Three new members of the green algal family Prasiolaceae (Prasiolales, Trebouxiophyceae) isolated from urban sites in Northern Germany

The Prasiolaceae is a small family of mainly sub-aerial multicellular green algae that is well known for the preference of its members for nutrient-enriched environments. In central and northwestern European cities with humid climate, for example, species of the largest genus <i>Prasiola</i> commonly occur at sites where dogs urinate, such as at street corners or bases of trees. The present study reports three minute new species in two new genera of the family Prasiolaceae discovered in cultures of material collected from nutrient-enriched urban sites in Northern Germany. Morphological and DNA sequence data based on plastid markers support the separation of <i>Prasibo cubiformis</i> gen. et sp. nov. <i>Prasiolotta rindii</i> gen. et sp. nov. and <i>Prasiolotta hercynia</i> sp. nov. from currently known genera and species of the Prasiolaceae. Mature thalli of <i>Prasiolotta</i> species can be distinguished from those of other members of the family by their irregular shape, comprising uni- to multiseriate filaments and small fan-shaped sections, with <i>Prasiolotta rindii</i> having slightly smaller cells than <i>Prasiolotta hercynia</i>. Young thalli of <i>Prasibo cubiformis</i> resembled tiny green gummy bear sweets, while developed ones comprised short filaments consisting of multiseriate cell packages. The multiseriate filaments occuring in both new genera may lead to confusion with the closely related genus <i>Prasiolopsis</i>, suggesting that for the correct identification of the smaller members of the Prasiolaceae, genetic data are essential. This study suggests that our knowledge of the diversity of terrestrial algae is still very incomplete, and that urban habitats may be a source of unexpected discoveries. New genera and species of Prasiolaceae were discovered in cultures.The cryptic diversity of green algal films is underestimated.Urban habitats remain a major repository of new taxa. New genera and species of Prasiolaceae were discovered in cultures. The cryptic diversity of green algal films is underestimated. Urban habitats remain a major repository of new taxa.