School of Marine Sciences

One method for determining population size and connectivity of marine species is through the examination of their genetics. A neutral marker such as the cytochrome c oxidase I (COI) gene can help establish genetic diversity and maternal gene flow among populations. COI was used in three studies to better understand three different marine species in Maine: two invasive crab species (Carcinus maenas and Hemigrapsus sanguineus) and a native bait worm (Glycera dibranchiata). For Carcinus maenas, the green crab that has been invasive in Maine since 1900, our results show that Northern haplotypes are limited in adult crabs to Mount Desert Island and north, indicating that the southern haplotype is selectively favored at some point during their life history or recruitment of northern larvae is limited south of Mount Desert Island. Hemigrapsus sanguineus, the Asian shore crab, has rapidly replaced Carcinus maenas, the green crab, as the most abundant crab on rocky shores in the northwest Atlantic since its introduction to the USA in 1988 from Japan. Our study showed that there have been large increases in population sizes of genetically diverse individuals that will likely affect the Maine intertidal ecosystem in years to come. Lastly, our COI analysis of the bait worm Glycera dibranchiata, a vital fishery in Maine, indicates well connected populations along the coast of Maine despite their short larval period. These genetic analyses were able to uncover population dynamics within these species that are difficult to ascertain through other sampling methods.