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Exper­i­ments on a small seashore ani­mal sug­gest that evo­luti­nary changes can­not res­cue ani­mals and plants from the threat posed by cli­mate change. The study pro­vides a first answer to a ques­tion a lot of sci­en­tists have been talk­ing about accord­ing to co-​author Eric San­ford. “Do organ­isms have the abil­ity to adapt to cli­mate change on a timescale of decades?”

The extent to which accli­ma­tion and genetic adap­ta­tion might buffer nat­ural pop­u­la­tions against cli­mate change is largely unknown. The crit­i­cal point is that many organ­isms are already at their envi­ron­men­tal lim­its, and nat­ural selec­tion won’t nec­es­sar­ily res­cue them. This empir­i­cal study is one of few which have char­ac­ter­ized genetic vari­a­tion in traits directly related to envi­ron­men­tal tol­er­ance lim­its. The cho­sen organ­ism was the broadly dis­trib­uted tide­pool cope­pod Tigri­o­pus cal­i­for­ni­cus. Ten gen­er­a­tions were reared under lab­o­ra­tory con­di­tions using ther­mal selec­tion pres­sure, try­ing to quan­tify ther­mal tol­er­ance and select for more heat-​tolerant animals.

The cope­pods, that orig­i­nated from eight dif­fer­ent geo­graph­i­cal loca­tions, showed lim­ited capac­ity to buffer against fur­ther increases in tem­per­a­ture. Though cope­pods from dif­fer­ent loca­tions showed wide vari­ablity in heat tol­er­ance, within each pop­u­la­tion it was impos­si­ble to increase the heat tol­er­ance fur­ther than a half-​degree Cel­sius. This sug­gest that the genetic make-​up of these dif­fer­ent pop­u­la­tions is not very broad, which pre­vents selec­tion for a dif­fer­ent trait. There is lack of avail­able genes on pop­u­la­tion level that could sup­port such nat­ural selec­tion, which is prob­a­bly due to the fact that indi­vid­ual pop­u­la­tions of cope­pods live very iso­lated in con­fined rocky areas off the coast. The results sug­gest that mod­els assum­ing a uni­form cli­matic enve­lope may greatly under­es­ti­mate extinc­tion risk in species with strong local adap­ta­tion. Unfor­tu­nately this could also be the case for many other species of ani­mals and plants when their habi­tats have been frag­mented, for instance by human activ­i­ties. Gros­berg, one of the study authors, said it like this: “The crit­i­cal point is that many organ­isms are already at their envi­ron­men­tal lim­its, and nat­ural selec­tion won’t nec­es­sar­ily res­cue them.”

(Sources: Pro­ceed­ings of the Royal Soci­ety B., pub­lished online before print 08.06.2011; web­site UCDAVIS, 08.06.2011)