Venezuela

Abstract. The Indo-Pacific octocoral Xenia sp. has been reported as a successful invasive species of the Venezuelan coral reefs (Southeastern Caribbean Sea), and the first xeniid octocoral
with such invasive properties. This taxon has been recently identified, and assigned to a new genus and combination as Unomia stolonifera. Since its first appearance there, it has dispersed
along the shallow reefs, overgrowing any hard substrate, including corals and seagrass. Quantitative surveys revealed that U. stolonifera dominated all studied sites, featuring an average
percentage cover of 30 - 80%, far above that of the native corals or any other benthic taxa. An inverse relationship exists between the loss of diversity and the reduction in coral cover. The
spread of U. stolonifera in places where it has become established while displacing native benthic species and leads to a decrease in diversity and evenness of the benthic communities.
Dispersal of the invasive along the reefs has been intensified by drifting colonies, by colonies settled on detached Thalassia testudinum fragments and, additionally, by colonies entangled
on fish nets and consequently translocated. The present study explicitly demonstrates that this intensifying invasion is causing severe ecological damage to the Venezuelan reefs. Consequently, Unomia stolonifera, should be considered harmful invasive species that requires monitoring and management programs in the vicinity of already invaded reefs. The current
study highlights the ecological consequences of this new invasive species.