Troost Tineke A, Kooi Bob W, Kooijman Sebastiaan A L M
Faculty of Earth and Life Sciences, Department of Theoretical Biology, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
Math Biosci. 2005 Feb;193(2):159-82. doi: 10.1016/j.mbs.2004.06.010.
In evolutionary history, several events have occurred at which mixotrophs specialized into pure autotrophs and heterotrophs. We studied the conditions under which such events take place, using the Dynamic Energy Budget (DEB) theory for physiological rules of the organisms' metabolism and Adaptive Dynamics (AD) theory for evolutionary behavior of parameter values. We modeled a population of mixotrophs that can take up dissolved inorganic nutrients by autotrophic assimilation and detritus by heterotrophic assimilation. The organisms have a certain affinity for both pathways; mutations that occur in the affinities enable the population to evolve. One of the possible evolutionary outcomes is a branching point which provides an opportunity for the mixotrophic population to split up and specialize into separate autotrophs and heterotrophs. Evolutionary branching is not a common feature of the studied system, but is found to occur only under specific conditions. These conditions depend on intrinsic properties such as the cost function, the level of the costs and the boundaries of the trait space: only at intermediate cost levels and when an explicit advantage exists to pure strategies over mixed ones may evolutionary branching occur. Usually, such an advantage (and hence evolutionary branching) can be induced by interference between the two affinities, but this result changes due to the constraints on the affinities. Now, only some of the more complicated cost functions give rise to a branching point. In contrast to the intrinsic properties, extrinsic properties such as the total nutrient content or light intensity were found to have no effect on the evolutionary outcomes at all.
在进化史上，发生过几次混合营养生物特化为纯自养生物和异养生物的事件。我们利用动态能量平衡（DEB）理论来描述生物体新陈代谢的生理规则，并用适应性动态（AD）理论来描述参数值的进化行为，研究了此类事件发生的条件。我们对一群混合营养生物进行了建模，它们可以通过自养同化吸收溶解的无机养分，并通过异养同化摄取碎屑。这些生物体对这两种途径都有一定的亲和力；亲和力发生的突变使种群得以进化。一种可能的进化结果是一个分支点，它为混合营养生物种群分裂并特化为单独的自养生物和异养生物提供了机会。进化分支并非所研究系统的常见特征，而是仅在特定条件下才会出现。这些条件取决于内在属性，如成本函数、成本水平以及性状空间的边界：只有在中等成本水平且纯策略相对于混合策略存在明显优势时，才可能发生进化分支。通常，这种优势（进而导致进化分支）可能由两种亲和力之间的干扰引发，但由于对亲和力的限制，这一结果会发生变化。现在，只有一些更复杂的成本函数会产生一个分支点。与内在属性不同，总养分含量或光照强度等外在属性被发现对进化结果完全没有影响。
