The geographic mosaic of sex and infection in lake populations of a New Zealand snail at multiple spatial scales

Understanding how sexual and asexual forms of the same species coexist is a challenge for evolutionary biology. The Red Queen hypothesis predicts that sex is favored by parasite-mediated selection against common asexual genotypes, leading to the coexistence of sexual and asexual hosts. In a geographic mosaic, where the risk of infection varies in space, the theory also predicts that sexual reproduction would be positively correlated with disease prevalence. We tested this hypothesis in lake populations of a New Zealand freshwater snail, Potamopyrgus antipodarum, by comparing pairwise difference matrices for infection frequency and male frequency using partial Mantel tests. We conducted the test at three spatial scales: among lakes on the South Island, among depths within an intensively sampled lake (Lake Alexandrina), and within depths at Lake Alexandrina. We found that the difference in infection risk and the difference in the proportion of sexual snails were significantly and positive...

解析同一物种的有性与无性生殖个体共存机制，是进化生物学领域的一项核心挑战。红皇后假说（Red Queen hypothesis）预测：寄生虫介导的针对常见无性基因型的选择会对有性生殖产生选择优势，最终促成有性与无性生殖宿主的共存。在感染风险存在空间异质性的地理镶嵌格局中，该理论同样预测：有性生殖频率与疾病流行率呈正相关关系。我们以新西兰淡水螺*Potamopyrgus antipodarum*的湖泊种群为研究对象，通过偏曼特尔检验（partial Mantel test）比较感染频率与雄性频率的成对差异矩阵，对该假说进行验证。本研究设置三类空间尺度开展检验：南岛各湖泊之间、高强度采样的亚历山德里娜湖（Lake Alexandrina）内不同水深之间，以及亚历山德里娜湖同一水深内部。研究结果显示，感染风险差异与有性螺类占比差异之间存在显著的正向相关关系……