The brain's calendar: neural mechanisms of seasonal timing

Polyploidization leads to salt stress resilience via ethylene signaling in citrus plants

Polyploidization is a common occurrence in the evolutionary history of flowering plants, significantly contributing to their adaptability and diversity. However, the molecular mechanisms behind these adaptive advantages are not well understood. Through comprehensive phenotyping of diploid and tetraploid clones from Citrus and Poncirus genera, we discovered that genome doubling significantly enhances salt stress resilience. Epigenetic and transcriptomic analyses revealed that increased ethylene production in the roots of tetraploid plants was associated with hypomethylation and enhanced chromatin accessibility of the ACO1 gene. This increased ethylene production activates the transcription of reactive oxygen species scavenging genes and stress-related hormone biosynthesis genes. Consequently, tetraploid plants exhibited superior root functionality under salt stress, maintaining improved cytosolic K+/Na+ homeostasis. To genetically validate the link between salt stress resilience and ACO1 expression, we generated overexpression and knockout lines, confirming the central role of ACO1 expression regulation following genome doubling in salt stress resilience. Our work elucidates the molecular mechanisms underlying the role of genome doubling in stress resilience. We also highlight the importance of chromatin dynamics in fine-tuning ethylene gene expression and activating salt stress resilience pathways, offering valuable insights into plant adaptation and crop genome evolution.

Ongoing convergent evolution of a selfing syndrome threatens plant-pollinator interactions

Plant-pollinator interactions evolved early in the angiosperm radiation. Ongoing environmental changes are however leading to pollinator declines that may cause pollen limitation to plants and change the evolutionary pressures shaping plant mating systems. We used resurrection ecology methodology to contrast ancestors and contemporary descendants in four natural populations of the field pansy (Viola arvensis) in the Paris region (France), a depauperate pollinator environment. We combine population genetics analysis, phenotypic measurements and behavioural tests on a common garden experiment. Population genetics analysis reveals 27% increase in realized selfing rates in the field during this period. We documented trait evolution towards smaller and less conspicuous corollas, reduced nectar production and reduced attractiveness to bumblebees, with these trait shifts convergent across the four studied populations. We demonstrate the rapid evolution of a selfing syndrome in the four studied plant populations, associated with a weakening of the interactions with pollinators over the last three decades. This study demonstrates that plant mating systems can evolve rapidly in natural populations in the face of ongoing environmental changes. The rapid evolution towards a selfing syndrome may in turn further accelerate pollinator declines, in an eco-evolutionary feedback loop with broader implications to natural ecosystems.

Resurrected seeds from herbarium specimens reveal rapid evolution of drought resistance in a selfing annual

PREMISE

Increased aridity and drought associated with climate change are exerting unprecedented selection pressures on plant populations. Whether populations can rapidly adapt, and which life history traits might confer increased fitness under drought, remain outstanding questions.

METHODS

We utilized a resurrection ecology approach, leveraging dormant seeds from herbarium collections to assess whether populations of Plantago patagonica from the semi-arid Colorado Plateau have rapidly evolved in response to approximately ten years of intense drought in the region. We quantified multiple traits associated with drought escape and drought resistance and assessed the survival of ancestors and descendants under simulated drought.

RESULTS

Descendant populations displayed a significant shift in resource allocation, in which they invested less in reproductive tissues and relatively more in both above- and below-ground vegetative tissues. Plants with greater leaf biomass survived longer under terminal drought; moreover, even after accounting for the effect of increased leaf biomass, descendant seedlings survived drought longer than their ancestors.

CONCLUSIONS

Our results document rapid adaptive evolution in response to climate change in a selfing annual and suggest that shifts in tissue allocation strategies may underlie adaptive responses to drought in arid or semi-arid environments. This work also illustrates a novel approach, documenting that under specific circumstances, seeds from herbarium specimens may provide an untapped source of dormant propagules for future resurrection experiments.

Accounting for trait variability and coordination in predictions of drought-induced range shifts in woody plants

Functional traits offer a promising avenue to improve predictions of species range shifts under climate change, which will entail warmer and often drier conditions. Although the conceptual foundation linking traits with plant performance and range shifts appears solid, the predictive ability of individual traits remains generally low. In this review, we address this apparent paradox, emphasizing examples of woody plants and traits associated with drought responses at the species' rear edge. Low predictive ability reflects the fact not only that range dynamics tend to be complex and multifactorial, as well as uncertainty in the identification of relevant traits and limited data availability, but also that trait effects are scale- and context-dependent. The latter results from the complex interactions among traits (e.g. compensatory effects) and between them and the environment (e.g. exposure), which ultimately determine persistence and colonization capacity. To confront this complexity, a more balanced coverage of the main functional dimensions involved (stress tolerance, resource use, regeneration and dispersal) is needed, and modelling approaches must be developed that explicitly account for: trait coordination in a hierarchical context; trait variability in space and time and its relationship with exposure; and the effect of biotic interactions in an ecological community context.

Altitude, latitude and climate zone as determinants of mountain hare (Lepus timidus) coat colour change

Local adaptation to annually changing environments has evolved in numerous species. Seasonal coat colour change is an adaptation that has evolved in multiple mammal and bird species occupying areas that experience seasonal snow cover. It has a critical impact on fitness as predation risk may increase when an individual is mismatched against its habitat's background colour. In this paper, we investigate the correlation between landscape covariates and moult timing in a native winter-adapted herbivore, the mountain hare (Lepus timidus), throughout Norway. Data was collected between 2011 and 2019 at 678 camera trap locations deployed across an environmental gradient. Based on this data, we created a Bayesian multinomial logistic regression model that quantified the correlations between landscape covariates and coat colour phenology and analysed among season and year moult timing variation. Our results demonstrate that mountain hare moult timing is strongly correlated with altitude and latitude with hares that live at higher latitudes and altitudes keeping their winter white coats for longer than their conspecifics that inhabit lower latitudes and altitudes. Moult timing was also weakly correlated with climate zone with hares that live in coastal climates keeping their winter white coats for longer than hares that live in continental climates. We found evidence of some among year moult timing variation in spring, but not in autumn. We conclude that mountain hare moult timing has adapted to local environmental conditions throughout Norway.

Rapid evolution of selfing syndrome traits in Viola arvensis revealed by resurrection ecology

PREMISE

As part of global change, climate warming and pollinator decline are expected to affect plant phenology and plant-pollinator interactions. This paper aims at characterizing rapid evolution of life history traits and floral traits over two decades in the wild pansy (Viola arvensis), a common weed in agrosystems.

METHODS

We used a resurrection ecology approach with genotypes sampled in 1991 and 2012 from a population in Burgundy (France). The species has a mixed mating system (hereafter: mixed selfer) and presents a floral polymorphism. To correct for maternal effects, we measured plant traits in the second generation in a common garden (after a refreshing generation) to characterize plant evolution during the two decades. In addition, historical population selfing rates in 1991 and 2012 were inferred from microsatellites markers through heterozygote deficiency and identity disequilibrium.

RESULTS

Phenotypic data revealed a significant advance in flowering date, reduced flower sizes and a higher propensity of plants to set seed by autonomous selfing. Moreover, we detected a change in color morph frequency with an increase of the pale morph frequency. In accordance with phenotypic data, the neutral genetic data revealed an increase in historical selfing rates from 0.68 in 1991 to 0.86 in 2012.

CONCLUSIONS

Taken together, such data suggest that the wild pansy, a mixed selfer, is evolving a selfing syndrome that may be the consequence of reduced pollinator activity in agrosystems.

Rapid-cycling Brassica rapa evolves even earlier flowering under experimental drought

PREMISE

Changes in climate can impose selection on populations and may lead to rapid evolution. One such climatic stress is drought, which plant populations may respond to with escape (rapid growth and early flowering) or avoidance (slow growth and efficient water-use). However, it is unclear if drought escape would be a viable strategy for populations that already flower early from prior selection.

METHODS

In an experimental evolution study, we subjected rapid-cycling Brassica rapa (RCBr), which was previously selected for early flowering, to four generations of experimental drought or watered conditions. We then grew ancestral and descendant populations concurrently under drought and watered conditions to assess evolution, plasticity, and adaptation.

RESULTS

The RCBr populations that evolved under drought had earlier flowering and lower water-use efficiency than the populations that evolved under watered conditions, indicating evolutionary divergence. The drought descendants also had a trend of earlier flowering compared to ancestors, indicating evolution. Evolution of earlier flowering under drought followed the direction of selection and increased fitness and was consistent with studies in natural and experimental populations of this species, suggesting adaptive evolution.

CONCLUSIONS

We found rapid adaptive evolution of drought escape in RCBr and little evidence for constraints on flowering time evolution, even though RCBr already flowers extremely early. Our results suggest that some populations may harbor sufficient genetic variation for evolution even after strong selection has occurred. Our study also illustrates the utility of combining artificial selection, experimental evolution, and the resurrection approach to study the evolution of functional traits.

What determines the evolutionary trajectories of wild plant species? Approaches to the study of quantitative fitness-related traits

Wild plant species provide excellent examples of qualitative traits that evolve in response to environmental challenges (e.g., flower color, heavy metal tolerance, cyanogenesis, and male sterility). In addition to such discrete characters, a dazzling array of continuously distributed, quantitative traits are expressed at every phase of the life cycle. These traits are known or suspected to have evolved by natural selection because they are heritable, differ among populations or closely related taxa occupying distinct habitats, and have individual phenotypes associated with survival and reproductive success. This special issue [American Journal of Botany 109(11)] focuses on the tools and approaches for detecting or inferring the ecological and genetic factors contributing to changes in genetically based variation of quantitative traits within or among populations, or causing their divergence among taxa. The assembled articles use one or more of three primary approaches to detect the process or outcome of natural selection on morphological, life history, reproductive, chemical, and physiological quantitative traits: the analysis of phenotypic or artificially imposed selection to detect direct and indirect selection on traits whose function is well-understood; common garden experiments, including reciprocal transplants and "resurrection" experiments; and quantitative genetic analyses designed to detect and to estimate the environmental and genetic sources of phenotypic variation or to forecast short-term evolutionary change. Together, these articles examine and reveal the adaptive capacity of quantitative traits and the genetically based constraints that may limit their directional evolutionary change, thereby informing and testing inferences, hypotheses, and predictions concerning the evolutionary trajectories of wild plant species.

Context-dependent concordance between physiological divergence and phenotypic selection in sister taxa with contrasting phenology and mating systems

PREMISE

The study of phenotypic divergence of, and selection on, functional traits in closely related taxa provides the opportunity to detect the role of natural selection in driving diversification. If the strength or direction of selection in field populations differs between taxa in a pattern that is consistent with the phenotypic difference between them, then natural selection reinforces the divergence. Few studies have sought evidence for such concordance for physiological traits.

METHODS

Herbarium specimen records were used to detect phenological differences between sister taxa independent of the effects on flowering time of long-term variation in the climate across collection sites. In the field, physiological divergence in photosynthetic rate, transpiration rate, and instantaneous water-use efficiency were recorded during vegetative growth and flowering in 13 field populations of two taxon pairs of Clarkia, each comprising a self-pollinating and a outcrossing taxon.

RESULTS

Historically, each selfing taxon flowered earlier than its outcrossing sister taxon, independent of the effects of local long-term climatic conditions. Sister taxa differed in all focal traits, but the degree and (in one case) the direction of divergence depended on life stage. In general, self-pollinating taxa had higher gas exchange rates, consistent with their earlier maturation. In 6 of 18 comparisons, patterns of selection were concordant with the phenotypic divergence (or lack thereof) between sister taxa.

CONCLUSIONS

Patterns of selection on physiological traits measured in heterogeneous conditions do not reliably reflect divergence between sister taxa, underscoring the need for replicated studies of the direction of selection within and among taxa.

Local adaptation of seed and seedling traits along a natural aridity gradient may both predict and constrain adaptive responses to climate change

PREMISE

Variation in seed and seedling traits underlies how plants interact with their environment during establishment, a crucial life history stage. We quantified genetic-based variation in seed and seedling traits in populations of the annual plant Plantago patagonica across a natural aridity gradient, leveraging natural intraspecific variation to predict how populations might evolve in response to increasing aridity associated with climate change in the Southwestern U.S.

METHODS

We quantified seed size, seed size variation, germination timing, and specific leaf area in a greenhouse common garden, and related these traits to the climates of source populations. We then conducted a terminal drought experiment to determine which traits were most predictive of survival under early-season drought.

RESULTS

All traits showed evidence of clinal variation-seed size decreased, germination timing accelerated, and specific leaf area increased with increasing aridity. Populations with more variable historical precipitation regimes showed greater variation in seed size, suggestive of past selection shaping a diversified bet-hedging strategy mediated by seed size. Seedling height, achieved via larger seeds or earlier germination, was a significant predictor of survival under drought.

CONCLUSIONS

We documented substantial interspecific trait variation as well as clinal variation in several important seed and seedling traits, yet these slopes were often opposite to predictions for how individual traits might confer drought tolerance. This work shows that plant populations may adapt to increasing aridity via correlated trait responses associated with alternative life history strategies, but that trade-offs might constrain adaptive responses in individual traits.

Continuous inbreeding affects genetic variation, phenology, and reproductive strategy in ex situ cultivated Digitalis lutea

PREMISE

Ex situ cultivation is important for plant conservation, but cultivation in small populations may result in genetic changes by drift, inbreeding, or unconscious selection. Repeated inbreeding potentially influences not only plant fitness, but also floral traits and interactions with pollinators, which has not yet been studied in an ex situ context.

METHODS

We studied the molecular genetic variation of Digitalis lutea from a botanic garden population cultivated for 30 years, a frozen seed bank conserving the original genetic structure, and two current wild populations including the source population. In a common garden, we studied the effects of experimental inbreeding and between-population crosses on performance, reproductive traits, and flower visitation of plants from the garden and a wild population.

RESULTS

Significant genetic differentiation was found between the garden population and the wild population from which the seeds had originally been gathered. After experimental selfing, inbreeding depression was only found for germination and leaf size of plants from the wild population, indicating a history of inbreeding in the smaller garden population. Moreover, garden plants flowered earlier and had floral traits related to selfing, whereas wild plants had traits related to attracting pollinators. Bumblebees visited more flowers of outbred than inbred plants and of wild than garden plants.

CONCLUSIONS

Our case study suggests that high levels of inbreeding during ex situ cultivation can influence reproductive traits and thus interactions with pollinators. Together with the effects of genetic erosion and unconscious selection, these changes may affect the success of reintroductions into natural habitats.

Evolution of plant drought strategies and herbivore tolerance after two decades of climate change

Ongoing global warming, coupled with increased drought frequencies, together with other biotic drivers may have resulted in complex evolutionary adaptation. The resurrection approach, comparing ancestors raised from stored seeds with their contemporary descendants under common conditions, is a powerful method to test for recent evolution in plant populations. We used 21-26-yr-old seeds of four European plant species - Matthiola tricuspidata, Plantago crassifolia, Clinopodium vulgare and Leontodon hispidus - stored in seed banks together with re-collected seeds from their wild populations. To test for evolutionary changes, we conducted a glasshouse experiment that quantified heritable changes in plant responses to drought and simulated insect herbivory. In three out of the four studied species, we found evidence that descendants had evolved shorter life cycles through faster growth and flowering. Shifts in the osmotic potential and leaf dry matter content indicated that descendants also evolved increased drought tolerance. A comparison of quantitative genetic differentiation (Q_ST ) vs neutral molecular differentiation (F_ST ) values, using double digest restriction-site associated DNA (ddRAD) genotyping data, suggested that directional selection, and therefore adaptive evolution, was underlying some of the observed phenotypic changes. In summary, our study revealed evolutionary changes in plant populations over the last decades that are consistent with adaptation of drought escape and tolerance as well as herbivory avoidance.

Adaptive significance of flowering time variation across natural seasonal environments in Arabidopsis thaliana

The relevance of flowering time variation and plasticity to climate adaptation requires a comprehensive empirical assessment. We investigated natural selection and the genetic architecture of flowering time in Arabidopsis through field experiments in Europe across multiple sites and seasons. We estimated selection for flowering time, plasticity and canalization. Loci associated with flowering time, plasticity and canalization by genome-wide association studies were tested for a geographic signature of climate adaptation. Selection favored early flowering and increased canalization, except at the northernmost site, but was rarely detected for plasticity. Genome-wide association studies revealed significant associations with flowering traits and supported a substantial polygenic inheritance. Alleles associated with late flowering, including functional FRIGIDA variants, were more common in regions experiencing high annual temperature variation. Flowering time plasticity to fall vs spring and summer environments was associated with GIGANTEA SUPPRESSOR 5, which promotes early flowering under decreasing day length and temperature. The finding that late flowering genotypes and alleles are associated with climate is evidence for past adaptation. Real-time phenotypic selection analysis, however, reveals pervasive contemporary selection for rapid flowering in agricultural settings across most of the species range. The response to this selection may involve genetic shifts in environmental cuing compared to the ancestral state.

Plasticity, pleiotropy and fitness trade-offs in Arabidopsis genotypes with different telomere lengths

Telomere length has been implicated in the organismal response to stress, but the underlying mechanisms are unknown. Here we examine the impact of telomere length changes on the responses to three contrasting abiotic environments in Arabidopsis, and measure 32 fitness, developmental, physiological and leaf-level anatomical traits. We report that telomere length in wild-type and short-telomere mutants is resistant to abiotic stress, while the elongated telomeres in ku70 mutants are more plastic. We detected significant pleiotropic effects of telomere length on flowering time and key leaf physiological and anatomical traits. Furthermore, our data reveal a significant genotype by environment (G × E) interaction for reproductive fitness, with the benefits and costs to performance depending on the growth conditions. These results imply that life-history trade-offs between flowering time and reproductive fitness are impacted by telomere length variation. We postulate that telomere length in plants is subject to natural selection imposed by different environments.

Phenological displacement is uncommon among sympatric angiosperms

Interactions between species can influence successful reproduction, resulting in reproductive character displacement, where the similarity of reproductive traits - such as flowering time - among close relatives growing together differ from when growing apart. Evidence for the overall prevalence and direction of this phenomenon, and its stability under environmental change, remains untested across large scales. Using the power of crowdsourcing, we gathered phenological information from over 40 000 herbarium specimens, and investigated displacement in flowering time across 110 animal-pollinated species in the eastern USA. Overall, flowering time displacement is not common across large scales. However, displacement is generally greater among species pairs that flower close in time, regardless of direction. Furthermore, with climate change, the flowering times of closely related species are predicted, on average, to shift further apart by the mid-21^st century. We demonstrate that the degree and direction of phenological displacement among co-occurring closely related species pairs varies tremendously. However, future climate change may alter the differences in reproductive timing among many of these species pairs, which may have significant consequences for species interactions and gene flow. Our study provides one promising path towards understanding how the phenological landscape is structured and may respond to future environmental change.

A comparative transcriptome and proteomics study of post-partum ovarian cycle arrest in yaks (Bos grunniens)

Post-partum ovarian cycle arrest is the main factor affecting yak reproductive efficiency. There are few reports regarding the molecular regulatory mechanism of post-partum oestrus at transcriptome and proteome levels in yaks. Our previous studies focussed on the ovaries of yaks with post-partum ovarian cycle arrest and post-partum oestrus yaks. In this study, RNA sequencing transcriptomic study was combined with quantitative proteomic analyses to identify post-partum ovarian cycle-related genes and proteins. Consequently, 1,149 genes and 24 proteins were found to be up- or downregulated during post-partum oestrus. The analysis of differentially regulated genes identified three gene or protein pairs that were synchronously upregulated and no gene or protein pairs that were synchronously downregulated, suggesting that these upregulated genes may regulate the post-partum ovarian cycle. The functional classification of these differentially expressed genes and proteins indicated their connection with the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the gonadotrophin-releasing hormone (GnRH) signalling pathway. In this study, a total of six genes and two proteins involved in the oocyte meiosis, the oestrogen signalling pathway, the progesterone-mediated oocyte maturation and the GnRH signalling pathway were identified. The CSNK1A1, M91_09723, M91_11326, M91_21439, M91_19073, SHC2, Atf6b, M91_03062, HSPCA and calmodulin could regulate oestrus, respectively, in the post-partum so as to control the anoestrus status.

Region-specific phenological sensitivities and rates of climate warming generate divergent temporal shifts in flowering date across a species' range

PREMISE

Forecasting how species will respond phenologically to future changes in climate is a major challenge. Many studies have focused on estimating species- and community-wide phenological sensitivities to climate to make such predictions, but sensitivities may vary within species, which could result in divergent phenological responses to climate change.

METHODS

We used 743 herbarium specimens of the mountain jewelflower (Streptanthus tortuosus, Brassicaceae) collected over 112 years to investigate whether individuals sampled from relatively warm vs. cool regions differ in their sensitivity to climate and whether this difference has resulted in divergent phenological shifts in response to climate warming.

RESULTS

During the past century, individuals sampled from warm regions exhibited a 20-day advancement in flowering date; individuals in cool regions showed no evidence of a shift. We evaluated two potential drivers of these divergent responses: differences between regions in (1) the degree of phenological sensitivity to climate and (2) the magnitude of climate change experienced by plants, or (3) both. Plants sampled from warm regions were more sensitive to temperature-related variables and were subjected to a greater degree of climate warming than those from cool regions; thus our results suggest that the greater temporal shift in flowering date in warm regions is driven by both of these factors.

CONCLUSIONS

Our results are among the first to demonstrate that species exhibited intraspecific variation in sensitivity to climate and that this variation can contribute to divergent responses to climate change. Future studies attempting to forecast temporal shifts in phenology should consider intraspecific variation.

Time-of-Day-Dependent Effects of Bromocriptine to Ameliorate Vascular Pathology and Metabolic Syndrome in SHR Rats Held on High Fat Diet

The treatment of type 2 diabetes patients with bromocriptine-QR, a unique, quick release micronized formulation of bromocriptine, improves glycemic control and reduces adverse cardiovascular events. While the improvement of glycemic control is largely the result of improved postprandial hepatic glucose metabolism and insulin action, the mechanisms underlying the drug's cardioprotective effects are less well defined. Bromocriptine is a sympatholytic dopamine agonist and reduces the elevated sympathetic tone, characteristic of metabolic syndrome and type 2 diabetes, which potentiates elevations of vascular oxidative/nitrosative stress, known to precipitate cardiovascular disease. Therefore, this study investigated the impact of bromocriptine treatment upon biomarkers of vascular oxidative/nitrosative stress (including the pro-oxidative/nitrosative stress enzymes of NADPH oxidase 4, inducible nitric oxide (iNOS), uncoupled endothelial nitric oxide synthase (eNOS), the pro-inflammatory/pro-oxidative marker GTP cyclohydrolase 1 (GTPCH 1), and the pro-vascular health enzyme, soluble guanylate cyclase (sGC) as well as the plasma level of thiobarbituric acid reactive substances (TBARS), a circulating marker of systemic oxidative stress), in hypertensive SHR rats held on a high fat diet to induce metabolic syndrome. Inasmuch as the central nervous system (CNS) dopaminergic activities both regulate and are regulated by CNS circadian pacemaker circuitry, this study also investigated the time-of-day-dependent effects of bromocriptine treatment (10 mg/kg/day at either 13 or 19 h after the onset of light (at the natural waking time or late during the activity period, respectively) among animals held on 14 h daily photoperiods for 16 days upon such vascular biomarkers of vascular redox state, several metabolic syndrome parameters, and mediobasal hypothalamic (MBH) mRNA expression levels of neuropeptides neuropeptide Y (NPY) and agouti-related protein (AgRP) which regulate the peripheral fuel metabolism and of mRNA expression of other MBH glial and neuronal cell genes that support such metabolism regulating neurons in this model system. Such bromocriptine treatment at ZT 13 improved (reduced) biomarkers of vascular oxidative/nitrosative stress including plasma TBARS level, aortic NADPH oxidase 4, iNOS and GTPCH 1 levels, and improved other markers of coupled eNOS function, including increased sGC protein level, relative to controls. However, bromocriptine treatment at ZT 19 produced no improvement in either coupled eNOS function or sGC protein level. Moreover, such ZT 13 bromocriptine treatment reduced several metabolic syndrome parameters including fasting insulin and leptin levels, as well as elevated systolic and diastolic blood pressure, insulin resistance, body fat store levels and liver fat content, however, such effects of ZT 19 bromocriptine treatment were largely absent versus control. Finally, ZT 13 bromocriptine treatment reduced MBH NPY and AgRP mRNA levels and mRNA levels of several MBH glial cell/neuronal genes that code for neuronal support/plasticity proteins (suggesting a shift in neuronal structure/function to a new metabolic control state) while ZT 19 treatment reduced only AgRP, not NPY, and was with very little effect on such MBH glial cell genes expression. These findings indicate that circadian-timed bromocriptine administration at the natural circadian peak of CNS dopaminergic activity (that is diminished in insulin resistant states), but not outside this daily time window when such CNS dopaminergic activity is naturally low, produces widespread improvements in biomarkers of vascular oxidative stress that are associated with the amelioration of metabolic syndrome and reductions in MBH neuropeptides and gene expressions known to facilitate metabolic syndrome. These results of such circadian-timed bromocriptine treatment upon vascular pathology provide potential mechanisms for the observed marked reductions in adverse cardiovascular events with circadian-timed bromocriptine-QR therapy (similarly timed to the onset of daily waking as in this study) of type 2 diabetes subjects and warrant further investigations into related mechanisms and the potential application of such intervention to prediabetes and metabolic syndrome patients as well.

Reproductive Seasonality Affects In Vitro Embryo Production Outcomes in Adult Goats

Reproductive seasonality may have a considerable influence on the efficiency of assisted reproductive technologies in seasonal species. This study evaluated the effect of season on cleavage, blastocyst rates and quality of in vitro produced (IVP) goat embryos. In total, 2348 cumulus-oocyte complexes (COCs) were recovered from slaughterhouse ovaries and subjected to the same IVP system throughout 1.5 years (49 replicates). The odds ratio (OR) among seasons was calculated from values of cleavage and blastocyst rates in each season. Cleavage rate was lower (p < 0.05) in spring (anestrus), in comparison with either autumn (peak of breeding season) or summer, while the winter had intermediate values. Furthermore, lower OR of cleavage was observed in spring. Blastocyst formation rate (from initial number of COCs) was higher (p < 0.05) in autumn (52 ± 2.5%) when compared with the other seasons (combined rates: 40 ± 1.9%). Moreover, its OR was higher (p < 0.05) in autumn compared to all other seasons and impaired in the spring compared to winter (OR: 0.54) and summer (OR: 0.48). Embryo hatchability and blastocyst cell number were similar (p > 0.05) among seasons. In conclusion, the breeding season leads to improved oocyte developmental competence, resulting in higher cleavage and blastocyst yield, whereas embryo quality remained similar throughout the years.

Population responses to a historic drought across the range of the common monkeyflower (Mimulus guttatus)

PREMISE

Due to climate change, more frequent and intense periodic droughts are predicted to increasingly pose major challenges to the persistence of plant populations. When a severe drought occurs over a broad geographical region, independent responses by individual populations provide replicated natural experiments for examining the evolution of drought resistance and the potential for evolutionary rescue.

METHODS

We used a resurrection approach to examine trait evolution in populations of the common monkeyflower, Mimulus guttatus, exposed to a record drought in California from 2011 to 2017. Specifically, we compared variation in traits related to drought escape and avoidance from seeds collected from 37 populations pre- and post-drought in a common garden. In a parallel experiment, we evaluated fitness in two populations, one which thrived and one which was nearly extirpated during the drought, under well-watered and dry-down conditions.

RESULTS

We observed substantial variation among populations in trait evolution. In the subset of populations where phenotypes changed significantly, divergence proceeded along trait correlations with some populations flowering rapidly with less vegetative tissue accumulation and others delaying flowering with greater vegetative tissue accumulation. The degree of trait evolution was only weakly correlated with drought intensity but strongly correlated with initial levels of standing variation. Fitness was higher in the post-drought than pre-drought accessions in both treatments for the thriving population, but lower in both treatments for the nearly extirpated population.

CONCLUSIONS

Together, our results indicate that evolutionary responses to drought are context dependent and reflect the standing genetic variation and genetic correlations present within populations.

Toward reliable habitat suitability and accessibility models in an era of multiple environmental stressors

Global biodiversity declines, largely driven by climate and land-use changes, urge the development of transparent guidelines for effective conservation strategies. Species distribution modeling (SDM) is a widely used approach for predicting potential shifts in species distributions, which can in turn support ecological conservation where environmental change is expected to impact population and community dynamics. Improvements in SDM accuracy through incorporating intra- and interspecific processes have boosted the SDM field forward, but simultaneously urge harmonizing the vast array of SDM approaches into an overarching, widely adoptable, and scientifically justified SDM framework. In this review, we first discuss how climate warming and land-use change interact to govern population dynamics and species' distributions, depending on species' dispersal and evolutionary abilities. We particularly emphasize that both land-use and climate change can reduce the accessibility to suitable habitat for many species, rendering the ability of species to colonize new habitat and to exchange genetic variation a crucial yet poorly implemented component of SDM. We then unite existing methodological SDM practices that aim to increase model accuracy through accounting for multiple global change stressors, dispersal, or evolution, while shifting our focus to model feasibility. We finally propose a roadmap harmonizing model accuracy and feasibility, applicable to both common and rare species, particularly those with poor dispersal abilities. This roadmap (a) paves the way for an overarching SDM framework allowing comparison and synthesis of different SDM studies and (b) could advance SDM to a level that allows systematic integration of SDM outcomes into effective conservation plans.

Plant adaptation to climate change - Where are we?

Climate change poses critical challenges for population persistence in natural communities, agriculture and environmental sustainability, and food security. In this review, we discuss recent progress in climatic adaptation in plants. We evaluate whether climate change exerts novel selection and disrupts local adaptation, whether gene flow can facilitate adaptive responses to climate change, and if adaptive phenotypic plasticity could sustain populations in the short term. Furthermore, we discuss how climate change influences species interactions. Through a more in-depth understanding of these eco-evolutionary dynamics, we will increase our capacity to predict the adaptive potential of plants under climate change. In addition, we review studies that dissect the genetic basis of plant adaptation to climate change. Finally, we highlight key research gaps, ranging from validating gene function, to elucidating molecular mechanisms, expanding research systems from model species to other natural species, testing the fitness consequences of alleles in natural environments, and designing multifactorial studies that more closely reflect the complex and interactive effects of multiple climate change factors. By leveraging interdisciplinary tools (e.g., cutting-edge omics toolkits, novel ecological strategies, newly-developed genome editing technology), researchers can more accurately predict the probability that species can persist through this rapid and intense period of environmental change, as well as cultivate crops to withstand climate change, and conserve biodiversity in natural systems.

Reproduction in female wild cattle: Influence of seasonality on ARTs

Wild cattle species, often considered less alluring than certain conservation-dependent species, have not attracted the same level of interest as the charismatic megafauna from the general public, private or corporate donors, and other funding agencies. Currently, most wild cattle populations are vulnerable or threatened with extinction. The implementation of reproductive technologies to maintain genetically healthy cattle populations in situ and ex situ has been considered for more than 30 years. Protocols developed for domestic cattle breeds have been used with some success in various wild cattle species. However, inherent differences in the natural life history of these species makes extrapolation of domestic cattle protocols difficult, and in some cases, minimally effective. Reproductive seasonality, driven by either photoperiod or nutritional resource availability, has significant influence on the success of assisted reproductive technologies (ARTs). This review focuses on the physiological processes that differ in breeding (ovulatory) and non-breeding (anovulatory) seasons in female cattle, and the potential methods used to overcome these challenges. Techniques to be discussed within the context of seasonality include: estrus synchronization and ovulation induction, ovarian superstimulation, artificial insemination (AI), multiple ovulation embryo transfer (MOET), and ovum pick-up (OPU) with in vitro fertilization (IVF) and embryo transfer (ET).

Natural variation on whole-plant form in the wild is influenced by multivariate soil nutrient characteristics: natural selection acts on root traits

PREMISE

In the complex soil nutrient environments of wild populations of annual plants, in general, low nutrient availability restricts growth and alters root-shoot relationships. However, our knowledge of natural selection on roots in field settings is limited. We sought to determine whether selection acts directly on root traits and to identify which components of the soil environment were potential agents of selection.

METHODS

We studied wild native populations of Arabidopsis thaliana across 4 years, measuring aboveground and belowground traits and analyzing soil nutrients. Using multivariate methods, we examined patterns of natural selection and identified soil attributes that contributed to whole-plant form. In a common garden experiment at two field sites with contrasting soil texture, we examined patterns of selection on root and shoot traits.

RESULTS

In wild populations, we uncovered selection for above- and belowground size and architectural traits. We detected variation through time and identified soil components that influenced fruit production. In the garden experiment, we detected a distinct positive selection for total root length at the site with greater water-holding capacity and negative selection for measures of root architecture at the field site with reduced nutrient availability and water holding capacity.

CONCLUSIONS

Patterns of natural selection on belowground traits varied through time, across field sites and experimental gardens. Simultaneous investigations of above- and belowground traits reveal trait functional relationships on which natural selection can act, highlighting the influence of edaphic features on evolutionary processes in wild annual plant populations.

The soil microbial community alters patterns of selection on flowering time and fitness-related traits in Ipomoea purpurea

PREMISE

Plant flowering time plays an important role in plant fitness and thus evolutionary processes. Soil microbial communities are diverse and have a large impact, both positive and negative, on the host plant. However, owing to few available studies, how the soil microbial community may influence the evolutionary response of plant populations is not well understood. Here we sought to uncover whether belowground microbial communities act as an agent of selection on flowering and growth traits in the common morning glory, Ipomoea purpurea.

METHODS

We performed a controlled greenhouse experiment in which genetic lines of I. purpurea were planted into either sterilized soils or in soils that were sterilized and inoculated with the microbial community from original field soil. We could thus directly test the influence of alterations to the microbial community on plant growth, flowering, and fitness and assess patterns of selection in both soil microbial environments.

RESULTS

A more complex soil microbial community resulted in larger plants that produced more flowers. Selection strongly favored earlier flowering when plants were grown in the complex microbial environment than compared to sterilized soil. We also uncovered a pattern of negative correlational selection on growth rate and flowering time, indicating that selection favored different combinations of growth and flowering traits in the simplified versus complex soil community.

CONCLUSIONS

Together, these results suggest the soil microbial community is a selective agent on flowering time and ultimately that soil microbial community influences important plant evolutionary processes.

Interannual variation in season length is linked to strong co-gradient plasticity of phenology in a montane annual plant

Species are commonly distributed along latitudinal and elevational gradients of growing season length to which they might respond via phenotypic plasticity and/or adaptive genetic differentiation. However, the relative contribution of these processes and whether plasticity, if it occurs, facilitates expansion along season-length gradients remain unclear, but are important for predicting species fates during anthropogenic change. We quantified phenological trait variation in the montane annual Rhinanthus minor for three generations at 12 sites across 900 m of elevation in the Canadian Rocky Mountains and conducted a reciprocal transplant experiment for two generations among nine sites. We compared clines and interannual variation of phenological traits between natural and transplanted individuals. Season length declined by c. 37% along our elevational gradient and, as expected, plants emerged, reached first flower and made their first seed in c. 41% fewer growing degree days under shorter growing seasons. Although reciprocal transplants revealed modest genetic differentiation across elevation, trait clines primarily were due to striking co-gradient plasticity that paralleled genetic differentiation. Co-gradient plasticity likely evolved in response to considerable interannual variation in season length across our elevational transect, and should prepare R. minor to make adaptive changes to phenology in response to ongoing climate change predicted for montane environments.

Island woodiness underpins accelerated disparification in plant radiations

The evolution of secondary (insular) woodiness and the rapid disparification of plant growth forms associated with island radiations show intriguing parallels between oceanic islands and tropical alpine sky islands. However, the evolutionary significance of these phenomena remains poorly understood and the focus of debate. We explore the evolutionary dynamics of species diversification and trait disparification across evolutionary radiations in contrasting island systems compared with their nonisland relatives. We estimate rates of species diversification, growth form evolution and phenotypic space saturation for the classical oceanic island plant radiations - the Hawaiian silverswords and Macaronesian Echium - and the well-studied sky island radiations of Lupinus and Hypericum in the Andes. We show that secondary woodiness is associated with dispersal to islands and with accelerated rates of species diversification, accelerated disparification of plant growth forms and occupancy of greater phenotypic trait space for island clades than their nonisland relatives, on both oceanic and sky islands. We conclude that secondary woodiness is a prerequisite that could act as a key innovation, manifest as the potential to occupy greater trait space, for plant radiations on island systems in general, further emphasizing the importance of combinations of clade-specific traits and ecological opportunities in driving adaptive radiations.

Water availability drives population divergence and sex-specific responses in a dioecious plant

PREMISE

Water availability is an important abiotic factor, resulting in differences between plant species growing in xeric and mesic habitats. Species with populations occurring in both habitat types allow examination of whether water availability has acted as a selective force at the intraspecific level. Investigating responses to water availability with a dioecious species allows determination of whether males and females, which often have different physiologies and life histories, respond differently.

METHODS

An experiment varying water availability was performed under an outdoor rain-out shelter using plants from two mesic and two xeric populations of the dioecious plant Silene latifolia. Early growth rate, flowering propensity, flower size, and specific leaf area were measured. At the end of the season, the plants were harvested, aboveground and root biomass were measured, and the total number of flowers and fruit produced were counted.

RESULTS

Compared to the two mesic populations, plants from the two xeric populations grew more slowly, were less likely to flower, took longer to flower, had thicker leaves, invested less in aboveground biomass and more in root biomass, produced fewer flowers and fruit, but were more likely to live. Many traits exhibited significant habitat type × treatment interactions. Compared to the xeric populations, males-but not females-from mesic populations had less root biomass and greatly reduced their flower production in response to low water availability.

CONCLUSIONS

Mesic and xeric populations responded in ways congruent with water availability being a selective force for among-population divergence, especially for males.

Mobilizing the community of biodiversity specimen collectors to effectively detect and document outliers in the Anthropocene

PREMISE

Biological outliers (observations that fall outside of a previously understood norm, e.g., in phenology or distribution) may indicate early stages of a transformative change that merits immediate attention. Collectors of biodiversity specimens such as plants, fungi, and animals are on the front lines of discovering outliers, yet the role collectors currently play in providing such data is unclear.

METHODS

We surveyed 222 collectors of a broad range of taxa, searched 47 training materials, and explored the use of 170 outlier terms in 75 million specimen records to determine the current state of outlier detection and documentation in this community.

RESULTS

Collectors reported observing outliers (e.g., about 80% of respondents observed morphological and distributional outliers at least occasionally). However, relatively few specimen records include outlier terms, and imprecision in their use and handling in data records complicates data discovery by stakeholders. This current state appears to be at least partly due to the absence of protocols: only one of the training materials addressed documenting and reporting outliers.

CONCLUSIONS

We suggest next steps to mobilize this largely untapped, yet ideally suited, community for early detection of biotic change in the Anthropocene, including community activities for building relevant best practices.

Rapid and repeated local adaptation to climate in an invasive plant

Biological invasions provide opportunities to study evolutionary processes occurring over contemporary timescales. To explore the speed and repeatability of adaptation, we examined the divergence of life-history traits to climate, using latitude as a proxy, in the native North American and introduced European and Australian ranges of the annual plant Ambrosia artemisiifolia. We explored niche changes following introductions using climate niche dynamic models. In a common garden, we examined trait divergence by growing seeds collected across three ranges with highly distinct demographic histories. Heterozygosity-fitness associations were used to explore the effect of invasion history on potential success. We accounted for nonadaptive population differentiation using 11 598 single nucleotide polymorphisms. We revealed a centroid shift to warmer, wetter climates in the introduced ranges. We identified repeated latitudinal divergence in life-history traits, with European and Australian populations positioned at either end of the native clines. Our data indicate rapid and repeated adaptation to local climates despite the recent introductions and a bottleneck limiting genetic variation in Australia. Centroid shifts in the introduced ranges suggest adaptation to more productive environments, potentially contributing to trait divergence between the ranges.

Integrating herbarium specimen observations into global phenology data systems

PREMISE OF THE STUDY

The Plant Phenology Ontology (PPO) was originally developed to integrate phenology observations of whole plants across different global observation networks. Here we describe a new release of the PPO and associated data pipelines that supports integration of phenology observations from herbarium specimens, which provide historical and modern phenology data.

METHODS AND RESULTS

Critical changes to the PPO include key terms that describe how measurements from parts of plants, which are captured in most imaged herbarium specimens, relate to whole plants. We provide proof of concept for ingesting annotations from imaged herbarium sheets of Prunus serotina, the common black cherry. We then provide an example analysis of changes in flowering timing over the past 125 years, demonstrating the value of integrating herbarium and observational phenology data sets.

CONCLUSIONS

These conceptual and technical advances will support the addition of phenology data from herbaria, but also could be expanded upon to facilitate the inclusion of data from photograph-based citizen science platforms. With the incorporation of herbarium phenology data, new historical baseline data will strengthen the capability to monitor, model, and forecast plant phenology changes.

Interacting effects of genetic variation for seed dormancy and flowering time on phenology, life history, and fitness of experimental Arabidopsis thaliana populations over multiple generations in the field

Major alleles for seed dormancy and flowering time are well studied, and can interact to influence seasonal timing and fitness within generations. However, little is known about how this interaction controls phenology, life history, and population fitness across multiple generations in natural seasonal environments. To examine how seed dormancy and flowering time shape annual plant life cycles over multiple generations, we established naturally dispersing populations of recombinant inbred lines of Arabidopsis thaliana segregating early and late alleles for seed dormancy and flowering time in a field experiment. We recorded seasonal phenology and fitness of each genotype over 2 yr and several generations. Strong seed dormancy suppressed mid-summer germination in both early- and late-flowering genetic backgrounds. Strong dormancy and late-flowering genotypes were both necessary to confer a winter annual life history; other genotypes were rapid-cycling. Strong dormancy increased within-season fecundity in an early-flowering background, but decreased it in a late-flowering background. However, there were no detectable differences among genotypes in population growth rates. Seasonal phenology, life history, and cohort fitness over multiple generations depend strongly upon interacting genetic variation for dormancy and flowering. However, similar population growth rates across generations suggest that different life cycle genotypes can coexist in natural populations.

Explaining the apparent paradox of persistent selection for early flowering

Decades of observation in natural plant populations have revealed pervasive phenotypic selection for early flowering onset. This consistent pattern seems at odds with life-history theory, which predicts stabilizing selection on age and size at reproduction. Why is selection for later flowering rare? Moreover, extensive evidence demonstrates that flowering time can and does evolve. What maintains ongoing directional selection for early flowering? Several non-mutually exclusive processes can help to reconcile the apparent paradox of selection for early flowering. We outline four: selection through other fitness components may counter observed fecundity selection for early flowering; asymmetry in the flowering-time-fitness function may make selection for later flowering hard to detect; flowering time and fitness may be condition-dependent; and selection on flowering duration is largely unaccounted for. In this Viewpoint, we develop these four mechanisms, and highlight areas where further study will improve our understanding of flowering-time evolution.

Evolution and the duration of a doomed population

Many populations are doomed to extinction, but little is known about how evolution contributes to their longevity. We address this by modeling an asexual population consisting of genotypes whose abundances change independently according to a system of continuous branching diffusions. Each genotype is characterized by its initial abundance, growth rate, and reproductive variance. The latter two components determine the genotype's "risk function" which describes its per capita probability of extinction at any time. We derive the probability distribution of extinction times for a polymorphic population, which can be expressed in terms of genotypic risk functions. We use this to explore how spontaneous mutation, abrupt environmental change, or population supplementation and removal affect the time to extinction. Results suggest that evolution based on new mutations does little to alter the time to extinction. Abrupt environmental changes that affect all genotypes can have more substantial impact, but, curiously, a beneficial change does more to extend the lifetime of thriving than threatened populations of the same initial abundance. Our results can be used to design policies that meet specific conservation goals or management strategies that speed the elimination of agricultural pests or human pathogens.

Leptin levels, seasonality and thermal acclimation in the Microbiotherid marsupial Dromiciops gliroides: Does photoperiod play a role?

Mammals of the Neotropics are characterized by a marked annual cycle of activity, which is accompanied by several physiological changes at the levels of the whole organism, organs and tissues. The physiological characterization of these cycles is important, as it gives insight on the mechanisms by which animals adjust adaptively to seasonality. Here we studied the seasonal changes in blood biochemical parameters in the relict South American marsupial Dromiciops gliroides ("monito del monte" or "little mountain monkey"), under semi-natural conditions. We manipulated thermal conditions in order to characterize the effects of temperature and season on a battery of biochemical parameters, body mass and adiposity. Our results indicate that monitos experience an annual cycle in body mass and adiposity (measured as leptin levels), reaching a maximum in winter and a minimum in summer. Blood biochemistry confirms that the nutritional condition of animals is reduced in summer instead of winter (as generally reported). This was coincident with a reduction of several biochemical parameters in summer, such as betahydroxybutyrate, cholesterol, total protein concentration and globulins. Monitos seem to initiate winter preparation during autumn and reach maximum body reserves in winter. Hibernation lasts until spring, at which time they use fat reserves and become reproductively active. Sexual maturation during summer would be the strongest energetic bottleneck, which explains the reductions in body mass and other parameters in this season. Overall, this study suggests that monitos anticipate the cold season by a complex interaction of photoperiodic and thermal cues.

Natural history collections as windows on evolutionary processes

Natural history collections provide an immense record of biodiversity on Earth. These repositories have traditionally been used to address fundamental questions in biogeography, systematics and conservation. However, they also hold the potential for studying evolution directly. While some of the best direct observations of evolution have come from long-term field studies or from experimental studies in the laboratory, natural history collections are providing new insights into evolutionary change in natural populations. By comparing phenotypic and genotypic changes in populations through time, natural history collections provide a window into evolutionary processes. Recent studies utilizing this approach have revealed some dramatic instances of phenotypic change over short timescales in response to presumably strong selective pressures. In some instances, evolutionary change can be paired with environmental change, providing a context for potential selective forces. Moreover, in a few cases, the genetic basis of phenotypic change is well understood, allowing for insight into adaptive change at multiple levels. These kinds of studies open the door to a wide range of previously intractable questions by enabling the study of evolution through time, analogous to experimental studies in the laboratory, but amenable to a diversity of species over longer timescales in natural populations.

Plant fitness in a rapidly changing world

Modern reliance on fossil fuels has ushered in extreme temperatures globally and abnormal precipitation patterns in many regions. Although the climate is changing rapidly, other agents of natural selection such as photoperiod remain constant. This decoupling of previously reliable environmental cues shifts adaptive landscapes, favors novel suites of traits and likely increases the extinction risk of local populations. Here, I examine the fitness consequences of changing climates. Meta-analyses demonstrate that simulated future climates depress viability and fecundity components of fitness for native plant species in the short term, which could reduce population growth rates. Contracting populations that cannot adapt or adjust plastically to new climates might not be capable of producing sufficient migrants to track changing conditions.

Constrained growth flips the direction of optimal phenological responses among annual plants

Phenological changes among plants due to climate change are well documented, but often hard to interpret. In order to assess the adaptive value of observed changes, we study how annual plants with and without growth constraints should optimize their flowering time when productivity and season length changes. We consider growth constraints that depend on the plant's vegetative mass: self-shading, costs for nonphotosynthetic structural tissue and sibling competition. We derive the optimal flowering time from a dynamic energy allocation model using optimal control theory. We prove that an immediate switch (bang-bang control) from vegetative to reproductive growth is optimal with constrained growth and constant mortality. Increasing mean productivity, while keeping season length constant and growth unconstrained, delayed the optimal flowering time. When growth was constrained and productivity was relatively high, the optimal flowering time advanced instead. When the growth season was extended equally at both ends, the optimal flowering time was advanced under constrained growth and delayed under unconstrained growth. Our results suggests that growth constraints are key factors to consider when interpreting phenological flowering responses. It can help to explain phenological patterns along productivity gradients, and links empirical observations made on calendar scales with life-history theory.

Project Baseline: An unprecedented resource to study plant evolution across space and time

PREMISE OF THE STUDY

Project Baseline is a seed bank that offers an unprecedented opportunity to examine spatial and temporal dimensions of microevolution during an era of rapid environmental change. Over the upcoming 50 years, biologists will withdraw genetically representative samples of past populations from this time capsule of seeds and grow them contemporaneously with modern samples to detect any phenotypic and molecular evolution that has occurred during the intervening time.

METHODS

We carefully developed this living genome bank using protocols to enhance its experimental value by collecting from multiple populations and species across a broad geographical range in sites that are likely to be preserved into the future. Seeds are accessioned with site and population data and are stored by maternal line under conditions that maximize seed longevity. This open-access resource will be available to researchers at regular intervals to evaluate contemporary evolution.

KEY RESULTS

To date, the Project Baseline collection includes 100-200 maternal lines of each of 61 species collected from over 831 populations on sites that are likely to be preserved into the future across the United States (∼78,000 maternal lines). Our strategically designed collection circumvents some problems that can cloud the results of "resurrection" studies involving naturally preserved or existing seed collections that are available fortuitously.

CONCLUSIONS

The resurrection approach can be coupled with long-established and newer techniques over the next five decades to elucidate genetic change and thereby vastly improve our understanding of temporal and spatial changes in phenotype and the evolutionary processes underlying it.

Large-scale adaptive differentiation in the alpine perennial herb Arabis alpina

Information about the incidence and magnitude of local adaptation can help to predict the response of natural populations to a changing environment, and should be of particular interest in arctic and alpine environments where the effects of climate change are expected to be severe. To quantify adaptive differentiation in the arctic-alpine perennial herb Arabis alpina, we conducted reciprocal transplant experiments for 3 yr between Spanish and Scandinavian populations. At the sites of one Spanish and one Scandinavian population, we planted seedlings representing two Spanish and four Scandinavian populations, and recorded survival, flowering propensity and fecundity. The experiment was replicated in two subsequent years. The results demonstrate strong adaptive differentiation between A. alpina populations from the two regions. At the field site in Spain, survival and fruit production of Spanish populations were higher than those of Scandinavian populations, while the opposite was true at the site in Scandinavia, and these differences were consistent across years. By comparison, fitness varied little among populations from the same region. The results suggest that the magnitude and geographical scale of local adaptation need to be considered in predictions of the effects of global change on the dynamics of arctic and alpine plant populations.

Innovative empirical approaches for inferring climate-warming impacts on plants in remote areas

The prediction of the effects of climate warming on plant communities across the globe has become a major focus of ecology, evolution and biodiversity conservation. However, many of the frequently used empirical approaches for inferring how warming affects vegetation have been criticized for decades. In addition, methods that require no electricity may be preferred because of constraints of active warming, e.g. in remote areas. Efforts to overcome the limitations of earlier methods are currently under development, but these approaches have yet to be systematically evaluated side by side. Here, an overview of the benefits and limitations of a selection of innovative empirical techniques to study temperature effects on plants is presented, with a focus on practicality in relatively remote areas without an electric power supply. I focus on methods for: ecosystem aboveground and belowground warming; a fuller exploitation of spatial temperature variation; and long-term monitoring of plant ecological and microevolutionary changes in response to warming. An evaluation of the described methodological set-ups in a synthetic framework along six axes (associated with the consistency of temperature differences, disturbance, costs, confounding factors, spatial scale and versatility) highlights their potential usefulness and power. Hence, further developments of new approaches to empirically assess warming effects on plants can critically stimulate progress in climate-change biology.

On selection for flowering time plasticity in response to density

Different genotypes often exhibit opposite plastic responses in the timing of the onset of flowering with increasing plant density. In experimental studies, selection for accelerated flowering is generally found. By contrast, game theoretical studies predict that there should be selection for delayed flowering when competition increases. Combining different optimality criteria, the conditions under which accelerated or delayed flowering in response to density would be selected for are analysed with a logistic growth simulation model. To maximize seed production at the whole-stand level (simple optimization), selection should lead to accelerated flowering at high plant density, unless very short growing seasons select for similar onset of flowering at all densities. By contrast, selection of relative individual fitness will lead to delayed flowering when season length is long and/or growth rates are high. These different results give a potential explanation for the observed differences in direction of the plastic responses within and between species, including homeostasis, as a result of the effect of the variation in season length on the benefits of delayed flowering. This suggests that limited plasticity can evolve without the costs and limits that are currently thought to constrain the evolution of plasticity.

Cross-country differences in basal and stress-induced cortisol secretion in older adults

Objective

Several studies have emphasized the association between socioeconomic status (SES) and inadequate response of the biological stress system. However, other factors related to SES are rarely considered, such as cultural values, social norms, organization, language and communication skills, which raises the need to investigate cross-country differences in stress response. Although some studies have shown differences in cortisol levels between immigrants and natives, there is no cross-country evidence regarding cortisol levels in country-native elders. This is particularly important given the high prevalence of stress-related disorders across nations during aging. The current study examined basal diurnal and reactive cortisol levels in healthy older adults living in two different countries.

Methods

Salivary cortisol of 260 older adults from Canada and Brazil were nalyzed. Diurnal cortisol was measured in saliva samples collected at home throughout two working days at awakening, 30 min after waking, 1400 h, 1600 h and before bedtime. Cortisol reactivity was assessed in response to the Trier Social Stress Test (TSST) in both populations.

Results

Our results showed that even under similar health status, psychological and cognitive characteristics, Brazilian elders exhibited higher basal and stress-induced cortisol secretion compared to the Canadian participants.

Conclusion

These findings suggest that country context may modulate cortisol secretion and could impact the population health.