| 1. |
- Cortazar-Chinarro, Maria, et al.
(författare)
-
Drift, selection, or migration? : Processes affecting genetic differentiation and variation along a latitudinal gradient in an amphibian
- 2017
-
Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 17
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Past events like fluctuations in population size and post-glacial colonization processes may influence the relative importance of genetic drift, migration and selection when determining the present day patterns of genetic variation. We disentangle how drift, selection and migration shape neutral and adaptive genetic variation in 12 moor frog populations along a 1700 km latitudinal gradient. We studied genetic differentiation and variation at a MHC exon II locus and a set of 18 microsatellites. Results: Using outlier analyses, we identified the MHC II exon 2 (corresponding to the beta-2 domain) locus and one microsatellite locus (RCO8640) to be subject to diversifying selection, while five microsatellite loci showed signals of stabilizing selection among populations. STRUCTURE and DAPC analyses on the neutral microsatellites assigned populations to a northern and a southern cluster, reflecting two different post-glacial colonization routes found in previous studies. Genetic variation overall was lower in the northern cluster. The signature of selection on MHC exon II was weaker in the northern cluster, possibly as a consequence of smaller and more fragmented populations. Conclusion: Our results show that historical demographic processes combined with selection and drift have led to a complex pattern of differentiation along the gradient where some loci are more divergent among populations than predicted from drift expectations due to diversifying selection, while other loci are more uniform among populations due to stabilizing selection. Importantly, both overall and MHC genetic variation are lower at northern latitudes. Due to lower evolutionary potential, the low genetic variation in northern populations may increase the risk of extinction when confronted with emerging pathogens and climate change.
|
|
| 2. |
- Luquet, Emilien, et al.
(författare)
-
Post-glacial colonization routes coincide with a life-history breakpoint along a latitudinal gradient
- 2019
-
Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 32:4, s. 356-368
-
Tidskriftsartikel (refereegranskat)abstract
- Although adaptive divergence along environmental gradients has repeatedly been demonstrated, the role of post‐glacial colonization routes in determining phenotypic variation along gradients has received little attention. Here, we used a hierarchical QST–FST approach to separate the roles of adaptive and neutral processes in shaping phenotypic variation in moor frog (Rana arvalis) larval life histories along a 1,700 km latitudinal gradient across northern Europe. This species has colonized Scandinavia via two routes with a contact zone in northern Sweden. By using neutral SNP and common garden phenotypic data from 13 populations at two temperatures, we showed that most of the variation along the gradient occurred between the two colonizing lineages. We found little phenotypic divergence within the lineages; however, all phenotypic traits were strongly diverged between the southern and northern colonization routes, with higher growth and development rates and larger body size in the north. The QST estimates between the colonization routes were four times higher than FST, indicating a prominent role for natural selection. QST within the colonization routes did not generally differ from FST, but we found temperature‐dependent adaptive divergence close to the contact zone. These results indicate that lineage‐specific variation can account for much of the adaptive divergence along a latitudinal gradient.
|
|
| 3. |
- Meyer-Lucht, Yvonne, et al.
(författare)
-
Genetic basis of amphibian larval development along a latitudinal gradient : Gene diversity, selection and links with phenotypic variation in transcription factor C/EBP-1
- 2019
-
Ingår i: Molecular Ecology. - : WILEY. - 0962-1083 .- 1365-294X. ; 28:11, s. 2786-2801
-
Tidskriftsartikel (refereegranskat)abstract
- Ectotherm development rates often show adaptive divergence along climatic gradients, but the genetic basis for this variation is rarely studied. Here, we investigated the genetic basis for phenotypic variation in larval development in the moor frog Rana arvalis from five regions along a latitudinal gradient from Germany to northern Sweden. We focused on the C/EBP-1 gene, a transcription factor associated with larval development time. Allele frequencies at C/EBP-1 varied strongly among geographical regions. Overall, the distribution of alleles along the gradient was in concordance with the dual post-glacial colonization routes into Scandinavia, with a large number of alleles exclusively present along the southern colonization route. Only three of 38 alleles were shared between the routes. Analysis of contemporary selection on C/EBP-1 showed divergent selection among the regions, probably reflecting adaptation to the local environmental conditions, although this was especially strong between southern and northern regions coinciding also with lineages from different colonization routes. Overall, the C/EBP-1 gene has historically been under purifying selection, but two specific amino acid positions showed significant signals of positive selection. These positions showed divergence between southern and northern regions, and we suggest that they are functionally involved in the climatic adaptation of larval development. Using phenotypic data from a common garden experiment, we found evidence for specific C/EBP-1 alleles being correlated with larval development time, suggesting a functional role in adaptation of larval development to large-scale climatic variation.
|
|
| 4. |
- Mörch, Patrik Rödin, et al.
(författare)
-
Latitudinal divergence in a widespread amphibian: Contrasting patterns of neutral and adaptive genomic variation
- 2019
-
Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 28:12, s. 2996-3011
-
Tidskriftsartikel (refereegranskat)abstract
- Stochastic effects from demographic processes and selection are expected to shape the distribution of genetic variation in spatially heterogeneous environments. As the amount of genetic variation is central for long‐term persistence of populations, understanding how these processes affect variation over large‐scale geographical gradients is pivotal. We investigated the distribution of neutral and putatively adaptive genetic variation, and reconstructed demographic history in the moor frog (Rana arvalis) using 136 individuals from 15 populations along a 1,700‐km latitudinal gradient from northern Germany to northern Sweden. Using double digest restriction‐site associated DNA sequencing we obtained 27,590 single nucleotide polymorphisms (SNPs), and identified differentiation outliers and SNPs associated with growing season length. The populations grouped into a southern and a northern cluster, representing two phylogeographical lineages from different post‐glacial colonization routes. Hybrid index estimation and demographic model selection showed strong support for a southern and northern lineage and evidence of gene flow between regions located on each side of a contact zone. However, patterns of past gene flow over the contact zone differed between neutral and putatively adaptive SNPs. While neutral nucleotide diversity was higher along the southern than the northern part of the gradient, nucleotide diversity in differentiation outliers showed the opposite pattern, suggesting differences in the relative strength of selection and drift along the gradient. Variation associated with growing season length decreased with latitude along the southern part of the gradient, but not along the northern part where variation was lower, suggesting stronger climate‐mediated selection in the north. Outlier SNPs included loci involved in immunity and developmental processes.
|
|
| 5. |
- Rödin Mörch, Patrik, et al.
(författare)
-
Divergence and plasticity of larval life-history align at different spatial scales in a high-latitude amphibian
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Understanding divergence and plasticity of fitness associated traits along climatic gradients is important in order to understand how populations will respond to environmental change. Here we investigated larval life history evolution of the moor frog (Rana arvalis) along two climatic gradients of contrasting spatial scale: along a 1700km latitudinal gradient and in a small-scale wetland network with contrasting environments. In both systems, we conducted a common garden experiment where we raised tadpoles in two temperature treatments and measured two larval life-history traits (larval period and mass at metamorphosis) and their plasticity. We also utilized ddRAD-seq to conduct QST-FST comparisons and genotype-phenotype association studies in both systems. In the wetland network, we found low levels of genetic differentiation, but evidence of adaptive divergence in larval period and in plasticity of mass at metamorphosis. Along the latitudinal gradient, we found strong neutral genetic differentiation and evidence of selection on trait means and their plasticity for both larval period and mass at metamorphosis. These results suggest that patterns of climatic selection on traits means and plasticity largely align across different spatial scales. Finally, we identified a number of SNPs associated with the two larval-life history traits and plasticity. Several rad-tags matched genes and proteins involved in immunity and developmental processes, pointing to the potential importance of development rate-immunity trade-offs shaping life-history evolution in temperate amphibians along climatic gradients.
|
|
