Starvation responses of invasive and non-invasive Eurytemora affinis populations

Abstract

Within the past century, the copepod Eurytemora affinis have invaded freshwater from saline sources throughout the Northern Hemisphere. Two genetically divergent clades (Atlantic and North Atlantic) of E. affinis coexist in the St. Lawrence estuary, but only the Atlantic clade was able to invade into freshwater ecosystem. A common-garden reaction norm experiment was performed on populations from these two clades to determine their differences in survival and development time across three food levels (high, medium and low) in fresh water. The populations were fed with the freshwater alga Rhodomonas minuta. The developmental progress and survival of the populations were monitored throughout the experiment. The results indicated that the population from the invasive Atlantic clade is more starvation resistant and has faster development time to adulthood. The differences between the populations might be due to their different osmoregulatory mechanisms and energy usages. These different physiological responses to starvation are likely to have functional consequences for the populations' ability to expand their ranges into novel environments.