Macip-Ríos Rodrigo, Brauer-Robleda Pablo, Casas-Andreu Gustavo, Arias-Cisneros María de Lourdes, Sustaita-Rodríguez Víctor Hugo
Instituto de Ciencias de Gobierno y Desarrollo Estratégico, Benemérita Universidad Autonome de Puebla. 4 Sur 104, Edificio Carolino, Tercer Patio, Centro Histórico CP 72000, México.
Zoolog Sci. 2012 Jan;29(1):60-5. doi: 10.2108/zsj.29.60.
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.
最优后代大小理论指出，自然选择应通过在后代大小和后代数量之间进行优化来平衡繁殖输出。如果一个物种已经进化出最优后代大小，那么体型较大的雌性通过简单地产出更多最优大小的后代，其适合度应该会增加。相反，当后代大小未达到最优时，形态限制假说可能适用，在这种情况下，母体适合度通过产出母亲身体能够产出的最大数量的最大后代而增加。我们对窝卵数、卵大小和体型数据采用对数-对数异速生长回归方法，以检验最优后代大小理论和形态限制假说在墨西哥南部的墨西哥泥龟（Kinosternon integrum）中的应用。我们的结果表明，当对所有数据进行综合分析时，这种龟似乎遵循形态限制假说，但当数据按小体型（腹甲长度<140毫米）和大体型雌性（腹甲长度>140毫米）划分时，仅在大体型雌性中支持最优后代（卵）大小理论，而在小体型雌性中支持形态限制假说。因此，我们的结果表明，随着墨西哥泥龟雌性从性成熟时的体型生长到最大体型，它们可能会以两种不同的、与体型相关的方式提高其适合度。
