Last time around, we brought forth evidence against organismal “dumbness”—the notion that species found only in defined climatic environments will go extinct if the climate changes beyond their range. We picked on cute little Nemo, and “found,” much like in the animation, that his kind (Amphiprion ocellaris) could actually survive far beyond their somewhat circumscribed tropical reef climate.
The key was the notion of plasticity—the concept that, despite being linked to a fixed genetic compliment, or genotype, the products of those genes (the “phenotype”) changed along with the environment, allowing organisms some degree of insurance against climate change. How this comes about through evolution remains a mystery, though we may occasionally indulge in a bit of high speculation.
“Science,” according to the late, great philosopher Karl Popper, is comprised of theories that are capable of making what he called “difficult predictions.” The notion that gravity bends light would be one of those made by relativity, and it was shown to be true by Sir Arthur Eddington in the 1919 total solar eclipse. It just happened to be in totality in the Pleiades star cluster (also the corporate logo of Subaru), and, sure enough, the stars closest to the eclipsed sun’s limb apparently moved towards it when compared to their “normal” positions.
So we have been interested in a truly difficult test of phenotypic plasticity, and we think we found one.
How about a clam that lives in the bottom of the great Southern Ocean surrounding Antarctica? Specifically, the burrowing clam Laternula elliptica. According to a recent (2017) paper by Catherine Waller of the University of Hull (in the, perhaps temporarily, United Kingdom) “75 percent of the recorded specimens [of L. elliptica] are from localities shallower than 100 m,” where the populations are exposed to “low and stable water temperatures in the range of -1.9 to +1.8 °C” (the remaining 25 percent inhabit cooler waters of the continental slope down to ~700m).
Now let’s bring the critters into the lab and torture them with climate change. Experimental analyses revealed that this saltwater clam suffers “50 percent failure in essential biological activities at 2-3°C and complete loss of function at 5°C,” rendering L. elliptica a fine example of a dumb organism—or so it was thought!
During the austral summer of 2007, Waller et al. sampled the intertidal zone (region of the coast that is submerged at high tide, but above water and in the air at low tide) at locations along James Ross Island, East Antarctic Peninsula, writing that “prior to this study, there have been no reports of [L. elliptica] animals surviving the more variable environmental conditions of the littoral [intertidal] zone south of the Antarctic Circumpolar Current.” To their great surprise, however, they report finding specimens of this clam at densities “similar to many subtidal locations,” ranging in age from one to eight years.
In other words, if the depths of the Southern Ocean warmed several degrees, they would still be happy as clams!
Commenting on their findings, the five United Kingdom researchers state that “the presence of this species in intertidal sediments raises questions about their physiological tolerances and capacity to cope with warming sea temperatures.”
We respectfully disagree. It provides answers. Indeed, for at the time of their collection by Waller et al., temperatures within the sediment were measured at 7.5°C while air temperatures were even greater at 10°C—both values far above laboratory-defined tolerance limits! This discrepancy between laboratory and field temperature tolerances, in the words of the authors, “has major implications for our understanding and interpretation of the physiological tolerances of Antarctic shallow water marine organisms. If one of the best-studied model species can be found surviving far beyond its predicted environmental envelope, then our use [of] laboratory-based experimental results may underestimate the ability of polar organisms to cope with environmental change.”
And so it is that laboratory-based analyses showing negative impacts of rising temperatures on ostensibly dumb organisms should be taken with a large grain of salt, and we can be much more optimistic for their future survival.
This seems to be an important phenomenon, to say the least. So try searching for the words “phenotypic plasticity” in the entire 829-page 2014 U.S. “National Assessment” of the effects of global warming on our country. You won’t get one hit.
You will find one “plasticity” in a citation on Pacific Salmon. Here’s what the Assessment says:
Rising temperatures will increase disease and/or mortality in several iconic salmon species, especially for spring/summer Chinook and sockeye in the interior Columbia and Snake River basins.
And here’s what the actual paper says:
Climate change might produce conflicting selection pressures in different life stages, which will interact with plastic (i.e. nongenetic) changes in various ways. To clarify these interactions, we present a conceptual model of how changing environmental conditions shift phenotypic optima and, through plastic responses, phenotype distributions, affecting the force of selection. Our predictions are tentative because we lack data on the strength of selection, heritability, and ecological and genetic linkages among many of the traits discussed here. Despite the challenges involved in experimental manipulation of species with complex life histories, such research is essential for full appreciation of the biological effects of climate change.
The U.S. Global Change Research Program, which puts out these horrible Assessments, consumes $2.3 billion per year. Is that all you get for your money, a massive distortion of what a paper actually says?
Crozier, L.G. et al., 2008. Potential responses to climate change in organisms with complex life histories: evolution and plasticity in Pacific salmon. Evol Appl. 2008 May;1(2):252-70. doi: 10.1111/j.1752-4571.2008.00033.x.
Waller, C.L., Overall, A., Fitzcharles, E.M. and Griffiths, H. 2017. First report of Laternula elliptica in the Antarctic intertidal zone. Polar Biology 40: 227-230.