Demographic cost and mechanisms of adaptation to environmental stress in resurrected Daphnia
subject: Cladocera, copper pollution, Lake Orta, Life-history responses, Perturbation analyses, Population Ecology
description: A characteristic feature of the Daphnia (Crustacea: Cladocera) life cycle are the so-called ephippia, which are fertilised eggs that need to undergo diapause. When they are shed by the female, they sink to the lake bottom, where they may become embedded in the sediment and may remain viable for decades. Extracting and hatching ephippia in the laboratory and subjecting resurrected lineages to conditions representative of historic lake environments allows retrospective investigation of life-history responses to environmental change. Here we reanalyse data from such a resurrection experiment (Piscia et al., 2015: Bull. Environ. Contam. Toxicol. 94:46–51). Contemporary and past lineages of Daphnia galeata Sars 1863 were obtained from Lake Orta (Italy), a deep, subalpine lake with a well-documented history of industrial copper pollution. Experimental Daphnia were subjected to three copper treatments representative of two levels of historic as well as to current (i.e., unpolluted) lake conditions, and life-table data were collected. With these data at hand, we first estimated vital rates (survival, maturation, and reproduction) and used these rates to project the asymptotic population growth rates (λ) for each population-by-treatment combination. Next, we performed life-table response experiments (LTRE) to estimate the contributions of the vital rates to observed differences in λ. Finally, we used elasticity analysis to explore the functional relationship between λ and each of the vital rates. We found that survival rates were only compromised at elevated copper levels. Moreover, past, resurrected Daphnia had a higher λ at low copper concentrations compared to unpolluted conditions, but a lower λ when exposed to high copper levels. Contemporary Daphnia, on the other hand, only reproduced successfully in unpolluted water. Under these conditions, however, they had a higher population growth rate than the past Daphnia, suggesting a cost of copper tolerance in the latter. Thi…
creator: Stefan Sommer, Roberta Piscia, Marina M. Manca, Diego Fontaneto, Arpat Ozgul
source: Journal of Limnology
publisher: PAGEPress Publications
date: 2016
language: EN
identifier: DOI: 10.4081/jlimnol.2016.1292
coverage: Environmental sciences, Geography. Anthropology. Recreation, Physical geography