Publication Date:
2022-05-26
Description:
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy at the Massachusetts Institute of Technology
and the Woods Hole Oceanographic Institution
September 2005
Description:
The overarching goal of this thesis was to investigate marine benthic invertebrate
phylogenetics and population genetics, focused on the phylum Annelida. Recent
expansions of molecular methods and the increasing diversity of available markers have
allowed more complex and fine-scale questions to be asked at a variety of taxonomic
levels. At the phylogenetic level, whole mitochondrial genome sequencing of two
polychaetes (the deep-sea tubeworm Riftia pachyptila and the intertidal bamboo worm
Clymenella torquata) supports the placement of leeches and oligochaetes within the
polychaete radiation, in keeping with molecular evidence and morphological
reinvestigations. This re-interpretation, first proposed by others, synonomizes
"Annelida" and "Polychaeta", and lends further support to the inclusion of echiurids,
siboglinids (previously called vestimentiferans) within annelids, and sipunculans as close
allies. The complete mt-genome of C. torquata was then rapidly screened to obtain
markers useful in short timescale population genetics. Two quickly evolving
mitochondrial markers were sequenced from ten populations of C. torquata from the Bay
of Fundy to New Jersey to investigate previous hypotheses that the Cape Cod, MA
peninsula is a barrier to gene flow in the northwest Atlantic. A barrier to gene flow was
found, but displaced south of Cape Cod, between Rhode Island and Long Island, NY.
Imposed upon this pattern was a gradient in genetic diversity presumably due to previous
glaciation, with northern populations exhibiting greatly reduced diversity relative to
southern sites. These trends in C. torquata, combined with other recent short time scale
population genetic research, highlight the lack of population genetics models relevant to
marine benthic invertebrates. To this end, I constructed a model including a typical
benthic invertebrate life cycle, and described the patterns of genetic differentiation at the
juvenile and adult stages. Model analysis indicates that selection operating at the postsettlement
stage may be extremely important in structuring genetic differentiation
between populations and life stages. Further, it demonstrates how combined genetic
analysis of sub-adult and adult samples can provide more information about population
dynamics than either could alone.
Description:
Financial support was provided by an Academic Programs Office fellowship, a CICOR
fellowship and research grant, and a National Science Foundation research grant.
Keywords:
Benthic animals
;
Annelida
;
Animal population genetics
;
Larvae
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
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