Higher genetic variance of prey defense promotes fluctuation-dependent species coexistence

Understanding the stable coexistence of competing species despite the
competitive exclusion principle has been a central topic in ecology.
Previous studies revealed that rapid contemporary evolution can promote
species coexistence, but the mechanisms behind coexistence are not fully
understood. A recent study showed that predator evolution can promote
fluctuation-dependent species coexistence. Here, I propose a new mechanism
where prey rapid evolution due to high genetic variance can also promote
fluctuation-dependent coexistence of competing predator species. Previous
experimental and theoretical studies demonstrated that the rapid evolution
of a prey defense trait can cause predator-prey population cycles.
Although those studies focused on a system with a single predator species,
I show that the population fluctuations driven by prey rapid evolution can
promote the coexistence of two competing predator species via a
gleaner-opportunist trade-off. By expanding the framework of modern
coexistence theory, I further show how prey rapid evolution can increase
the niche difference of competing predators and simultaneously affect the
competitive ability difference via population cycles. Given the propensity
for oscillatory dynamics and prey rapid evolution (due to large population
sizes and genetic variance) in nature, I argue that this expansion of
coexistence theory provides an important solution to the coexistence
paradox.