The decline of Myriophyllum spicatum in a eutrophic Wisconsin lake

Abstract

The recent changes in the submersed macrophyte communities of Lake Wingra, Wisconsin, have been dominated by the dynamics of one exotic species. After a decade of abundance, Myriophyllum spicatum has undergone a sustained decline in the Madison lakes. A pattern of explosive growth followed by declining abundance may describe most M. spicatum invasions.No simple single-factor explanation can adequately account for the biomass dynamics of M. spicatum in Lake Wingra. The decline in M. spicatum biomass appears to be the result of a complex of synergistically interacting factors, perhaps including nutrients, epiphytes, competitors, and parasites or pathogens.Invasions of lake districts by M. spicatum are hypothesized to follow a wave pattern. When interlake distances are accounted for, departure from a simple wave is hypothesized to result from lags in infestation of lakes which are not susceptible to colonization by M. spicatum. Several testable hypotheses are suggested by this view of M. spicatum invasions.