Adaptation of Stagnicola palustris to Rapid Climate Change in the Baltic Sea

Rapid climate change is one of the most pressing environmental issues in the world, with Scandinavia andthe Arctic among those projected to be most strongly affected. Faced with a changing environment,organisms may respond in three ways – by adaptation, migration or extinction. Adaptation can occurthrough phenotypic plasticity or microevolution, and while phenotypic responses to climate change arewell described, examples showing microevolution are rare. To be able to predict the effects of climatechange, an assessment of a species’ evolutionary potential to increased temperature is necessary.I studied whether snail populations subjected to a 30 year warming experiment have been able to adapt tothe new climate regimen. Two populations of Stagnicola palustris originating from areas affected bycooling water discharge from the nuclear power plant in Forsmark, Sweden (with increased watertemperatures by 4-10 °C) and two control populations from unaffected areas were used in thisexperiment. Laboratory reared F3 offspring were raised for 28 weeks in a common garden setup at fourdifferent temperature treatments (12-24 °C) and shell length, snail mass and higher survival weremeasured.Both warm-origin populations appeared able to have adapted to the increased temperatures, though bydifferent means. Snail growth showed evidence of co-gradient variation (after 6 and 18 weeks) and localadaptation (after 28 weeks) in one of the warm-origin populations. The other warm-origin population, onthe other hand, appeared to have acquired adaptation by increasing its survival to the higher temperaturescompared to the other three populations.My results suggest that organisms can adapt rapidly to a warmer environment. However, the effects ofimproved growth and survival on population fitness and persistence remain unclear and need to be studied further