Abstract

Question: Is there a clinal covariation between life-history traits and metabolic rate? Hypothesis: Reproductive output will negatively covary with metabolic rate along an intraspecific latitudinal gradient. Methods: In a common garden design we studied metabolic rate in five populations of the common terrestrial isopod, Porcellio laevis, over a range of 15° of latitude in Chile. We also measured life-history variables in the same populations. Conclusions: Female body mass, female size at first reproduction, egg and juvenile size, and reproductive output were negatively correlated with mean annual air temperature and positively correlated with latitude. In contrast, metabolic rate and egg number were positively correlated with temperature and negatively correlated with latitude. Individuals inhabiting cooler climates (i.e. southern populations) tended to have lower metabolic rates. We found a significant, negative phenotypic correlation between metabolism and reproductive output for all studied populations, in a gradual and consistent direction along the latitudinal gradient. © 2006 Marco A. Lardies.