Hoekstra Luke A, Weber Rachel C, Bronikowski Anne M, Janzen Fredric J
Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, Iowa, USA.
Evol Ecol Res. 2018;19:639-657.
Individual growth rates both comprise and determine life-history phenotypes. Despite decades of interest in understanding the relationship between individual growth and life history, chelonian longevity has limited our ability to robustly estimate individual growth curves that span the life of both sexes.
(1) Do patterns of growth in size and shape differ between the sexes of the painted turtle, ? (2) Does individual variation in size and shape affect female reproductive effort?
Using 30 years of field data on shell morphology of a single population of painted turtles, we used principal components analysis to summarize multivariate size and shape. We assessed the ability of three non-linear growth models - the logistic, Gompertz, and von Bertalanffy - to predict size-at-age and used model comparison to justify sex-specific model fits. We correlated age-specific size and shape of females with their reproductive efforts.
Model comparison supported separate fits of the von Bertalanffy growth function for each sex; non-overlapping confidence intervals imply differences in sex-specific asymptotic size, but not growth rate. Higher-order axes of variation in shell morphology described significant sexual dimorphism in shell shape related to the sphericity and curviness of the shell. Shell sphericity of females covaried with clutch size, mean egg mass, and total clutch mass. Irrespective of shell morphology, we found evidence of an egg number versus egg mass trade-off. Yet, females who matured at a larger size produced greater reproductive efforts.
个体生长率既构成又决定生活史表型。尽管数十年来人们一直对理解个体生长与生活史之间的关系感兴趣，但龟类的长寿限制了我们可靠估计涵盖两性一生的个体生长曲线的能力。
（1）锦龟两性之间的大小和形状生长模式是否不同？（2）大小和形状的个体差异是否会影响雌性的繁殖投入？
利用对单一锦龟种群30年的壳形态学野外数据，我们使用主成分分析来总结多变量大小和形状。我们评估了三种非线性生长模型——逻辑斯蒂模型、冈珀茨模型和冯·贝塔朗菲模型——预测年龄大小的能力，并使用模型比较来证明特定性别的模型拟合是合理的。我们将雌性特定年龄的大小和形状与其繁殖投入进行了关联。
模型比较支持对每种性别分别拟合冯·贝塔朗菲生长函数；不重叠的置信区间意味着特定性别渐近大小存在差异，但生长率不存在差异。壳形态学的高阶变异轴描述了与壳的球形度和弯曲度相关的壳形状的显著两性异形。雌性的壳球形度与窝卵数、平均卵质量和总窝卵质量相关。无论壳形态如何，我们都发现了卵数与卵质量权衡的证据。然而，成熟时体型较大的雌性产生的繁殖投入更大。
