Measuring Daphnia life history in the wild: The efficacy of individual field cages

• Published in: Ecology and evolution Vol. 11; no. 23; pp. 16927 - 16935
• Main Authors: O’Connor, Michael, Sadler, Daniel E., Brunner, Franziska S., Reynolds, Alan, White, Nicola, Price, Stephen, Plaistow, Stewart J.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.12.2021; John Wiley and Sons Inc; Wiley
• Subjects: Age; Algae; Animals; Cages; Daphnia; Design; Evolution; Evolutionary biology; Experiments; field cage; field experiment; Food; Food resources; Free flow; Laboratories; Life history; Life history studies; multivariate phenotype; Nutrition; Organisms; Realism; field cage; Daphnia; field experiment; multivariate phenotype; life history
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.8326

Life‐history studies are often conducted in a laboratory environment where it is easy to assay individual animals. However, factors such as temperature, photoperiod, and nutrition vary greatly between laboratory and field environments, making it difficult to compare results. Consequently, there is a need to study individual life histories in the field, but this is currently difficult in systems such as Daphnia where it is not possible to mark and track individual animals. Here, we present a proof of principle study showing that field cages are a reliable method for collecting individual‐level life‐history data in Daphnia magna. As a first step, we compared the life history of paired animals reared outside and inside cages to test the hypothesis that cages allow free flow of algal food resources. We then used a seminatural mesocosm setting to compare the performance of individual field cages versus glass jars refilled with mesocosm water each day. We found that cages did not inhibit food flow and that differences in life histories between three clones detected in the jar assays were also detectable using the much less labor‐intensive field cages. We conclude that field cages are a feasible approach for collecting individual‐level life‐history data in systems such as Daphnia where individual animals cannot be marked and tracked. There is a need to study individual life histories in the field, but this is currently difficult in systems such as Daphnia where it is not possible to mark and track individual animals. Here, we test the hypothesis that field cages are a useful method for collecting individual‐level life‐history data in Daphnia magna. We provide evidence that our cage design allows the collection of realistic, reliable, and repeatable measurements of life‐history data in the natural setting, as animals inside the cages experience the environment in the same way as those outside.