Can species adapt to climate change within decades?

Do organisms have the ability to adapt to climate change on a timescale of decades?

A study published in the recent online journal Proceedings of the Royal Society B set out to test that question with the little West Coast tidepool copepod, Tigriopus californicus, which normally shows an ability to tolerate wide ranges in temperatures.

Photo: Ron Burton

University of California at Davis lead author Morgan Kelly brought the little critters into a lab, selecting eight populations native within a range of 17 degrees latitude. She then reared 10 generations of each population under differing water temperatures to test the force of evolution and see which would survive.

The results showed only two of the 10 able to adapt to higher temperatures. In particular, the northern populations lacked the capacity to acclimate to the temperatures found in the populations in the southern range.

The researchers point out that the variations among populations of T. californicus is relatively high. Yet the inability to adapt to the wider temperature extremes shows a limit in the species’ genetic resources. The researchers say this “highlights a fundamental limitation of present attempts to model biological responses to climate change.”

Most modeling assumes that every population of the same species has the same environmental tolerance. So they do a poor job of predicting extinction rates until conditions reach the most extreme within a species’ geographical range. The northern varieties of T. californicus, for example, live awfully close to their temperature edge. In spring summer months they are 1.8 degrees Fahrenheit away from lethal temperatures.

Extinction with warming temperatures can thus happen in a patchwork way, they explain, with some populations going under while others survive. Why does this matter? If that happens, the overall gene pool declines, a potentially deadly situation for a species’ trying to adapt to a changing world.

If T. californicus populations are at the edge of survival along the Pacific coastline, surely other species are at or near their capacity to respond to further warming, at least at present rates.

To understand species extinction, the researchers say a more complicated set of inputs need to be considered. Among them, the capacity of local populations to respond.