This thesis investigates the ecological genetics of the Marsh Fritillary butterfly in the British Isles using microsatellite markers. This is broken down into four questions. The first question to be addressed is what is the population differentiation across a broad landscape? The second question asks what the population differentiation is on a similar geographical scale when populations are isolated by water? The third question asks what management units can be identified at local and regional scales? The final question addresses the genetic composition and diversity of a reintroduced population with reference to the source populations.
This study suggests that movements of <400m occur frequently and within that distance populations cannot be considered separate even when occupying discreet patches of habitat. Movements of >4km occur but infrequently enough for patches this distance apart to be considered separate populations, with significant pairwise Fst values detected at this range. Previous studies, mainly based on observation and recapture studies, have estimated the dispersal range to be between 300m-20km. The upper limit of dispersal was not determined but the 20km previous proposed is commensurate with this study.
Strong evidence for spacial structuring and population differentiation was found over relatively short distances (<12km). Isolation by distance was observed only in the most geographically separated dataset (Ireland), suggesting that at shorter distances (<100km) the landscape matrix may have more of an effect on dispersal than straight line distance. Water is not a barrier to dispersal and pairwise Fst for island populations is similar to equivalent mainland population pairs over the same distance. It is also theorised that multi-generational stepping-stone dispersal may occur in both terrestrial and mixed terrestrial-open water habitats.
Levels of genetic diversity in reintroduced populations whose donor stock was an admixture bred from two separate areas was found to be similar or higher than that of natural populations. Populations reintroduced from the same captive stock began to show population differentiation nine generations after reintroduction.
Most populations examined exhibited low observed heterozygosity and departures from Hardy-Weinberg equilibrium, implying that this is normal for the species. Genetic variation is unevenly distributed across the landscape although analysis showed that this was not easily explained by landscape features. The management implications of findings are discussed and suggest genetic evidence can inform management decisions. Specifically, genetic diversity is not equally distributed across the landscape and this needs to be taken into consideration if planning landscape level intervention. When designating management units, sites which are <400m apart should be treated as a single population and managed together, while sites which are >4km apart are separate populations and should be treated as separate management units.
|Date of Award||24 Oct 2019|
|Supervisor||PAUL ASHTON (Director of Studies) & MICHAEL POWELL (Supervisor)|
- Euphydryas aurinia;
- Marsh Fritillary
- ecological genetics
- gene flow