Rapid Physiological Responses of the European Green Crab to Rising Temperatures
Kelley, A.L., de Rivera, C.E. and Buckley, B.A. 2011. Intraspecific variation in thermotolerance and morphology of the invasive European green crab, Carcinus maenas, on the west coast of North America. Journal of Experimental Marine Biology and Ecology 409: 70-78.
Employing this approach in their study of the European green crab (Carcinus maenas), Kelley et al. measured the upper lethal thermal thresholds of two populations of the invasive species living at the southern and northern limits of its current range on the west coast of North America - Sea Drift Lagoon, Stinson Beach California (CA; 37°54'27.82"N) and Pipestem Inlet, Vancouver Island, British Columbia (BC; 49°02.3'N), which are separated from each other by 1200 km of coastline - where "ambient sea surface temperature in the northern part of the North American west coast range is 5 to 10°C lower, depending on the time of year, than near the southern range limit," and where the species expansion from its initial introduction at the south end of its range to its current northern end occurred over a period of only about twenty years. In doing so, the three U.S. scientists determined that the warm-adapted southern CA group of crabs had the highest level of organismal thermotolerance, as well as the greatest degree of heat shock protein 70 (Hsp70) production; and they additionally discovered that carapace widths of both male and female C. maenas individuals from CA were significantly smaller than those found in BC.
With respect to their findings, Kelley et al. say they "provide evidence that the northeastern Pacific population of C. maenas has incurred a shift in thermal tolerance compared to its southern counterpart," and that "thermal adaptation at the level of the phenotype is a likely cause due to the short timescale of the invasion and the genetic connectivity of the two populations." These observations thus enabled them to state - and with a good degree of confidence - that over a period of a mere two decades, "it is possible that a large, northern cold-water phenotype may have already arisen," which further suggests that the reverse of this phenomenon could also have occurred over the same length of time if the driving force for phenotypic change had arisen due to the crabs migrating from a cooler to a warmer environment, or - by further inference - that it could have occurred during a period of equivalent climatic warming in the same physical setting without any relocation occurring. Whatever the case may be, it is yet another example of a species demonstrating that it has the capacity to do what it needs to do to successfully cope with projected global warming, and without the need to migrate to accomplish it.
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