Testing the roles of vertical transmission and drought stress in the prevalence of heritable fungal endophytes in annual grass populations
Testing the roles of vertical transmission and drought stress in the prevalence of heritable fungal endophytes in annual grass populations
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DOI：
10.1111/nph.15215
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发表时间：
2018-08-01
期刊：
影响因子：
9.4
通讯作者：
Miller, Tom E. X.
中科院分区：
文献类型：
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作者：
Cavazos, Brittany R.;Bohner, Teresa F.;Miller, Tom E. X.
有益的遗传性共生体预计将在宿主群体中达到很高的流行率，但许多共生体的流行率处于中等水平。理论预测，健康效益和垂直传播效率的平衡可能会相互作用，以稳定中间流行率。我们建立了草宿主（黑麦草）种群，其遗传性内生真菌（Epicloe ocultans）的流行率有所不同，使我们能够通过跟踪一代人的流行率变化来推断长期平衡。我们操纵了环境应激源（降水量增加），我们假设这会降低共生的适应性益处，并通过用不含内生菌的种子替换内生菌阳性种子来改变垂直传播的效率。内生菌和降水量增加都增加了寄主的适应性，但共生效应在干燥处理中并不更强，这表明共生的益处与耐旱性无关。传播减少将推断的平衡流行率从 42.6% 抑制到 11.7%。然而，降水量增加并没有改变流行率，这与它没有改变健身效益的结果一致。我们的结果表明，失败的传播可以影响可遗传微生物的流行率，并且由于允许共生体增加（健身效益）但阻止它们达到固定（失败的传播）的力量，中间流行率可以是一个稳定的平衡。
Beneficial inherited symbionts are expected to reach high prevalence in host populations, yet many are observed at intermediate prevalence. Theory predicts that a balance of fitness benefits and efficiency of vertical transmission may interact to stabilize intermediate prevalence.We established populations of grass hosts (Lolium multiflorum) that varied in prevalence of a heritable fungal endophyte (Epichloe occultans), allowing us to infer long-term equilibria by tracking change in prevalence over one generation. We manipulated an environmental stressor (elevated precipitation), which we hypothesized would reduce the fitness benefits of symbiosis, and altered the efficiency of vertical transmission by replacing endophyte-positive seeds with endophyte-free seeds.Endophytes and elevated precipitation both increased host fitness, but symbiont effects were not stronger in the drier treatment, suggesting that benefits of symbiosis were unrelated to drought tolerance. Reduced transmission suppressed the inferred equilibrium prevalence from 42.6% to 11.7%. However, elevated precipitation did not modify prevalence, consistent with the result that it did not modify fitness benefits.Our results demonstrate that failed transmission can influence the prevalence of heritable microbes and that intermediate prevalence can be a stable equilibrium due to forces that allow symbionts to increase (fitness benefits) but prevent them from reaching fixation (failed transmission).