Data from: The role of inbreeding depression and mating system in the evolution of heterostyly

We investigated the role of morph-based differences in the expression of inbreeding depression in loss of the mid-styled morph from populations of tristylous Oxalis alpina as proposed by theoretical analyses. The extent of self-compatibility of reproductive morphs, the degree of self-fertilization, and the magnitude of inbreeding depression were investigated in three populations of O. alpina differing in their tristylous incompatibility relationships. All three populations exhibited significant inbreeding depression. In two populations with highly modified tristylous incompatibility, manifested as increased reciprocal compatibility between short- and long-styled morphs, substantial self-compatibility and self-fertilization of mid-styled morphs was detected, and expected to result in expression of inbreeding depression in the progeny of mid-styled morphs in the natural populations. In contrast, significant self-fertility of the mid-styled morph was absent from the population with typical tristylous incompatibility, and no self-fertilization could be detected. Although self-fertilization and expression of inbreeding depression should result in selection against the mid-styled morph in the later stages of the transition from tristyly to distyly, in O. alpina selection against the mid-styled morph in the early phases of the evolution of distyly is likely due to genic selection against mid alleles associated with modified tristylous incompatibility, rather than expression of inbreeding depression.

本研究依据理论分析提出的假说，探究了花形态（morph）差异对花柱三态（tristylous）高山酢浆草（Oxalis alpina）种群中中花柱形态（mid-styled morph）丢失过程中近交衰退（inbreeding depression）表达的调控作用。我们针对三个具有不同花柱三态不亲和（tristylous incompatibility）特征的高山酢浆草种群，调查了其生殖形态的自交亲和（self-compatibility）程度、自体受精（self-fertilization）水平，以及近交衰退的强度。三个研究种群均表现出显著的近交衰退现象。在两个经高度改造的花柱三态不亲和种群中，其典型特征为短花柱形态与长花柱形态间的相互亲和性显著提升；研究检测到中花柱形态具备较强的自交亲和性与自体受精能力，且推测该特性会导致自然种群中中花柱形态子代出现近交衰退现象。与之相反，在具备典型花柱三态不亲和机制的种群中，未观察到中花柱形态存在显著的自交可育性，也未检测到自体受精事件。尽管在从花柱三态向花柱二态（distyly）演化的后期阶段，自体受精与近交衰退的表达会对中花柱形态产生负选择压，但在高山酢浆草花柱二态演化的早期阶段，对中花柱形态的负选择更可能源于与改造后花柱三态不亲和机制相关的中花柱等位基因（mid alleles）的基因选择（genic selection），而非近交衰退的直接表达。