Invasive Species Trouble Spots: Tracking The Spread Of European Green Crabs In The Gulf Of Maine From An Upstream Retention Zone

Margaretsville Lighthouse, Nova Scotian shore of the Bay of Fundy. Sampling was completed on the intertidal below the lighthouse. Photo by A. Blakeslee.
Margaretsville Lighthouse, Nova Scotian shore of the Bay of Fundy. Sampling was completed on the intertidal below the lighthouse. Photo by A. Blakeslee.
Significance

Invasive species pose a significant threat to global biodiversity. The rate of their introduction is increasing. Understanding better the conditions that allow introductions to become established populations may prove critical for protecting biodiversity.

This project aims to test a universal theory regarding retention zones as they pertain to both genetic diversity in the coastal ocean and nonindigenous species invasion dynamics.

  • Funded by: Gulf of Maine Area Program
Project Summary:

Using the nonindigenous green crab Carcinus maenas as a case study, researchers will explore invasion dynamics and retention-zone theory by examining the geographic patterns of alleles.

Location:

Coastal region from Canadian Maritimes through the Gulf of Maine, 2007

Project Detail:

This project proposes to investigate a coastal phenomenon that has implications for both genetic diversity and invasive species. Previous work by Byers and Pringle (2006) established a relationship between larval settlement rates and mean advective flow. Basically, larvae must develop and settle at sufficiently quick rates that they avoid being washed out of a suitable habitat or a population will not be established. Alternatively, a persistent population can also be maintained if a source population exists upstream that can supply new recruits to a suitable habitat. This theory pertains to individual species, but can also apply to the existence of alleles within a species (Pringle and Wares, 2007).

Sampling location in Chance Harbor on the New Brunswick shore of the Bay of Fundy. Photo by A. Blakeslee.
Sampling location in Chance Harbor on the New Brunswick shore of the Bay of Fundy. Photo by A. Blakeslee.

Using the invasion by the European green crab (Carcinus maenas) that is currently underway in the Gulf of Maine, two predictions by Pringle and Wares (2007) will be evaluated. The first is that alleles may be lost due to heavy influx of alleles from an upstream source or retention zone. The second is that a strong gradient in selection or a break in alongshore larval transport is essential for geographic allele diversity to be maintained.

Collections were completed and genetic analysis has begun on approximately 20 young-of-year green crabs (Carcinus maenas) collected from 30 sites. Results will be compared with data from in 2002 to indicate the speed of movements (since 2000 and 2002) of a recently invaded haplotype (on the CO1 gene) from northern Nova Scotia across the Gulf of Maine. Changes in the genetic cline were detected in the first 2 years studied (Roman. 2006). Adding this analysis from 2007 will allow mapping of the spreading rate and population genetic influence of a cryptic invader.

Bibliography:
  • J. E. Byers and J. M. Pringle. 2006. Going against the flow: retention, range limits and invasions in advective environments. Marine Ecology-Progress Series 313:27-41.
  • J. Roman. 2006. Diluting the founder effect: cryptic invasions expand a marine invader’s range. Proceedings of the Royal Society B-Biological Sciences 273:2453-2459.
  • J. M. Pringle and J. Wares. 2007. Going against the flow: Maintenance of alongshore variation in allele frequency in a coastal ocean. Marine Ecology-Progress Series 335:69-84.