Body size or mass is generally seen as one of the main factors which structure food webs . A large number of evolutionary models have shown that indeed, the  evolution of body size (or mass) can give rise to URLanized trophic levels with complex between and within trophic interactions. However, because these models have often very different assumptions , sometimes arbitrary, it is difficult to evaluate what are the real key factors that determine food webs evolution, and whether these models' results are robust or not . In this paper, we first review the different adaptive dynamics models, especially highlighting when their assumptions strongly differ. Second, we propose a general model which encompasses all previous models . We show that our model recovers all previous models' results under identical assumptions. However, most importantly, we also show that, when relaxing some of their hypotheses, previous models give rise to degenerate food webs. Third, we show that the assumptions made regarding the form of biomass conversion efficiency are key for food webs evolution, a parameter which was neglected in previous models. We conclude by discussing the implication of biomass conversion efficiency, and by questioning the relevance of such models to study the evolution of food webs.
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 URLanised 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.
D
generally seen as
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which structure food webs
underlying food webs structure
A
adaptive
R
URLanized
URLanised
R
because these models have often very different assumptions , sometimes arbitrary, it is difficult to evaluate what are the real key factors that determine food webs evolution, and whether these models' results are robust or not
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
D
first review the different adaptive dynamics models, especially highlighting when their assumptions strongly differ. Second, we
R
which encompasses all previous models . We show that our model recovers all previous models' results under identical assumptions. However, most importantly, we also show that, when relaxing some of their hypotheses, previous models give rise to degenerate
encompassing most previous models which allows to show that relaxing arbitrary assumptions gives rise to unrealistic
R
Third, we show that the assumptions made regarding the form of
We then show that considering
R
are
dependent on species size is certainly
R
evolution, a parameter which was neglected in previous models. We conclude by discussing the implication of biomass conversion efficiency, and by questioning the relevance of such models to study the evolution
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