Postdoctoral Research Fellowship in Molecular Evolution

种子油的组成在不同的分类群之间差别很大，可能是由于选择放松的结果，也可能是由于一个物种的种子在特定情况下选择了或反对某些成分的结果。初步分析表明，种子中饱和脂肪和不饱和脂肪的比例存在纬度变化；平均而言，热带物种的饱和和不饱和脂肪含量是温带物种的2到4倍以上。这里提出的工作旨在确定这种差异的适应性意义是否在于选择较低的油凝固温度在低温萌发的温带物种。采用系统发育和实验相结合的方法加强研究。两组植物被使用：Viguiera complex （Asteraceae）和tribe Cyclantherae（葫芦科）。对于每个物种中选定的物种，确定了油的凝固温度和成分，然后绘制了系统发育图，以确定这些性状的进化模式。Viguiera复合体的系统发育是已知的，而Cyclantherae的系统发育将从DNA序列数据中确定。通过实验确定油固化温度对生长温度的塑性响应程度。最后，对种子在不同温度下发芽的表现进行评估和检查，看是否符合假设。

The composition of seed oils varies widely between taxa and could either be the result of relaxation from selection or selection for or against certain compositions given the particular circumstances of the seeds of a species. Preliminary analyses show clearly that there is a latitudinal shift in the proportion of saturated vs. unsaturated fat in seeds; on average, tropical species have 2 to more than 4 times the saturated vs. unsaturated fat content of temperate species. The work proposed here seeks to determine whether the adaptive significance of this difference lies in selection for lower oil solidification temperatures in cool germinating temperate species. Both phylogenetic and experimental methods are employed to strengthen the investigation. Two groups of plants are employed: the Viguiera complex (Asteraceae) and the tribe Cyclantherae (Cucurbitaceae). For selected species in each, oil solidification temperature and composition are determined and then mapped on phylogenies to determine the pattern of evolution of these traits. The phylogeny of the Viguiera complex is known, and that of the Cyclantherae will be determined from DNA sequence data. Experiments will be conducted to determine the degree of plasticity of oil solidification temperature in response to growing temperature. Finally, the performance of seeds germinating at different temperatures will be assessed and checked to see if it is in accordance with the hypothesis.