Molecular support for Pleistocene persistence of the continental Antarctic moss Bryum argenteum

Abstract

We examined sequence variation of ITS and phy2 for Bryum argenteum from Antarctica, sub-Antarctic, New Zealand and Australia to understand better taxonomic delimitations and resolve relationships between these geographic regions. Bryum argenteum has been recorded as two species, B. argenteum and B. subrotundifolium, in all four regions with the latter now referred to as B. argenteum var. muticum. We found disagreement between taxon delimitations (based on morphology) and molecular markers. All continental Antarctic specimens consistently formed a monophyletic sister group that consisted of both morphologically identified B. argenteum varieties, separate to all non-Antarctic specimens (also consisting of both varieties). We suggest, contrary to previous records, that all continental Antarctic (Victoria Land) populations are referable to B. argenteum var. muticum, while sub-Antarctic, Australian and New Zealand populations included here are B. argenteum var. argenteum. Additionally, since there was less genetic diversity within Victoria Land, Antarctica, than observed between non-Antarctic samples, we suggest that this is, in part, due to a potentially lower rate of DNA substitution and isolation in northern and southern refugia within Victoria Land since the Pleistocene.