Abstract
If an organism's juvenile and adult life stages inhabit different environments, certain traits may need to be independently adapted to each environment. In many organisms, a move to a different environment during ontogeny is accompanied by metamorphosis. In such organisms phenotypic induction early in ontogeny can affect later phenotypes. In laboratory experiments we first investigated correlations between body morphology and the locomotor performance traits expressed in different life stages of the common frog, Rana temporaria: swimming speed and acceleration in tadpoles; and jump-distance in froglets. We then tested for correlations between these performances across life stages. We also subjected tadpoles to unchanging or decreasing water levels to explore whether decreasing water levels might induce any carry-over effects. Body morphology and performance were correlated in tadpoles; morphology and performance were correlated in froglets: hence body shape and morphology affect performance within each life stage. However, performance was decoupled across life stages, as there was no correlation between performance in tadpoles and performance in froglets. While size did not influence tadpole performance, it was correlated with performance of the metamorphosed froglets. Experiencing decreasing water levels accelerated development time, which resulted in smaller tadpoles and froglets, i.e., a carry-over effect. Interestingly, decreasing water levels positively affected the performance of tadpoles, but negatively affected froglet performance. Our results suggest that performance does not necessarily have to be correlated between life stages. However, froglet performance is size dependent and carried over from the tadpole stage, suggesting that some important size-dependent characters cannot be decoupled via metamorphosis.
Highlights
Organisms that live in different environments during ontogeny are faced with the constraint that it might be difficult to optimise responses, via adaptation, to the various selection pressures that operate in each habitat
In the present study we focus on how morphology and locomotor behaviour is correlated across life stages
We address the following questions: 1) Do individuals that perform well as tadpoles perform well as froglets? 2) How is the behavioural performance of tadpoles and froglets related to their morphology? 3) How does the relationship between locomotor performance and morphology within a life stage differ between unstressed tadpoles raised in a constant water environment, and stressed tadpoles raised in an environment with decreasing water levels simulating pool drying?
Summary
Organisms that live in different environments during ontogeny are faced with the constraint that it might be difficult to optimise responses, via adaptation, to the various selection pressures that operate in each habitat. It is of interest to examine if and how phenotypic induction early in ontogeny affects later phenotypes Such knowledge is important if we want to predict how changes in one environment affect phenotypes in another environment. Frogs provide an excellent system in which to study how morphological and behavioural traits are related across life stages. This is because most frogs spend the first stage of their life in an aquatic environment, which selects for a different suite of traits than do the terrestrial or amphibious environments occupied by adults. While several studies have examined the relationship between morphological traits across life stages in frogs e.g. We ask whether larval stages (tadpoles) that perform well in terms of their locomotor behaviour in one environment, perform well as juvenile adults (froglets) in another environment
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