A floristic survey of the genus Micrasterias in northern Michigan.

Abstract

This is a brief floristic survey of Micrasterias species in ten habitats near Douglas Lake in Northern Lower Michigan and several habitats in the eastern portion of Michigan? Upper Peninsula. Northern Lower Michigan and the Upper Peninsula are home to a great variety of wetland habitats. These habitats support a rich diversity of desmids, both in numbers of individuals and species. As a general rule, high desmid diversity is found in habitats with neutral to low pH, thus bogs and fens were chosen as sample sites typically have a pH around 4, while fens can range from a pH of 4 up to as high as 7.5 (Crum, 1992). Previous surveys have revealed a prolific diversity of desmid species native to northern Michigan (Nichols 1931, Prescott 1935). Nichols and Ackley contributed a list of 325 species and varieties of desmids in 1932. Prescott and Magnotta, in a 1935 survey which included only four habitats, were able to contribute an additional 46 species and varieties of desmids to this list. Micrasterias is a genus of the Family Desmidiaceae in the Order Zygnematales. The basic cell design consists of relatively flat cells exhibiting bilateral and bipolar symmetry. The cell is divided by a deep median sinus into two semicells. The semicells are again divided into 3 lobes, one polar lobe and two lateral lobes. The polar lobe is the most conservative feature of the cell and is often key to species identification (Prescott, 1977). Micrasterias is one of the most aesthetically pleasing of the desmids, most cells being relatively large and displaying a wide variety of geometric variations on the basic cell design.