DISSERTATION RESEARCH: Possible evolution of a novel ZW chromosome system in a hybrid laboratory population of the copepod Tigriopus californicus

在有性繁殖的生物中，雄性和雌性通过多种方式分配给后代，最常见的是通过性染色体（人类、苍蝇的XX雌性和XY雄性；鸟类、蝴蝶的ZW雌性和ZZ雄性）。尽管近亲物种的性别决定机制常常不同，但人们对它们进化的原因却知之甚少。海洋甲壳类动物加利福尼亚虎爪有许多遗传隔离的种群和多基因（遗传，但非染色体）性别决定。先前对实验室创造的杂交种群的研究表明，雌性而不是雄性在整个染色体上通常是杂合的（每个原始种群都有一个副本），这表明它可能是Z/W性染色体。该项目将对来自该杂交种群及其野生祖先的个体进行下一代DNA测序，以确定每个种群的性别决定机制，并确定该杂交种群是否进化出新的性染色体。这个项目调查了地球上最丰富的动物群体之一——桡足类动物性别决定的遗传基础。性染色体是进化的一个可预测的结果。性染色体在杂交群体中的出现表明，性别决定机制的开关可能是杂交诱导的基因组破坏的结果。鉴于由于人类驱动的过程（如物种引入和气候变化引起的范围转移），自然种群中杂交现象日益增多，这一点尤为重要。此外，该项目还将包括对本科生的广泛指导，以及在加州长滩太平洋水族馆举办的进化和科学交流研讨会

Among sexually reproducing organisms, the allocation of maleness and femaleness to offspring occurs in many ways, most familiarly, via sex chromosomes (XX females and XY males in humans, flies; ZW females and ZZ males in birds, butterflies). Although closely-related species often differ in their sex determination mechanisms, why those evolve is poorly understood. The marine crustacean Tigriopus californicus has many genetically isolated populations and polygenic (genetic, but non-chromosomal) sex determination. Previous work with a laboratory-created hybrid population revealed that females, but not males, are often heterozygous across an entire chromosome (bearing one copy from each original population), suggesting that it could be acting as a Z/W sex chromosome. This project will use next-generation DNA sequencing on individuals from this hybrid population and its wild progenitors to identify identify the sex determination mechanism in each population and to ascertain whether the hybrid population has evolved a novel sex chromosome.This project investigates the genetic basis of sex determination in copepods, one of the most abundant animal groups on the planet. Sex chromosomes are a predictable outcome of evolution. The emergence of a sex chromosome in a hybrid population would suggest that sex determination mechanism switches could be a consequence of hybridization-induced genomic disruption. This is especially important in light of the increasing hybridization occurring in natural populations due to human-driven processes, such as species introductions and climate change-induced range shifts. In addition, the project will include extensive mentoring of undergraduates, and an evolution and science communication workshop at the Aquarium of the Pacific, Long Beach, CA