Update on the Holantarctic Sphagnum ×falcatulum s.l. (Sphagnaceae) complex: S. irritans is associated with the allo-diploid plants

Abstract

The Holantarctic Sphagnum ×falcatulum s.l. is a cryptic species complex comprised of the allo-allo-triploid S. ×falcatulum s.s. and its immediate progenitors: the haploid (S. cuspidatum) and an unnamed allo-diploid species. The Holantarctic distributions of the members of this complex are presently unclear. Prior genetic study has shown that (1) amphi-Pacific S. ×falcatulum s.s. is the most widespread Sphagna in the Holantarctic, (2) S. cuspidatum is present in Queensland, Australia, and (3) the allo-diploid plants occur on South Island, New Zealand. Using genetic and morphological analyses, we document the occurrence of S. ×falcatulum s.s. on mainland Australia and on North Island, New Zealand as well as the occurrence of the allo-diploid plants on Chatham Island, New Zealand. The allo-diploid plants on South Island and those on Chatham Island are found to be closely related and the Chatham Island population appears to have been established by long distance dispersal. It is concluded that the type of S. irritans, which was collected on Chatham Island, and the three Chatham Island allo-diploid specimens are the same taxon. Thus the allo-diploid plants are assigned to S. ×irritans. Having a history of inter-subgeneric hybridisation, there is notable morphological variation associated with S. ×irritans. Although several morphotypes occur in the South Island population, just one morphotype was detected among the Chatham Island specimens examined. Further study is required to determine both the genetic divergence between these two island populations as well as the taxonomic status of the various morphotypes associated with S. ×irritans.