Nitellopsis obtusa (Desv.) J. Groves, 1919 (Charophyta: Characeae): new records from southern Michigan, USA with notes on environmental parameters known to influence its distribution

Starry stonewort, Nitellopsis obtusa (Desv.) J. Groves, 1919, is deemed an invasive aquatic macroalga in North America where there is considerable concern about the impact of this species on lake ecology. During floristic inventories to characterize charophyte diversity in Michigan, we documented the occurrence of N. obtusa from seven inland lakes, confirming the expansion of this species into Cass and Van Buren Counties in the southwestern region of the state. We provide a description of the species along with morphological characters that distinguish it from other genera in the Characeae. Detailed voucher specimen information, including aquatic vascular plant associates, substrate type, pH, total alkalinity, and water depth, is presented for each collection site. Modes of dispersal and habitat parameters known to influence the distribution of N. obtusa are considered.