Biological invasions result in major shifts in the geographic distributions of species and species assemblages. Invasions have occurred since life began on Earth. However, in recent time, the temporal and spatial pattern of invasions has changed dramatically, driven largely by human transfers (see Vector Ecology).

Our research explores the biogeography of marine organisms from several vantage points, with particular emphasis on bays and estuaries:

• Patterns of biological invasions. Several aspects of our research measure invasion patterns. Intensive surveys of marine fouling communities provide standardized, contemporary measures of non-native species diversity across sites and over time. Synthesis of cumulative records from a diverse range of sources, including literature and museum collections, provide historical information on invasions that resides in several database resources.
   
• Range limits of native and non-native species. We explore what sets the range limits for contiguous populations, along a coastline. Our research is designed to (a) characterize the distribution of both native and non-native populations, (b) test hypotheses about factors that limit distribution and spread, and (c) develop predictions about the potential and realized range of species. A major focus of this work is on non-native populations, but we are also interested in comparisons between native and non-native populations.
   
• Spatial patterns of diversity. Our research also examines patterns of diversity across latitudes, ocean basins, and various other geographic scales. We are focusing on patterns of alpha and beta diversity, as well as functional group diversity, partitioning the relative effects of native and non-native components to the overall patterns.