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

杂交区是杂交后代与其亲本种群/物种相比具有混合遗传组成和物理外观的地理区域。通过研究杂交区域的基因组差异，研究人员可以更好地了解哪些差异导致了新物种的形成，以及区分物种的基因组区域。这些知识与系统学以外的许多领域有关，包括生态学、保护生物学，甚至农业。该研究项目主要研究南美洲蜥蜴属（Liolaemus）中的物种，并使用基因组工具调查杂交带的年龄，它们是如何形成的，以及自然选择和性选择如何维持遗传界限。虽然在北温带系统中研究了许多杂交带，但在南温带系统中得到的关注相对较少。本研究将培养一名具有多种系统方法的研究生和具有实地、实验室和分析方法的本科生。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。这项研究的结果将在华盛顿州西雅图的伯克自然历史和文化博物馆通过展览和演讲广泛传播。本研究将对菲茨林氏Liolaemus fitzingerii类群中三个物种对的杂交和比较物种差异进行研究。在某种程度上，这一假设将得到验证，即这些混合带是在大约12000年前冰川后范围扩张后的二次接触中形成的。使用限制性内切位点相关DNA测序（RADseq）方法生成全基因组单核苷酸多态性（SNP）数据，以估计三个不同杂交区物种之间的遗传和地理转变。SNP数据也将用于估计进化关系和划分物种。将SNP数据与注释的基因组对齐将能够识别基因组中参与维持该群体物种边界的区域。总之，这些数据将为杂交区域内发生的基因组变化提供新的线索，并为驱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.