Howard-Williams, Emma
(2013)
A Phylogeographic Study of
Arenaria ciliata and Arenaria
norvegica in Ireland and Europe.
PhD thesis, National University of Ireland Maynooth.
Abstract
The unusual distribution of Irish
ora and fauna has intrigued and
eluded biogeographers for centuries and remains the subject of ongo-
ing debate. The conventional hypothesis for the postglacial coloniza-
tion of Ireland across an Irish-British land-bridge has come under in-
creasing scrutiny, with a growing body of evidence suggesting Ireland
may have been a refugium during the last glacial cycle. In addition
a strong affinity to Iberian populations is evident among much of the
islands's native
ora and fauna. This study focused on the disjunctly
distributed arctic-alpine plant Arenaria ciliata, and its close arctic
relative, A. norvegica, in an effort to characterise and date the earli-
est links between Ireland and Continental Europe and to investigate
the possibility for in situ survival of populations of these species in
Ireland during the last glacial maximum.
Twenty-nine populations of the target species were sampled through-
out their range in Europe. Four separate chloroplast regions were
sequenced: psbA-trnH, rpl32 -trnL, trnK -matK and matK, and the in-
ternal transcribed spacer region of the nuclear ribosomal DNA (ITS).
The chloroplast and ITS sequences were analyzed using maximum
likelihood, haplotype networks, and a molecular clock analysis using
Bayesian inference. Amplified fragment length polymorphism (AFLP)
markers were generated for all populations sampled using three selec-
tive primers and the obtained data were analysed using neighbour-
joining analysis, networks, AMOVAs and direct analysis of the frag-
ments.
The results indicate a complex glacial history for these two species,
where the consensus of the analysis demonstrates phylogeographic
patterns indicative of Pleistocene glacial survival in situ, with evi-
dence for cryptic refugia in Ireland, Rum and Svalbard, and multiple
colonization events for A. ciliata. In contrast, the phylogeographic
patterns obtained for A. norvegica are, for the most part, typical of
a recent post-glacial expansion, with very low sequence divergence
between individuals and populations.
Evidence for in situ survival of the Ben Bulben population of A.
ciliata is presented. This population contains multiple unique hap-
lotypes, many private AFLP fragments, distinct genetic structuring
and the molecular clock analysis indicates an ancient divergence for
the Ben Bulben population. This indicates an origin for this resident
population much earlier than the last glacial maximum, predating the
origin of the A. norvegica haplotypes. AFLP genotypes show distinct
grouping for the Ben Bulben and Svalbard populations. Similari-
ties in the genetic distinctiveness of populations from Rum, Svalbard
and Ben Bulben indicate the possiblity that these locations represent
cryptic Pleistocene refugia for A. ciliata.
Taxonomic distinctions between A. ciliata and A. norvegica are com-
plex, though, a distinct genetic grouping for individuals of A. norvegica
is demonstrated, albeit as a monophyletic group within A. ciliata. In-
congruences between the chloroplast and nuclear ITS sequences con-
found this issue, and highlight the possibility of hybridisation events
between these species. AFLP markers show a distinct clustering for A.
norvegica genotypes and demonstrate the suitability of AFLP markers
in discriminating between closely related taxa. None of the recognized
subspecies of the A. ciliata complex could be clearly discriminated
based on the molecular markers implemented in this study.
This study provides the first evidence for the survival of a terrestrial
plant species in situ in Ireland throughout the Pleistocene glacial
cycles.
Item Type: |
Thesis
(PhD)
|
Keywords: |
Phylogeographic Study; Arenaria ciliata; Arenaria
norvegica; Ireland; Europe; |
Academic Unit: |
Faculty of Science and Engineering > Biology |
Item ID: |
6750 |
Depositing User: |
IR eTheses
|
Date Deposited: |
08 Jan 2016 09:45 |
URI: |
|
Use Licence: |
This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available
here |
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