I have broad interests in the evolutionary biology and ecology of marine invertebrates and fishes. Currently my research is focused in two major areas. First, I work on the ecology of mating and fertilization in species that release gametes into the water (broadcast spawners). These organisms dominate the marine fauna, but produce rapidly-dispersed gametes and zygotes that are difficult if not impossible to observe and follow, so little is known of their reproductive ecology. In past and present projects, I have genetically “marked” adults using allozymes and now microsatellite DNAs, placed them into controlled field mating experiments, then determined parentage of their offspring. With this approach, I have estimated how fertilization success of bryozoans relates to their hermaphroditism. Similarly, my colleagues and I have studied self-fertilization and measured sperm competition in a variety of invertebrates. Each of these topics is of widespread relevance to reproduction in the sea. How marine organisms become reproductively isolated during speciation is my second major research emphasis. Reproductive barriers between broadcast spawners like sea urchins do not often involve courtship and mating behavior, but instead evolve due to changes in recognition molecules on the surfaces of the eggs and sperm. In a collaborative project, I studied the evolution of these molecules in sea urchin species that were split by closure of the Isthmus of Panamá just 3 million years ago. By cloning the cDNAs of sperm-egg recognition proteins, comparing their cDNA sequences, and assaying fertilization, we found strong evidence for a link between sperm protein evolution and the presence of barriers to fertilization between species. In another ongoing project in marine speciation research, my colleagues and I are examining the recent radiation of mating preferences and color pattern differences in a group of Caribbean coral reef fishes. We are using phylogenetic and population genetic analyses of mtDNA and microsatellite DNA, combined with experimental and observational studies of mating behavior in this work.  Click here to view my laboratory poster (pdf).

McCartney, M.A., Keller, G. and H.A. Lessios. In press. Dispersal barriers in tropical oceans and speciation of Atlantic and eastern Pacific Echinometra sea urchins. Molecular Ecology.

McCartney, M.A. 1997. Sex allocation and male fitness gain in a colonial, hermaphroditic marine invertebrate. Evolution 51:127-140.

Yund, P.O. and M.A. McCartney. 1994. Male reproductive success in sessile invertebrates: competition for fertilizations. Ecology 75:2151-2167.