新物种的出现分为两种情况：通常情况下是由于配偶选择特异性导致的基因隔离，当杂交不能进行时，新物种便产生了；还有一种较为少见的同域物种生成作用（sympatric speciation），指的是新物种出现于没有地理和物理隔离的单一群体中。同域物种生成作用最为典型的例子是苹果实蝇，这种实蝇曾以山楂树果实为食，随后开始以苹果为食，继而进化出了基因型完全不同的新蝇类。数学模型研究显示，配偶选择、竞争、可用资源多样性是引起同域物种生成作用的三大关键因素。

图：苹果实蝇

国立数学与生物合成研究所的博士后X.Thibert-Plante与麦吉尔大学的A.P.Hendry副教授采用了新的研究模型对同域物种生成作用进行了研究，较之以前的仅关注一两项因素的研究模型，新研究模型能够同时关注三大关键因素。Thibert-Plante说，新模型能够使他们综合考虑各项因素的影响以及它们相互之间的关系，至少，可用资源的多样性是形成生物多样性的一个有效途径。结果显示，个体间竞争较其他两项因素相比，就显得不那么重要了。

不过，就算是在理想状况下，同域物种生成作用也极少在模型中发生。但这并不意味着，它在自然界就不重要了，有一点可以明确，配偶选择可使群体基于资源而变得更为专门化，也使个体更加多产。

原文出处：

European Society For Evolutionary Biology     doi:10.1111/j.1420-9101.2008.01627.x

Five questions on ecological speciation addressed with individual-based simulations

X.Thibert Plante，A.P.Hendry

We use an individual-based simulation model to investigate factors influencing progress toward ecological speciation. We find that environmental differences can quickly lead to the evolution of substantial reproductive barriers between a population colonizing a new environment and the ancestral population in the old environment. Natural selection against immigrants and hybrids was a major contributor to this isolation, but the evolution of sexual preference was also important. Increasing dispersal had both positive and negative effects on population size in the new environment and had positive effects on natural selection against immigrants and hybrids. Genetic divergence at unlinked, neutral genetic markers was low, except when environmental differences were large and sexual preference was present. Our results highlight the importance of divergent selection and adaptive divergence for ecological speciation. At the same time, they reveal several interesting nonlinearities in interactions between environmental differences, sexual preference, dispersal and population size.