as the Pliocene (ca. 5 – 3.4 Ma), and the best-fitting historical biogeographic model is a DIVA-like (exclusively vicariant) model using BIOGEOBEARS in RASP4, with a low probability of peripatry. Accordingly, these molecular and fossil data appear congruent with the pattern observed among angiosperms, despite the propensity for long-distance dispersal of wind-blown spores in pteridophytes. The lack of evidence for peripatry in this lineage may be related to the presence of short-lived green spores in onocleoid ferns; however, this hypothesis requires further investigation.