Data from: Evidence of opposing fitness effects of parental heterozygosity and relatedness in a critically endangered marine turtle?

How individual genetic variability relates to fitness is important in understanding evolution and the processes affecting populations of conservation concern. Heterozygosity-fitness correlations (HFCs) have been widely used to study this link in wild populations, where key parameters that affect both variability and fitness, such as inbreeding, can be difficult to measure. We used estimates of parental heterozygosity and genetic similarity (‘relatedness’) derived from 32 microsatellite markers to explore the relationship between genetic variability and fitness in a population of the critically endangered hawksbill turtle, Eretmochelys imbricata. We found no effect of maternal MLH (multilocus heterozygosity) on clutch size or egg success rate, and no single-locus effects. However, we found effects of paternal MLH and parental relatedness on egg success rate that interacted in a way that may result in both positive and negative effects of genetic variability. Multicollinearity in these tests was within safe limits, and null simulations suggested the effect was not an artefact of using paternal genotypes reconstructed from large samples of offspring. Our results could imply a tension between inbreeding and outbreeding depression in this system, which is biologically feasible in turtles: female-biased natal philopatry may elevate inbreeding risk and local adaptation, and both processes may be disrupted by male-biased dispersal. Although this conclusion should be treated with caution due to a lack of significant identity disequilibrium, our study shows the importance of considering both positive and negative effects when assessing how variation in genetic variability affects fitness in wild systems.

个体遗传变异与适合度之间的关联，对于理解演化以及影响受保护关注种群的各类过程具有重要意义。杂合度-适合度关联（Heterozygosity-fitness correlations, HFCs）已被广泛应用于野生种群的该关联研究中，而在野生种群中，同时影响遗传变异与适合度的关键参数（如近交）往往难以直接测定。我们基于32个微卫星标记（microsatellite）得到的亲本杂合度与遗传相似性（即‘亲缘关系’）的估计值，对极度濒危的玳瑁（Eretmochelys imbricata）种群的遗传变异与适合度之间的关联展开探究。我们未发现母体多位点杂合度（multilocus heterozygosity, MLH）对窝卵数或卵孵化成功率存在影响，也未检测到单基因座效应。但我们发现父本多位点杂合度与亲本亲缘关系对卵孵化成功率存在交互效应，这种交互模式可能使遗传变异同时产生正向与负向影响。本研究中的多重共线性（multicollinearity）处于安全阈值范围内，且零值模拟结果表明，该效应并非利用大量子代样本重构的父本基因型所带来的人为假象。我们的研究结果暗示，该系统中可能存在近交衰退与远交衰退之间的权衡关系，这在海龟类群中具有生物学可行性：雌性偏向的出生地保真行为可能提升近交风险与局部适应能力，而雄性偏向的扩散过程则可能对这两种过程造成干扰。尽管由于未检测到显著的身份不平衡（identity disequilibrium），该结论仍需谨慎对待，但本研究表明，在野生系统中评估遗传变异对适合度的影响时，同时兼顾正向与负向效应具有重要意义。