| 1. |
- Abbott, J. K., et al.
(författare)
-
Patterns of differentiation in a colour polymorphism and in neutral markers reveal rapid genetic changes in natural damselfly populations
- 2008
-
Ingår i: Molecular Ecology. - : Wiley-Blackwell. - 0962-1083 .- 1365-294X. ; 17:6, s. 1597-1604
-
Tidskriftsartikel (refereegranskat)abstract
- The existence and mode of selection operating on heritable adaptive traits can be inferred by comparing population differentiation in neutral genetic variation between populations (often using F-ST values) with the corresponding estimates for adaptive traits. Such comparisons indicate if selection acts in a diversifying way between populations, in which case differentiation in selected traits is expected to exceed differentiation in neutral markers [F-ST (selected) > F-ST (neutralfl, or if negative frequency-dependent selection maintains genetic polymorphisms and pulls populations towards a common stable equilibrium [FST (selected) < F-ST (neutral)]. Here, we compared F-ST values for putatively neutral data (obtained using amplified fragment length polymorphism) with estimates of differentiation in morph frequencies in the colour-polymorphic damselfly Ischnura elegans. We found that in the first year (2000), population differentiation in morph frequencies was significantly greater than differentiation in neutral loci, while in 2002 (only 2 years and 2 generations later), population differentiation in morph frequencies had decreased to a level significantly lower than differentiation in neutral loci. Genetic drift as an explanation for population differentiation in morph frequencies could thus be rejected in both years. These results indicate that the type and/or strength of selection on morph frequencies in this system can change substantially between years. We suggest that an approach to a common equilibrium morph frequency across all populations, driven by negative frequency-dependent selection, is the cause of these temporal changes. We conclude that inferences about selection obtained by comparing F-ST values from neutral and adaptive genetic variation are most useful when spatial and temporal data are available from several populations and time points and when such information is combined with other ecological sources of data.
|
|
| 2. |
- Bensch, Staffan, et al.
(författare)
-
Amplified fragment length polymorphism analysis identifies hybrids between two subspecies of warblers.
- 2002
-
Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 11:3, s. 473-481
-
Tidskriftsartikel (refereegranskat)abstract
- In the western Pyrenees (Southwest France and Northwest Spain), a narrow hybrid zone exists between the common chiffchaff Phylloscopus (collybita) collybita and the Iberian chiffchaff Phylloscopus (c.) brehmii. In this zone, which is approximately 20 km wide, mixed matings and individuals singing the songs of both taxa occur at substantial frequencies (24 and 8.6%, respectively), suggesting frequent hybridization. Previous studies have shown very weak mitochondrial gene flow (Nm = 0.065), whereas four microsatellites suggested much higher nuclear gene flow (Nm = 4.9). In this study we used the amplified fragment length polymorphism (AFLP) method in order to identify hybrids and early backcrosses. We typed 91 birds from both allopatric and sympatric areas for 12 informative AFLP markers (of > 141 polymorphic fragments), obtained by screening 13 AFLP primer combinations. These individuals were previously typed for song (brehmii, collybita or mixed singers), mitochondrial DNA (mtDNA) haplotype and allelic genotypes at four microsatellite loci. Assignment tests demonstrated that in the zone of sympatry, a substantial number of intermediate genotypes existed among the birds previously believed to be pure collybita and brehmii, based on song and mtDNA haplotype. The majority of the mixed singers had intermediate genotypes. Our data suggest that the fraction of the adult population having a hybrid origin (hybrids or backcrosses) is in the order of 10%. With such a frequency of genetic hybrids, there would have been much more mtDNA introgression than observed, had female hybrids been perfectly fertile/viable. This result is consistent with male-biased gene flow and Haldane's rule.
|
|
| 3. |
- Bensch, Staffan, et al.
(författare)
-
Genetic, morphological, and feather isotope variation of migratory willow warblers show gradual divergence in a ring.
- 2009
-
Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 18:14, s. 3087-96
-
Tidskriftsartikel (refereegranskat)abstract
- The circular distribution of the willow warbler Phylloscopus trochilus around the Baltic Sea shares many features with the classic examples of ring species; however, the system is much younger. It has previously been shown that a secondary contact zone is located in central Scandinavia, where there are narrow clines for several morphological traits coincident with a migratory divide. Here we analyse multiple traits and genes from > 1700 males captured on breeding territories at 77 sites spread around the Baltic Sea to test the following hypothesis. If the secondary contact zone in Scandinavia is a result of divergence in two allopatric refuge populations during the last glaciation, we expect to find a similar secondary contact zone somewhere else around the circular distribution. Our results show that the trait clines were wider and displaced from each other along the eastern side of the Baltic Sea. Analyses of 12 microsatellite loci confirmed that the genome is very similar between the terminal forms (F(ST) = 0). Two AFLP-derived markers filtered out from a genomic scan instead appear to be maintained by selection. These markers exhibited steep clines at the secondary contact zone in Scandinavia, but as for the phenotypic traits, had vastly different cline centres east of the Baltic Sea. The trait clines along the ring distribution outside the Scandinavian secondary contact zone thus seem to have been shaped by independent action of selection or drift during the process of postglacial colonization.
|
|
| 4. |
- Eroukhmanoff, Fabrice, et al.
(författare)
-
Rapid adaptive divergence between ecotypes of an aquatic isopod inferred from F-ST-Q(ST) analysis
- 2009
-
Ingår i: Molecular Ecology. - Oxford, United Kingdom : Wiley-Blackwell. - 0962-1083 .- 1365-294X. ; 18:23, s. 4912-4923
-
Tidskriftsartikel (refereegranskat)abstract
- Divergent natural selection is often thought to be the principal factor driving phenotypic differentiation between populations. We studied two ecotypes of the aquatic isopod Asellus aquaticus which have diverged in parallel in several Swedish lakes. In these lakes, isopods from reed belts along the shores colonized new stonewort stands in the centre of the lakes and rapid phenotypic changes in size and pigmentation followed after colonization. We investigated if selection was likely to be responsible for these observed phenotypic changes using indirect inferences of selection (F-ST-Q(ST) analysis). Average Q(ST) for seven quantitative traits were higher than the average F-ST between ecotypes for putatively neutral markers (AFLPs). This suggests that divergent natural selection has played an important role during this rapid diversification. In contrast, the average Q(ST) between the different reed ecotype populations was not significantly different from the mean F-ST. Genetic drift could therefore not be excluded as an explanation for the minor differences between allopatric populations inhabiting the same source habitat. We complemented this traditional F-ST-Q(ST) approach by comparing the F-ST distributions across all loci (n = 67-71) with the Q(ST) for each of the seven traits. This analysis revealed that pigmentation traits had diverged to a greater extent and at higher evolutionary rates than size-related morphological traits. In conclusion, this extended and detailed type of F-ST-Q(ST) analysis provides a powerful method to infer adaptive phenotypic divergence between populations. However, indirect inferences about the operation of divergent selection should be analyzed on a per-trait basis and complemented with detailed ecological information.
|
|
| 5. |
- Hansson, Bengt, et al.
(författare)
-
Increase of genetic variation over time in a recently founded population of great reed warblers (Acrocephalus arundinaceus) revealed by microsatellites and DNA fingerprinting
- 2000
-
Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 9:10, s. 1529-1538
-
Tidskriftsartikel (refereegranskat)abstract
- Genetic similarity within pairs of individuals was examined using both 10 polymorphic microsatellite loci and multi-locus DNA fingerprinting profiles in a semi-isolated population of great reed warblers at Lake Kvismaren, south Central Sweden, in 1987-1993. The population was founded by a few individuals in 1978, followed by a gradual increase in numbers until 1988, since when the population has remained relatively stable with about 60 breeding birds. We have previously found that high genetic similarity between pairmates in the population during the early part of the study period reduced egg hatching success, and hence reproductive success. The measures of pairwise genetic similarity, microsatellite allele sharing and DNA fingerprinting band sharing, were highly correlated with pedigree-based relatedness. Both microsatellite and DNA fingerprinting similarities between pair-mates declined significantly over the study period, and the pattern was most pronounced in the DNA fingerprinting data. Analyses restricted to the microsatellite data showed that the average annual microsatellite similarity between pairwise combinations of individuals, as well as individual homozygosity in males, declined significantly over the study period, and that several immigrants carrying novel alleles entered the population during the study. Hence, the temporal decline in genetic similarity of mates in the population is probably a consequence of increased immigration, facilitated by the recent expansion of the species in the region. These results suggest that the population has now recovered genetically, or is in the process of recovering, from a recent founder event.
|
|
| 6. |
- Hellgren, Olof, et al.
(författare)
-
Bird hosts, blood parasites and their vectors--associations uncovered by molecular analyses of blackfly blood meals.
- 2008
-
Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 17:6, s. 1605-13
-
Tidskriftsartikel (refereegranskat)abstract
- The level of host specificity of blood-sucking invertebrates may have both ecological and evolutionary implications for the parasites they are transmitting. We used blood mealsfrom wild-caught blackflies for molecular identification of parasites and hosts to examine patterns of host specificity and how these may affect the transmission of avian blood parasites of the genus Leucocytozoon. We found that five different species of ornithophilic blackflies preferred different species of birds when taking their blood meals. Of the blackflies that contained avian blood meals, 62% were infected with Leucocytozoon parasites, consisting of 15 different parasite lineages. For the blackfly species, there was a significant association between the host width (measured as the genetic differentiation between the used hosts) and the genetic similarity of the parasites in their blood meals. The absence of similar parasite in blood meals from blackflies with different host preferences is interpreted as a result of the vector–host associations. The observed associations between blackfly species and host species are therefore likely to hinder parasites to be transmitted between different host-groups, resulting in ecologically driven associations between certain parasite lineages and hosts species.
|
|
| 7. |
- Langefors, Åsa, et al.
(författare)
-
Screening of Mhc variation in Atlantic salmon (Salmo salar) : a comparison of restriction fragment length polymorphism (RFLP), denaturing gradient gel electrophoresis (DGGE) and sequencing
- 2000
-
Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 9:2, s. 215-219
-
Tidskriftsartikel (refereegranskat)abstract
- We compared three different molecular methods currently used for screening of Mhc variation in population studies of Atlantic salmon. Restriction fragment length polymorphism (RFLP) of the entire class II gene detected 22 haplotypes. Seventeen exon 2 sequences were obtained from individuals carrying the 22 haplotypes, two of which had not been detected by RFLP. The six alleles (27%) detected by RFLP and not by exon 2 sequencing probably resulted from sequence variation outside exon 2. Within exon 2, RFLP differentiated 88% of the sequences. Alternatively, denaturing gradient gel electrophoresis (DGGE) performed under two run conditions detected 94% of the sequence variation. Both RFLP using different probes, and the two PCR-based methods using three different primer pairs, suggest that there is only a single Mhc class II B gene in the Baltic populations of Atlantic salmon.
|
|
| 8. |
- Pommier, Thomas, et al.
(författare)
-
Global patterns of diversity and community structure in marine bacterioplankton
- 2007
-
Ingår i: Molecular Ecology. - : Blackwell Publishing Ltd. - 0962-1083 .- 1365-294X. ; 16:4, s. 867-880
-
Tidskriftsartikel (refereegranskat)abstract
- Because of their small size, great abundance and easy dispersal, it is often assumed that marine planktonic microorganisms have a ubiquitous distribution that prevents any structured assembly into local communities. To challenge this view, marine bacterioplankton communities from coastal waters at nine locations distributed world-wide were examined through the use of comprehensive clone libraries of 16S ribosomal RNA genes, used as operational taxonomic units (OTU). Our survey and analyses show that there were marked differences in the composition and richness of OTUs between locations. Remarkably, the global marine bacterioplankton community showed a high degree of endemism, and conversely included few cosmopolitan OTUs. Our data were consistent with a latitudinal gradient of OTU richness. We observed a positive relationship between the relative OTU abundances and their range of occupation, i.e. cosmopolitans had the largest population sizes. Although OTU richness differed among locations, the distributions of the major taxonomic groups represented in the communities were analogous, and all local communities were similarly structured and dominated by a few OTUs showing variable taxonomic affiliations. The observed patterns of OTU richness indicate that similar evolutionary and ecological processes structured the communities. We conclude that marine bacterioplankton share many of the biogeographical and macroecological features of macroscopic organisms. The general processes behind those patterns are likely to be comparable across taxa and major global biomes.
|
|
| 9. |
- Stenström, A, et al.
(författare)
-
Genetic variation and clonal diversity in four clonal sedges (Carex) along the Arctic coast of Eurasia
- 2001
-
Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 10:2, s. 497-513
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the structure of genetic variation (at both ramet- and genet-level) and clonal diversity within and among populations in the four closely related arctic clonal sedges Carex bigelowii, C. ensifolia, C. lugens and C. starts by use of allozyme markers. Compared to other sedges and arctic plants, the studied taxa all had high levels of genetic variation, both within populations and taxa. These taxa contained most of the total gene diversity (H-T) within populations and a small part of the diversity among populations (G(ST) ranged 0.05-0.43). Carex bigelowii had genetic variation (H-S = 0.173, mean for populations) at a comparable level to other outbreeding arctic plants and to other widespread, rhizomatous and mainly outbreeding Carex species. In contrast, C. ensifolia (H-S = 0.335), C. lugens (H-S = 0.339) and C. stans (H-S = 0.294) had within-population variations that were higher than in most other studied Carex species and for arctic plants in general. Genetic variation was not related to any tested environmental variable, but it was lower in areas deglaciated only 10 000 years BP compared to areas deglaciated 60 000 years BP or not glaciated at all during the Weichselian. All the populations were multiclonal, except for two populations of C. starts that were monoclonal. In contrast to genetic variation, clonal diversity decreased with latitude and did not differ between areas with different times of deglaciation. In accordance with previous studies, C. bigelowii and C. lugens were found to be outbreeding, while C. ensifolia and C. stans had mixed mating systems.
|
|
| 10. |
- Hoffman, Eric A., et al.
(författare)
-
Genetic structure in the coral-reef-associated Banggai cardinalfish, Pterapogon kauderni
- 2005
-
Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 14:5, s. 1367-1375
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we used 11 polymorphic microsatellite loci to show that oceanic distances as small as 2–5 km are sufficient to produce high levels of population genetic structure (multilocus FST as high as 0.22) in the Banggai cardinalfish(Pterapogon kauderni), a heavily exploited reef fish lacking a pelagic larval dispersal phase. Global FST among all populations, separated by a maximum distance of 203 km, was 0.18 (RST = 0.35). Moreover, two lines of evidence suggest that estimates of FST may actually underestimate the true level of genetic structure. First, within-locus FST values were consistently close to the theoretical maximum set by the average within-population heterozygosity. Second, the allele size permutation test showed that RST values were significantly larger than FST values, indicating that populations have been isolated long enough for mutation to have played a role in generating allelic variation among populations. The high level of microspatial structure observed in this marine fish indicates that life history traits such as lack of pelagic larval phase and a good homing ability do indeed play a role in shaping population genetic structure in the marine realm.
|
|
