Modelling the two-locus architecture of divergent pollinator adaptation: how variation in SAD paralogues affects fitness and evolutionary divergence in sexually deceptive orchids

Divergent selection by pollinators can bring about strong reproductive isolation via changes at few genes of large effect. This has recently been demonstrated in sexually deceptive orchids, where studies (1) quantified the strength of reproductive isolation in the field; (2) identified genes that appear to be causal for reproductive isolation; and (3) demonstrated selection by analysis of natural variation in gene sequence and expression. In a group of closely related Ophrys orchids, specific floral scent components, namely n-alkenes, are the key floral traits that control specific pollinator attraction by chemical mimicry of insect sex pheromones. The genetic basis of species-specific differences in alkene production mainly lies in two biosynthetic genes encoding stearoyl–acyl carrier protein desaturases (SAD) that are associated with floral scent variation and reproductive isolation between closely related species, and evolve under pollinator-mediated selection. However, the implicati...

传粉媒介介导的趋异选择可通过少数效应显著的基因的变化，引发强烈的生殖隔离。这一结论近期在性欺骗型兰科植物中得到了证实：相关研究（1）在野外环境中量化了生殖隔离的强度；（2）鉴定出了与生殖隔离存在因果关联的基因；（3）通过分析基因序列与基因表达的自然变异，证实了选择作用的存在。在一组近缘眉兰属（Ophrys）植物中，特定的花香成分——即正构烯烃（n-alkenes）——是通过模拟昆虫性信息素的化学拟态，实现专一性传粉吸引的关键花部性状。烯烃合成的物种特异性差异的遗传基础，主要由两个编码硬脂酰-酰基载体蛋白去饱和酶（stearoyl–acyl carrier protein desaturases，SAD）的生物合成基因构成；这些基因与近缘物种间的花香变异和生殖隔离相关，并处于传粉媒介介导的选择压力之下。然而，其含意……