Background:

Codium fragile is a green alga that inhabits the Pacific coast of Baja California, Mexico, whose first records date back to 1909. This species has several subspecies, one of them Codium fragile subsp. fragile, originally from Japan, has proven to be an invasive organism in different parts of the world.

Objectives:

Confirm the presence or absence of this invasive strain on the coast of the Mexican Pacific, comparing with individuals from Japan, the United States and Mexico using molecular tools.

Methods:

We analyzed 20 individuals of the different species recorded for the Mexican Pacific and ten outside the region, including two as outgroup. The genomic DNA was extracted using the Sanger method, regions of the psb and 23S markers were amplified, the sequences obtained were edited and aligned in MEGA and MESQUITE, subsequently phylogenetic analyses of maximum likelihood were carried out in PAUP and MEGA and Bayesian inference in MrBayes. Genetic distances were obtained in MEGA and PAUP.

Results:

It is shown that, genetically, the individuals from Mexico integrate a clade different from the Asian entity, with inter-species genetic distances that were located at 6% for the 23S marker, while for the subclades of C. fragile the distance between them was 0.4%. For psb, the distance was 25% between species and 2.2% between these two subspecies.

Conclusions:

Individuals from California and Mexico nested in the native clade C. fragile, while others also from California are recognized with that of Japan as belonging to the invasive clade (C. fragile subsp. fragile). At the moment, the absence of this invasive strain in the Pacific of Mexico is confirmed.