DISSERTATION RESEARCH: Hybrid zone formation and comparative genomic divergences in South American lizards (Iguania: Liolaemidae)

杂交区是指与其亲本种群/物种相比，杂交后代具有混合遗传组成和外貌的地理区域。通过研究杂交区的基因组差异，研究人员可以更好地了解哪些差异是导致新物种形成的原因，以及区分物种的基因组区域。这些知识涉及到系统学以外的许多领域，包括生态学、保护生物学，甚至农业。这项研究项目专注于南美蜥蜴属Liolaemus内的物种，并使用基因组工具调查杂交区域的年龄、它们如何形成，以及自然选择和性选择如何维持遗传边界。虽然在北方温带系统中已经研究了许多杂交带，但南部温带系统却相对较少受到关注。本研究将对一名研究生进行多种系统方法的培训，并对本科生进行现场、实验室和分析方法的培训。该项目还将通过与阿根廷研究人员的合作加强国际科学基础设施。这项研究的结果将通过华盛顿州西雅图的伯克自然历史和文化博物馆的展示和演示广泛传播。这项拟议的研究将调查柳杉种群中三个物种对之间的杂交和比较物种的差异。在一定程度上，这一假设将得到检验，即这些混合带是由于大约12,000年前冰川后山脉扩张后的二次接触而形成的。全基因组单核苷酸多态(SNP)数据将使用限制位点相关DNA测序(RADseq)方法生成，以估计三个不同杂交区物种之间的遗传和地理转变。SNP数据还将用于估计进化关系和划分物种。将SNP数据与带注释的基因组进行比对，将能够识别基因组中与维持这一组中物种边界有关的区域。总之，这些数据将为杂交区内发生的基因组变化提供新的线索，并为推动新物种形成的机制提供新的见解。

Hybrid zones are geographical areas where hybrid offspring have mixed genetic composition and physical appearances compared to their parent populations/species. By studying genomic divergence in hybrid zones, researchers can better understand which differences are responsible for the formation of new species, and also the genomic regions that separate species. Such knowledge is relevant to many fields beyond systematics, including ecology, conservation biology, and even agriculture. This research project focuses on species within the South American lizard genus, Liolaemus, and uses genomic tools to investigate the age of hybrid zones, how they form, and how natural and sexual selection maintain genetic boundaries. Although many hybrid zones have been studied in northern temperate systems, southern temperate systems have received comparatively little attention. This research will train one graduate student in diverse systematic methods and undergraduates in field, laboratory and analytical methods. The project will also enhance international scientific infrastructure through collaborations with Argentinian researchers. Results from this research will be broadly disseminated through displays and presentations at the Burke Museum of Natural History and Culture in Seattle, WA. The proposed research will investigate hybridization and comparative species divergences across three species pairs in the Liolaemus fitzingerii group. In part, the hypothesis will be tested that these hybrid zones have formed due to secondary contact following post-glacial range expansions approximately 12,000 years ago. Genome-wide single nucleotide polymorphism (SNP) data will be generated using the restriction site-associated DNA sequencing (RADseq) method to estimate the genetic and geographic transitions between species in three separate hybrid zones. SNP data will also be used to estimate evolutionary relationships and delimit species. Aligning the SNP data to an annotated genome will enable the identification of regions of the genome that are involved in maintaining species boundaries in this group. Together, these data will shed new light on the genomic changes that occur within hybrid zones, and provide novel insights into the mechanisms driving the formation of new species.