Body size or mass is one of the main factors underlying food webs structure. A large number of evolutionary models have shown that indeed, the adaptive evolution of body size (or mass) can give rise to hierarchically organised trophic levels with complex between and within trophic interactions. However, these models generally make strong arbitrary assumptions on how traits evolve, casting doubts on their robustness. In particular, biomass conversion efficiency is always considered independent of the predator and prey size, which contradicts with the literature. In this paper, we propose a general model encompassing most previous models which allows to show that relaxing arbitrary assumptions gives rise to unrealistic food webs. We then show that considering biomass conversion efficiency dependent on species size is certainly key for food webs adaptive evolution because realistic food webs can evolve, making obsolete the need of arbitrary constraints on traits' evolution. We finally conclude that, on the one hand, ecologists should pay attention to how biomass flows into food webs in models. On the other hand, we question more generally the robustness of evolutionary models for the study of food webs.

中文翻译：

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将转换效率确定为食物网适应性进化的关键机制：向前还是向后？

身体大小或质量是食物网结构的主要因素之一。大量的进化模型表明，实际上，身体大小（或质量）的适应性进化可以产生层次结构的营养水平，在营养之间和内部相互作用复杂。然而，这些模型通常对特征如何演变做出强烈的武断假设，从而对其稳健性产生怀疑。特别是，生物质转化效率总是被认为与捕食者和猎物大小无关，这与文献相矛盾。在本文中，我们提出了一个包含大多数先前模型的通用模型，该模型可以表明放宽任意假设会导致不切实际的食物网。然后我们表明，考虑依赖于物种大小的生物量转化效率无疑是食物网适应性进化的关键，因为现实的食物网可以进化，从而不再需要对性状进化的任意约束。我们最终得出结论，一方面，生态学家应该关注生物量如何流入模型中的食物网。另一方面，我们更普遍地质疑食物网研究进化模型的稳健性。