Thermal Plasticity in Swedish Pool Frogs

Writing that "phenotypic plasticity, the capacity of a genotype to produce distinct phenotypes under different environmental conditions, is a common and powerful method of adaptation in nature," Orizaola and Laurila (2009) investigated variations in temperature-induced plasticity in larval life-history traits among populations of an isolated metapopulation of pool frogs (Rana lessonae) in Central Sweden. This they did by exposing larvae from three closely-located populations to two temperatures (20 and 25°C) in the laboratory and then documenting their growth and development responses at the two different temperatures.

According to the two Swedish researchers, results indicated that (1) "in general, larvae exposed to warmer temperature experienced higher survival and metamorphosed faster," that (2) there "were differences among the populations in both trait mean values and in the plastic responses," and that (3) "among-family variation within populations was found in growth rate and time to metamorphosis, as well as in plasticity suggesting that these traits have a capacity to evolve."

Based on these findings, Orizaola and Laurila state that they found "strong population differentiation at a microgeographic scale in life-history characteristics and temperature-induced plasticity in [the] isolated amphibian metapopulation," and that in spite of "the near absence of molecular genetic variation within [the] metapopulation, [their] study detected strong variation in trait means and plastic responses both among and within populations, possibly suggesting that natural selection is shaping life-history traits of the local populations [italics added]," which phenomenon may be preparing them for things to come -- such as even further warming -- by providing them "ample phenotypic variation" to deal with a potentially warming environment.