Abstract Attributing biological explanations to observed ecogeographical and ecological patterns require eliminating potential statistical and sampling artifacts as alternative explanations of the observed patterns. Here, we assess the role of sample size, statistical power, and geographic inclusivity on the general validity and statistical significance of relationships between body size and latitude for 3 well-studied species of turtles. We extend those analyses to emphasize the importance of using statistically robust data in determining macroecological patterns. We examined intraspecific trends in body size with latitude in Chelydra serpentina, Chrysemys picta, and Trachemys scripta using Pearson’s correlations, diagnostic tests for influential points, and resampling. Existing data were insufficient to ascertain a latitudinal trend in body size for C. serpentina or T. scripta. There was a significant relationship for C. picta, however, resampling analyses show that, on average, 16 of the 23 available independent populations were needed to demonstrate a significant relationship and that at least 20 of 23 populations were required to obtain a statistically powerful correlation between body size and latitude. Furthermore, restricting the latitudes of populations resampled shows that body size trends of C. picta were largely due to leveraging effects of populations at the edge of the species range. Our results suggest that broad inferences regarding ecological trends in body size should be made with caution until underlying (intraspecific) patterns in body size can be statistically and conclusively demonstrated.

中文翻译：

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检测体型趋势：种内分析的经验和统计要求

摘要 将生物学解释归因于观察到的生态地理和生态模式需要消除潜在的统计和采样伪像作为对观察到的模式的替代解释。在这里，我们评估了样本大小、统计能力和地理包容性对 3 种研究充分的海龟物种的体型和纬度之间关系的一般有效性和统计显着性的作用。我们扩展了这些分析，以强调使用统计上可靠的数据来确定宏观生态模式的重要性。我们使用 Pearson 相关性、影响点的诊断测试和重采样检查了 Chelydra serpentina、Chrysemys picta 和 Trachemys scripta 中体型随纬度的种内趋势。现有数据不足以确定 C. serpentina 或 T. scripta 体型的纬度趋势。C. picta 存在显着相关性，但是，重采样分析表明，平均而言，需要 23 个可用独立种群中的 16 个才能证明显着关系，并且至少需要 23 个种群中的 20 个才能获得统计上强大的相关性在体型和纬度之间。此外，限制重新采样的种群的纬度表明 C. picta 的体型趋势主要是由于种群在物种范围边缘的杠杆作用。我们的结果表明，在体型的潜在（种内）模式可以统计和最终证明之前，应谨慎对体型的生态趋势进行广泛的推论。