Section of Ecology, University of Turku, FI-20014, Turku, Finland.
Ann Bot. 2011 Sep;108(3):547-55. doi: 10.1093/aob/mcr174. Epub 2011 Jul 28.
Inbreeding via self-fertilization may have negative effects on plant fitness (i.e. inbreeding depression). Outbreeding, or cross-fertilization between genetically dissimilar parental plants, may also disrupt local adaptation or allelic co-adaptation in the offspring and again lead to reduced plant fitness (i.e. outbreeding depression). Inbreeding and outbreeding may also increase plant vulnerability to natural enemies by altering plant quality or defence. The effects of inbreeding and outbreeding on plant size and response to herbivory in the perennial herb, Vincetoxicum hirundinaria, were investigated.
Greenhouse experiments were conducted using inbred and outbred (within- and between-population) offspring of 20 maternal plants from four different populations, quantifying plant germination, size, resistance against the specialist folivore, Abrostola asclepiadis, and tolerance of simulated defoliation.
Selfed plants were smaller and more susceptible to damage by A. asclepiadis than outcrossed plants. However, herbivore biomass on selfed and outcrossed plants did not differ. The effects of inbreeding on plant performance and resistance did not differ among plant populations or families, and no inbreeding depression at all was found in tolerance of defoliation. Between-population outcrossing had no effect on plant performance or resistance against A. asclepiadis, indicating a lack of outbreeding depression.
Since inbreeding depression negatively affects plant size and herbivore resistance, inbreeding may modify the evolution of the interaction between V. hirundinaria and its specialist folivore. The results further suggest that herbivory may contribute to the maintenance of a mixed mating system of the host plants by selecting for outcrossing and reduced susceptibility to herbivore attack, and thus add to the growing body of evidence on the effects of inbreeding on the mating system evolution of the host plants and the dynamics of plant-herbivore interactions.
自交（通过自体受精）可能对植物适应性（即自交衰退）产生负面影响。异交，或遗传上不同的亲代植物之间的杂交，也可能破坏后代的局部适应性或等位基因共适应，再次导致植物适应性降低（即异交衰退）。自交和异交也可能通过改变植物质量或防御来增加植物对天敌的脆弱性。本研究调查了自交和异交对多年生草本植物舞鹤草(Vincetoxicum hirundinaria)大小和对食草动物侵害反应的影响。
使用来自四个不同种群的 20 个母株的自交和异交（同种群内和种群间）后代进行温室实验，量化植物的萌发、大小、对专食性食草动物三裂叶野葛(Abrostola asclepiadis)的抗性以及对模拟刈割的耐受性。
自交植物比异交植物更小，更容易受到 A. asclepiadis 的损害。然而，自交和异交植物上的食草动物生物量没有差异。自交对植物表现和抗性的影响在不同种群或家系中没有差异，而且在刈割耐受性方面根本没有自交衰退。种群间异交对植物表现和对 A. asclepiadis 的抗性没有影响，表明不存在异交衰退。
由于自交衰退对植物大小和食草动物抗性产生负面影响，因此自交可能会改变舞鹤草与其专食性食草动物之间相互作用的进化。研究结果进一步表明，食草动物可能通过选择异交和降低对食草动物攻击的敏感性来促进宿主植物混合交配系统的维持，并因此增加了关于自交对宿主植物交配系统进化和植物-食草动物相互作用动态影响的证据。
