Interdisciplinary Seminar: Maxwell Tice-Lewis

An interdisciplinary seminar presented by UNC-CH Department of Marine Sciences graduate student, Maxwell Tice-Lewis.

Seminar Title: When invasion becomes range expansion: Carcinus maenas on the Pacific coast of North America

Abstract: Biological invasions are a leading cause of global biodiversity decline and result in substantial economic costs. In the last century, improvements in transoceanic shipping have mediated exponential increases in marine invasions worldwide through ballast water transport of larvae. Following the initial invasion, introduced species may subsequently spread and expand their ranges altering biological community structure and natural resources over biogeographic provincial scales. In 1989, European green crabs (Carcinus maenas) had invaded portions of San Francisco Bay, the most invaded estuary on Earth. C. maenas is a model organism in a model system through which to view marine invasion and range expansion­­– it is adaptable to a wide range of abiotic conditions, is a habitat and resource generalist, and is readily able to disperse via utilization of natural wind and density-driven oceanic currents. In 1997-1998, a combination of seasonal current patterns characteristic to the California Current System, augmented by ENSO strengthening of northward currents and a warm, positive Pacific Decadal Oscillation phase facilitated range expansion of the initial SF Bay C. maenas population into Oregon, Washington and British Columbia. Dispersal and population growth in the expanded range has followed during subsequent positive ENSO and PDO years, which contribute to increased water temperatures extending longer into the spring months. Understanding the underlying mechanisms driving this marine invasion and range expansion offers insights for predicting and preparing for invasions by nonnative species with similar traits.