Department of Biological Sciences, North Dakota State University, Fargo, North Dakota, United States of America.
PLoS One. 2011;6(8):e22310. doi: 10.1371/journal.pone.0022310. Epub 2011 Aug 31.
Contemporary evolution following assisted colonization may increase the probability of persistence for refuge populations established as a bet-hedge for protected species. Such refuge populations are considered "genetic replicates" that might be used for future re-colonization in the event of a catastrophe in the native site. Although maladaptive evolutionary divergence of captive populations is well recognized, evolutionary divergence of wild refuge populations may also occur on contemporary time scales. Thus, refuge populations may lose their "value" as true genetic replicates of the native population. Here, we show contemporary evolutionary divergence in body shape in an approximately 30-year old refuge population of the protected White Sands pupfish (Cyprinodon tularosa) resulting in a body-shape mismatch with its native environment.
METHODOLOGY/PRINCIPAL FINDINGS: Geometric morphometic data were collected from C. tularosa cultures raised in experimental mesocosms. Cultures were initiated with fish from the two native populations, plus hybrids, in high or low salinity treatments representing the salinities of the two native habitats. We found that body shape was heritable and that shape variation due to phenotypic plasticity was small compared to shape variation due to population source. C. tularosa from the high salinity population retained slender body shapes and fish from the low salinity population retained deep body shapes, irrespective of mesocosm salinity. These data suggest that the observed divergence of a recently established pupfish population was not explained by plasticity. An analysis of microsatellite variation indicated that no significant genetic drift occurred in the refuge population, further supporting the adaptive nature of changes in body shape. These lines of evidence suggest that body shape divergence of the refuge population reflects a case of contemporary evolution (over a 30-year period).
CONCLUSIONS/SIGNIFICANCE: These results suggest assisted colonization can introduce novel, and/or relaxed selection, and lead to unintended evolutionary divergence.
受人为协助的殖民活动后出现的当代进化，可能会增加避难种群得以持续的概率，这些避难种群是为受保护物种建立的避险措施。这些避难种群被认为是“遗传复制品”，在原生地发生灾难时，可用于未来的再殖民。尽管人们已经充分认识到圈养种群的适应性进化分歧，但野生避难种群的进化分歧也可能在当代时间尺度上发生。因此，避难种群可能会失去其作为原生种群真正遗传复制品的“价值”。在这里，我们展示了受保护的白沙沙丘小鱼（Cyprinodon tularosa）的一个约 30 年历史的避难种群在体型上出现的当代进化分歧，导致其与原生环境的体型不匹配。
方法/主要发现：从小鱼在实验中生长的中观模型中收集了 Cyprinodon tularosa 的几何形态计量数据。这些种群是从两个原生种群以及它们的杂交种群中引入的，分为高盐和低盐处理，分别代表了两个原生栖息地的盐度。我们发现，体型是可遗传的，而且由于表型可塑性引起的形状变化与由于种群来源引起的形状变化相比很小。来自高盐种群的小鱼保留了细长的体型，而来自低盐种群的小鱼保留了深的体型，无论中观模型的盐度如何。这些数据表明，最近建立的小鱼种群的观察到的分歧不能用可塑性来解释。对微卫星变异的分析表明，避难种群没有发生显著的遗传漂变，这进一步支持了体型变化的适应性。这些证据表明，避难种群的体型分歧反映了当代进化（30 年期间）的一个例子。
结论/意义：这些结果表明，人为协助的殖民活动可以引入新的和/或放松的选择，并导致意外的进化分歧。
