DISSERTATION RESEARCH: Does Transgressive Segregation in Physiological Niche Explain the Rapid Spread of Invasive Genes into a Native Population

主要的快速进化变化是众所周知的，但潜在的机制以及这些变化如何影响生存和繁殖往往不清楚。该项目将通过调查引进蝾螈物种的成功和地理传播是否是与本地物种杂交的结果来解决快速进化变化的过程。虽然外来物种的引入被认为导致了快速进化，但人们仍然不清楚这种情况发生的频率、涉及的因素以及这是否促进了引入物种的成功和传播。有时引进的物种与本地物种杂交并产生可存活的后代，这些后代表现出在任何亲本物种中都不存在的极端特征值。例如，后代可能比亲本物种更大，或者对环境压力的耐受性更强。这种杂交后代有可能在竞争中战胜亲本物种，或者在没有亲本物种占据的新环境中定居。由于杂交而产生的极端性状值-越界分离-在可存活的后代中是罕见的。然而，当它发生时，后代可以以全新的方式与环境相互作用，导致快速的进化变化。研究人员将研究一种濒临灭绝的本土物种——加利福尼亚虎蝾螈和一种密切相关的引进物种——横纹蝾螈之间的基因混合，以验证一种假设，即侵略性隔离导致了本土物种的极端快速进化。数据将揭示生活史、生理学和栖息地如何结合起来决定两个物种重叠和杂交的区域的遗传模式。该项目还包括对本科生和研究生的培训，针对K-12学生的教育计划，以及为保护管理人员举办的讲习班。在体型大小方面，虎纹Ambystoma tigrinum mavortium和加州麻的杂交品种表现出海侵分离，并且表现出比本地品种更强的耐热性。然而，我们仍然不知道生态重要性状的越界分离是否是影响被称为“超级入侵”的基因在本地种群中极快传播的主要因素。研究人员将测量和比较本地、引进和杂交虎蝾螈在多个生命阶段的代谢率、失水率、对同密度的应激反应和热耐受性，这些类别对预测在加州真实景观上的传播很重要。本地和杂交蝾螈的数据将通过圈养的本地和杂交蝾螈个体来生成。亲代的非本地蝾螈将从其本地范围内的几个野生种群和目前在与本地物种重叠区域之外的引入种群中收集。然后，所获得的信息将与一种新的种群遗传模拟一起使用，以在当前和潜在的未来条件下，对真实的加利福尼亚景观中本地和非本地基因型的扩散和持久性产生强大的机制预测。

Major rapid evolutionary changes are well known, but the underlying mechanisms and how these changes influence survival and reproduction are often unclear. This project will address the process of rapid evolutionary change by investigating whether the success and geographic spread of an introduced salamander species is the result of interbreeding with a native species. Although the introduction of non-native species is thought to lead to rapid evolution, it is still not understood how often this occurs, the factors involved, and whether this promotes the success and spread of the introduced species. Sometimes introduced species hybridize with native species and produce viable offspring that exhibit extreme trait values not present in either parental species. For example, offspring may be bigger than either parental species or have an increased tolerance to environmental stressors. Potentially, such hybrid offspring can outcompete the parental species or colonize new environments not occupied by either parental species. The production of extreme trait values due to interbreeding - transgressive segregation - is rare in viable offspring. However, when it occurs the offspring can interact with the environment in entirely new ways, leading to rapid evolutionary change. The researchers will study genetic mixing between an endangered native species, the California tiger salamander, and a closely related introduced species, the barred salamander, to test the hypothesis that transgressive segregation has led to extremely rapid evolution in the native species. Data will reveal how life history, physiology, and habitat combine to determine genetic pattern across a region where the two species overlap and hybridize. The project also includes the training of undergraduate and graduate students, educational programs targeting K-12 students, and workshops for conservation managers. Hybrids between Ambystoma tigrinum mavortium and A. californiense exhibit transgressive segregation with respect to body size and exhibit a broader thermal tolerance than natives. However, we still do not know whether transgressive segregation of ecologically important traits is a major factor affecting the extremely rapid spread of what are being labeled "superinvasive" genes into native populations. The researchers will measure and compare metabolic rates, rates of water loss, stress response to conspecific density, and thermal tolerance at multiple life stages in native, introduced, and hybrid tiger salamanders, the categories that matter for predicting spread on the real California landscape. Data on native and hybrid salamanders will be generated using a captive colony of salamanders of native and hybrid individuals. Parental, non-native salamanders will be collected from several wild populations within their native range and from an introduced population that is currently outside the zone of overlap with the native species. Information learned will then be used along with a novel population genetic simulation to generate robust mechanistic predictions of dispersal and persistence of native and nonnative genotypes within the real California landscape under current and potential future conditions.