Molecular Ecology of the Barnacle Megabalanus coccopoma Over its Introduced Range in the Southeastern U.S.
Zardus, John D.
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Invasion ecology is emerging as an increasingly important field as scientists try to understand the extent of human influence on the environment. The dispersal of introduced species may be studied on a global scale through the use of advanced molecular tools. The recent arrival of Megabalanus coccopoma, a Pacific tropical barnacle, to the southeastern coast of the United States provides an opportunity to study its establishment and subsequent expansion northward using these molecular tools. The genetic variation of populations of M. coccopoma along the southeastern coast of the U.S. was characterized through analysis of nuclear and mitochondrial DNA. These analyses yielded high genetic diversity with low nucleotide diversity. The near absence of genetic structure suggests a well-mixed population with high larval dispersal; however, thirteen individuals from a single population in Florida were highly divergent, suggesting recruitment from an unknown and highly divergent source population or a cryptic species. Haplotype data suggest possible hybrization between the anomalous individuals and M. coccopoma. Following initial anthropogenic transport, ocean currents play a key role in the spread and establishment of this barnacle, while limited studies suggest that salinity and temperature are the most important abiotic factors determining its distributional limits. Ocean currents and salinity patterns in the southeastern U.S. show very little variation across the last 30 years, whereas ocean surface temperatures have increased across successive years. The warming of the eastern coastal waters of the U.S. provides an avenue for the range expansion of M. coccopoma, and likely other tropical and subtropical marine species. While this study establishes a baseline genetic characterization of the species in a newly invaded habitat, basic ecological studies are needed to fully understand the influence of abiotic factors on the distribution of M. coccopoma survival and dispersal.