| 1. |
- Cortés, Andrés J., 1989-
(författare)
-
On The Big Challenges of a Small Shrub : Ecological Genetics of Salix herbacea L
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The response of plants to climate change is among the main questions in ecology and evolution. Faced with changing conditions, populations may respond by adapting, going extinct or migrating. Fine-scale environmental variation offers a unique mosaic to explore these alternatives. In this thesis, I used ecological surveys, field experiments and molecular methods to study the range of possible responses at a very local scale in the alpine dwarf willow Salix herbacea L. Since gene flow may impact the potential for adaptation and migration, I first explored whether phenological divergence driven by snowmelt patterns impacts gene flow. I found that sites with late snowmelt work as sinks of the genetic diversity, as compared to sites with early snowmelt. I also used a combined approach that looked at the selection, heritability and genomic architecture of ecologically-relevant traits, as well as genomic divergence across the snowmelt mosaic. In this way, I was able to understand which genomic regions may relate to phenological, growth and fitness traits, and which regions in the genome harbor genetic variation associated with late- and early- snowmelt sites. I found that most of the genomic divergence driven by snowmelt is novel and is localized in few regions. Also, Salix herbacea has a strong female bias. Sex bias may matter for adaptation to climate change because different sexes of many dioecious species differ in several functions that may fluctuate with changing conditions. I found that the bias is uniform across environments and is already present at seeds and seedlings. A polygenic sex determination system together with transmission distortion may be maintaining the bias. Overall, fast-evolving microhabitat-driven genomic divergence and, at the same time, genetically-based trait variation at a larger scale may play a role for the ability of S. herbacea to persist in diverse and variable conditions.
|
|
| 2. |
- Luo, Yonghai, et al.
(författare)
-
A Single Nucleotide Deletion in Gibberellin20-oxidase1 Causes Alpine Dwarfism in Arabidopsis
- 2015
-
Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 168:3, s. 930-937
-
Tidskriftsartikel (refereegranskat)abstract
- Alpine dwarfism is widely observed in alpine plant populations and often considered a high-altitude adaptation, yet its molecular basis and ecological relevance remain unclear. In this study, we used map-based cloning and field transplant experiments to investigate dwarfism in natural Arabidopsis (Arabidopsis thaliana) accessions collected from the Swiss Alps. A loss-of-function mutation due to a single nucleotide deletion in gibberellin20-oxidase1 (GA5) was identified as the cause of dwarfism in an alpine accession. The mutated allele, ga5-184, was found in two natural Arabidopsis populations collected from one geographic region at high altitude, but was different from all other reported ga5 null alleles, suggesting that this allele has evolved locally. In field transplant experiments, the dwarf accession with ga5-184 exhibited a fitness pattern consistent with adaptation to high altitude. Across a wider array of accessions from the Swiss Alps, plant height decreased with altitude of origin, but fitness patterns in the transplant experiments were variable and general altitudinal adaptation was not evident. In general, our study provides new insights into molecular basis and possible ecological roles of alpine dwarfism, and demonstrates the importance of the GA-signaling pathway for the generation of ecologically relevant variation in higher plants.
|
|
| 3. |
- Luo, Y., et al.
(författare)
-
The roles of genetic drift and natural selection in quantitative trait divergence along an altitudinal gradient in Arabidopsis thaliana
- 2015
-
Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 114:2, s. 220-228
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding how natural selection and genetic drift shape biological variation is a central topic in biology, yet our understanding of the agents of natural selection and their target traits is limited. We investigated to what extent selection along an altitudinal gradient or genetic drift contributed to variation in ecologically relevant traits in Arabidopsis thaliana. We collected seeds from 8 to 14 individuals from each of 14 A. thaliana populations originating from sites between 800 and 2700 m above sea level in the Swiss Alps. Seed families were grown with and without vernalization, corresponding to winter-annual and summer-annual life histories, respectively. We analyzed putatively neutral genetic divergence between these populations using 24 simple sequence repeat markers. We measured seven traits related to growth, phenology and leaf morphology that are rarely reported in A. thaliana and performed analyses of altitudinal clines, as well as overall Q(ST)-F-ST comparisons and correlation analyses among pair-wise Q(ST), F-ST and altitude of origin differences. Multivariate analyses suggested adaptive differentiation along altitude in the entire suite of traits, particularly when expressed in the summer-annual life history. Of the individual traits, a decrease in rosette leaf number in the vegetative state and an increase in leaf succulence with increasing altitude could be attributed to adaptive divergence. Interestingly, these patterns relate well to common within- and between-species trends of smaller plant size and thicker leaves at high altitude. Our results thus offer exciting possibilities to unravel the underlying mechanisms for these conspicuous trends using the model species A. thaliana.
|
|
| 4. |
- Sedlacek, Janosch, et al.
(författare)
-
The Response of the Alpine Dwarf Shrub Salix herbacea to Altered Snowmelt Timing : Lessons from a Multi-Site Transplant Experiment
- 2015
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:4
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is altering spring snowmelt patterns in alpine and arctic ecosystems, and these changes may alter plant phenology, growth and reproduction. To predict how alpine plants respond to shifts in snowmelt timing, we need to understand trait plasticity, its effects on growth and reproduction, and the degree to which plants experience a home-site advantage. We tested how the common, long-lived dwarf shrub Salix herbacea responded to changing spring snowmelt time by reciprocally transplanting turfs of S. herbacea between early-exposure ridge and late-exposure snowbed microhabitats. After the transplant, we monitored phenological, morphological and fitness traits, as well as leaf damage, during two growing seasons. Salix herbacea leafed out earlier, but had a longer development time and produced smaller leaves on ridges relative to snowbeds. Longer phenological development times and smaller leaves were associated with reduced sexual reproduction on ridges. On snowbeds, larger leaves and intermediate development times were associated with increased clonal reproduction. Clonal and sexual reproduction showed no response to altered snowmelt time. We found no home-site advantage in terms of sexual and clonal reproduction. Leaf damage probability depended on snowmelt and thus exposure period, but had no short-term effect on fitness traits. We conclude that the studied populations of S. herbacea can respond to shifts in snowmelt by plastic changes in phenology and leaf size, while maintaining levels of clonal and sexual reproduction. The lack of a home-site advantage suggests that S. herbacea may not be adapted to different microhabitats. The studied populations are thus unlikely to react to climate change by rapid adaptation, but their responses will also not be constrained by small-scale local adaptation. In the short term, snowbed plants may persist due to high stem densities. However, in the long term, reduction in leaf size and flowering, a longer phenological development time and increased exposure to damage may decrease overall performance of S. herbacea under earlier snowmelt.
|
|
