Literaturdatenbank
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Rollinson, N., & Brooks, R. J. (2008). Optimal offspring provisioning when egg size is “constrained”: a case study with the painted turtle chrysemys picta. Oikos, 117(1), 144–151.
Added by: Admin (14 Aug 2008 20:34:35 UTC) |
| Resource type: Journal Article BibTeX citation key: Rollinson2008 View all bibliographic details  |
Categories: General Keywords: Chrysemys, Chrysemys picta, Emydidae, Fortpflanzung = reproduction, Morphologie = morphology, Schildkröten = turtles + tortoises Creators: Brooks, Rollinson Collection: Oikos |
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| Abstract |
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Classic egg size theory predicts that, in a given environment, there is a level of maternal investment per offspring that will maximize maternal fitness. However, positive correlations among egg size and female body size are observed within populations in diverse animal taxa. A popular explanation for this phenomenon is that, in some populations, morphological constraints on egg size, such as ovipositor size (insects) or pelvic aperture width (lizards and turtles), limit egg size. Egg size may therefore increase with female body size due to body size-specific constraints on investment per offspring, coupled with selection towards an optimal egg size. We use 17 years of data from a population of painted turtles Chrysemys picta to evaluate this hypothesis. In accordance with our predictions, we find that (1) morphological constraints on egg size are apparent only in relatively small females, similarly (2) egg mass exhibits a strong asymptotic relationship with female body size, suggesting egg mass is optimized only at large body sizes, (3) clutch size, not egg mass, varies with female condition, and (4) clutch size varies more than egg mass across years. Contrary to our predictions, we observe that (5) the egg mass-clutch size tradeoff is not less pronounced at large body sizes. Our data do not fully support the traditional hypothesis, and recent models suggest that this hypothesis is indeed overly simplistic. When the selective environment of a female's offspring is influenced by her phenotype, optimal egg size may vary among maternal phenotypes. This concept can explain correlations among egg size and body size in many taxa, as well as the patterns observed in the present study. In this paradigm, a tight coupling of aperture width (or other `constraints') and egg size may occur in small females, even when such morphological features are not causally related to variation in egg size. In this spirit, we question validity of invoking morphological constraints to explain covariation among egg size and female body size.
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