Increase in density of genetically diverse invasive Asian shore crab (Hemigrapsus sanguineus) populations in the Gulf of Maine

Abstract

Hemigrapsus sanguineus, the Asian shore crab, has rapidly replaced Carcinus maenas, the green crab, as the most abundant crab on rocky shores in the northwest Atlantic since its introduction to the United States (USA) in 1988. The northern edge of this progressing invasion is the Gulf of Maine, where Asian shore crabs are only abundant in the south. We compared H. sanguineus population densities to those from published 2005 surveys and quantified genetic variation using the cytochrome c oxidase subunit I gene. We found that the range of H. sanguineus had extended northward since 2005, that population density had increased substantially (at least 10-fold at all sites), and that Asian shore crabs had become the dominant intertidal crab species in New Hampshire and southern Maine. Despite the significant increase in population density of H. sanguineus, populations only increased by a factor of 14 in Maine compared to 70 in southern New England, possibly due to cooler temperatures in the Gulf of Maine. Genetically, populations were predominantly composed of a single haplotype of Japanese, Korean, or Taiwanese origin, although an additional seven haplotypes were found. Six of these haplotypes were of Asian origin, while two are newly described. Large increases in population sizes of genetically diverse individuals in Maine will likely have a large ecological impact, causing a reduction in populations of mussels, barnacles, snails, and other crabs, similar to what has occurred at southern sites with large populations of this invasive crab species.

Exploring larval phenology as predictor for range expansion in an invasive species

“…The application of WLR for the range distribution in N America was validated by the fact that the duration of development for our local population matched that obtained for a population from N America (Epifanio et al ). In consistence with hypotheses made in previous studies (Stephenson et al , Lord and Williams ), WLR correctly predicted the limits of distribution in N America. Both the sharp limits observed in the distribution of H. sanguineus and predicted by WLR coincide with a strong temperature gradient in the Gulf of Maine in summer (Kolber et al ).…”

“…In addition, range limits in both North American populations and those in the native range (east Asia) correlate with similar minimum summer temperatures (Stephenson et al ). Both introductions are recent and gene flow maintained by larval dispersal may currently limit the capacity of H. sanguineus to evolve larval thermal tolerance; indeed, little genetic spatial difference and high gene flow have been found for the North American populations (Lord and Williams ). This is consistent with the fact that evidence of local adaptation is less common in marine than in terrestrial species (Sunday et al ).…”

“…Predictions for North America were carried out to address the first objective, i.e. to determine if WLR would correctly predict the northern distribution limit for a region where population range expansion has been monitored and is known with high spatial detail (Stephenson et al , Lord and Williams ). Validation was carried out by visual check of the match between model predictions and observations of range limit and by correlations of observed crab densities (Lord and Williams ) and values of WLR.…”

Mechanisms of possible self-limitation in the invasive Asian shore crab Hemigrapsus sanguineus

“…On the North American east coast, H. sanguineus was first noted in 1988 in Cape May, New Jersey 24 , where it was most likely introduced via ballast water, perhaps multiple times 26 . Over the next few years it rapidly spread from mid-coast Maine to North Carolina 26 , where H. sanguineus displaced other species of crabs 27 , 28 and became the numerically dominant crab species over much of this range 29 , 30 . High densities of 100–200 individuals m -2 have been documented throughout much of its range 28 , 31 – 33 .…”

Temporal dynamics of genetic clines of invasive European green crab (Carcinus maenas) in eastern North America

“…In addition, the anthropogenic transport of individuals via ship traffic and other anthropogenic vectors (e.g., see Blakeslee et al., ; Cohen, Carlton, & Fountain, ; Fowler et al., ) could also influence the future distribution and population structure of C. maenas . It also remains unclear how C. maenas distributions could be influenced by competition with the more recent invader the Asian shore crab ( Hemigrapsus sanguineus ) (Lord & Williams, ). Altogether, several factors may contribute to ongoing changes in spatial genetic structure, and given the reported differences in behaviour, physiology and reproduction between C. maenas from different regions (Best et al., ; Rossong et al., ; Tepolt & Somero, ), temporal genetic sampling over 5‐ to 10‐year intervals should be implemented to monitor these potential changes and help facilitate more appropriate management strategies.…”