Sexual selection studies widely estimate several metrics, but values may be inaccurate because standard field methods for studying wild populations produce limited data (e.g., incomplete sampling, inability to observe copulations directly). We compared four selection metrics (Bateman gradient, opportunity for sexual selection, opportunity for selection, and $s_{\max }^{\prime }$) estimated with simulated complete and simulated limited data for 15 socially monogamous songbird species with extrapair paternity (4%–54% extrapair offspring). Inferring copulation success from offspring parentage creates nonindependence between these variables and systematically underestimates copulation success. We found that this introduces substantial bias for the Bateman gradient, opportunity for sexual selection, and $s_{\max }^{\prime }$. Notably, 47.5% of detected Bateman gradients were significantly positive for females, suggesting selection on females to copulate with multiple males, although the true Bateman gradient was zero. Bias generally increased with the extent of other sources of data limitations tested (nest predation, male infertility, and unsampled floater males). Incomplete offspring sampling introduced bias for all of the metrics except the Bateman gradient, while incomplete sampling of extrapair sires did not introduce additional bias when sires were a random subset of breeding males. Overall, our findings demonstrate how biases due to field data limitations can strongly impact the study of sexual selection.

中文翻译：

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通用字段数据限制可能会使性别选择指标产生重大偏差。

性选择研究广泛估计了几种指标，但由于用于野外种群研究的标准野外方法产生的数据有限（例如，采样不完整，无法直接观察交配），其值可能不准确。我们比较了四个选择指标（贝特曼梯度，性选择的机会，选择的机会和$s_{\mathrm{最高}}^{\prime }$），使用模拟完整和有限模拟数据对15种具有超配对亲子关系的社会一夫一族鸣禽物种（后代超配对的4％–54％）进行了估计。从后代父母身份推断交配成功会导致这些变量之间的非独立性，并系统地低估了交配成功。我们发现这给Bateman梯度，性选择机会和$s_{\mathrm{最高}}^{\prime }$。值得注意的是，检测到的Bateman梯度中有47.5％的雌性显着为阳性，这表明尽管真正的Bateman梯度为零，但还是选择雌性来交配多个雄性。偏见通常随着测试数据限制的其他来源（巢捕食，雄性不育和未采样的浮游动物）而增加。不完整的后代采样对除Bateman梯度以外的所有指标均产生了偏倚，而当成对是雄性成年雄性的随机子集时，对对父本的不完全采样并没有引入额外的偏见。总体而言，我们的发现表明，由于田间数据有限而造成的偏见如何严重影响性选择研究。