Trait adaptation enhances species coexistence and reduces bistability in an intraguild predation module

<p><span>Disentangling how species coexist in an intraguild predation (IGP) module is a great step towards understanding biodiversity conservation in complex natural food webs. Trait variation enabling </span><span>individual species</span><span> to adjust</span><span> to ambient conditions may facilitate coexistence. However, it is still unclear how </span><span>co-adaptation of </span><span>all species within the IGP module</span><span>, constrained by complex</span><span> trophic </span><span>interactions</span><span> and </span><span>trade-offs among species-specific traits,</span><span> interactively affects species coexistence and population dynamics.</span> <span>We developed an adaptive IGP model allowing prey and predator species to mutually adjust their </span><span>species-specific</span><span> defensive and offensive strategies to each other. We investigated species persistence, the temporal variation of population dynamics, and the occurrence of bistability in IGP models without and with trait adaptation along a gradient of enrichment</span><span> represented by </span><span>carrying capacity of the basal prey for </span><span>different</span><span> widths</span><span> and speeds of trait adaptation within each species</span><span>. </span><span>Results showed that trait adaptation within multiple species greatly enhanced the coexistence of all three species in the module. A larger width of trait adaptation facilitated species coexistence independent of the speed of trait adaptation at lower enrichment levels, while a sufficiently large and fast trait adaptation promoted species coexistence at higher enrichment levels. Within the oscillating regime, increasing the speed of trait adaptation reduced the temporal variability of biomasses of all species. Finally, species co-adaptation strongly reduced the presence of bistability and promoted the attractor with all three species coexisting.</span> <span>These findings resolve the contradiction between the widespread occurrence of IGP in nature and the theoretical predictions that IGP should only occur under restricted conditions and lead to unstable population dynamics, which broadens the mechanisms presumably underlying the maintenance of IGP modules in nature. Generally, this study </span><span>demonstrates</span> <span>a decisive role of mutual adaptation among complex trophic interactions, </span><span>for enhancing interspecific diversity and </span><span>stabilizing </span><span>food web </span><span>dynamics, arising e.g. from </span><span>intraspecific diversity.</span></p>