Predicting the impacts of co-extinctions on phylogenetic diversity in mutualistic networks

An important bias in the estimations of threatened evolutionary history is that extinctions are considered as independent events. However, the extinction of a given species may affect the vulnerability of its partners and cause extinction cascades. Co-extinctions are likely not random in the tree of life and may cause the loss of large amounts of unique evolutionary history. Here, we propose a method to assess the consequences of co-extinctions for the loss of evolutionary history and to identify conservation priorities. We advise considering both the complexity of the interaction networks and the phylogenetic complementarities of extinction risks among species. Using this approach, we demonstrated how co-extinction events can prune the tree of life using various species loss scenarios. As a case study, we identified pollinators for which extinctions would greatly impact plant phylogenetic diversity within local pollination networks from Europe. We also identified species features that may result in the highest losses of phylogenetic diversity. Our approach highlights the consequences of co-extinctions on the loss of evolutionary history and may help address various conservation issues related to co-extinctions and their impacts on biodiversity.