The geographic mosaic of arms race coevolution is closely matched to prey population structure
The geographic mosaic of arms race coevolution is closely matched to prey population structure
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DOI：
10.1002/evl3.184
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发表时间：
2020-06-09
影响因子：
5
通讯作者：
Brodie, Edmund D., III
中科院分区：
文献类型：
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作者：
Hague, Michael T. J.;Stokes, Amber N.;Brodie, Edmund D., III
相互适应是军备竞赛共同进化的标志。当地的天敌之间的相互适应应该产生一个地理马赛克模式，这两个物种在其共享的范围大致匹配的能力。然而，生态相关性状的镶嵌变异也可能来自与相互选择无关的过程，如种群结构或当地环境条件。我们测试了这些替代的过程是否可以解释在地理马赛克的军备竞赛协同进化之间的抗性束带蛇（Thamnophis sirtalis）和有毒蝾螈（Taricha granulosa）的性状变异。我们发现，捕食者的抗性和猎物毒素水平在功能上相匹配的共同发生的人口，这表明镶嵌变化的军备两个物种的结果从当地的压力相互选择。出于同样的原因，抗蛇性的表型和遗传变异偏离了种群遗传分化的中性预期，显示出蝾螈适应当地毒素水平的明显特征。相反，蝾螈毒素水平最好预测蝾螈种群之间的遗传分化，并在较小程度上，由当地环境和蛇的抵抗力。夸张的军备表明，共同进化发生在某些热点，但猎物的人口结构似乎是特别的影响，在整个地理镶嵌在两个物种的局部表型变异。我们的研究结果意味着，过程以外的互惠选择，如历史地理和环境压力，代表了一个重要的来源的变化，在地理镶嵌的共同进化。这种模式支持地理镶嵌理论中“性状再混合”的作用，即非适应性力量决定物种间相互作用的空间变异的过程。
Reciprocal adaptation is the hallmark of arms race coevolution. Local coadaptation between natural enemies should generate a geographic mosaic pattern where both species have roughly matched abilities across their shared range. However, mosaic variation in ecologically relevant traits can also arise from processes unrelated to reciprocal selection, such as population structure or local environmental conditions. We tested whether these alternative processes can account for trait variation in the geographic mosaic of arms race coevolution between resistant garter snakes (Thamnophis sirtalis) and toxic newts (Taricha granulosa). We found that predator resistance and prey toxin levels are functionally matched in co-occurring populations, suggesting that mosaic variation in the armaments of both species results from the local pressures of reciprocal selection. By the same token, phenotypic and genetic variation in snake resistance deviates from neutral expectations of population genetic differentiation, showing a clear signature of adaptation to local toxin levels in newts. Contrastingly, newt toxin levels are best predicted by genetic differentiation among newt populations, and to a lesser extent, by the local environment and snake resistance. Exaggerated armaments suggest that coevolution occurs in certain hotspots, but prey population structure seems to be of particular influence on local phenotypic variation in both species throughout the geographic mosaic. Our results imply that processes other than reciprocal selection, like historical biogeography and environmental pressures, represent an important source of variation in the geographic mosaic of coevolution. Such a pattern supports the role of "trait remixing" in the geographic mosaic theory, the process by which non-adaptive forces dictate spatial variation in the interactions among species.