近亲繁殖的花卉多态性经常被打破,由于同源风格的形成,导致了自体受精的进化。这里,远端报春花中花卉多态性的丧失,一种限制在川西的亚高山物种,中国,通过调查交配系统转变的生态相关性和遗传后果进行了检查。解决了几个关键问题。(1)什么是频率,远端和同型种群中花形态的地理分布和繁殖特征?(2)海拔升高是否会影响传粉媒介服务和种群近亲繁殖的可能性?(3)同体起源的频率和种群遗传多样性的数量和分布的破坏的后果是什么?
对整个P.oreodoxa范围内的14个种群进行了采样,并记录变形频率和花卉特征。微卫星位点的多态性和叶绿体DNA(cpDNA)变异用于量化种群遗传结构和种群之间的遗传关系。进行了控制性授粉和花粉管生长和繁殖力的研究,以确定种群的相容性状况及其自主自花授粉的设施。最后,比较了长舌和短舌传粉媒介对不同海拔的远端和同型种群的访问率,以确定海拔升高是否与传粉媒介服务的恶化有关。
与大多数杂种相反,P.oreodoxa的远端和同型变体都是高度自相容的,但只有同系物具有自主自花授粉的设施。同质花序在开放授粉后的果实和种子比远端花序明显更多。长舌传粉者的访视在同风格种群中显着降低,昆虫的总体探视率随海拔升高而下降。同源种群的遗传多样性明显较低,有证据表明在较高海拔地区近亲繁殖增加。cpDNA变异的模式与种群之间从远端到同态和有限的基因流的多个过渡相一致。
这项研究的结果支持了这样的假设,即远端P.oreodoxa的花卉多态性的多重丧失与不令人满意的传粉服务有关,由于自主自花授粉,同种型受益于生殖保证。
The outbreeding floral polymorphism heterostyly frequently breaks down, resulting in the evolution of self-fertilization as a result of homostyle formation. Here, the loss of floral polymorphism in distylous Primula oreodoxa, a sub-alpine species restricted to western Sichuan,
China, was examined by investigating the ecological correlates and genetic consequences of mating system transitions. Several key questions were addressed. (1) What are the frequencies, geographical distribution and reproductive characteristics of floral morphs in distylous and homostylous populations? (2) Does increased elevation influence pollinator service and the likelihood of inbreeding in populations? (3) How often has homostyly originated and what are the consequences of the breakdown of distyly for the amounts and distribution of genetic diversity in populations?
Fourteen populations throughout the range of P. oreodoxa were sampled, and morph frequencies and floral characteristics were recorded. Polymorphism at microsatellite loci and chloroplast DNA (cpDNA) variation were used to quantify population genetic structure and genetic relationships among populations. Controlled pollinations and studies of pollen tube growth and fertility were conducted to determine the compatibility status of populations and their facility for autonomous self-pollination. Finally, visitation rates of long- and short-tongued pollinators to distylous and homostylous populations at different elevations were compared to determine if increased elevation was associated with deterioration in pollinator service.
In contrast to most heterostylous species, both distylous and homostylous morphs of P. oreodoxa are highly self-compatible, but only homostyles have the facility for autonomous self-pollination. Homostyles set significantly more fruit and seeds following open pollination than the distylous morphs. Visitation by long-tongued pollinators was significantly lower in homostylous populations, and overall rates of insect visitation decreased with elevation. Genetic diversity was significantly lower in homostylous populations, with evidence of increased inbreeding at higher elevation. Patterns of cpDNA variation were consistent with multiple transitions from distyly to homostyly and limited gene flow among populations.
The results of this study support the hypothesis that the multiple loss of floral polymorphism in distylous P. oreodoxa is associated with unsatisfactory pollinator service, with homostyles benefiting from reproductive assurance as a result of autonomous self-pollination.