Foy Patrick D, Loetzerich Sara R, Boxler David, Burgess Edwin R, Trout Fryxell R T, Gerry Alec C, Hinkle Nancy C, Machtinger Erika T, Olds Cassandra, Tarone Aaron M, Watson Wes, Scott Jeffrey G, Meisel Richard P
Department of Biology and Biochemistry, University of Houston, Houston, TX.
Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE.
J Hered. 2024 Oct 15. doi: 10.1093/jhered/esae056.
Sex chromosomes often differ between closely related species and can even be polymorphic within populations. Species with multifactorial sex determination segregate for multiple different sex determining loci within populations, making them uniquely informative of the selection pressures that drive the evolution of sex chromosomes. The house fly (Musca domestica) is a model species for studying multifactorial sex determination because male determining genes have been identified on all six of the chromosomes, which means that any chromosome can be a "proto-Y". Natural populations of house fly also segregate for a recently derived female-determining locus, meaning house flies also have a proto-W chromosome. The different proto-Y chromosomes are distributed along latitudinal clines on multiple continents, their distributions can be explained by seasonality in temperature, and they have temperature-dependent effects on physiological and behavioral traits. It is not clear, however, how the clinal distributions interact with the effect of seasonality on the frequencies of house fly proto-Y and proto-W chromosomes across populations. To address this question, we measured the frequencies of house fly proto-Y and proto-W chromosomes across nine populations in the United States of America. We confirmed the clinal distribution along the eastern coast of North America, but it is limited to the eastern coast. In contrast, annual mean daily temperature range predicts proto-Y chromosome frequencies across the entire continent. Our results therefore suggest that temperature heterogeneity can explain the distributions of house fly proto-Y chromosomes in a way that does not depend on the cline.
性染色体在亲缘关系较近的物种之间往往存在差异，甚至在种群内部也可能具有多态性。具有多因素性别决定的物种在种群中会分离出多个不同的性别决定位点，这使得它们对于驱动性染色体进化的选择压力具有独特的信息价值。家蝇（Musca domestica）是研究多因素性别决定的模式物种，因为已在所有六条染色体上鉴定出雄性决定基因，这意味着任何一条染色体都可能是“原始Y染色体”。家蝇的自然种群中还分离出了一个最近衍生的雌性决定位点，这意味着家蝇也有原始W染色体。不同的原始Y染色体分布在多个大陆的纬度梯度上，它们的分布可以用温度的季节性来解释，并且它们对生理和行为特征具有温度依赖性影响。然而，尚不清楚这种梯度分布如何与季节性对不同种群家蝇原始Y染色体和原始W染色体频率的影响相互作用。为了解决这个问题，我们测量了美国九个种群中家蝇原始Y染色体和原始W染色体的频率。我们证实了沿北美东海岸的梯度分布，但仅限于东海岸。相比之下，年平均日温度范围可以预测整个大陆的原始Y染色体频率。因此，我们的结果表明，温度异质性可以以一种不依赖于梯度的方式解释家蝇原始Y染色体的分布。
