General Zoology, Institute of Biology, Martin-Luther-University Halle-Wittenberg, Hoher Weg 8, 06120, Halle (Saale), Germany.
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Deutscher Platz 5e, 04103, Leipzig, Germany.
BMC Evol Biol. 2018 Dec 19;18(1):196. doi: 10.1186/s12862-018-1313-z.
Adaptation to local host plants may impact a pollinator's population genetic structure by reducing gene flow and driving population genetic differentiation, representing an early stage of ecological speciation. South African Rediviva longimanus bees exhibit elongated forelegs, a bizarre adaptation for collecting oil from floral spurs of their Diascia hosts. Furthermore, R. longimanus foreleg length (FLL) differs significantly among populations, which has been hypothesised to result from selection imposed by inter-population variation in Diascia floral spur length. Here, we used a pooled restriction site-associated DNA sequencing (pooled RAD-seq) approach to investigate the population genetic structure of R. longimanus and to test if phenotypic differences in FLL translate into increased genetic differentiation (i) between R. longimanus populations and (ii) between phenotypes across populations. We also inferred the effects of demographic processes on population genetic structure and tested for genetic markers underpinning local adaptation. RESULTS: Populations showed marked genetic differentiation (average F = 0.165), though differentiation was not statistically associated with differences between populations in FLL. All populations exhibited very low genetic diversity and were inferred to have gone through recent bottleneck events, suggesting extremely low effective population sizes. Genetic differentiation between samples pooled by leg length (short versus long) rather than by population of origin was even higher (F = 0.260) than between populations, suggesting reduced interbreeding between long and short-legged individuals. Signatures of selection were detected in 1119 (3.8%) of a total of 29,721 SNP markers, CONCLUSIONS: Populations of R. longimanus appear to be small, bottlenecked and isolated. Though we could not detect the effect of local adaptation (FLL in response to floral spurs of host plants) on population genetic differentiation, short and long legged bees appeared to be partially differentiated, suggesting incipient ecological speciation. To test this hypothesis, greater resolution through the use of individual-based whole-genome analyses is now needed to quantify the degree of reproductive isolation between long and short legged bees between and even within populations.
对当地宿主植物的适应可能会通过减少基因流和驱动种群遗传分化来影响传粉者的种群遗传结构，这代表了生态物种形成的早期阶段。南非的 Rediviva longimanus 蜜蜂具有细长的前腿，这是一种奇异的适应方式，用于从它们的 Diascia 宿主的花距中收集油。此外，R. longimanus 的前腿长度（FLL）在种群之间存在显著差异，据推测这是由 Diascia 花距长度的种群间变异所导致的选择造成的。在这里，我们使用了一种 pooled restriction site-associated DNA sequencing（pooled RAD-seq）方法来研究 R. longimanus 的种群遗传结构，并测试 FLL 的表型差异是否会导致（i）R. longimanus 种群之间以及（ii）种群之间的遗传分化增加。我们还推断了人口统计过程对种群遗传结构的影响，并测试了支持局部适应的遗传标记。结果：种群表现出明显的遗传分化（平均 F = 0.165），尽管分化与 FLL 之间的种群差异没有统计学上的关联。所有种群的遗传多样性都非常低，据推测它们经历了最近的瓶颈事件，这表明有效种群规模极低。根据腿长（短与长）而不是起源种群对样本进行分组的遗传分化（F = 0.260）甚至高于种群之间的遗传分化，这表明长腿和短腿个体之间的杂交减少。在总共 29721 个 SNP 标记中，检测到了 1119 个（3.8%）选择标记的存在。结论：R. longimanus 的种群似乎很小，处于瓶颈和孤立状态。虽然我们无法检测到局部适应（对宿主植物花距的 FLL 反应）对种群遗传分化的影响，但短腿和长腿蜜蜂似乎已经部分分化，这表明生态物种形成的初期阶段已经出现。为了验证这一假设，现在需要通过使用基于个体的全基因组分析来获得更大的分辨率，以量化长腿和短腿蜜蜂之间甚至在种群内部的繁殖隔离程度。
