Earth & Environment - Posted by Andy Fell-UC Davis on Wednesday, June 22, 2011 9:05 - 3 Comments 
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Copepods, tiny shrimplike creatures, and other animals and plants are having a hard time keeping up with increasing temperatures brought on by global warming. (Credit: Morgan Kelly)
UC DAVIS (US) — Climate change is leaving animals and plants little wiggle room, pushing them to the edge of their heat tolerance level.
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A new study, published in the journal Proceedings of the Royal Society B, tracks the struggle for survival of the tiny tide pool copepod, Tigriopus californicus, that has shown little ability to evolve tolerance to increased heat.
The shrimplike animals are about a millimeter long and live in tide pools on rocky outcrops high in the splash zone from Alaska to Baja California.
“This is a question a lot of scientists have been talking about,” says Eric Sanford, associate professor of evolution and ecology at the University of California, Davis. “Do organisms have the ability to adapt to climate change on a timescale of decades?”
Graduate student Morgan Kelly, the first author of the paper, collected copepods from eight locations between Oregon and Baja California and grew them in the lab for 10 generations, subjecting them to increased heat stress to select for more heat-tolerant animals.
At the outset, copepods from different locations showed wide variability in heat tolerance. But within those populations, Kelly was able to coax only about a half-degree Celsius (about one degree Fahrenheit) of increased heat tolerance over 10 generations. In most groups, the increase in heat tolerance had hit a plateau before that point.
In the wild, copepods can withstand a temperature swing of 20 degrees Celsius a day.
Although copepods are widespread geographically, individual populations are very isolated, confined to a single rocky outcrop where wave splash can carry them between pools—meaning there is very little flow of new genes across the population as a whole.
“It’s been assumed that widespread species have a lot of genetic capacity to work with, but this study shows that may not be so,” says Rick Grosberg, professor of evolution and ecology.
Many other species of animals, birds and plants face stress from climate change, and their habitats have also been fragmented by human activity—perhaps more than we realize, he says.
“The critical point is that many organisms are already at their environmental limits, and natural selection won’t necessarily rescue them.”
The study was funded by the National Science Foundation.
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3 Comments
Angelo DePalma
Of course many organisms are at their environmental limits. They are adapted to the environment they are in and if there is a change they adapt to the new situation through natural selection. This is elemental evolution theory. It is the 5% at the end of the limits that adapt and produce an organism able to accept the change. The change is what produces new species.
G
There is no “pace” to evolution. The concept doesn’t make sense. Every case is particular and different for every species. The proper way to think of the question is are there ANY individuals CURRENTLY in a given population that can survive at a higher temperature, and will any of those individuals gain an advantage over other individuals at that temperature. Until random mutation introduces a new genotype, the only thing that can happen is a shift among the existing phenotypes. Mutations in a particular gene generally occur once every 100,000 to 1,000,000 individuals, and in general those mutations mostly delete the gene, and only rarely leave it with altered functionality. So everything depends on the number of genes controlling a trait, and the number of individuals being produced over the time period. If a single gene codes for a protein that denatures above a given temperature killing the individual you will need hundreds of millions of new individuals to have a chance that it changes in a helpful way. Characteristics like height are influenced by hundreds or thousands of genes, so new genotypes might be introduced much more often. Every case will be different depending on what’s limiting a species’s heat tolerance. Species that are up against a hard physical limit will perish quickly. Ones that are a long way from physical limits will persist longer and their population trends will depend on the proportion of individuals who are better suited to the conditions to the proportion of the individuals that are less well suited; the severity of the difference between those individuals; and the rate at which those types of individuals reproduce. Again it’s highly specific to each species. There is no “pace” of evolution. Evolution is not animate, nor are species. Species do not actively “evolve”. The effects of evolution on the distribution of traits within a species however may be observed over time.
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I don’t understand. These creatures live from Alaska to Baja California. Evidently they can withstand temperatures ranging from the 70s-80s to the 40s (Fahrenheit). It would seem that their temperature tolerance as a species is quite broad, and their individual temperature tolerance quite robust as well. Where is the beef here?