Phylogeography of three parasitic
nematode
throughout the range of their hosts (Blarina)
Host-parasite
associations provide outstanding models in studies of evolutionary
biology. Though varied studies have addressed coevolutionary
issues using higher-level taxa, few lower level, phylogeographic
studies of parasites and their hosts have been conducted. The aim
of this project is to characterize the population genetic
structure and phylogeography of three congeneric species of
parasitic nematode contrasted with the phylogeography of their
hosts. The parasitic nematodes, genus Longistriata (Trichostrongyloidea;
Heligmosomidae) live in the upper half of the small intestine of Blarina
(Insectivora: Soricidae). Adult worms mate in the intestine and
eggs of the nematode are deposited with the feces of the shrew.
Nematode embryos develop to the infective third-stage juvenile
that remains stationary until able to infect the next shrew by
ingestion or penetration. As many parasitic nematodes, these three
species of Longistriata has negligible dispersal ability
and gene flow is assumed to be dependent on the dispersal of the
host. The hosts are the three species of short-tailed shrews (Blarina)
that are distributed parapatrically throughout the eastern half of
North America. The three species of parasites are unique to these
shrews. The pattern and amount of "tracking" between the
parasites and host mtDNA genealogies will be used to interpret the
historical host-parasite interactions -- do these parasites
"recognize" boundaries between host species or
populations? Do all three species of Longistriata show the
same evolutionary patterns to each other or to their hosts? The
study will be the first phylogeographic approach to compare the
gene genealogy from species of Blarina, contrasted with
that of three species of parasites. This study provides a unique
opportunity to investigate the following: 1) the
coevolutionary /phylogeographic relationships at a local
geographic (nematode in a host contact zone) versus regional
geographic (nematodes throughout their range) scales 2) to
compare the phylogeographic patterns of three parasites, each with
unique evolutionary histories.
Host-parasite
associations provide outstanding models in studies of evolutionary
biology. Though varied studies have addressed coevolutionary
issues using higher-level taxa, few lower level, phylogeographic
studies of parasites and their hosts have been conducted. The aim
of this project is to characterize the population genetic
structure and phylogeography of three congeneric species of
parasitic nematode contrasted with the phylogeography of their
hosts. The parasitic nematodes, genus Longistriata (Trichostrongyloidea;
Heligmosomidae) live in the upper half of the small intestine of Blarina
(Insectivora: Soricidae). Adult worms mate in the intestine and
eggs of the nematode are deposited with the feces of the shrew.
Nematode embryos develop to the infective third-stage juvenile
that remains stationary until able to infect the next shrew by
ingestion or penetration. As many parasitic nematodes, these three
species of Longistriata has negligible dispersal ability
and gene flow is assumed to be dependent on the dispersal of the
host. The hosts are the three species of short-tailed shrews (Blarina)
that are distributed parapatrically throughout the eastern half of
North America. The three species of parasites are unique to these
shrews. The pattern and amount of "tracking" between the
parasites and host mtDNA genealogies will be used to interpret the
historical host-parasite interactions -- do these parasites
"recognize" boundaries between host species or
populations? Do all three species of Longistriata show the
same evolutionary patterns to each other or to their hosts? The
study will be the first phylogeographic approach to compare the
gene genealogy from species of Blarina, contrasted with
that of three species of parasites. This study provides a unique
opportunity to investigate the following: 1) the
coevolutionary /phylogeographic relationships at a local
geographic (nematode in a host contact zone) versus regional
geographic (nematodes throughout their range) scales 2) to
compare the phylogeographic patterns of three parasites, each with
unique evolutionary histories.