Data and code from: Effects of ploidy on relationship between outbreeding response and fitness in a plant selfing species

Outbreeding response, the phenotypic differences observed between selfed
parental lines and their outcrossed offspring, can influence the evolution
of selfing strategies. However, such an effect remains poorly understood
in non-crop species. We explored the phenotypic outbreeding response
variation across ploidy levels in Erysimum incanum, a predominantly
selfing plant complex with diploid, tetraploid, and hexaploid populations
distributed across the Iberian Peninsula and Morocco. We performed
controlled within-population crosses to generate offspring with varying
heterozygosity levels across ploidy types. We quantified individual,
flower, and reproductive traits, and we estimated fitness components, and
assessed trait modularity and phenotypic integration to see how
heterozygosity affects trait coordination. Tetraploids showed the
strongest and most consistently positive outbreeding responses,
particularly in gamete production. Trait-specific outbreeding responses
were positively associated with fitness across ploidy levels. Increasing
heterozygosity was linked to a reduction in phenotypic integration,
suggesting a loosening of trait correlations. Results show that
outbreeding response is ploidy-dependent and functionally connected to
fitness and it may act as a selective force promoting outcrossing in
highly inbred lineages. We suggest that outbreeding response is a dynamic
and evolvable trait, with implications for mating system transitions and
diversification in selfing plant populations. Outbreeding response in
Erysimum incanum is both ploidy-dependent and functionally tied to
fitness, highlighting its potential role in promoting outcrossing and
driving mating system evolution in inbred plant populations.

远交响应（outbreeding response）指自交亲本株系与其远交后代之间的表型差异，可影响自交策略的演化进程。然而，该效应在非作物物种中仍未被充分阐明。本研究以镰萼糖芥（Erysimum incanum）为研究对象——该类群以自交为主，包含二倍体、四倍体与六倍体种群，分布于伊比利亚半岛及摩洛哥境内——探讨了不同倍性水平下的表型远交响应变异。我们通过种群内控制性杂交实验，在不同倍性类群中获得了杂合度水平各异的后代。我们对个体、花部及繁殖性状进行了量化，估算了适合度组分，并评估了性状模块性与表型整合情况，以探究杂合度如何影响性状协调机制。四倍体个体展现出最强且最具一致性的正向远交响应，尤以配子生成相关性状最为显著。不同性状的远交响应强度与所有倍性类群的适合度均呈正相关关系。杂合度提升与表型整合程度降低存在关联，提示性状间的相关性趋于松散。研究结果表明，远交响应具有倍性依赖性，且在功能上与适合度紧密相关，其可能作为选择压力，在高度自交的株系中促进远交行为。我们提出，远交响应是一类动态且可演化的性状，对自交植物种群的交配系统转变与物种分化具有重要启示。镰萼糖芥的远交响应兼具倍性依赖性与功能适合度关联性，这凸显了其在促进自交植物种群远交行为、驱动交配系统演化过程中的潜在作用。