Inbreeding depression, though challenging to identify in nature, may play an important role in regulating the dynamics of small and isolated populations. Conversely, greater expression of genetic load can enhance opportunities for natural selection. Conditional expression concentrates these opportunities for selection and may lead to failure of detection. This study investigates the possibility for age-dependent expression of inbreeding depression in a critically endangered population of rock iguanas, C. nubila caymanensis. We employ heterozygote-fitness correlations (HFCs) to examine the contributions of individual genetic factors to body size, a fitness-related trait. Non-significant reductions in homozygosity (up to 7%) were detected between neonates and individuals surviving past their first year, which may reflect natural absorption of inbreeding effects by this small, fecund population. The majority of variation in neonate body size was attributed to maternal or environmental effects (i.e. clutch identity and incubation length); however, heterozygosity across 22 microsatellite loci also contributed significantly and positively to model predictions. Conversely, effects of heterozygosity on fitness were not detectable when adults were examined, suggesting that inbreeding depression in body size may be age-dependent in this taxon. Overall, these findings emphasize the importance of taking holistic, cross-generational approaches to genetic monitoring of endangered populations.

中文翻译：

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杂合性 - 健康相关性揭示了极度濒危岩鬣蜥新生儿体型的近亲繁殖下降

近交衰退虽然在自然界中难以识别，但可能在调节小而孤立的种群动态方面发挥重要作用。相反，基因负荷的更多表达可以增加自然选择的机会。条件表达式集中了这些选择机会，并可能导致检测失败。本研究调查了在极度濒危的岩鬣蜥 C. nubila caymanensis 种群中近交衰退的年龄依赖性表达的可能性。我们采用杂合体健康相关性 (HFC) 来检查个体遗传因素对体型（一种与健康相关的特征）的贡献。在新生儿和存活超过第一年的个体之间检测到纯合度的非显着降低（高达 7%），这可能反映了这个小而多产的种群对近亲繁殖效应的自然吸收。新生儿体型的大部分变化归因于母体或环境影响（即离合器身份和孵化时间）；然而，跨 22 个微卫星位点的杂合性也对模型预测做出了显着且积极的贡献。相反，当检查成年人时，无法检测到杂合性对健康的影响，这表明近亲繁殖体型降低可能与该分类群的年龄有关。总体而言，这些发现强调了对濒危种群进行遗传监测的整体、跨代方法的重要性。离合器身份和孵化长度）；然而，跨 22 个微卫星位点的杂合性也对模型预测做出了显着且积极的贡献。相反，当检查成年人时，无法检测到杂合性对健康的影响，这表明近亲繁殖体型降低可能与该分类群的年龄有关。总体而言，这些发现强调了对濒危种群进行遗传监测的整体、跨代方法的重要性。离合器身份和孵化长度）；然而，跨 22 个微卫星位点的杂合性也对模型预测做出了显着且积极的贡献。相反，当检查成年人时，无法检测到杂合性对健康的影响，这表明近亲繁殖体型降低可能与该分类群的年龄有关。总体而言，这些发现强调了对濒危种群进行遗传监测的整体、跨代方法的重要性。