The biogeographic history and contemporary origins of north american arctic marine macroalgae
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Date
2018
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University of New Brunswick
Abstract
Arctic coastal communities are expected to change in response to warming
climate trends, and yet basic information is lacking in these systems. Marine macroalgae
provide an opportunity to examine historical migration pathways into the Arctic, and
may serve as a model system for future changes. In this thesis, phylogeographic and
population level biogeographic patterns were examined in Arctic marine macroalgae.
Multiple markers were used to examine phylogeographic patterns in 14 trans-Arctic
lineages of red marine macroalgae and determine what role the opening of the Bering
Strait and Pleistocene glaciation had on contemporary biogeographic distributions.
Results confirmed the opening of the Bering Strait resulted in a predominantly Pacificto-
Arctic/Atlantic movement of species, while Pleistocene glaciation did not appear to
play a significant role in promoting trans-Arctic speciation events. The Last Glacial
Maximum, however, is hypothesized to have extirpated marine coastal populations in
the Northwest Atlantic, with subsequent recolonization out of the Northeast Atlantic.
DNA barcode data were used to determine if trans-Atlantic populations of brown and
red macroalgae were consistent with this hypothesis. Contrary to the historical
consensus, isolation times in 60% of the species examined suggested populations were
not recently derived from Europe. Sequence data were also used to assess recolonization
pathways of marine macroalgae into the Arctic following the Last Glacial Maximum. Of
the 100 species with Arctic populations examined (including brown, green, and red
macroalgae), 39 had uncertain origins, 46 had origins in the North Atlantic, five had
origins in the Pacific and the Atlantic, while the remaining 10 had origins in the North
Pacific. Pacific contributions to Arctic recolonization, however, were inferred in 9 of the 12 best sampled species. Surprisingly, 18 genetic groups and some Arctic haplotypes in
28 species were not assignable to Atlantic or Pacific populations. The results from this
thesis indicated that the Pacific Ocean has played a major role in establishing Arctic and
North Atlantic lineages/populations of marine macroalgae. In addition, some marine
populations may have survived glaciation in the Arctic basin, reducing the role of
recolonization pathways out of the Atlantic and/or Pacific.