Theory predicts that the strength of male mate choice should vary depending on male quality when higher-quality males receive greater fitness benefits from being choosy. This pattern extends to differences in male body size, with larger males often having stronger pre- and post-copulatory preferences than smaller males. We sought to determine whether large males and small males differ in the strength (or direction) of their preference for large, high-fecundity females using the fruit fly, Drosophila melanogaster. We measured male courtship preferences and mating duration to show that male body size had no impact on the strength of male mate choice; all males, regardless of their size, had equally strong preferences for large females. To understand the selective pressures shaping male mate choice in males of different sizes, we also measured the fitness benefits associated with preferring large females for both large and small males. Male body size did not affect the benefits that males received: large and small males were equally successful at mating with large females, received the same direct fitness benefits from mating with large females, and showed similar competitive fertilization success with large females. These findings provide insight into why the strength of male mate choice was not affected by male body size in this system. Our study highlights the importance of evaluating the benefits and costs of male mate choice across multiple males to predict when differences in male mate choice should occur.

中文翻译：

---

雄性果蝇的体型大小并不影响雄性果蝇对优质雌性果蝇的择偶强度。

理论预测，当较高质量的雄性通过挑剔而获得更大的健康益处时，雄性择偶的强度应该根据雄性的质量而变化。这种模式延伸到雄性体型的差异，较大的雄性通常比较小的雄性有更强的交配前和交配后偏好。我们试图利用果蝇（Drosophila melanogaster）来确定大型雄性和小型雄性对大型、高繁殖力雌性的偏好强度（或方向）是否不同。我们测量了雄性的求爱偏好和交配持续时间，结果表明雄性的体型对雄性择偶的强度没有影响；所有雄性，无论体型大小，都对体型较大的雌性有着同样强烈的偏好。为了了解影响不同体型雄性择偶的选择性压力，我们还测量了与体型较大和体型较小的雄性相比，更喜欢体型较大的雌性所带来的健康益处。雄性体型大小并不影响雄性获得的好处：大型和小型雄性在与大型雌性交配时同样成功，从与大型雌性交配中获得相同的直接健康益处，并且与大型雌性表现出类似的竞争受精成功率。这些发现让我们深入了解为什么在这个系统中雄性择偶的强度不受雄性体型的影响。我们的研究强调了评估多个雄性择偶的收益和成本的重要性，以预测何时会出现雄性择偶差异。