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Explaining spatial heterogeneity in population dynamics and genetics from spatial variation in resources for a large
Adrienne L Contasti1, Emily J Tissier, Jill F Johnstone
1Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Plos One
|November 3, 2012
Summary
Habitat quality variations drive genetic differences in Sable Island feral horses. Spatial gradients in resources lead to distinct population dynamics and genetic structures, not inbreeding depression.
Area of Science:
- Ecology
- Population Genetics
- Conservation Biology
Background:
- Fine-scale spatial variation in genetic relatedness and inbreeding is observed in vertebrate populations.
- The underlying causes of these genetic patterns, particularly in relation to habitat quality and population dynamics, are often not fully understood.
Purpose of the Study:
- To test the hypothesis that spatial patterns in genetics of Sable Island feral horses result from variations in population dynamics linked to habitat quality.
- To investigate the relationship between habitat heterogeneity, population structure, and genetic variation in this island population.
Main Methods:
- Hierarchical cluster analysis of water sources to identify habitat quality gradients.
- Indicator analysis of forage species (sandwort and beach pea) availability.
- Quantification of a west-east gradient in freshwater access and food resources.
- Analysis of population dynamics (density, body condition, survival, reproduction) across island segments.
Main Results:
- A west-east gradient in habitat quality was identified, with better access to freshwater and forage in the west.
- The horse population clustered into three segments (west, central, east) with differing local dynamics.
- Population density, body condition, and reproductive success were highest in the west and decreased eastward.
- Genetic analysis showed highest inbreeding in the west and outbreeding in the east, mirroring habitat quality and population dynamics.
Conclusions:
- Habitat gradients significantly influence fine-scale population dynamics and genetic structuring in feral horse populations.
- Inbreeding depression does not appear to be a primary limiting factor for this population.
- Spatial heterogeneity in habitat quality can predict fine-scale genetic variation within continuous populations.
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