Using Modern Coexistence Theory to understand community disassembly

Community disassembly examines how species extinction alters ecological communities. Sometimes, the extinction of one species can trigger the loss of others, known as secondary extinction. These secondary extinctions often result from complex species interactions, complicating the identification of underlying mechanisms. Here, we leverage Modern Coexistence Theory to identify when and why secondary extinctions occur. To identify when secondary extinctions occur, we introduce the Community Disassembly Graph, that uses invasion growth rates to identify transitions between coexisting communities due to extinction. When a secondary extinction is identified, we decompose the invasion growth rates associated with the secondary extinction to understand why it occurs. We demonstrate the utility of this framework by applying it to models in which different species interactions - competition, facilitation, and predation - contribute significantly to secondary extinctions. Our results show Modern Coexistence Theory offers a flexible and interpretable approach to understanding when and why secondary extinctions occur.