Metabolism and life-history correlates in a lowland and highland population of a terrestrial isopod

Abstract

Ectotherms distributed along environmental gradients often show marked variation in physiological and life-history traits. Different life-history phenotypes may be correlated with variations in maintenance metabolism. We measured life-history traits and metabolic rate (VO2) of the common wood louse (Porcellio laevis Latreille, 1804) from a lowland population and a highland population in northern Chile. We measured VO2at 5, 12, 18, and 25 °C. Wood lice from different altitudes exhibited large variations in life-history traits, which were correlated with changes in VO2. Fecundity of wood lice decreased and egg volume, offspring size, and reproductive output of females increased in highland populations compared with lowland populations. Isopods from the highland had a higher VO2than those from lowland habitats for almost all temperatures. However, when we considered VO2at 5 °C, VO2was lowest in the high-altitude isopods. In addition, since the highest thermal sensitivity values in the VO2–temperature curves were found at the lowest and highest temperature ranges for the highland population rather than for the lowland population, our study did not support the metabolic cold-adaptation hypothesis. We concluded that differences in VO2between the populations contributed to the difference in reproductive output by wood lice from cold and warm habitats.