Dissertation Research: Geographic Range Limits of Monkeyflowers (Mimulus): Testing the Roles of Gene flow, Trade-offs and Population Dynamics

每个物种都在有限的地理区域内生存和繁殖。虽然分布的限制是普遍的，很少有人知道的进化限制，阻碍范围扩大。本研究将探讨猴花（Mimulus lewisii和M。红雀属）在加州的塞拉内华达州山脉的海拔范围内。项目的目标是确定生命阶段，特征和环境因素，减少生存和繁殖的范围限制，并进行经验测试的范围限制模型。范围边界可能会出现，因为中心和边缘种群之间的交配产生的后代不适合边缘环境。为了测试这个模型，将比较边缘环境中中心边缘与边缘边缘后代的生存和繁殖。或者，特质之间的相关性可能会限制适应的方向，从而产生范围限制，其中不产生适合边缘环境的一组特质。将通过比较在范围限制下的最佳性状值与物种的实际性状值来测试该模型。 地理范围界限的起源和维持是达尔文首先讨论的进化之谜，但150年后的实验数据有限。范围限制也是自然资源保护主义者的一个重要话题，因为物种的分布预计将向两极和更高海拔地区转移，以应对全球气候变化。然而，如果不知道在范围边界处操作的过程，则很难准确预测这种分布变化的幅度。

Every species survives and reproduces in a limited geographic area. Although distribution limits are universal, little is known about the evolutionary constraints that hinder range expansion. This study will examine range limits of monkey-flowers (Mimulus lewisii and M. cardinalis) across their elevation ranges in California's Sierra Nevada Mountains. Project goals are to identify life stages, traits, and environmental factors that decrease survival and reproduction at range limits and to conduct empirical tests of models of range limits. Range boundaries may arise because matings between central and edge populations create offspring unfit for the edge environment. To test this model, the survival and reproduction of central-edge versus edge-edge offspring will be compared in the edge environment. Alternatively, correlations among traits may constrain the direction of adaptation, creating range limits where a set of traits appropriate for the edge environment is not produced. This model will be tested by comparing optimum trait values at the range limit to species' actual trait values. The origin and maintenance of geographic range limits are evolutionary riddles first discussed by Darwin, yet 150 years later experimental data are limited. Range limits are also a topic of importance to conservationists because species' distributions are forecasted to shift towards the poles and to higher elevations in response to global climate change. However, without knowledge of the processes operating at range boundaries, accurate predictions about the magnitude of such distribution shifts are difficult.