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Measuring top-down vs. bottom-up effects: Contribution analysis of birth rate in Daphniaтезисы доклада
- Авторы: Polishchuk L.V., Vijverberg J., Voronov D.A., Mooij W.M.
- Сборник: IX International Symposium on Cladocera (Verbania, Italy, 2-8 October 2011): Book of Abstracts
- Тезисы
- Год издания: 2011
- Первая страница: 30
- Последняя страница: 30
- Аннотация: Top-down (predation) and bottom-up (food) effects are among the key forces that drive population dynamics and shape ecological communities, but which of them plays a leading role in a given environment often remains unknown. Using the cladoceran Daphnia as a model organism, we propose a new population metric to measure the relative strength of top-down vs. bottom-up effects. The metric is the ratio of contributions of changes in proportion of adults and fecundity to the resulting change in birth rate. Changes in fecundity F reflect the strength of bottom-up effect because fecundity depends chiefly on food. Changes in proportion of adults A reflect the strength of top-down effect because predators, such as planktivorous fish and planktonic invertebrate predators, are typically size-selective. Both F and A contribute to birth rate, which appears as a common currency with which to compare the effects of food and predators on the population of interest. We performed laboratory experiments and computer simulations to test the use of this metric, and to calibrate it. Both types of tests consistently show that when bottom-up effect is strong and top-down effect is weak, the ratio of the absolute values of contributions, |ConA|/|ConF|, is 0.5-0.7. In contrast, when bottom-up effect is weak and top-down effect is strong, with the latter mimicking fish preying upon adult daphnids, |ConA|/|ConF| is 2.0-2.2. When bottom-up and top-down effects are both intermediate, with the latter mimicking invertebrate predators preying upon juvenile daphnids, |ConA|/|ConF| is intermediate, but it is not clear whether it is closer to 0.7 or 2.0. The present findings, therefore, allow one to distinguish between two strong effects, the one due to fish and the other due to food, though may not allow disentangling a weaker effect caused by invertebrate predators from either of the strong effects.
- Добавил в систему: Полищук Леонард Владимирович