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Quantitative genetic variation in declining plant populations

Ellmer, Maarten LU (2009)
Abstract
The ecological and genetic effects of habitat fragmentation are an issue of major concern in current conservation biology. Habitat fragmentation results in smaller habitat areas and as a consequence smaller and more isolated populations. Many habitats have become fragmented through human activities such as forestry and agricultural development. In Sweden, for example, the area of species-rich, semi-natural grasslands has decreased by more than 90% since the 1870s.

The aim of this thesis was to examine the quantitative genetic effects of small population size and population fragmentation, with particular emphasis on the variation in evolutionarily relevant phenotypic characters. The thesis includes experimental studies of... (More)
The ecological and genetic effects of habitat fragmentation are an issue of major concern in current conservation biology. Habitat fragmentation results in smaller habitat areas and as a consequence smaller and more isolated populations. Many habitats have become fragmented through human activities such as forestry and agricultural development. In Sweden, for example, the area of species-rich, semi-natural grasslands has decreased by more than 90% since the 1870s.

The aim of this thesis was to examine the quantitative genetic effects of small population size and population fragmentation, with particular emphasis on the variation in evolutionarily relevant phenotypic characters. The thesis includes experimental studies of inbreeding depression and bottleneck effects as well as studies designed to reveal quantitative genetic effects of human-induced habitat fragmentation. The species used in the inbreeding/bottleneck experiment was Nigella degenii (Ranunculaceae) while Briza media (Poaceae) and Saxifraga granulata (Saxifragaceae) was used in the study of habitat fragmentation.

Comparison of selfed and outbred offspring of Nigella revealed significant inbreeding depression in primary components of fitness but also in morphological and phenological characters that here diverged within the study species. The bottleneck experiment showed line-specific changes in genetic covariance structure but also indicated that bottlenecked populations generally have a lower adaptive potential than the ancestral population.

There was no clear evidence that genetic drift, founder events and diversifying selection have played major roles in structuring the quantitative genetic variation within Briza in the study area. In contrast to the Briza study, several characters in Saxifraga were significantly correlated with habitat descriptors assumed to reflect selection pressures (e.g. current grazing pressure and percent cover of trees or shrubs). Again, no effect of drift and founder events were detected.

The results for Briza and Saxifraga indicate that quantitative genetic effects of habitat fragmentation may be of lesser concern for conservation than more immediate effects on species diversity or short-term population viability. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Nordal, Inger, Department of Biology, University of Oslo, P.O Box 1045 Blindern, N-0316 Oslo, Norway
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Saxifraga granulata, Briza media, Nigella degenii, bottleneck, Inbreeding depression, founder effects, drift, quantitative genetic, diversifying selection, habitat fragmentation, small populations
pages
133 pages
defense location
BlÄ Hallen at the Department of Ecology, Ecology Building, Sölvegatan 37, Lund
defense date
2009-10-02 10:00
ISBN
978-91-7105-300-8
language
English
LU publication?
yes
id
6370fe2a-eac0-473d-9f53-ff8d3b4d0093 (old id 1471555)
date added to LUP
2009-09-07 13:33:58
date last changed
2016-09-19 08:45:16
@phdthesis{6370fe2a-eac0-473d-9f53-ff8d3b4d0093,
  abstract     = {The ecological and genetic effects of habitat fragmentation are an issue of major concern in current conservation biology. Habitat fragmentation results in smaller habitat areas and as a consequence smaller and more isolated populations. Many habitats have become fragmented through human activities such as forestry and agricultural development. In Sweden, for example, the area of species-rich, semi-natural grasslands has decreased by more than 90% since the 1870s. <br/><br>
The aim of this thesis was to examine the quantitative genetic effects of small population size and population fragmentation, with particular emphasis on the variation in evolutionarily relevant phenotypic characters. The thesis includes experimental studies of inbreeding depression and bottleneck effects as well as studies designed to reveal quantitative genetic effects of human-induced habitat fragmentation. The species used in the inbreeding/bottleneck experiment was Nigella degenii (Ranunculaceae) while Briza media (Poaceae) and Saxifraga granulata (Saxifragaceae) was used in the study of habitat fragmentation.<br/><br>
Comparison of selfed and outbred offspring of Nigella revealed significant inbreeding depression in primary components of fitness but also in morphological and phenological characters that here diverged within the study species. The bottleneck experiment showed line-specific changes in genetic covariance structure but also indicated that bottlenecked populations generally have a lower adaptive potential than the ancestral population. <br/><br>
There was no clear evidence that genetic drift, founder events and diversifying selection have played major roles in structuring the quantitative genetic variation within Briza in the study area. In contrast to the Briza study, several characters in Saxifraga were significantly correlated with habitat descriptors assumed to reflect selection pressures (e.g. current grazing pressure and percent cover of trees or shrubs). Again, no effect of drift and founder events were detected.<br/><br>
The results for Briza and Saxifraga indicate that quantitative genetic effects of habitat fragmentation may be of lesser concern for conservation than more immediate effects on species diversity or short-term population viability.},
  author       = {Ellmer, Maarten},
  isbn         = {978-91-7105-300-8},
  keyword      = {Saxifraga granulata,Briza media,Nigella degenii,bottleneck,Inbreeding depression,founder effects,drift,quantitative genetic,diversifying selection,habitat fragmentation,small populations},
  language     = {eng},
  pages        = {133},
  school       = {Lund University},
  title        = {Quantitative genetic variation in declining plant populations},
  year         = {2009},
}