摘要：Freshwater ecosystems are an easy target for invasive species given that aquatic plants possess specific traits that enhance rapid spread and colonization. The significant lack of knowledge on ecological demands and the current distribution of aquatic aliens is a crucial limitation to the effective protection and management of water bodies. In Slovakia, there are two established alien macrophytes that are widely distributed throughout the country: Elodea canadensis Michx. and Elodea nuttallii (Planch.) H. St. John. We focused on the temporal dynamics of colonization and the current distribution of both species, their ecological requirements and their effects on native flora and vegetation. We gathered 415 records of occurrence, including 168 for E. canadensis and 247 for E. nuttallii. Both Elodea species showed different temporal patterns of colonization of native aquatic habitats. Although the occurrence probability of E. nuttallii stabilized after an initial steep increase, the probability of E. canadensis occurrence showed a decreasing tendency over recent decades. The probability of species occurrence was significantly related to altitude and climatic characteristics. Mean January temperature emerged as the best predictor of the species distribution. Assessing the impact of both species, our results showed that elodeas contribute to the homogenization of natural aquatic communities. Specifically, species richness and beta diversity were lower in relevés with higher abundance of elodeas compared with uninvaded relevés.
