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Genetic resources have to be managed appropriately to mitigate the impact of climate change. For many wildland plants, conservation will require knowledge of the climatic factors affecting intraspecific genetic variation to minimize maladaptation. Knowledge of the interaction between traits and climate can focus management resources on vulnerable populations, provide guidance for seed transfer, and enhance fitness and resilience under changing climates. In this study, traits of big sagebrush (Artemisia tridentata) were examined among common gardens located in different climates. We focus on two subspecies, wyomingensis and tridentata, that occupy the most imperiled warm-dry spectrum of the sagebrush biome. Populations collected across the sagebrush biome were recorded for flower phenology and survival. Mixed-effects models examined each trait to evaluate genetic variation, environmental effects, and adaptive breadth of populations. Climate variables derived from population-source locations were significantly associated with these traits (P < 0.0001), explaining 31% and 11% of the flower phenology and survival variation, respectively. To illustrate our model and assess variability in prediction, we examine fixed and focal point seed transfer approaches to map contemporary and climate model ensemble projections in two different regions of the sagebrush biome. A comparison of seed transfer areas predicts that populations from warmer climates become more prevalent, replacing colder-adapted populations by mid-century. However, these warm-adapted populations are often located along the trailing edge, margins of the species range predicted to be lost due to a contraction of the climatic niche. Management efforts should focus on the collection and conservation of vulnerable populations and prudent seed transfer to colder regions where these populations are projected to occur by mid-century. Our models provide the foundation to develop an empirical, climate-based seed transfer system for current and future restoration of big sagebrush., (Published 2018. This article is a U.S. Government work and is in the public domain in the USA.)

Key message: Black spruce ecotypes exhibit temperature-adapted bud burst, while bud set is independent of temperature. Warmer conditions could advance bud burst, but no direct effect is expected for bud set Phenological adjustment is a key adaptive trait closely associated with the environment. Species spreading over a wide geographical range can evolve ecotypes that are able to grow and reproduce under particular local conditions. We compared the thermal conditions during bud phenology in black spruce [Picea mariana (Mill.) BSP] populations to assess the differences among ecotypes. The phases of bud burst and bud set were monitored weekly during 2015, 2017 and 2018 in saplings growing in a common garden, and originating from a latitudinal range across the whole closed boreal forest of Quebec, Canada. Provenances from the northern sites exhibited both earlier bud burst and bud set, with differences of 8 and 11 days, respectively, between the northern and southern provenances. Bud burst occurred under colder temperatures in provenances from the northern sites. The phase of open bud occurred at 4 °C in the northernmost provenance, compared to 8 °C in the southernmost one. Bud set occurred in summer, when temperatures still exceeded 20 °C, and no difference was observed between provenances. Black spruce populations exhibit a clear clinal differentiation in ecotypes showing temperature-adapted bud burst of the apical meristem. The need to complete formation of the winter bud and hardening before autumn leads bud set to being independent of the air temperature. Warmer conditions can affect the timings of spring phenology by anticipating bud burst in black spruce, although no direct effect may be expected for bud set. [ABSTRACT FROM AUTHOR]

Reproductive diapause is a primary mechanism used by arthropods to synchronize their life cycle with seasonal changes in temperate regions. Our study species, Drosophila montana, represents the northern insect species where flies enter reproductive diapause under short day conditions and where the precise timing of diapause is crucial for both survival and offspring production. We have studied clinal variation in the critical day length for female diapause induction (CDL) and their overall susceptibility to enter diapause (diapause incidence), as well as the temperature sensitivity of these traits. The study was performed using multiple strains from four latitudinal clines of the species – short clines in Finland and Alaska and long clines in the Rocky Mountains and the western coast of North America – and from one population in Kamchatka, Russia. CDL showed strong latitudinal clines on both continents, decreasing by one hour per five degrees decline in latitude, on average. CDL also decreased in all populations along with an increase in fly rearing temperature postponing the diapause to later calendar time, the effects of temperature being stronger in southern than in northern population. Female diapause incidence was close to 100% under short day/low temperature conditions in all populations, but decreased below 50% even under short days in 19°C in the southern North American western coast populations and in 22°C in most populations. Comparing a diversity of climatic data for the studied populations showed that while CDL is under a tight photoperiodic regulation linked with latitude, its length depends also on climatic factors determining the growing season length. Overall, the study deepens our understanding of how spatial and environmental parameters affect the seasonal timing of an important biological event, reproductive diapause and helps to estimate the evolutionary potential of insect populations to survive in changing climatic conditions. [ABSTRACT FROM AUTHOR]

Pleistocene glacial periods have had a major influence on the geographical patterns of genetic structure of species in tropical montane regions. However, their effect on morphological differentiation among populations of cloud forest plants remains virtually unexplored. Here, we address this question by testing whether geographical patterns of morphological variation in Ocotea psychotrioides can be explained by the intensity of climate change occurring during 130,000 years. For this, we measured vegetative and reproductive traits for 96 individuals from 36 localities registered across the species’ distribution range. Species distribution models and multivariate statistics were used to investigate geographical patterns of morphological variation and test their association with current and past climatic conditions. Leaf size and pubescence in O. psychotrioides showed a latitudinal pattern of clinal variation that does not fit the geographical gradient of increasing leaf size towards lower latitudes observed globally among plants. Instead, the observed clinal variation conforms to a pattern of increasing leaf size towards higher latitudes. However, our analyses showed weak to non-significant association between morphology and current climate. Interestingly, our analyses showed that predicted shifts in the distribution range of O. psychotrioides during the last 130,000 years were accompanied by significant changes in climatic conditions, particularly temperature seasonality and precipitation. Accordingly, climatic instability showed a better fit to the observed patterns of leaf size and pubescence variation than current climate conditions. These results suggest that climatic instability during the Pleistocene glacial periods might play a key role in promoting morphological differentiation among populations of cloud forest plants. [ABSTRACT FROM AUTHOR]

Species exhibiting colour polymorphism are thought to have an ecological advantage at the landscape scale, because spatial segregation of alternatively adapted ecotypes into diverse habitats can increase the species' niche breadth and thus confer greater geographic range size. However, morph frequencies are also influenced by intrapopulational processes such as frequency- or density-dependent social interactions. To identify how social feedback may affect clinal variation in morph frequencies, we investigated reciprocal interactions between morph-specific thermal tolerance, local climatic conditions and social environments, in the context of a colour-morph frequency cline associated with a recent range expansion in blue-tailed damselflies ( Ischnura elegans) in Sweden. Cold tolerances of gynochromes (female-like female morph) were positively correlated with local gynochrome frequencies, suggesting a positive frequency-dependent fitness benefit. In contrast, androchrome (male-mimic female morph) cold tolerances were improved following recent exposure to cold weather, suggesting a beneficial environmental acclimation effect. Thus, according to an environment-matching hypothesis for clinal variation, androchrome frequencies should therefore increase towards the (cooler) range limit. In contrast to this prediction, gynochrome frequencies increased at the expanding range limit, consistent with a positive frequency-dependent social feedback that is beneficial when invading novel climates. Our results suggest that when phenotypes or fitnesses are affected by interactions with conspecifics, beneficial social effects on environmental tolerances may (i) facilitate range shifts, and (ii) reverse or counteract typical patterns of intraspecific interactions and environment-matching clines observed in stable populations observed over broader geographic scales. [ABSTRACT FROM AUTHOR]

Aim Spatial autocorrelation analysis of genetic diversity was combined with ecological niche modelling (ENM) to better infer how ecological and evolutionary processes underlie population structure in Eugenia dysenterica, a widely distributed tree in the 'Cerrado' region of Central Brazil. Location 'Cerrado' region, Central Brazil. Methods Data were derived from 11 microsatellite loci in 23 populations of E. dysenterica, totalling 249 allele frequencies. The expected heterozygosity (He) within populations and the first principal coordinates extracted from pairwise FST and from the difference between RST and FST among populations were correlated with shifts in suitability from ENM. Frequencies were then analysed using a spatial autocorrelation analysis based on Moran's I and Mantel tests to contrast population differentiation for mean allele frequencies, allele size and shifts in suitability since the Last Glacial Maximum inferred from ENM. Results Spatial correlograms based on Moran's I and Mantel tests showed a linear decrease in autocorrelation with distance, which revealed north-west-south-east gradients in allele frequencies, genetic diversity and differences between RST and FST. These spatial patterns varied among loci and alleles, and the strongest spatial patterns were found for more common alleles with higher levels of differentiation among populations and for those correlated with shifts in ENM suitability. Main conclusions Current genetic diversity and population structure in E. dysenterica can be explained by geographical range shifts associated with Quaternary climate dynamics, thus demonstrating the value of applying spatial analyses to study the ecological and evolutionary processes underlying differentiation even within populations possessing a continuous distribution. [ABSTRACT FROM AUTHOR]

In an age of rapid global change, it is imperative that we continue to improve our understanding of factors that govern genetic differentiation in plants to inform biologically reasonable predictions for the future and enlighten conservation and restoration practices. In this special issue, we have assembled a set of original research and reviews that employ diverse approaches, both classic and contemporary, to illuminate patterns of phenotypic and genetic variation, probe the underlying evolutionary processes that have contributed to these patterns, build predictive models, and test evolutionary hypotheses. Our goal was to underscore the unique insights that can be obtained through the complementary and distinct studies of plant populations across species' geographic ranges. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Although our awareness of ploidy diversity has expanded with the application of flow cytometry, we still know little about the extent to which cytotypes within mixed-ploidy populations are genetically differentiated across environmental gradients. METHODS: To address this issue, we reared 14 populations of Solidago altissima spanning the prairie-forest ecotone in Minnesota in a common garden with a watering treatment. We assessed ploidy frequencies and measured survival, flowering phenology, and plant architectural traits for 4 years. KEY RESULTS: All populations harbored multiple cytotypes; prairie populations were dominated by tetraploids, forest populations by hexaploids. Diploids and polyploids differed significantly for 84% of the traits. Beyond average differences, the slope of trait values covaried with latitude and longitude, but this relationship was stronger for diploids than the other two polyploid cytotypes as indicated by numerous ploidy x latitude and ploidy x longitude interactions. For example, the timing of flowering of the cytotypes overlapped in populations sampled from the northeastern hemiboreal forest but differed significantly between cytotypes sampled from populations in the southwestern prairie. The watering treatments had weak effects, and there were no ploidy differences for phenotypic plasticity. CONCLUSIONS: Our data show that diploids have diverged genetically to a greater extent than polyploids along the environmental dines sampled in this study. Moreover, different environments favor phenotypic convergence over divergence among cytotypes for some traits. Differences in ploidy frequency and phenotypic divergence among cytotypes across gradients of temperature and precipitation are important considerations for restoration in an age of climate change. [ABSTRACT FROM AUTHOR]

Climate is a major selective force in nature. Exploring patterns of inter- and intraspecific genetic variation in functional traits may explain how species have evolved and may continue evolving under future climate change. Photoprotective pigments play an important role in short-term responses to climate stress in plants but knowledge of their long-term role in adaptive processes is lacking. In this study, our goal was to determine how photoprotective mechanisms, morphological traits and their plasticity have evolved in live oaks (Quercus series Virentes) in response to different climatic conditions. For this purpose, seedlings originating from 11 populations from four live oak species (Quercus virginiana, Q. geminata, Q. fusiformis and Q. oleoides) were grown under contrasting common environmental conditions of temperature (tropical vs temperate) and water availability (droughted vs well-watered). Xanthophyll cycle pigments, anthocyanin accumulation, chlorophyll fluorescence parameters and leaf anatomical traits were measured. Seedlings originating from more mesic source populations of Q. oleoides and Q. fusiformis increased the xanthophyll de-epoxidation state under water-limiting conditions and showed higher phenotypic plasticity for this trait, suggesting adaptation to local climate. Likewise, seedlings originating from warmer climates had higher anthocyanin concentration in leaves under cold winter conditions but not higher de-epoxidation state. Overall, our findings suggest that (i) climate has been a key factor in shaping species and population differences in stress tolerance for live oaks, (ii) anthocyanins are used under cold stress in species with limited freezing tolerance and (iii) xanthophyll cycle pigments are used when photoprotection under drought conditions is needed. [ABSTRACT FROM AUTHOR]

Abstract: Flowering time is a major determinant of plant reproductive success and adaptation to local climatic conditions. Vernalization, i.e. a prolonged period of low temperature, is one of the processes controlling flowering time. This study investigates vernalization responses in natural populations of Arabidopsis thaliana from higher latitudes and their significance for local adaptation. Twenty-seven A. thaliana populations were collected across latitudinal (59–68°N) and altitudinal gradients (2–850m a.s.l.) in Norway, and the populations were screened for responses to 5 different vernalization treatments. These populations represent the northernmost limit of the species distribution worldwide. Variations in vernalization sensitivity and vernalization saturation were tested for relationships with altitude, distance from the ocean and climatic factors associated with the site of origin. The results showed that these traits were associated with both altitude and distance from the ocean. Populations originating from higher altitudes and inland locations were more sensitive and required less time to saturate their vernalization requirement than populations from lower altitudes at coastal locations. Analyses among inland populations revealed higher contribution of distance from the ocean than altitude to the variation in vernalization responses. These results indicate that the continental-oceanic climatic gradient generate clinal variation in adaptive traits. [Copyright &y& Elsevier]

Understanding the adaptive basis of life history variation is a central goal in evolutionary ecology. The use of model species enables the combination of molecular mechanistic knowledge with ecological and evolutionary questions, but the study of life history variation in natural environments is required to merge these disciplines. Here, we tested for clinal variation in life history and associated traits along an environmental and altitudinal gradient in the model species Arabidopsis thaliana. Seventeen natural populations of A. thaliana were geo-referenced in northeastern Spain on a gradient in which precipitation increases but maximum spring temperature and minimum winter temperature decrease with altitude. One hundred and eighty-nine genotypes from the 17 populations were grown under uniform controlled conditions. Variations in traits related to biomass allocation, fecundity, phenology and vegetative growth were tested for relationships with the altitude and climatic variables associated with the home sites. Aboveground mass, number of rosette leaves at bolting, developmental time and seed weight increased with the home site's altitude. Root allocation, vegetative growth during winter and number of seeds decreased with altitude. We suggest that the differences among home sites provide clues to the variation in adaptive strategies associated with the climatic gradient. We compared these results with adaptations and clinal relationships reported for other species and with molecular mechanisms described in Arabidopsis. [ABSTRACT FROM AUTHOR]

Climate change will test the evolutionary potential of many narrowly distributed plants, especially in alpine environments. We test for adaptation to elevation of an alpine forb, Craspedia lamicola, across three narrow replicated elevation transects and compare findings with a recent study in the grass Poa hiemata across the same range. Low-elevation plants exhibited larger (yet fewer in number) leaves per plant compared with high-elevation plants. Reciprocal transplant and common garden experiments indicated that differences due to elevation were predominantly environmentally determined, with only a small heritable component for leaf number. Plants did not exhibit a native-site advantage in terms of survival, and selection analyses showed no association between trait variation and fitness. Patterns contrast to recent findings in the grass P. hiemata, highlighting that levels of plastic and genetic variation and responses to climate change may vary markedly between species inhabiting the same environment. Differences in adaptive potential may lead to reduced ecosystem stability and compositional changes in plant communities under continued climate change. [ABSTRACT FROM AUTHOR]

Alpine environments are particularly susceptible to environmental changes associated with global warming but there is potential for alpine plants to adapt to warming if local adaptation occurs and gene flow allows genotypes adapted to low altitudes to colonize higher altitude sites. Here we examine the adaptive potential of a common alpine grass, Poa hiemata, within the restricted alpine habitat of Australian mountains, across a narrow altitudinal gradient replicated in three areas. Grasses at high altitude sites had shorter leaf lengths and larger circumferences than those at lower sites. Transplant experiments with clonal material and plants grown from seed indicated that these differences were partly genetic, with environmental and genetic factors both contributing to the differences between altitudes. Differences in altitudinal forms were also evident in a common garden experiment. Plants showed a home-site advantage in terms of survival. A fitness analysis indicated that at high altitude sites, selection favored plants with short leaves and larger circumferences, whereas these traits were selected in the opposite direction at the low altitude sites. These findings indicate cogradient selection and potential for both plastic and genotypic shifts in response to climate change in P. hiemata. [ABSTRACT FROM AUTHOR]

Fisher's fundamental theorem states that heritable variation for net fitness sets a limit to the rate of response to natural selection. How will temperate (i.e. cold-tolerant) species cope with contemporary rapid global warming? Using three-fold replicated lines of Drosophila subobscura that had been allowed to evolve for 4 years (between 32 and 59 generations) at 13 °C (cold), 18 °C (the supposed optimum temperature), and 22 °C (warm) I assess here how net fitness changes according to thermal environments. Net fitness was estimated following the classical approach in population genetics of competing over a number of generation in outbred experimental populations multiple wild-type O chromosomes (homologous to arm 3R in D. melanogaster) independently derived from each base thermal stock in an otherwise homogeneous genetic background against a balancer chromosome. Warm-adapted populations (‘warm-adapted O chromosomes’) performed comparatively well at all tested temperatures. However, net fitness was severely reduced in cold-adapted populations when transferred to warmer conditions. It seems, therefore, that thermal fitness breath for D. subobscura flies is positively associated to temperature. These findings are discussed in relation to the fast world-wide clinal shifts in the frequency of genetic markers correlated with current climate change. [ABSTRACT FROM AUTHOR]

Climate change will alter natural selection on native plant populations. Little information is available to predict how selection will change in the future and how populations will respond. Insight can be obtained by comparing selection regimes in current environments to selection regimes in environments similar to those predicted for the future. To mimic predicted temporal change in climate, three natural populations of the annual legume Chamaecrista fasciculata were sampled from a climate gradient in the Great Plains and progeny of formal crosses were reciprocally planted back into common gardens across this climate gradient. In each garden, native populations produced significantly more seed than the other populations, providing strong evidence of local adaptation. Phenotypic selection analysis conducted by site showed that plants with slower reproductive development, more leaves, and thicker leaves were favored in the most southern garden. Evidence of clinal variation in selection regimes was also found; selection coefficients were ordered according to the latitude of the common gardens. The adaptive value of native traits was indicated by selection toward the mean of local populations. Repeated clinal patterns in linear and nonlinear selection coefficients among populations and within and between sites were found. To the extent that temporal change in climate into the future will parallel the differences in selection across this spatial gradient, this study suggests that selection regimes will be displaced northward and different trait values will be favored in natural populations. [ABSTRACT FROM AUTHOR]