Benthic marine macroalgae non-native to Mexico: An update (2024) for the Mexican Pacific

Background. There is concern about marine algae introduced in geographical areas other than their known distribution. These species are known as non-native. Goals. A discussion and an update of those species considered alien to the Mexican Pacific flora. Methods. The information published until 2024 was analyzed, gathering data on morphology, reproduction, molecular information, years of registration, and distribution of each species. The criterion for determining if it belonged to the non-native category was based on the availability of molecular information. To determine their current status, reproduction data, permanence time span, and distribution limits were considered. Results. There are 49 names of species considered non-native; 28 of them have been published in the compiled literature and 21 are new additions, which refer to recent records in the flora of the Mexican Pacific. Ten belong to Chlorophyta, 17 to Phaeophyceae, and 22 to Rhodophyta. Seventeen are restricted to the western coast of Baja California and 5 to the Gulf of California. Eight are distributed throughout the Mexican Pacific. Twenty-nine are recognized as populations of non-native species; 14 are cryptogenic. As for their current status, 9 are occasional and 20 are naturalized; none were considered invasive. Conclusions. The study of colonization in the Mexican Pacific faces several challenges, among them, the reliability of previously published data and their taxonomic and nomenclatural component, the consensus of the concepts used to characterize non-native species, the challenge of their detection, the stage of the populations and the effect of this colonization on the environment. Several of these challenges cannot be faced if we do not have a frequently updated and reliable census of the diversity of marine macroalgae in the Mexican Pacific.