DISSERTATION RESEARCH: A Test of Faster-X Evolution in Lepidoptera

生物多样性是通过新物种的形成而产生的。在一些生物中，特别是蝴蝶，物种之间的差异往往是由于X染色体上的基因，染色体负责决定性别。X染色体上的基因可能比常染色体基因进化得更快，这可以解释为什么X染色体在物种分化中起着如此重要的作用。X连锁基因的快速进化，或“快速X”进化，可以通过比较位于X染色体上的基因与其他染色体（常染色体）之间的DNA序列变化的数量来确定。为了验证这一假设，将分析云蝶和橙子硫蝶（Colias philodice和C. eurytheme，分别）。一些区别这些蝴蝶的特征，如翅膀色素沉着，配偶选择和生育能力，已经被遗传映射到X染色体上，提供了一个“最佳情况”系统来测试快速X进化假说。现代进化生物学家对种群内基因如何进化有着令人印象深刻的理解，但对物种之间差异的遗传基础的理解却很差。这项研究将阐明物种形成的遗传基础，为调节地球生物多样性的基本进化过程提供见解。它还将提供对允许不同物种持续存在的遗传属性的深入了解，当人类活动威胁到许多物种的灭绝时，这一点变得越来越重要。

Biodiversity is generated through the formation of new species. In several organisms, especially butterflies, differences among species are often due to genes on the X chromosome, the chromosome which is responsible for determining gender. Genes on the X chromosome may evolve faster than autosomal genes, which could explain why the X chromosome plays such a large role in the differentiation of species. Faster evolution of X-linked genes, or 'fast X' evolution, can be identified by comparing the number of DNA sequence changes between two species in genes located on the X chromosome compared to the other chromosomes, the autosomes. To test this hypothesis, DNA sequence will be analyzed from both X-linked and autosomal genes in the clouded and orange sulphur butterflies (Colias philodice and C. eurytheme, respectively). Several traits that distinguish these butterflies, such as wing pigmentation, mate selection, and fertility, have been genetically mapped to the X chromosome, providing a "best case" system to test the fast X evolution hypothesis.Modern evolutionary biologists have an impressive understanding of how genes evolve within populations, but a poorer understanding of the genetics underlying divergence among species. This research will illuminate the genetic basis of speciation, providing insights into the fundamental evolutionary processes that regulate biodiversity on Earth. It will also offer insight into genetic attributes that allow different species to persist together, which has become increasingly important when human activities threaten the extinction of many species.