Ecological experiments usually infer long-term processes from short-term data, and the analysis of geographic range limits is a good example. Species' geographic ranges may be limited by low fitness due to niche constraints, a hypothesis most directly tested by comparing the fitness of populations transplanted within and beyond the range. Such studies often fail to find beyond-range fitness declines strong enough to conclude that geographic range limits are solely imposed by niche limits. However, almost all studies only follow transplants for a single generation, which will underestimate the importance of niche limitation because critical but infrequent range-limiting events may be missed and methodological issues may artificially boost the fitness of beyond-range transplants. Here, we present the first multi-generation beyond-range transplant experiment that involves adequate replication and proper experimental controls. In 2005, experimental populations of the coastal dune plant Camissoniopsis cheiranthifolia were planted at four sites within and one site beyond the northern limit. Fitness of initial transplants was high beyond the limit, suggesting that the range was limited by dispersal and not niche constraints. To better address the niche-limitation hypothesis, we quantified density and fitness of descendant C. cheiranthifolia populations 12–14 yr (˜10 generations) after transplant. Average annual fruit production and density of reproductive individuals were as high beyond the range as at four comparable experimental populations and eight natural populations within the range, and the beyond-range population had more than tripled in size since it was planted. This provides unprecedented support for the conclusion that northern range limit of C. cheiranthifolia results from something other than niche limitation, likely involving constraints on local dispersal.

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超出物种自然范围的实验种群的长期持久性

生态实验通常从短期数据推断长期过程，地理范围限制的分析就是一个很好的例子。由于生态位限制，物种的地理范围可能受到低适应度的限制，这一假设最直接通过比较范围内和范围外移植种群的适应度来检验。此类研究通常无法发现超出范围的适应性下降足以得出地理范围限制仅由生态位限制强加的结论。然而，几乎所有的研究都只关注单代移植，这将低估生态位限制的重要性，因为可能会错过关键但不常见的范围限制事件，并且方法学问题可能会人为地提高超范围移植的适应性。这里，我们展示了第一个多代超范围移植实验，涉及充分的复制和适当的实验控制。2005年，沿海沙丘植物实验种群Camissoniopsis cheiranthifolia种植在北部界限内的四个地点和一个地点以外的地点。初始移植的适应度很高，超出了限制，这表明该范围受到分散而非生态位约束的限制。为了更好地解决生态位限制假设，我们量化了后代C 的密度和适应度。 移植后 12-14 年（~10 代）的cheiranthifolia种群。超出范围的平均年果实产量和繁殖个体的密度与范围内的四个可比较的实验种群和八个自然种群一样高，并且自种植以来，超出范围的种群规模增加了两倍多。这为以下结论提供了前所未有的支持：Ç。 cheiranthifolia不是生态位限制的结果，可能涉及对本地扩散的限制。