Comparing Ecology & Demography of Benthic Species in their Native and Introduced Ranges
Our ability to predict the ecological effects of invading species requires that we understand population-level changes that take place during invasions. By comparing the a demographic response variable, such as size-specific fecundity, reproductive schedule, density, or body size of the same species inside and outside its native range, the performance of the species can be evalutated. I am currently using such an approach with a variety of benthic organisms to determine whether demographic measures taken from native regions are predictive of what occurs after invasion.
Littorina saxatilis: We currently are measuring the genetic and demographic changes associated with a recent invasion of the rough periwinkle Littorina saxatilis (Olivi, 1792) by comparing newly colonized populations in San Francisco Bay to populations in its native range and source locality.
Snail census:
Gastropods provide a good model system for examining invasion processes, as gastropod invasions have been common and often resulted in significant ecological impacts. A good example is the periwinkle Littorina littorea that invaded the Western Atlantic shores of North America during the late 1800s to middle 1900s. A close relative of L. saxatilis, L. littorea now dominates many intertidal communities from Nova Scotia to Delaware, where it has significantly altered the physical habitat (Bertness 1984) and produced dramatic shifts in algal diversity patterns in New England (Lubchenco 1978). We believe L. saxatilis has a similar potential for widespread impacts in the San Francisco Bay ecosystem and elsewhere on the West Coast.
At present, in conjunction with NOAA, we are undertaking a pilot
program to determine whether local populations of Littorina saxatilis can
be eradicated from specific areas in San Francisco Bay. Additionally, we
are conducting a bay-wide survey to determine the extent and relative abundance
of this exotic snail in San Francisco Bay.
Heat treatment being applied to a sample plot:
After Heating:
