New #preprint online!
From friend to foe and back - Coevolutionary transitions in the mutualism-antagonism continuum
1st author Felix Jäger studied the dynamic nature of biotic interactions and identified an evolutionary #TippingPoint: a gradual change in environmental conditions may lead to an abrupt breakdown of #mutualism to #antagonism, which can‘t be reversed by restoring the initial conditions. 
bioRxiv · From friend to foe and back - Coevolutionary transitions in the mutualism-antagonism continuumInterspecific interactions evolve along a continuum ranging from mutualism to antagonism. Evolutionary theory so far focused mostly on parts of this continuum, notably on mechanisms that enable and stabilise mutualism. These mechanisms often involve partner discrimination ensuring that interaction intensity is higher with more cooperative partners. However, the gradual trajectory of coevolutionary transitions between mutualism and antagonism remains unclear. Here, we model how discrimination ability in one partner coevolves with cooperativeness in the other and analyse the resulting evolutionary trajectories in the mutualism-antagonism continuum. We show that strong ecological change, such as a radical host shift or colonisation of a new environment, can trigger transitions in both directions including back-and-forth transitions between antagonism and mutualism. Moreover, we find an evolutionary tipping point: a stable mutualism may break down to antagonism if the cost of either mutualistic service or discrimination ability gradually increases above a threshold beyond which this transition cannot be reversed by reducing costs again. Our study provides a new perspective on the evolution of biotic interactions and hence on the dynamic structure of ecological networks.
### Competing Interest Statement
The authors have declared no competing interest.