Adaptation Of Plant Populations Research Articles

Combining the resurrection approach with transplant experiments to investigate adaptation of plant populations to environmental change

Recent climatic changes, such as more frequent droughts and heatwaves, can lead to rapid evolutionary adaptations in plant populations. Such rapid evolution can be investigated using the resurrection approach by comparing plants raised from stored ancestral and contemporary seeds from the same population. This approach has so far only been used in common garden experiments, allowing to reveal genetic differentiation but not adaptation. In this study, we performed a novel approach by testing for evolutionary adaptation in natural plant populations using a resurrection study in combination with in situ transplantations. We cultivated seedlings from ancestors (23–26 years old) and contemporary descendants of three perennial species (Melica ciliata, Leontodon hispidus and Clinopodium vulgare) from calcareous grasslands in the greenhouse and transplanted them back to their collection sites. In addition, we sowed seeds of ancestors and descendants of two species (L. hispidus and C. vulgare) to the collection sites in order to investigate germination rates. In transplanted M. ciliata seedlings, we observed lower mortality and larger plant size in descendants compared to ancestors. This indicates that descendants are better adapted than ancestors to the current environmental conditions, which proved to be exceptionally hot and dry during the study period. Descendants of C. vulgare seedlings tended to be smaller and descendants of L. hispidus seedlings produced fewer leaves compared to their ancestors in their contemporary environmental conditions. In C. vulgare and L. hispidus, we found evolution towards faster germination, and especially descendant seeds of C. vulgare were better adapted to the unfavourable conditions during the experimental period. Concluding, we demonstrate that our novel approach to combine resurrection ecology with transplant experiments is a promising avenue to rigorously test for evolutionary adaptations in changing environments.

Phenotypic differentiation and diversifying selection in populations of Eruca sativa along an aridity gradient

BackgroundThe aridity gradient in the eastern Mediterranean offers an opportunity to investigate intra-specific genetic differentiation and local adaptation in plant populations. Here we used genetic (FST) and quantitative trait (PST) differentiation to assess local adaptation among three natural populations of Eruca sativa (Brassicaceae) distributed along a climatic range representing desert, semi-arid and Mediterranean habitats.ResultsAmplified fragment length polymorphism (AFLP) analysis revealed high genetic diversity in each population, but low genetic differentiation between populations and relatively high gene flow. Further phenotypic evaluation in a common garden experiment (conduced in a Mediterranean habitat) showed clear differences in phenological traits among populations (day of flowering and duration of the reproductive stage), shoot and root biomass, as well as fitness-related traits (total number of fruits and total seed weight). FST–PST comparison showed that PST values of the phenological traits, as well as below- and above-ground biomass and fitness-related traits, were higher than the FST values.ConclusionsOverall, our results support the identification of genotypic and phenotypic differentiation among populations of E. sativa. Furthermore, the FST–PST comparison supports the hypothesis that these were subjected to past diversifying selection. Thus, the results clearly demonstrate adaptive divergence among populations along an aridity gradient, emphasize the ecological value of early flowering time in arid habitats, and contribute to our understanding of the possible impact of climate change on evolutionary processes in plant populations.

Trait differentiation and adaptation of plants along elevation gradients.

Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta-analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.

Insect herbivory and plant adaptation in an early successional community.

To address the role of insect herbivores in adaptation of plant populations and the persistence of selection through succession, we manipulated herbivory in a long-term field experiment. We suppressed insects in half of 16 plots over nine years and examined the genotypic structure and chemical defense of common dandelion (Taraxacum officinale), a naturally colonizing perennial apomictic plant. Insect suppression doubled dandelion abundance in the first few years, but had negligible effects thereafter. Using microsatellite DNA markers, we genotyped >2500 plants and demonstrate that insect suppression altered the genotypic composition of plots in both sampling years. Phenotypic and genotypic estimates of defensive terpenes and phenolics from the field plots allowed us to infer phenotypic plasticity and the response of dandelion populations to insect-mediated natural selection. The effects of insect suppression on plant chemistry were, indeed, driven both by plasticity and plant genotypic identity. In particular, di-phenolic inositol esters were more abundant in plots exposed to herbivory (due to the genotypic composition of the plots) and were also induced in response to herbivory. This field experiment thus demonstrates evolutionary sorting of plant genotypes in response to insect herbivores that was in same direction as the plastic defensive response within genotypes.

Scales and drivers of local adaptation in Brassica nigra (Brassicaceae) populations

Although there is much empirical evidence for local adaptation in plant populations, spatial scales and drivers are still poorly understood. We used the annual species Brassica nigra to (1) test scales of differentiation and adaptation among coastal wetland and inland river-valley populations and (2) analyze herbivory as a potential driver of local plant adaptation. • In a common garden experiment, we compared seven populations collected at different geographic scales in both habitat types. To evaluate adaptation to herbivory, we removed the aphid Brevicoryne brassicae from half of the plants. In a reciprocal transplant experiment, we tested local adaptation in two coastal and two river-valley populations. Natural colonization by dominant herbivore species was recorded. • In the common garden, the river-valley populations showed a higher performance than the coastal ones, whereas large-scale differentiation within habitats was small. Such a differentiation among plant populations was also found in spontaneous infestation by several herbivore groups but not in the plant response to aphid removal. In the reciprocal transplant experiment at natural sites, both plant populations performed better in their home habitat, indicating local adaptation to environmental differences between coastal and river-valley sites. A lower aphid infestation on local plants suggests a contribution of herbivores to local plant adaptation and illustrates the need for reciprocal transplant experiments to evaluate this contribution. • Our study demonstrates that adaptive differentiation among habitats may be stronger at relatively small scales than large-scale adaptation within these habitats. It provides new insights into the role of herbivory in driving local plant adaptation.

Migration load in plants: role of pollen and seed dispersal in heterogeneous landscapes

Evolution of local adaptation depends critically on the level of gene flow, which, in plants, can be due to either pollen or seed dispersal. Using analytical predictions and individual-centred simulations, we investigate the specific influence of seed and pollen dispersal on local adaptation in plant populations growing in patchy heterogeneous landscapes. We study the evolution of a polygenic trait subject to stabilizing selection within populations, but divergent selection between populations. Deviations from linkage equilibrium and Hardy-Weinberg equilibrium make different contributions to genotypic variance depending on the dispersal mode. Local genotypic variance, differentiation between populations and genetic load vary with the rate of gene flow but are similar for seed and pollen dispersal, unless the landscape is very heterogeneous. In this case, genetic load is higher in the case of pollen dispersal, which appears to be due to differences in the distribution of genotypic values before selection.

Local Adaptation and Effects of Grazing among Seedlings of Two Native California Bunchgrass Species: Implications for Restoration

Abstract Adaptation to environmental factors may influence the germination and establishment of focal species in ecological restoration. Reciprocal transplants remain one of the best methods to detect local adaptation, but long‐term studies are often not feasible. We conducted reciprocal transplants of the native California bunchgrasses Elymus glaucus and Bromus carinatus between two central California locations to seek evidence of adaptation to local environmental conditions in a single growing season. Experimental plots at one location included grazed and ungrazed sites. The combination of locations and grazing treatments allowed us to determine whether the ability to detect evidence for adaptation depended on grazing regime. In addition, we measured the direct effects of grazing on seedling growth and survival concurrent with our investigation of local adaptation. We detected a homesite advantage for seedling growth or survival in both species, but the factors contributing to adaptive differentiation were species specific. Evidence of local adaptation was detected for seedling biomass in Bromus and for survivorship in Elymus. The homesite advantage observed in both species was greatly reduced under grazed conditions and in Elymus was significant only in the ungrazed plots. Climate and soil analyses detected significant differences between locations in five soil attributes and two climate variables. In particular, differences in exchangeable magnesium indicated that one of the two transplant locations consisted of serpentine soil, which is widely known to drive adaptation in plant populations. Together, these results suggest that it is possible to investigate the scale and factors involved in local adaptation with short‐term transplant studies.

The contribution of population genetic studies to plant conservation

Summary The objective of this paper is to outline the diverse ways in which population genetic analysis can be used to develop effective species conservation policies. Studies of the geographic distribution of genetic markers have provided us with novel insights into the origins of the Scottish flora. The results reinforce the need for a conservation policy that embraces change over time. Investigations of quantitative characters have demonstrated the existence of substantial local adaptation of plant populations within Scotland. This has implications for conservation management involving transplantation and restoration. Analysis of the diversity and distribution of genetic markers within populations of rare and declining Scottish species have highlighted populations that are of particular conservation concern, and assisted in developing management guidelines for these species. Current research centres on understanding and modelling the genetic behaviour of fragmented populations. Key issues include the a...

Inheritance of phenotypic plasticity in soft chess,Bromus mollis L. (Gramineae)

Phenotypic plasticity, measured by the phenotypic variation of a genotype living under diverse environments, was shown to be under genetic control in annual grass,Bromus mollis. Genetic polymorphism and phenotypic plasticity appear to be alternative strategies of adaptation in plant populations.

Reflections on the role of environmentally-governed reproductive versatility in the adaptation of plant populations

Reflections on the role of environmentally-governed reproductive versatility in the adaptation of plant populations