CAREER: Maintenance of Variation in a Developmental Pathway as a Result of Environmental Heterogeneity

动物发育成雄性还是雌性取决于环境因素或雄性和雌性之间的遗传差异。启动这种雄性/雌性决定的环境线索或基因在物种之间是不同的，甚至在一个物种内也是可变的。目前尚不清楚生态因素如何促进物种内雄性/雌性决定的遗传变异的维持。为了解决这一缺点，本研究使用家蝇作为模型系统，因为该物种在如何做出雄性/雌性决策方面存在很大差异。值得注意的是，男性发育有两种常见的开始方式，它们在地理分布上有所不同。一种决定雄性的变异在北纬地区占主导地位，而另一种在南方更常见。研究人员正在调查这两种不同的变异是否因为它们在不同的温度下都是有益的而得以维持。此外，家蝇的雌性发育可以独立于雄性决定变异而启动。研究人员还在调查是否启动男性发育的变异对女性有有害影响。这些拮抗作用可以进一步解释为什么家蝇种群的雄/雌决定存在差异。将本科学生培养为高中教师将有助于本研究。这些学生将与研究人员一起为现任教师提供继续教育培训。他们还将带领初中和高中课堂进行一些练习，用家蝇来说明遗传学和进化的核心概念。这些活动将影响来自服务不足社区的学生，这些社区在科学领域的代表性不足。为了确定自然选择如何维持雄性/雌性决定的差异，研究人员将实验室实验、自然种群调查和基因组技术结合起来。具体来说，该研究验证了一种假设，即雄性/雌性特异性基因型与环境的相互作用会影响作用于Y染色体的选择压力，从而维持家蝇雄性/雌性决定的变化。非常年轻的Y染色体的环境依赖性表型效应将通过实验室实验和高通量基因表达谱进行评估。对实验室种群和野外季节等位基因频率的预测将进行测试，并对适应性效应进行建模。抑制重组维持雄性决定基因与其他具有雄性/雌性拮抗或环境特异性效应的遗传变异之间的联系的假设将通过重组作图、基因组测序和群体遗传数据来评估X-Y分化。本研究将生态相关的选择压力和雄性-雌性冲突与基本发育途径的进化联系起来，将种群遗传学和发育进化结合在一个单一的框架中。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Whether an animal develops into a male or female depends on either environmental cues or genetic differences between males and females. The environmental cues or genes that initiate this male/female-determination differ across species, and they can even be variable within a species. It is not well understood how ecological factors contribute to the maintenance of genetic variation in male/female-determination within species. To address this shortcoming, this research uses the house fly as a model system because this species has substantial variation in how the male/female decision is made. Notably, there are two common ways that male development can be initiated, and they differ in their geographical distributions. One male-determining variant predominates at northern latitudes, and the other is more common in the south. The researchers are investigating if the two different variants are both maintained because they are beneficial at different temperatures. In addition, female development can be initiated independently from the male-determining variants in house fly. The researchers are also investigating if the variants that initiate male development have deleterious effects in females. These antagonistic effects could further explain why variation in male/female-determination is maintained in house fly populations. Undergraduate students training to be high school teachers will contribute to this research. Those students will work with the researchers to provide continuing education training to current teachers. They will also lead middle and high school classrooms in exercises that use house flies to illustrate core concepts in genetics and evolution. These activities will impact students from under-served communities that are under-represented in the sciences.To determine how natural selection can maintain variation in male/female-determination, the researchers are combining laboratory experiments, surveys of natural populations, and genomic techniques. Specifically, the research tests the hypothesis that male/female-specific genotype-by-environment interactions affect selection pressures acting on Y chromosomes to maintain variation in male/female-determination in house fly. The environment-dependent phenotypic effects of very young Y chromosomes will be assessed using laboratory experiments and high throughput gene expression profiling. Predictions about allele frequencies in laboratory populations and over seasons in the wild will be tested, and fitness effects will be modeled. The hypothesis that suppressed recombination maintains linkage between male-determining genes and other genetic variation with male/female-antagonistic or environment-specific effects will be evaluated using recombination mapping, genome sequencing, and population genetic data to test for X-Y differentiation. This research connects ecologically relevant selection pressures and male-female conflict with the evolution of an essential developmental pathway, joining population genetics and the evolution of development in a single framework.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.