DISSERTATION RESEARCH: The effects of sexual dimorphism on morphological diversification of Musteloidea

物种数量和解剖变异的不均匀多样性代表了生命之树中更令人困惑的进化模式之一。尽管越来越多的研究人员已经开始了解是什么导致了物种之间不平衡的多样性，但很少有研究人员研究单个物种内部的差异如何影响这些大范围的进化模式。变异的一个来源在于两性之间的差异。这项研究的主要目标是通过研究性别差异如何促进物种和表型多样性来建立进化理论。这项研究填补了我们对物种内部变异如何驱动更大的物种多样性模式的理解的关键空白。通过这项研究计划，科学家们将通过加州大学圣克鲁斯分校科学实习计划（SIP）对高中生进行指导，通过森林小型哺乳动物本科生研究计划（SMURF）对本科生进行培训，通过圣克鲁斯公共图书馆进行公开讲座，以及在比较脊椎动物解剖学方面的本科生教学，为培养下一代学生做出贡献。鼬类动物（獾、水獭、浣熊、臭鼬和鼬鼠）的头骨将被用作模型，在宏观进化尺度上研究两性二态性对表型差异的影响。Musteloids是一个分类学的富人和表型不同的进化枝的血统表现出不平衡模式的多样性。这组科学家将使用3D几何形态计量学，并开发新的比较方法来检验一种假设[H1a]，即结合性别的影响将揭示颅骨差异的增加。每个物种的雄性和雌性预计占据大部分不重叠的颅形态空间部分；此外，两性的纳入将填补以前在分析集中于单一性别时未被占用的形态空间。然后，研究人员将分别量化男性和女性随时间变化的颅骨差异率，并将其汇总在一起（物种意味着），以验证一种假设[H1b]，即合并性别增强了适应性辐射的模式（即，在接近生态机会的地方，进化速度迅速增加，随后速度放缓）。当使用汇集的男性和女性数据集时，预测颅骨进化的速率变化发生在中新世中期气候转变开始之后。最后，研究人员将通过验证假设[H2]来检验两性二态性的生态基础，该假设认为，在整个Musteloidea中，食肉性的程度与两性二态性在颅骨形状和大小上的进化相对应。因此，预计高食肉类鼠将表现出最高程度的颅骨性别二态性。我们怀疑这种超级食肉动物的差异是为了减轻两性之间的竞争。

Uneven diversity in both numbers of species and anatomical variability represents one of the more perplexing evolutionary patterns across the Tree of Life. Although an increasing number of researchers have begun to understand what drives uneven diversity between species, few researchers have examined how differences within single species can affect these broad scale evolutionary patterns. One source of variation lies in the difference between the sexes. The primary goal of this research is to build upon evolutionary theory by examining how sex differences contribute to species and phenotypic diversity. This research fills a critical gap in our understanding of how variation within species may drive larger patterns of species diversity. Through this research program, scientists will contribute to training the next generation of students through their mentorship of high school students through the UC Santa Cruz Science Internship Program (SIP), undergraduate student training in the Small Mammal Undergraduate Research in the Forest (SMURF) program, public talks through the Santa Cruz Public Library, and undergraduate teaching in Comparative Vertebrate Anatomy. The skulls of musteloids (badgers, otters, raccoons, skunks, and weasels) will be used as a model to examine the effects of sexual dimorphism on phenotypic disparity at the macroevolutionary scale. Musteloids are a taxonomically rich and phenotypically disparate clade whose lineages exhibit uneven patterns of diversity. The researchers will use 3D geometric morphometrics and develop new comparative methods to test the hypothesis [H1a] that incorporating the effects of sex will reveal increased cranial disparity. Males and females in each species are predicted to occupy mostly non-overlapping parts of cranial morphospace; furthermore, the inclusion of both sexes will fill morphospace that was previously unoccupied when the analysis focused on a single sex. The researchers will then quantify the rates of cranial disparity through time in males and females separately and pooled together (species means) to test the hypothesis [H1b] that incorporating sex enhances the pattern of adaptive radiation (i.e. rapid increases in evolutionary rates near ecological opportunity followed by a slowdown in rates). A rate shift in cranial evolution is predicted to occur just after the onset of the Mid-Miocene Climate Transition when using the pooled male and female dataset. Lastly, the researchers will examine an ecological basis for sexual dimorphism by testing the hypothesis [H2] that the degree of carnivory corresponds with the evolution of sexual dimorphism in cranial shape and size across Musteloidea. Therefore, hypercarnivorous musteloids are predicted to exhibit the highest degree of cranial sexual dimorphism. We suspect that this disparity in hypercarnivores is present to mitigate competition between the sexes.