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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.
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