Morphological and Phylogenetic Diversification in the Tamarins

这项研究的主要目的是了解罗望子属植物之间形态差异的进化起源。罗望子猴是一种高度多样化的新大陆猴子，栖息在亚马逊河流域和南美洲北海岸到巴拿马。它们显示出广泛的颅骨形态。利用之前收集的关于头骨形状遗传模式和物种间系统发育关系的信息，研究人员将检验一系列关于这一群体形态差异的进化起源的假说。这些研究将成为分析灵长类辐射形态多样性的模型。首先，他们将检验这一假设，即颅骨的可变性是由随机进化过程产生的，例如遗传漂移或随机变化的自然选择。如果这一假设没有被拒绝，那么所观察到的多样性可能不是通过对特定环境的特殊适应而产生的。接下来，他们将使用一棵解析良好的系统发育树，在姐妹群中创建一系列与系统发育无关的对比。他们将使用标准化的两组判别函数来描述这些对比中的每一个，并估计物种内的遗传协方差矩阵。这些判别函数中的每一个都代表了自然选择中产生相关组之间的形态差异所需的差异模式。结果将使用功能形态学的原理进行解释。具体的先验假设，如作为进化形态差异来源的整体大小的选择，也将得到检验。

The major objective of the proposed research is to develop an understanding of the evolutionary origins of morphological differences among tamarin species (genus Saguinus). Tamarins are a highly diverse group of New World Monkeys inhabiting Amazonia and the north coast of South America into Panama. They display a wide range of cranial morphologies. Using previously gathered information on patterns of inheritance of skull form and the phylogenetic relationships among the species, the researchers will test a series of hypotheses concerning the evolutionary origin of morphological differences in this group. The studies will serve as a model for analyzing morphological diversity in primate radiations. First, they will test the hypothesis that cranial variability arose by random evolutionary processes, such as genetic drift or randomly varying natural selection. If this hypothesis is not rejected, it is possible that the diversity observed did not arise by special adaptation to specific environments. Next they will use a well-resolved phylogenetic tree to create a series of phylogenetically-independent contrasts among sister groups. They will describe each of these contrasts using a two-group discriminant function standardized with an estimate of the within-species genetic covariance matrix. Each of these discriminant functions represents the pattern of differences in natural selection required to produce the observed morphological differences between related groups of tamarins. The results will be interpreted using the principles of functional morphology. Specific a priori hypotheses, such as selection on overall size as a source of evolutionary morphological divergence, will also be tested.