Analysis of the Enemy Release Hypothesis on the Material of the Central Russia Flora

The Enemy Release Hypothesis (ERH) is one of the most widespread explanations for the success of invasive species, suggesting that in secondary ranges introduced plants are released from phytophages and pathogens, which facilitates their expansion. However, the literature provides contradictory results, and empirical support for the hypothesis remains limited. In the present study, based on the flora of central European Russia (2550 species), we tested whether native, alien, and invasive species differ in the number of known natural enemies (phytophages and phytopathogens). The number of natural enemies was assessed at the genus and family levels using data from the Plant Parasites of Europe database. We found no significant differences in the number of pests between native and alien species, nor between alien and invasive plant species. Moreover, genera and families that include invasive species were characterized by a greater number of native species, which contradicts the expectations of the ERH and supports the pre-adaptation hypothesis. The proportion of invasive species within a genus positively correlated with the total number of species of that genus in the world flora, which may reflect the influence of phylogenetic and ecological diversity on invasion probability. Our results indicate the limited explanatory power of the Enemy Release Hypothesis and highlight the need to consider multiple additional factors when analyzing the success of alien species.