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Persistence and dispersal in a Southern Hemisphere glaciated landscape: the phylogeography of the spotted snow skink (Niveoscincus ocellatus) in Tasmania.

Cliff HB, Wapstra E, Burridge CP - BMC Evol. Biol. (2015)

Bottom Line: There was a high degree of mitochondrial haplotype diversity (96 unique haplotypes) and phylogeographic structure, where spatially distinct groups were associated with Tasmania's Northeast and a large area covering Southeast and Central Tasmania.Expansion in Central and Southeastern areas appears to have been more recent in both demographic and spatial contexts, than in Northeast Tasmania, which is consistent with inferences for other taxa of greater stability and persistence in Northeast Tasmania during the Last Glacial Maximum.These phylogeographic patterns indicate contrasting demographic histories of populations in close proximity to areas directly affected by glaciers in the Southern Hemisphere during the LGM.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia. hcliff11@gmail.com.

ABSTRACT

Background: The aim of this research was to identify the effects of Pleistocene climate change on the distribution of fauna in Tasmania, and contrast this with biotic responses in other temperate regions in the Northern and Southern Hemisphere that experienced glacial activity during this epoch. This was achieved by examining the phylogeographic patterns in a widely distributed Tasmanian endemic reptile, Niveoscincus ocellatus. 204 individuals from 29 populations across the distributional range of N. ocellatus were surveyed for variation at two mitochondrial genes (ND2, ND4), and two nuclear genes (β-globin, RPS8). Phylogenetic relationships were reconstructed using a range of methods (maximum parsimony, Bayesian inference and haplotype networks), and the demographic histories of populations were assessed (AMOVA, Tajima's D, Fu's Fs, mismatch distributions, extended Bayesian skyline plots, and relaxed random walk analyses).

Results: There was a high degree of mitochondrial haplotype diversity (96 unique haplotypes) and phylogeographic structure, where spatially distinct groups were associated with Tasmania's Northeast and a large area covering Southeast and Central Tasmania. Phylogeographic structure was also present within each major group, but the degree varied regionally, being highest in the Northeast. Only the Southeastern group had a signature of demographic expansion, occurring during the Pleistocene but post-dating the Last Glacial Maximum. In contrast, nuclear DNA had low levels of variation and a lack of phylogeographic structure, and further loci should be surveyed to corroborate the mitochondrial inferences.

Conclusions: The phylogeographic patterns of N. ocellatus indicate Pleistocene range and demographic expansion in N. ocellatus, particularly in the Southeast and Central areas of Tasmania. Expansion in Central and Southeastern areas appears to have been more recent in both demographic and spatial contexts, than in Northeast Tasmania, which is consistent with inferences for other taxa of greater stability and persistence in Northeast Tasmania during the Last Glacial Maximum. These phylogeographic patterns indicate contrasting demographic histories of populations in close proximity to areas directly affected by glaciers in the Southern Hemisphere during the LGM.

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Mitochondrial mismatch distributions for the (a) Northeastern and (b) Southeastern groups of Niveoscincus ocellatus. Histogram reflects coalescent simulation expectations for an exponentially expanding population while the solid line reflects the observed distributions
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Fig4: Mitochondrial mismatch distributions for the (a) Northeastern and (b) Southeastern groups of Niveoscincus ocellatus. Histogram reflects coalescent simulation expectations for an exponentially expanding population while the solid line reflects the observed distributions

Mentions: The Southeastern group was the only group with significant mtDNA Tajima’s D and Fu’s Fs, and an inability to reject the hypothesis of population expansion from the mismatch distribution (Fig. 4). The same result was observed when repeating these analyses while excluding Lake Mackenzie from the Southeast group. The Northwest group was not analysed due to the low sample size for this group. Given differences in sample size between the Northeast and Southeast groups (number of individuals per site often large for Northeast sites), we also randomly subsampled these sites to six individuals, but the results were qualitatively identical (non-significant Tajima’s D and Fu’s Fs, and significant mismatch distribution; haplotype diversity lower, and nucleotide diversity similar to the Southeast group).Fig. 4


Persistence and dispersal in a Southern Hemisphere glaciated landscape: the phylogeography of the spotted snow skink (Niveoscincus ocellatus) in Tasmania.

Cliff HB, Wapstra E, Burridge CP - BMC Evol. Biol. (2015)

Mitochondrial mismatch distributions for the (a) Northeastern and (b) Southeastern groups of Niveoscincus ocellatus. Histogram reflects coalescent simulation expectations for an exponentially expanding population while the solid line reflects the observed distributions
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4482293&req=5

Fig4: Mitochondrial mismatch distributions for the (a) Northeastern and (b) Southeastern groups of Niveoscincus ocellatus. Histogram reflects coalescent simulation expectations for an exponentially expanding population while the solid line reflects the observed distributions
Mentions: The Southeastern group was the only group with significant mtDNA Tajima’s D and Fu’s Fs, and an inability to reject the hypothesis of population expansion from the mismatch distribution (Fig. 4). The same result was observed when repeating these analyses while excluding Lake Mackenzie from the Southeast group. The Northwest group was not analysed due to the low sample size for this group. Given differences in sample size between the Northeast and Southeast groups (number of individuals per site often large for Northeast sites), we also randomly subsampled these sites to six individuals, but the results were qualitatively identical (non-significant Tajima’s D and Fu’s Fs, and significant mismatch distribution; haplotype diversity lower, and nucleotide diversity similar to the Southeast group).Fig. 4

Bottom Line: There was a high degree of mitochondrial haplotype diversity (96 unique haplotypes) and phylogeographic structure, where spatially distinct groups were associated with Tasmania's Northeast and a large area covering Southeast and Central Tasmania.Expansion in Central and Southeastern areas appears to have been more recent in both demographic and spatial contexts, than in Northeast Tasmania, which is consistent with inferences for other taxa of greater stability and persistence in Northeast Tasmania during the Last Glacial Maximum.These phylogeographic patterns indicate contrasting demographic histories of populations in close proximity to areas directly affected by glaciers in the Southern Hemisphere during the LGM.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia. hcliff11@gmail.com.

ABSTRACT

Background: The aim of this research was to identify the effects of Pleistocene climate change on the distribution of fauna in Tasmania, and contrast this with biotic responses in other temperate regions in the Northern and Southern Hemisphere that experienced glacial activity during this epoch. This was achieved by examining the phylogeographic patterns in a widely distributed Tasmanian endemic reptile, Niveoscincus ocellatus. 204 individuals from 29 populations across the distributional range of N. ocellatus were surveyed for variation at two mitochondrial genes (ND2, ND4), and two nuclear genes (β-globin, RPS8). Phylogenetic relationships were reconstructed using a range of methods (maximum parsimony, Bayesian inference and haplotype networks), and the demographic histories of populations were assessed (AMOVA, Tajima's D, Fu's Fs, mismatch distributions, extended Bayesian skyline plots, and relaxed random walk analyses).

Results: There was a high degree of mitochondrial haplotype diversity (96 unique haplotypes) and phylogeographic structure, where spatially distinct groups were associated with Tasmania's Northeast and a large area covering Southeast and Central Tasmania. Phylogeographic structure was also present within each major group, but the degree varied regionally, being highest in the Northeast. Only the Southeastern group had a signature of demographic expansion, occurring during the Pleistocene but post-dating the Last Glacial Maximum. In contrast, nuclear DNA had low levels of variation and a lack of phylogeographic structure, and further loci should be surveyed to corroborate the mitochondrial inferences.

Conclusions: The phylogeographic patterns of N. ocellatus indicate Pleistocene range and demographic expansion in N. ocellatus, particularly in the Southeast and Central areas of Tasmania. Expansion in Central and Southeastern areas appears to have been more recent in both demographic and spatial contexts, than in Northeast Tasmania, which is consistent with inferences for other taxa of greater stability and persistence in Northeast Tasmania during the Last Glacial Maximum. These phylogeographic patterns indicate contrasting demographic histories of populations in close proximity to areas directly affected by glaciers in the Southern Hemisphere during the LGM.

Show MeSH