Shadows over Caribbean reefs: Identification of a new invasive soft coral species,Xenia umbellata, in southwest Puerto Rico

Abstract

AbstractIn October 2023, several colonies of an alien soft coral species were reported on shallow reefs in southwest Puerto Rico. The soft coral was identified as a xeniid octocoral (species undetermined), resembling the octocoralUnomia stolonifera, which has invaded and overgrown reefs in Venezuela in recent years. To conclusively characterize the species of the invading xeniid, we employed multilocus barcoding targeting four genes (ND2, mtMutS, COI, and 28S) of three separate colonies across three locations in southwest Puerto Rico. Sequence comparisons with xeniid sequences from GenBank, including those from the generaXeniaandUnomia, indicated a 100% sequence identity (>3,000 bp combined) with the speciesXenia umbellata(Octocorallia : Malacalcyonacea : Xeniidae).Xenia umbellatais native to the Red Sea and to our knowledge, this represents the first confirmed case of this species as an invader on Caribbean reefs. Similar toU. stolonifera, X. umbellatais well known for its ability to rapidly overgrow substrate as well as tolerate environmental extremes. In addition,X. umbellatahas recently been proposed as a model system for tissue regeneration having the ability to regenerate completely from a single tentacle. These characteristics greatly amplifyX. umbellata’s potential to adversely affect any reef it invades. Our findings necessitate continued collaborative action between local management agencies and stakeholders in Puerto Rico, as well as neighboring islands, to monitor and control this invasion prior to significant ecological perturbation.