Diversity of Coccoid Algae in Minnesota and North Dakota Lakes

The coccoid algae (a.k.a ‘little green balls’) are important primary producers in freshwater communities, but very little is known about their diversity. This lack of knowledge results from the extremely small size and simple morphology of these organisms, which makes identification by light microscopy essentially impossible. However, molecular techniques allow differentiation of taxa at various levels and can ultimately lead to species identification. We have isolated several hundred cultures of coccoid algae from lakes and ponds in Itasca State Park in north‐western Minnesota and Arrowwood National Wildlife Refuge in central North Dakota. Many of these isolates have been examined by light microscopy, 18S rDNA PCR–RFLP analysis, and 18S rDNA sequence analysis. In addition, some taxa with multiple isolates have been examined by rbcL and ribosomal RNA ITS sequence analysis. Our results indicate a high level of diversity, including possible new species of Chlorella, Muriella, Pseudomuriella and Mychonastes, among others. We will discuss the results of our analyses, including implications for identification of taxa and higher level systematics. Supported by National Science Foundation Grants DBI‐00703867, MCB‐0084188 and DEB‐0128952.