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Alpine crossroads or origin of genetic diversity? Comparative phylogeography of two sympatric microgastropod species.

Weigand AM, Pfenninger M, Jochum A, Klussmann-Kolb A - PLoS ONE (2012)

Bottom Line: Consequently, we identify the Alpine Region as a significant 'hot-spot' for the formation of genetic diversity within European Carychium lineages.Passive dispersal via anthropogenic means best explains the presence of transatlantic European Carychium populations on the Azores and in North America.We conclude that passive (anthropogenic) transport could mislead the interpretation of observed phylogeographical patterns in general.

View Article: PubMed Central - PubMed

Affiliation: Department of Phylogeny and Systematics, Goethe University, Frankfurt am Main, Hesse, Germany. A.Weigand@bio.uni-frankfurt.de

ABSTRACT
The Alpine Region, constituting the Alps and the Dinaric Alps, has played a major role in the formation of current patterns of biodiversity either as a contact zone of postglacial expanding lineages or as the origin of genetic diversity. In our study, we tested these hypotheses for two widespread, sympatric microgastropod taxa--Carychium minimum O.F. Müller, 1774 and Carychium tridentatum (Risso, 1826) (Gastropoda, Eupulmonata, Carychiidae)--by using COI sequence data and species potential distribution models analyzed in a statistical phylogeographical framework. Additionally, we examined disjunct transatlantic populations of those taxa from the Azores and North America. In general, both Carychium taxa demonstrate a genetic structure composed of several differentiated haplotype lineages most likely resulting from allopatric diversification in isolated refugial areas during the Pleistocene glacial periods. However, the genetic structure of Carychium minimum is more pronounced, which can be attributed to ecological constraints relating to habitat proximity to permanent bodies of water. For most of the Carychium lineages, the broader Alpine Region was identified as the likely origin of genetic diversity. Several lineages are endemic to the broader Alpine Region whereas a single lineage per species underwent a postglacial expansion to (re)colonize previously unsuitable habitats, e.g. in Northern Europe. The source populations of those expanding lineages can be traced back to the Eastern and Western Alps. Consequently, we identify the Alpine Region as a significant 'hot-spot' for the formation of genetic diversity within European Carychium lineages. Passive dispersal via anthropogenic means best explains the presence of transatlantic European Carychium populations on the Azores and in North America. We conclude that passive (anthropogenic) transport could mislead the interpretation of observed phylogeographical patterns in general.

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Related in: MedlinePlus

Tests of population expansion for the most widespread MOTU per taxon.Mismatch distributions and values for the neutrality tests of Fu's FS and Tajima's D are provided for the haplotype lineages CTMOTU1 and CMMOTU1 (*** = p-value with significance level <0.00001). Solid and dotted lines indicate expected distributions after events of range expansion and the observed functions, respectively.
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pone-0037089-g006: Tests of population expansion for the most widespread MOTU per taxon.Mismatch distributions and values for the neutrality tests of Fu's FS and Tajima's D are provided for the haplotype lineages CTMOTU1 and CMMOTU1 (*** = p-value with significance level <0.00001). Solid and dotted lines indicate expected distributions after events of range expansion and the observed functions, respectively.

Mentions: Bayes factor (BF) tests of both datasets favor a scenario of constant population size over a scenario with exponential growth (BFCM = 2.099; BFCT = 6.482). The complete COI-dataset of CM provides no indication for an event of past population expansion (Table 2). However, both neutrality tests for the complete dataset of CT and MOTU1 of both species are significantly negative. Haplotype lineages of CMMOTU4 and CTMOTU6 demonstrate significantly negative results for Tajima's D only. We found no MOTU to be significantly negative for Fu's FS only. As shown by the respective unimodal mismatch distributions, the observed data for CMMOTU1 and CTMOTU1 are not significantly different from modeled distributions of population expansion (Fig. 6). Goodness-of-fit estimates are Hri = 0.095 (p = 0.327) and Hri = 0.265 (p = 0.407) for CMMOTU1 and CTMOTU1, respectively. The McDonald-Kreitman test revealed 71 polymorphic synonymous (Ps), 4 polymorphic non-synonymous (Pn), 6 fixed synonymous (Ms) and no fixed non-synonymous differences (Mn). Due to the lack of Mn, the McDonald-Kreitman test does not indicate that differences have been subject to positive selection. However, the selective pressure could have operated upon linked genes within the (single-molecule) mitochondrial genome. Moreover, even a significant result for positive selection does not necessarily exclude population expansion, as these differences could have enabled population expansion in the first place.


Alpine crossroads or origin of genetic diversity? Comparative phylogeography of two sympatric microgastropod species.

Weigand AM, Pfenninger M, Jochum A, Klussmann-Kolb A - PLoS ONE (2012)

Tests of population expansion for the most widespread MOTU per taxon.Mismatch distributions and values for the neutrality tests of Fu's FS and Tajima's D are provided for the haplotype lineages CTMOTU1 and CMMOTU1 (*** = p-value with significance level <0.00001). Solid and dotted lines indicate expected distributions after events of range expansion and the observed functions, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351404&req=5

pone-0037089-g006: Tests of population expansion for the most widespread MOTU per taxon.Mismatch distributions and values for the neutrality tests of Fu's FS and Tajima's D are provided for the haplotype lineages CTMOTU1 and CMMOTU1 (*** = p-value with significance level <0.00001). Solid and dotted lines indicate expected distributions after events of range expansion and the observed functions, respectively.
Mentions: Bayes factor (BF) tests of both datasets favor a scenario of constant population size over a scenario with exponential growth (BFCM = 2.099; BFCT = 6.482). The complete COI-dataset of CM provides no indication for an event of past population expansion (Table 2). However, both neutrality tests for the complete dataset of CT and MOTU1 of both species are significantly negative. Haplotype lineages of CMMOTU4 and CTMOTU6 demonstrate significantly negative results for Tajima's D only. We found no MOTU to be significantly negative for Fu's FS only. As shown by the respective unimodal mismatch distributions, the observed data for CMMOTU1 and CTMOTU1 are not significantly different from modeled distributions of population expansion (Fig. 6). Goodness-of-fit estimates are Hri = 0.095 (p = 0.327) and Hri = 0.265 (p = 0.407) for CMMOTU1 and CTMOTU1, respectively. The McDonald-Kreitman test revealed 71 polymorphic synonymous (Ps), 4 polymorphic non-synonymous (Pn), 6 fixed synonymous (Ms) and no fixed non-synonymous differences (Mn). Due to the lack of Mn, the McDonald-Kreitman test does not indicate that differences have been subject to positive selection. However, the selective pressure could have operated upon linked genes within the (single-molecule) mitochondrial genome. Moreover, even a significant result for positive selection does not necessarily exclude population expansion, as these differences could have enabled population expansion in the first place.

Bottom Line: Consequently, we identify the Alpine Region as a significant 'hot-spot' for the formation of genetic diversity within European Carychium lineages.Passive dispersal via anthropogenic means best explains the presence of transatlantic European Carychium populations on the Azores and in North America.We conclude that passive (anthropogenic) transport could mislead the interpretation of observed phylogeographical patterns in general.

View Article: PubMed Central - PubMed

Affiliation: Department of Phylogeny and Systematics, Goethe University, Frankfurt am Main, Hesse, Germany. A.Weigand@bio.uni-frankfurt.de

ABSTRACT
The Alpine Region, constituting the Alps and the Dinaric Alps, has played a major role in the formation of current patterns of biodiversity either as a contact zone of postglacial expanding lineages or as the origin of genetic diversity. In our study, we tested these hypotheses for two widespread, sympatric microgastropod taxa--Carychium minimum O.F. Müller, 1774 and Carychium tridentatum (Risso, 1826) (Gastropoda, Eupulmonata, Carychiidae)--by using COI sequence data and species potential distribution models analyzed in a statistical phylogeographical framework. Additionally, we examined disjunct transatlantic populations of those taxa from the Azores and North America. In general, both Carychium taxa demonstrate a genetic structure composed of several differentiated haplotype lineages most likely resulting from allopatric diversification in isolated refugial areas during the Pleistocene glacial periods. However, the genetic structure of Carychium minimum is more pronounced, which can be attributed to ecological constraints relating to habitat proximity to permanent bodies of water. For most of the Carychium lineages, the broader Alpine Region was identified as the likely origin of genetic diversity. Several lineages are endemic to the broader Alpine Region whereas a single lineage per species underwent a postglacial expansion to (re)colonize previously unsuitable habitats, e.g. in Northern Europe. The source populations of those expanding lineages can be traced back to the Eastern and Western Alps. Consequently, we identify the Alpine Region as a significant 'hot-spot' for the formation of genetic diversity within European Carychium lineages. Passive dispersal via anthropogenic means best explains the presence of transatlantic European Carychium populations on the Azores and in North America. We conclude that passive (anthropogenic) transport could mislead the interpretation of observed phylogeographical patterns in general.

Show MeSH
Related in: MedlinePlus