1 January 2012 Evidence for the Morphological Constraint Hypothesis and Optimal Offspring Size Theory in the Mexican Mud Turtle (Kinosternon integrum)
Rodrigo Macip-Ríos, Pablo Brauer-Robleda, Gustavo Casas-Andreu, María de Lourdes Arias-Cisneros, Víctor Hugo Sustaita-Rodríguez
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Abstract

Optimal offspring size theory states that natural selection should balance reproductive output by optimizing between offspring size and offspring number. If a species has evolved an optimal offspring size, the fitness of larger females should be increased by simply producing more offspring of an optimum size. In contrast, when offspring size is not optimized, the morphological constraint hypothesis may apply, and in this case, maternal fitness is increased by producing the greatest number of the largest offspring that mothers are physically capable of producing. We used a log-log allometric regression approach on clutch size, egg size, and body size data to test the application of optimal offspring size theory and the morphological constraint hypothesis in the Mexican mud turtle (Kinosternon integrum) in southern Mexico. Our results indicate that this turtle seems to follow the morphological constraint hypothesis when all data are analyzed together, but when data are divided between small (< 140 mm plastron length) and large females (> 140 mm plastron length), optimal offspring (egg) size theory was supported only in large females, while the morphological constraint hypothesis was supported in small females. Our results thus indicate that K. integrum females may increase their fitness in two different, size-dependent ways as they grow from size at sexual maturity to maximum body size.

© 2012 Zoological Society of Japan
Rodrigo Macip-Ríos, Pablo Brauer-Robleda, Gustavo Casas-Andreu, María de Lourdes Arias-Cisneros, and Víctor Hugo Sustaita-Rodríguez "Evidence for the Morphological Constraint Hypothesis and Optimal Offspring Size Theory in the Mexican Mud Turtle (Kinosternon integrum)," Zoological Science 29(1), 60-65, (1 January 2012). https://doi.org/10.2108/zsj.29.60
Received: 29 April 2011; Accepted: 1 August 2011; Published: 1 January 2012
KEYWORDS
clutch size-body size correlation
hypoallometry
morphological constraints
optimal offspring size theory
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