Low flexibility of metabolic capacity in subarctic and temperate cytotypes of Daphnia pulex

The goal of this study was to examine metabolic capacity in four clones of Daphnia pulex (differing in ploidy levels and geographic origin) after a 4-day exposure to different temperature and pH treatments. Citrate synthase, electron transport system and lactate dehydrogenase capacities were not different among clones and treatments. Our results do not support the hypothesis that polyploid clones have higher metabolic capacity than diploid clones under extreme environmental conditions. Other factors must explain the prevalence of polyploid clones in extreme habitats.