Temperature-related differences in life-history characteristics between diploid and polyploid clones of the Daphnia pulex complex

Abstract

This study compares life-history characteristics of diploid and polyploid clones of the Daphnia pulex complex at different temperatures to better comprehend their co-existence in the low Canadian arctic. Life-history experiments revealed that polyploid clones had larger eggs and neonates, as well as larger body sizes than diploid clones under 10°C, 17°C, and 24°C. In contrast to high temperature results, polyploid clones matured earlier than diploid clones at 10°C. Our results indicate that polyploid Daphnia may have a headstart over diploid clones at the beginning of the reproductive season when temperature are low. The similarity between cold tolerance in polyploids and organisms with large genomes suggests that it may be large cell size rather than large genomes or hybrid origin that is of selective value in cold environments.