New records of Spirogyra and Zygnema (Charophyceae, chlorophyta) in New Zealand

Filamentous zygnematalean algae frequently dominate periphyton assemblages in New Zealand streams, yet only 10 reliable species records of the most common genera, Spirogyra and Zygnema, exist. One of these species, S. clavata, was found again in a new survey of stream habitats, mainly in the South Island. Ten further species (nine of Spirogyra and one of Zygnema) are also described and identified. Morphology and interfertility are affected by polyploid series in Spirogyra, making current species concepts unsatisfactory. Identifications in this study emphasise zygospore ornamentation, which is the most stable and conserved character known.