Department of Biology, Indiana University, Bloomington, Indiana 47405.
Am Nat. 2013 Oct;182(4):484-93. doi: 10.1086/671996. Epub 2013 Aug 20.
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 positively correlated at all spatial scales. Our results thus suggest that parasite-mediated selection contributes to the long-term coexistence of sexual and asexual individuals in coevolutionary hotspots, and that the "warmth" of hotspots can vary on small spatial scales.
理解同一种物种的有性和无性形式如何共存是进化生物学面临的挑战。红皇后假说预测，性是寄生虫介导的选择对常见无性基因型的有利选择，导致有性和无性宿主共存。在地理镶嵌中，感染的风险在空间上变化，该理论还预测有性生殖与疾病流行呈正相关。我们通过使用偏 Mantel 检验比较新西兰淡水蜗牛 Potamopyrgus antipodarum 的湖种群的感染频率和雄性频率的成对差异矩阵，在三个空间尺度上检验了这一假设：南岛各湖泊之间、密集采样的湖泊（亚历山德拉湖）内的不同深度之间以及亚历山德拉湖内的不同深度之间。我们发现，在所有空间尺度上，感染风险的差异和有性蜗牛比例的差异均呈显著正相关。因此，我们的研究结果表明，寄生虫介导的选择有助于协同进化热点中长期有性和无性个体的共存，并且热点的“温暖”在小的空间尺度上可能会有所不同。
