Genome size variation affects song attractiveness in grasshoppers: evidence for sexual selection against large genomes

Genome size is largely uncorrelated to organismal complexity and adaptive scenarios. Genetic drift as well as intragenomic conflict have been put forward to explain this observation. We here study the impact of genome size on sexual attractiveness in the bow-winged grasshopper Chorthippus biguttulus. Grasshoppers show particularly large variation in genome size due to the high prevalence of supernumerary chromosomes that are considered (mildly) selfish, as evidenced by non-Mendelian inheritance and fitness costs if present in high numbers. We ranked male grasshoppers by song characteristics that are known to affect female preferences in this species and scored genome sizes of attractive and unattractive individuals from the extremes of this distribution. We find that attractive singers have significantly smaller genomes, demonstrating that genome size is reflected in male courtship songs and that females prefer songs of males with small genomes. Such a genome size dependent mate prefere...基因组大小（genome size）在很大程度上与生物体复杂度及适应性演化场景并无关联。遗传漂变（genetic drift）与基因组内冲突（intragenomic conflict）已被提出用以解释这一观测现象。本研究以弓翅蚱蜢（Chorthippus biguttulus）为研究对象，探讨基因组大小对其性吸引力的影响。蚱蜢类群的基因组大小变异幅度极大，这源于其体内普遍存在的额外染色体（supernumerary chromosomes）——这类染色体被认为具有（轻度）自私性，非孟德尔遗传（non-Mendelian inheritance）特性以及高拷贝数带来的适合度代价（fitness costs）均可佐证这一点。本研究基于已知会影响该物种雌性择偶偏好的鸣唱特征对雄性蚱蜢进行排序，并选取该分布两端的高吸引力与低吸引力个体，测定其基因组大小。结果发现，鸣唱具有吸引力的雄性个体基因组显著更小，这表明雄性的求偶鸣唱可反映其基因组大小，且雌性更偏好基因组较小的雄性的鸣唱信号。此类依赖基因组大小的择偶偏好……