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Orchid colonization: multiple parallel dispersal events and mosaic genetic structure in Dactylorhiza majalis ssp. lapponica on the Baltic island of Gotland.

Hedrén, Mikael LU ; Nordström Olofsson, Sofie LU and Paun, Ovidiu (2018) In Annals of Botany 122(6). p.1019-1031
Abstract (Swedish)
Background and Aims The island of Gotland in the Baltic Sea had no contact with surrounding continental areas since the withdrawal of the Weichselian ice sheet at ca 17 ka BP. Plants present on Gotland must have arrived by long distance dispersal, so populations are expected to exhibit reduced levels of genetic diversity compared with surrounding mainlands. However, orchids have very small seeds, which appear well-adapted for long-distance dispersal, and they should therefore be less affected than other plant species by colonization bottlenecks. The aim of this study was to analyse the genetic structure of orchids colonizing isolated islands, using the marsh orchid Dactylorhiza majalis ssp. lapponica as case study.
Methods More than... (More)
Background and Aims The island of Gotland in the Baltic Sea had no contact with surrounding continental areas since the withdrawal of the Weichselian ice sheet at ca 17 ka BP. Plants present on Gotland must have arrived by long distance dispersal, so populations are expected to exhibit reduced levels of genetic diversity compared with surrounding mainlands. However, orchids have very small seeds, which appear well-adapted for long-distance dispersal, and they should therefore be less affected than other plant species by colonization bottlenecks. The aim of this study was to analyse the genetic structure of orchids colonizing isolated islands, using the marsh orchid Dactylorhiza majalis ssp. lapponica as case study.
Methods More than 500 samples from 27 populations were analysed for 15 plastid and eight nuclear marker loci. Population diversity and differentiation patterns were compared for nuclear and plastid marker systems and analysed in relation to geographic location.
Key Results We found high genetic diversity but no clear geographic structure of genetic differentiation between populations on Gotland. However, the between-population differentiation in plastid and nuclear markers were correlated and the greatest diversity was found at sites at comparatively high elevations, which were the first to emerge above the water after the ice age.
Conclusions The regional population on Gotland has been established by a minimum of four dispersal events from continental regions. Subsequent gene flow between sites has not yet homogenized the differentiation pattern originating from initial colonization. We conclude that long-distance seed dispersal in orchids has a strong impact on structuring genetic diversity during periods of expansion and colonization, but contributes less to gene flow between populations once a stable population structure has been achieved.
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Abstract

Background and Aims

The island of Gotland in the Baltic Sea has had no contact with surrounding continental areas since the withdrawal of the Weichselian ice sheet at approx. 17 ka BP. Plants present on Gotland must have arrived by long-distance dispersal, so populations are expected to exhibit reduced levels of genetic diversity compared with populations on surrounding mainlands. However, orchids have very small seeds, which appear well adapted to long-distance dispersal, and they should therefore be less affected than other plant species by colonization bottlenecks. The aim of this study was to analyse the genetic structure of orchids colonizing isolated islands, using the marsh orchid Dactylorhiza majalis ssp. lapponica as... (More)

Background and Aims

The island of Gotland in the Baltic Sea has had no contact with surrounding continental areas since the withdrawal of the Weichselian ice sheet at approx. 17 ka BP. Plants present on Gotland must have arrived by long-distance dispersal, so populations are expected to exhibit reduced levels of genetic diversity compared with populations on surrounding mainlands. However, orchids have very small seeds, which appear well adapted to long-distance dispersal, and they should therefore be less affected than other plant species by colonization bottlenecks. The aim of this study was to analyse the genetic structure of orchids colonizing isolated islands, using the marsh orchid Dactylorhiza majalis ssp. lapponica as a case study.


Methods

More than 500 samples from 27 populations were analysed for 15 plastid and eight nuclear marker loci. Population diversity and differentiation patterns were compared for nuclear and plastid marker systems and analysed in relation to geographical location.


Key Results

We found high genetic diversity but no clear geographical structure of genetic differentiation between populations on Gotland. However, the between-population differentiation in plastid and nuclear markers were correlated and the greatest diversity was found at sites at comparatively high elevations, which were the first to emerge above the water after the Ice Age.


Conclusions

The regional population on Gotland has been established by a minimum of four dispersal events from continental regions. Subsequent gene flow between sites has not yet homogenized the differentiation pattern originating from initial colonization. We conclude that long-distance seed dispersal in orchids has a strong impact on structuring genetic diversity during periods of expansion and colonization, but contributes less to gene flow between populations once a stable population structure has been achieved.
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Annals of Botany
volume
122
issue
6
pages
1019 - 1031
publisher
Oxford University Press
external identifiers
  • scopus:85070860936
ISSN
0305-7364
DOI
10.1093/aob/mcy111
language
English
LU publication?
yes
id
f6b0fc53-d71c-424e-a65e-d6a66cf4e2f4
date added to LUP
2019-05-23 12:48:43
date last changed
2019-09-15 05:18:08
@article{f6b0fc53-d71c-424e-a65e-d6a66cf4e2f4,
  abstract     = {<br/>Background and Aims<br/><br/>The island of Gotland in the Baltic Sea has had no contact with surrounding continental areas since the withdrawal of the Weichselian ice sheet at approx. 17 ka BP. Plants present on Gotland must have arrived by long-distance dispersal, so populations are expected to exhibit reduced levels of genetic diversity compared with populations on surrounding mainlands. However, orchids have very small seeds, which appear well adapted to long-distance dispersal, and they should therefore be less affected than other plant species by colonization bottlenecks. The aim of this study was to analyse the genetic structure of orchids colonizing isolated islands, using the marsh orchid Dactylorhiza majalis ssp. lapponica as a case study.<br/><br/><br/>Methods<br/><br/>More than 500 samples from 27 populations were analysed for 15 plastid and eight nuclear marker loci. Population diversity and differentiation patterns were compared for nuclear and plastid marker systems and analysed in relation to geographical location.<br/><br/><br/>Key Results<br/><br/>We found high genetic diversity but no clear geographical structure of genetic differentiation between populations on Gotland. However, the between-population differentiation in plastid and nuclear markers were correlated and the greatest diversity was found at sites at comparatively high elevations, which were the first to emerge above the water after the Ice Age.<br/><br/><br/>Conclusions<br/><br/>The regional population on Gotland has been established by a minimum of four dispersal events from continental regions. Subsequent gene flow between sites has not yet homogenized the differentiation pattern originating from initial colonization. We conclude that long-distance seed dispersal in orchids has a strong impact on structuring genetic diversity during periods of expansion and colonization, but contributes less to gene flow between populations once a stable population structure has been achieved.<br/>},
  author       = {Hedrén, Mikael and Nordström Olofsson, Sofie and Paun, Ovidiu},
  issn         = {0305-7364},
  language     = {eng},
  month        = {06},
  number       = {6},
  pages        = {1019--1031},
  publisher    = {Oxford University Press},
  series       = {Annals of Botany},
  title        = {Orchid colonization: multiple parallel dispersal events and mosaic genetic structure in Dactylorhiza majalis ssp. lapponica on the Baltic island of Gotland.},
  url          = {http://dx.doi.org/10.1093/aob/mcy111},
  volume       = {122},
  year         = {2018},
}