The Return of Aquatic Vascular Plants into the Great Lakes Region after Late-Wisconsin Glaciation

Abstract

This paper traces the recolonization by selected aquatic vascular plants into the Great Lakes region after late-Wisconsin glaciation. The currently widespread genera, Myriophyllum, Nymphaea, Nuphar, Potamogeton, Sagittaria and Typha were chosen because they are most frequently recorded in pollen diagrams. The movements of these genera were inferred by obtaining published pollen diagrams in which these genera were recorded. Only those records were used which were radiocarbon dated or based on inferences from other sources which had been radiocarbon dated. The total number of pollen profiles deamed useful in the literature is about 32; but, unfortunately, most of them are from the eastern half of the United States. By plotting first occurrence data of the various genera, a time and location sequence was established for each. In general, the earliest records of most of these genera are from the Carolina-Virginia region. This may represent the southernmost extension of these genera during late-Wisconsin time. These genera are well documented next in the Massachusetts region. Then their distribution appears to spread out into Nova Scotia, Quebec, and the Great Lakes region. It appears that the Appalachian Mountains were an important barrier to the recolonization of glaciated areas by aquatic vascular plants in eastern United States. Since so few pollen diagrams exist from western United States, it is difficult to define the western or southwestern contribution to recolonization. A southern migration route in the Mississippi valley may be plausible. With additional pollen records and more complete dating of pollen diagrams, a better understanding of the movements of aquatic vascular plants may be obtainable.