Metamorphosis reverses the risk-taking behavioral phenotype in moor frog along a latitudinal gradient

Abstract

ABSTRACTUnderstanding how demographic processes and environmental conditions affect behavioral variation across populations is pivotal in evolutionary biology. However, as strong evidence accumulates for how these factors drive differences in behavior across populations, the role that such processes play in the link between behavior and life-history traits remains unclear. To study this, we collected moor frog eggs (Rana arvalis) from multiple populations ranging along a 1700 km latitudinal gradient in Northern Europe. We then raised tadpoles in a common garden experiment, assessing developmental growth and risk-taking behavior of over 300 individuals when reaching well-known larval developmental stages in anurans (tadpoles, Gosner stage 32, and froglets, Gosner stage 42). We found striking behavioral differences across regions and developmental stages. Specifically, tadpoles raised from northernmost regions took shorter times to leave a shelter, were more active and more exploratory in an open field test than tadpoles from southern populations. These behavioral patterns were reversed when individuals were evaluated as froglets in comparisons between these regions. Further analyses incorporating life-history traits indicated a strong association between developmental growth and time to leave the shelter, with contrasting patterns across developmental stages. Together, our results reflect a decoupling of correlations between behavioral and life history traits across developmental stages in species with complex life cycles as a response to the ecological and demographic constraints that they endure.