Native range genetic variation in <i>Arabidopsis thaliana</i> is strongly geographically structured and reflects Pleistocene glacial dynamics

Beck, James B.; Schmuths, Heike; Schaal, Barbara A.

doi:10.1111/j.1365-294x.2007.03615.x

Cited by 146 publications

(188 citation statements)

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“…This suggests a role for stochastic processes such as mutation and drift in shaping not only patterns of fixation of deleterious mutations, but potentially also outbreeding depression. Arabidopsis is highly selfing, which increases the likelihood of genetic drift, and ancestral populations of present day northern populations of Arabidopsis likely experienced genetic bottlenecks during northern range expansion following Pleistocene glaciation (Beck et al, 2008). Heterosis in C1 ↔ R1 and C2 ↔ R2 is consistent with the action of genetic drift in shaping genetic variation of selective importance.…”

Section: Discussionmentioning

confidence: 67%

“…Arabidopsis is a small, selfing annual with a broad native range that encompasses much of Europe and parts of Asia (Koornneef et al, 2004). Differentiation for neutral genetic markers exhibits a pattern of isolation by distance over broad scales (Beck et al, 2008), and reduced neutral genetic variation in northern populations is consistent with genetic drift because of population bottlenecks during range expansion following Pleistocene glaciations (Beck et al, 2008). A pattern of reduced genetic variation in northern compared with southern populations has also been reported within Scandinavia (Lewandowska-Sabat et al, 2010;Long et al, 2013).…”

Section: Introductionmentioning

confidence: 84%

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Heterosis and outbreeding depression in crosses between natural populations of Arabidopsis thaliana

2015

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Understanding the causes and architecture of genetic differentiation between natural populations is of central importance in evolutionary biology. Crosses between natural populations can result in heterosis if recessive or nearly recessive deleterious mutations have become fixed within populations because of genetic drift. Divergence between populations can also result in outbreeding depression because of genetic incompatibilities. The net fitness consequences of between-population crosses will be a balance between heterosis and outbreeding depression. We estimated the magnitude of heterosis and outbreeding depression in the highly selfing model plant Arabidopsis thaliana, by crossing replicate line pairs from two sets of natural populations (C ↔ R, B ↔ S) separated by similar geographic distances (Italy ↔ Sweden). We examined the contribution of different modes of gene action to overall differences in estimates of lifetime fitness and fitness components using joint scaling tests with parental, reciprocal F 1 and F 2 , and backcross lines. One of these population pairs (C ↔ R) was previously demonstrated to be locally adapted, but locally maladaptive quantitative trait loci were also found, suggesting a role for genetic drift in shaping adaptive variation. We found markedly different genetic architectures for fitness and fitness components in the two sets of populations. In one (C ↔ R), there were consistently positive effects of dominance, indicating the masking of recessive or nearly recessive deleterious mutations that had become fixed by genetic drift. The other set (B ↔ S) exhibited outbreeding depression because of negative dominance effects. Additional studies are needed to explore the molecular genetic basis of heterosis and outbreeding depression, and how their magnitudes vary across environments.

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Section: Discussionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 84%

Heterosis and outbreeding depression in crosses between natural populations of Arabidopsis thaliana

2015

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“…This weaker selection in Sweden provides a greater opportunity for the fixation of maladaptive alleles through random genetic drift. Second, reduced genetic variation in the northern part of the range, consistent with population bottlenecks during postglacial expansion (39), may have limited the adaptive potential of Swedish populations relative to Italian populations. Finally, recent climatic warming in Sweden, as reflected in marked shifts in tree lines to higher elevation (40), may have increased the relative fitness of some southern alleles.…”

Section: Discussionmentioning

confidence: 99%

Genetic mapping of adaptation reveals fitness tradeoffs in Arabidopsis thaliana

Ågren

Oakley

McKay

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

161

314

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Organisms inhabiting different environments are often locally adapted, and yet despite a considerable body of theory, the genetic basis of local adaptation is poorly understood. Unanswered questions include the number and effect sizes of adaptive loci, whether locally favored loci reduce fitness elsewhere (i.e., fitness tradeoffs), and whether a lack of genetic variation limits adaptation. To address these questions, we mapped quantitative trait loci (QTL) for total fitness in 398 recombinant inbred lines derived from a cross between locally adapted populations of the highly selfing plant Arabidopsis thaliana from Sweden and Italy and grown for 3 consecutive years at the parental sites (>40,000 plants monitored). We show that local adaptation is controlled by relatively few genomic regions of small to modest effect. A third of the 15 fitness QTL we detected showed evidence of tradeoffs, which contrasts with the minimal evidence for fitness tradeoffs found in previous studies. This difference may reflect the power of our multiyear study to distinguish conditionally neutral QTL from those that reflect fitness tradeoffs. In Sweden, but not in Italy, the local genotype underlying fitness QTL was often maladaptive, suggesting that adaptation there is constrained by a lack of adaptive genetic variation, attributable perhaps to genetic bottlenecks during postglacial colonization of Scandinavia or to recent changes in selection regime caused by climate change. Our results suggest that adaptation to markedly different environments can be achieved through changes in relatively few genomic regions, that fitness tradeoffs are common, and that lack of genetic variation can limit adaptation.O rganisms inhabiting different environments are often locally adapted, as demonstrated by experiments showing that local populations grown in their native sites outperform other populations (1-3). Despite a large body of theory, the genetic basis of local adaptation is poorly understood. Key unanswered questions include the number and effect sizes of adaptive loci, whether locally favored loci reduce fitness elsewhere (i.e., fitness tradeoffs), and whether the adaptive potential of populations is limited by insufficient genetic variation (4-11). The Fisherian view that adaptation is a function of many genes of small effect (12) has been challenged on theoretical grounds (4, 6), and recent empirical work indicates that genes with both large and small phenotypic effects contribute to differentiation in putatively adaptive traits (e.g., refs. 8 and 13). However, there are few direct estimates of the number of loci underlying fitness variation in native environments (14).Because natural environments are variable in both time and space, temporally replicated experiments are particularly important for distinguishing whether adaptive alleles are conditionally neutral [i.e., favored locally but neutral elsewhere (7, 15)] or are favored in one environment but disfavored in the other, reflecting an adaptive tradeoff (2, 7, 16). Evidence for conditi...

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“…The fragment portion 5 0 of the duplications was used to assign haplotypes to individual sequence. No new haplotypes were recovered compared with the related earlier publication of Ansell et al, (2007) and the haplotype network presented is reproduced from this study, with a minor modification, the network was rooted to the trnL-F IGS sequences of A. thaliana reported in Beck et al, (2008). Haplotype richness (R) with correction for the smallest regional sample size (n ¼ 60) through rarefaction was estimated using CONTRIB (Petit et al, 1998).…”

Section: Allozyme Variationmentioning

confidence: 99%