Habitat suitability estimated with probability of occurrence in species distribution models (SDMs) is used in conservation to identify geographic areas that are most likely to harbor individuals of interest. In theory, probability of occurrence is coupled with individual fitness so that individuals have higher fitness at the centre of their species environmental niche than at the edges, which we here define as ‘fitness‐centre' hypothesis. However, such relationship is uncertain and has been rarely tested across multiple species. Here, we quantified the relationship between coarse‐scale probability of occurrence projected with SDMs and individual fitness in 66 tree species native of North America. We used 1) field data of individuals' growth rate (height and diameter standardized by age) available from the United States Forest Inventory Analysis plots; and 2) common garden data collected from 23 studies reporting individual growth rate, survival, height and diameter of individuals originated from different provenances in United States and Canada. We show ‘fitness–centre' relationships are rare, with only 12% and 11% of cases showing a significant positive correlation for field and common garden data, respectively. Furthermore, we found the ‘fitness–centre' relationship is not affected by the precision of the SDMs and it does not depend upon dispersal ability and climatic breath of the species. Thus, although the ‘fitness–centre' relationship is supported by theory, it does not hold true in nearly any species. Because individual fitness plays a relevant role in buffering local extinction and range contraction following climatic changes and biotic invasions, our results encourage conservationists not to assume the ‘fitness–centre' relationship when modelling species distribution.

中文翻译：

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个体适应度与北美树木发生的粗略概率分离

在物种分布模型（SDM）中用发生概率估算的栖息地适宜性用于保护，以识别最有可能藏有关注个人的地理区域。从理论上讲，发生的可能性与个体适应度相关联，因此个体在其物种环境生态位的中心处比在边缘处具有更高的适应度，在这里我们将其定义为“适应中心”假说。但是，这种关系尚不确定，很少在多个物种之间进行过测试。在这里，我们量化了SDM预测的粗尺度发生概率与北美66种树种的个体适应度之间的关系。我们使用了1）个人的现场数据 可从美国森林清单分析区获得的增长率（按年龄标准化的高度和直径）；2）从23项研究中收集的公共花园数据，这些数据报告了来自美国和加拿大不同来源的个体的生长速度，存活率，身高和直径。我们显示“适合度-中心”关系很少见，只有12％和11％的案例分别与田间数据和公共花园数据显示显着正相关。此外，我们发现“适合度-中心”关系不受SDM精度的影响，并且不取决于物种的扩散能力和气候呼吸。因此，尽管“适合度—中心”关系得到了理论的支持，但它几乎在任何物种中都不成立。