Department of Evolutionary and Environmental Biology, Institute of Evolution, University of Haifa, Haifa, Israel.
Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Mol Ecol. 2018 Aug;27(15):3116-3130. doi: 10.1111/mec.14767. Epub 2018 Jul 11.
The fire ant Solenopsis invicta and its close relatives are highly invasive. Enhanced social cooperation may facilitate invasiveness in these and other invasive ant species. We investigated whether invasiveness in Solenopsis fire ants was accompanied by positive selection on sociobiological traits by applying a phylogenomics approach to infer ancient selection, and a population genomics approach to infer recent and ongoing selection in both native and introduced S. invicta populations. A combination of whole-genome sequencing of 40 haploid males and reduced-representation genomic sequencing of 112 diploid workers identified 1,758,116 and 169,682 polymorphic markers, respectively. The resulting high-resolution maps of genomic polymorphism provide high inference power to test for positive selection. Our analyses provide evidence of positive selection on putative ion channel genes, which are implicated in neurological functions, and on vitellogenin, which is a key regulator of development and caste determination. Furthermore, molecular functions implicated in pheromonal signalling have experienced recent positive selection. Genes with signatures of positive selection were significantly more often those overexpressed in workers compared with queens and males, suggesting that worker traits are under stronger selection than queen and male traits. These results provide insights into selection pressures and ongoing adaptation in an invasive social insect and support the hypothesis that sociobiological traits are under more positive selection than nonsocial traits in such invasive species.
红火蚁及其近缘种具有很强的入侵性。增强的社会合作可能有助于这些和其他入侵性蚂蚁物种的入侵性。我们通过应用系统基因组学方法推断古代选择，以及通过群体基因组学方法推断原生和引入的红火蚁种群中的近期和持续选择，来研究红火蚁的入侵性是否伴随着社会生物学特征的正选择。对 40 个单倍体雄性个体进行全基因组测序和对 112 个二倍体工蚁进行简化基因组测序，分别鉴定出了 1758116 个和 169682 个多态性标记。由此产生的基因组多态性高分辨率图谱提供了高推断能力，可用于检测正选择。我们的分析结果为离子通道基因的正选择提供了证据，离子通道基因与神经功能有关，而卵黄蛋白原是发育和等级决定的关键调节剂。此外，与信息素信号分子功能相关的基因也经历了近期的正选择。具有正选择特征的基因在工蚁中表达的频率明显高于在蚁后和雄蚁中表达的频率，这表明工蚁的特征受到更强的选择，而蚁后和雄蚁的特征则受到较弱的选择。这些结果为入侵性社会昆虫的选择压力和正在进行的适应提供了深入的了解，并支持这样的假设，即社会性特征比非社会性特征在这些入侵物种中受到更强的正选择。
