A principalchallenge in testing the role of natural selection in speciation is to connect the build-up of reproductive isolation between populations to divergence of ecologically important traits.
检验自然选择在物种形成中的作用的一个主要挑战是，将生殖隔离的出现与有着生态学重要性的特征联系起来。
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These are the principal spiritual handholds I have found to possess enduring value. They offer both an exciting challenge and a calm assurance. They are the things I believe.