Foliose species of New Zealand red algae: diversity in the genusTsengia(Tsengiaceae, Halymeniales), includingT. northlandica sp. nov.

Identification of foliose red algae is particularly problematic as many of the characters used, such as general overall habit, colour, and texture, are often dependent on environmental or developmental characteristics of the specimen in question. One foliose red algal genus that has received little attention and is quite common in parts of New Zealand isTsengia. Collections of multiple foliose specimens ofTsengiafrom various locations and habitats in New Zealand have highlighted the wide morphological variation that exists within single species. Our molecular data clearly show three foliose species ofTsengia, two of which are associated with previous names (T. laingii, Nemastoma laciniatum) common in southern New Zealand, and one species described from this study,T. northlandica sp. nov., from northern New Zealand. The discovery of another foliose species ofTsengiain Stewart Island suggests greater diversity in this group that will only increase the difficulty in determining species from field collections. While these foliose species are distinct using various molecular species delimitation techniques, morphologically they are extremely diverse (plastic) with overlapping habits.