Smith Lecture: Invasive Species, Mass Extinction, and Speciation: How Biogeography Impacts the History of Life
Invasive species, such as zebra mussels and kudzu, cause billions of dollars' worth of economic damage in America each year. These species include organisms that proliferate in environments outside their ancestral range following introduction by humans. Biologists are intensively studying the impacts of the invaders on native ecosystems, but they are limited to studies of years or decades. Species invasions, however, also happened in the geologic past due to natural causes, such as intervals of sea level rise. Paleontologists can study these ancient invasions to learn about the longer term (thousands of years) impacts of invasive species. In this presentation, I will analyze the impacts the invasive species have had during two different intervals in the geologic past: the Late Devonian mass extinction and the Late Ordovician Richmondian Invasion. During both of these intervals, the shallow seas that covered eastern North America experienced waves of interbasinal species invasions. The Late Devonian invasions triggered one of the largest biodiversity crises in Earth's history, primarily by stopping the formation of new species. Invasive species were a key factor in depressing speciation. The Richmondian Invasion resulted in fundamental changes to ecosystem structure. Speciation depression and niche evolution both occurred coincident with this regional invasion. The relative roles of invasive species in driving biodiversity change during these two intervals will be examined and then linked with the potential long-term impacts of modern invasive species.