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Positive phenotypic correlations among life‐history traits remain in the absence of differential resource ingestion
Author(s) -
Olijnyk Adriana M.,
Nelson William A.
Publication year - 2013
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/1365-2435.12015
Subject(s) - biology , resource acquisition is initialization , life history theory , trait , ecology , trade off , avian clutch size , resource (disambiguation) , life history , evolutionary biology , reproduction , resource allocation , economics , computer network , computer science , market economy , programming language
SummaryA central tenet of life‐history theory states that individuals are constrained from maximizing all aspects of fitness simultaneously through negative correlations among life‐history traits, known as trade‐offs. Although evidence for trade‐offs is abundant, a surprising number of taxa reveal positive correlations where trade‐offs are expected. Previous studies suggest two mechanisms to explain the lack of trade‐offs in situations where they are predicted by theory: differential resource acquisition and multidimensional trait constraints expressed in the presence of genetic variation. However, there is no direct empirical evidence supporting either hypothesis. Using individuals from multiple genotypes of the cyclic parthenogenic freshwater zooplankton, D aphnia pulicaria , we conducted life‐history experiments that prevented two key aspects of these mechanisms from operating. The experiments were conducted under a range of resources from levels causing near‐starvation to levels of resource abundance yielding a mean clutch size of 4–5 eggs. Growth, reproduction and survival were measured for each individual. Contrary to expectations, we found strong positive correlations among life‐history traits in the absence of both differential resource ingestion, which is one form of differential resource acquisition, and genetic variation. These positive correlations emerge from differential resource utilization , which is one of the steps along the resource ingestion‐utilization‐allocation pathway. Our results demonstrate that strong positive correlations among life‐history traits emerge from variation among individuals in an underappreciated aspect of their energy budget. This alternative mechanism has different implications for understanding life‐history evolution, and reinforces the potential role that physiological ecology has in shaping life‐history trait correlations.