The molecular systematics and population genetics of four coastal ctenophores and scyphozoan jellyfish of the United States Atlantic and Gulf of Mexico

The goal of this dissertation was to employ molecular genetic techniques to address several taxonomic and biogeographic questions in four species of gelatinous zooplankton along the U.S. Atlantic and Gulf of Mexico coasts.;While the lion's mane jellyfish Cyanea capillata was previously considered to exhibit a cosmopolitan distribution, DNA sequence data presented here indicated that animals collected from the U.S. Atlantic and Gulf coasts represent novel species of Cyanea. Both morphological and molecular data distinguished three distantly related groups in U.S. waters: coastal Atlantic, estuarine Atlantic and Gulf of Mexico.;The sea nettle "Chrysaora quinquecirrha" is an ecologically important jellyfish along the U.S. Atlantic and Gulf coasts. DNA sequence analysis indicated that "C. quinquecirrha" is actually made up of two distantly related species, a coastal Atlantic species (C. quinquecirrha s. str.) and one found in Atlantic estuaries and the Gulf of Mexico (Chrysaora sp.). Further phylogeographic and population genetic analysis of Chrysaora sp. indicated extremely limited dispersal between estuaries, with each estuarine population genetically isolated from every other.;The ctenophore Mnemiopsis is native to the eastern coast of the Americas, but has invaded the Black Sea ecosystem. While two species (M. leidyi and M. mccradyi) were previously thought to exist, DNA sequence data indicated one species of Mnemiopsis . Phylogeographic and population genetic analyses showed significant population structure in the native range, with one population occurring in the southern region of South America and two in North America, separated by Cape Hatteras. Analysis of invasive ctenophores indicated decreased haplotype diversity consistent with a population bottleneck, but individuals were genetically similar to both populations found in North America.;The ctenophore Beroe ovata is native to the same region as Mnemiopsis and has also invaded the Black Sea. While the name Beroe ovata has historically been used to describe two morphologically different ctenophores from the western Atlantic and from the Mediterranean, DNA sequence data presented here reflected morphology, with Mediterranean Beroe nearly identical to Beroe cucumis from the Atlantic and Pacific. Black Sea Beroe ovata were genetically identical to western Atlantic Beroe ovata, confirming a long distance invasion.