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Genetic Variation and Evolution of Floral Display in Primula farinosa
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Plant Ecology and Evolution.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, I combine molecular analyses, common-garden and field experiments to examine how evolutionary and ecological processes influence patterns of genetic variation among and within populations of the declining, insect-pollinated, self-incompatible, perennial herb Primula farinosa. More specifically I examined 1) whether genetic diversity at neutral marker loci was related to habitat fragmentation and habitat stability, 2) whether floral display and flowering time were more strongly differentiated among populations than were putatively neutral marker loci, 3) whether adaptive population differentiation could be detected on a local spatial scale, and 4) whether floral display differentially affected male and female reproductive success.

Genetic diversity at neutral marker loci was lower within fragmented populations on the Swedish mainland than within the more densely occurring populations on the island Öland, SE Sweden. On Öland, fluctuations in population size were more pronounced on thin than on deep soils, but genetic diversity was not related to soil depth. Among-population genetic differentiation in scape length and flowering time was stronger than that of neutral marker loci, which is consistent with divergent selection acting on these traits. Water availability should influence the length of the growing season and thus the time available for fruit maturation, but flowering time in a common-garden experiment was not related to estimates of water availability at sites of origin. In a reciprocal transplant experiment conducted among four populations separated by up to a few kilometres and growing in environment differing in water availability and grazing intensity, no evidence of local adaption was observed. Finally, in a field experiment, interactions with pollinators and antagonists differentially affected selection on floral display through male and female function.

Taken together, the results indicate that habitat connectivity and environmental heterogeneity contribute to high neutral and adaptive genetic variation in Primula farinosa on the island Öland, SE Sweden, and illustrate that effects on both male and female reproductive success need to be considered to understand fully the evolution of floral display.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 40 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1112
Keyword [en]
natural selection, flowering time, population differentiation, local adaptation, male reproductive success
National Category
Ecology Evolutionary Biology Genetics
Identifiers
URN: urn:nbn:se:uu:diva-215508ISBN: 978-91-554-8850-5 (print)OAI: oai:DiVA.org:uu-215508DiVA: diva2:687562
Public defence
2014-02-28, Zootissalen, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2014-02-06 Created: 2014-01-14 Last updated: 2014-02-10
List of papers
1. Genetic diversity and structure of the declining herb Primula farinosa across different spatial scales
Open this publication in new window or tab >>Genetic diversity and structure of the declining herb Primula farinosa across different spatial scales
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Habitat fragmentation and reduced population sizes are important threats to biodiversity. These changes increase the influence of genetic drift and are therefore expected to lead to reduced genetic diversity and increased population differentiation. We analysed patterns of genetic variation in the declining herb Primula farinosa in Sweden. On the mainland, P. farinosa has scattered, isolated occurrences due to habitat fragmentation, whereas on the island of Öland, southeast Sweden, the species remains common. On Öland, populations were sampled on both shallow soils, where fluctuations in population size are substantial, and on deep soils, where populations are more stable. Genetic diversity was investigated at 12 putatively neutral microsatellite loci and at a floral display locus influencing plant fitness. Genetic diversity was found to be lower and more strongly structured on the mainland than on Öland, which is consistent with lower gene flow and increased influence of genetic drift in mainland than in Öland populations. On Öland, genetic diversity was not related to soil depth, suggesting that differences in the magnitude of fluctuations in population size are less important for the structuring of genetic variation in P. farinosa. Moreover, population differentiation was stronger at the floral display locus compared to microsatellite loci, consistent with divergent selection acting on floral display on Öland. Taken together, our findings indicate that to maintain genetic diversity in P. farinosa, management should promote gene flow among populations and variation in the direction of selection on floral display.

Keyword
Conservation, Population connectivity, Divergent selection, Population size fluctuation, Environmental heterogeneity, Perennial herb
National Category
Ecology Genetics
Identifiers
urn:nbn:se:uu:diva-215505 (URN)
Available from: 2014-01-14 Created: 2014-01-14 Last updated: 2014-02-10
2. Genetic differentiation in flowering time of a short-lived perennial herb driven by divergent selection
Open this publication in new window or tab >>Genetic differentiation in flowering time of a short-lived perennial herb driven by divergent selection
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Because flowering time influences the time available for fruit maturation, the optimal flowering time should vary among environments that differ in the length of the growing season. With field surveys and a common-garden experiment, we documented variation in flowering time among 20 populations of the perennial herb Primula farinosa growing on soils of different water availability within an 8 x 5 km area on the island Öland, SE Sweden. We tested the hypotheses that (a) among-population variation in flowering time in the field reflects genetic differentiation, (b) among-population differentiation in flowering time is larger than that at putatively neutral marker loci, and (c) genetic differentiation in flowering time is related to water availability at the sites of origin. Among-population variation in a common-garden experiment was positively correlated with variation observed among populations at their sites of origin, and among-population differentiation for start of flowering was significantly higher than at putatively neutral marker loci. In the field, flowering start tended to be positively related to soil moisture. However, among-population differentiation observed in the common-garden experiment was not related to variation in measures of water availability at the sites of origin, suggesting that factors other than soil characteristics influence the evolution of flowering time in this system of populations. The results indicate that variation in flowering time observed among natural populations of P. farinosa is the result of both genetic differentiation and phenotypic plasticity, and are consistent with divergent selection on flowering time. 

Keyword
Adaptation; Environmental heterogeneity; Flowering start; Phenology; Primula farinosa; Soil depth; Water availability
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-215433 (URN)
Available from: 2014-01-13 Created: 2014-01-13 Last updated: 2014-02-10
3. A demographic assessment of local adaptation in a grassland perennial herb
Open this publication in new window or tab >>A demographic assessment of local adaptation in a grassland perennial herb
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Habitat heterogeneity in abiotic and biotic factors drives the evolution of adaptive population differentiation. Assessments of local adaptation among populations of perennial plants are commonly based on estimates of one or a few fitness components in reciprocal transplant experiments. However, natural selection does not act on fitness components but on life-time fitness, and local adaptation should therefore ideally be assessed based on integrated measures of the performance during the entire life cycle. We transplanted seedlings and adult plants reciprocally among four populations of the perennial herb Primula farinosa differing in abiotic and biotic conditions on the island of Öland, SE Sweden. We recorded survival, growth, flowering and fruit production during three consecutive years (2010-2012) and used integral projection models to quantify variation in total fitness, estimated as population growth rate. Transplant site had large effects on most aspects of plant performance, and the effects of population of origin on survival, growth, flowering propensity and fruit production varied among sites for several year × cohort combinations. However, no evidence of local adaptation, expressed through single fitness components or total fitness, was found. The results suggest that populations of P. farinosa differ genetically in traits influencing fitness, but these differences do not match current selection regimes. This study provides a template for how reciprocal transplant experiments can be combined with long-term demographic studies and population models to assess local adaptation in long-lived species based on estimates of total fitness.

Keyword
Demography, Integral Projection Models, Life-time fitness, Primula farinosa, Reciprocal transplant
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-215434 (URN)
Available from: 2014-01-13 Created: 2014-01-13 Last updated: 2014-02-10
4. Differential effects of floral display on female and male reproductive success in the hermaphroditic herb Primula farinosa
Open this publication in new window or tab >>Differential effects of floral display on female and male reproductive success in the hermaphroditic herb Primula farinosa
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A prominent floral display increases attractiveness to pollinators, but may be associated with a cost in terms of increased risk of damage from antagonists.  If damage to reproductive parts by grazers and seed predators mostly occurs after pollen dispersal, a large floral display may benefit both female and male reproductive functions, while costs may predominantly be expressed through female function. The hermaphroditic herb Primula farinosa is dimorphic for floral display with a long-scaped morph, which displays its flowers well above the ground, and a short-scaped morph, which displays its flowers close to the ground. We conducted a field experiment with genotyped plants at two sites to examine whether scape morph differentially affects female and male reproductive success and whether the two scape morphs mate assortatively. Female reproductive success was assessed by quantifying seed production and male siring success by genotyping offspring. The intensity of seed predation differed between experimental sites (59% vs. 9% of fruits attacked), whereas differences in grazing damage were smaller and not statistically significant (9% vs. 6%). At the site where seed predation was high, the long-scaped morph produced significantly fewer seeds, but sired more offspring than did the short-scaped morph. At the other site, the two morphs did not differ significantly in seed production or siring success. The scape morphs did not mate assortatively. The results indicate that interactions with pollinators and antagonists can differentially affect selection on floral display through male and female function and could potentially lead to a relationship between floral display and plant functional gender. They further demonstrate that a full understanding of selection on floral traits requires that selection through both male and female reproductive success is considered.

Keyword
Assortative mating, Biotic interactions, Functional gender, Paternity analyses, Siring success
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-215432 (URN)
Available from: 2014-01-13 Created: 2014-01-13 Last updated: 2014-02-10

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