Phenological responses to multiple environmental drivers under climate change: insights from a long-term observational study and a manipulative field experiment

Testing the evolutionary potential of an alpine plant: phenotypic plasticity in response to growth temperature outweighs parental environmental effects and other genetic causes of variation

Phenotypic plasticity and rapid evolution are fundamental processes by which organisms can maintain their function and fitness in the face of environmental changes. Here we quantified the plasticity and evolutionary potential of an alpine herb Wahlenbergia ceracea. Utilizing its mixed-mating system, we generated outcrossed and self-pollinated families that were grown in either cool or warm environments, and that had parents that had also been grown in either cool or warm environments. We then analysed the contribution of environmental and genetic factors to variation in a range of phenotypic traits including phenology, leaf mass per area, photosynthetic function, thermal tolerance, and reproductive fitness. The strongest effect was that of current growth temperature, indicating strong phenotypic plasticity. All traits except thermal tolerance were plastic, whereby warm-grown plants flowered earlier, grew larger, and produced more reproductive stems compared with cool-grown plants. Flowering onset and biomass were heritable and under selection, with early flowering and larger plants having higher relative fitness. There was little evidence for transgenerational plasticity, maternal effects, or genotype×environment interactions. Inbreeding delayed flowering and reduced reproductive fitness and biomass. Overall, we found that W. ceracea has the capacity to respond rapidly to climate warming via plasticity, and the potential for evolutionary change.

Natural selection on floral volatiles and other traits can change with snowmelt timing and summer precipitation

Climate change is disrupting floral traits that mediate mutualistic and antagonistic species interactions. Plastic responses of these traits to multiple shifting conditions may be adaptive, depending on natural selection in new environments. We manipulated snowmelt date over three seasons (3-11 d earlier) in factorial combination with growing-season precipitation (normal, halved, or doubled) to measure plastic responses of volatile emissions and other floral traits in Ipomopsis aggregata. We quantified how precipitation and early snowmelt affected selection on traits by seed predators and pollinators. Within years, floral emissions did not respond to precipitation treatments but shifted with snowmelt treatment depending on the year. Across 3 yr, emissions correlated with both precipitation and snowmelt date. These effects were driven by changes in soil moisture. Selection on several traits changed with earlier snowmelt or reduced precipitation, in some cases driven by predispersal seed predation. Floral trait plasticity was not generally adaptive. Floral volatile emissions shifted in the face of two effects of climate change, and the new environments modulated selection imposed by interacting species. The complexity of the responses underscores the need for more studies of how climate change will affect floral volatiles and other floral traits.

Native arbuscular mycorrhizal fungi drive ecophysiology through phenotypic integration and functional plasticity under the Sonoran desert conditions

Knowledge is scarce to what extent environmental drivers and native symbiotic fungi in soil induce abrupt (short-term), systemic (multiple traits), or specific (a subset of traits) shifts in C3 plants' ecophysiological/mycorrhizal responses. We cultivated an emblematic native C3 species (Capsicum annuum var. glabriusculum, "Chiltepín") to look at how the extreme heat of the Sonoran desert, sunlight regimes (low = 2, intermediate = 15, high = 46 mol m2 d-1) and density of native arbuscular mycorrhizal fungi in soil (low AMF = 1% v/v, high AMF = 100% v/v), drive shifts on mycorrhizal responses through multiple functional traits (106 traits). The warming thresholds were relentlessly harsh even under intensive shade (e.g. superheat maximum thresholds reached ranged between 47-63°C), and several pivotal traits were synergistically driven by AMF (e.g. photosynthetic capacity, biomass gain/allometry, and mycorrhizal colonization traits); whereas concurrently, sunlight regimes promoted most (76%) alterations in functional acclimation traits in the short-term and opposite directions (e.g. survival, phenology, photosynthetic, carbon/nitrogen economy). Multidimensional reduction analysis suggests that the AMF promotes a synergistic impact on plants' phenotypic integration and functional plasticity in response to sunlight regimes; however, complex relationships among traits suggest that phenotypic variation determines the robustness degree of ecophysiological/mycorrhizal phenotypes between/within environments. Photosynthetic canopy surface expansion, Rubisco activity, photosynthetic nitrogen allocation, carbon gain, and differential colonization traits could be central to plants' overall ecophysiological/mycorrhizal fitness strengthening. In conclusion, we found evidence that a strong combined effect among environmental factors in which AMF are key effectors could drive important trade-offs on plants' ecophysiological/mycorrhizal fitness in the short term.

Local climate and vernalization sensitivity predict the latitudinal patterns of flowering onset in the crop wild relative Linum bienne Mill

BACKGROUND AND AIMS

The timing of flowering onset is often correlated with latitude, indicative of climatic gradients. Flowering onset in temperate species commonly requires exposure to cold temperatures, known as vernalization. Hence, population differentiation of flowering onset with latitude might reflect adaptation to the local climatic conditions experienced by populations.

METHODS

Within its western range, seeds from Linum bienne populations (the wild relative of cultivated Linum usitatissimum) were used to describe the latitudinal differentiation of flowering onset to determine its association with the local climate of the population. A vernalization experiment including different crop cultivars was used to determine how vernalization accelerates flowering onset, in addition to the vernalization sensitivity response among populations and cultivars. Additionally, genetic differentiation of L. bienne populations along the latitudinal range was scrutinized using microsatellite markers.

KEY RESULTS

Flowering onset varied with latitude of origin, with southern populations flowering earlier than their northern counterparts. Vernalization reduced the number of days to flowering onset, but vernalization sensitivity was greater in northern populations compared with southern ones. Conversely, vernalization delayed flowering onset in the crop, exhibiting less variation in sensitivity. In L. bienne, both flowering onset and vernalization sensitivity were better predicted by the local climate of the population than by latitude itself. Microsatellite data unveiled genetic differentiation of populations, forming two groups geographically partitioned along latitude.

CONCLUSIONS

The consistent finding of latitudinal variation across experiments suggests that both flowering onset and vernalization sensitivity in L. bienne populations are under genetic regulation and might depend on climatic cues at the place of origin. The association with climatic gradients along latitude suggests that the climate experienced locally drives population differentiation of the flowering onset and vernalization sensitivity patterns. The genetic population structure suggests that past population history could have influenced the flowering initiation patterns detected, which deserves further work.

A Long-Lived Alpine Perennial Advances Flowering under Warmer Conditions but Not Enough to Maintain Reproductive Success

AbstractAssessing whether phenological shifts in response to climate change confer a fitness advantage requires investigating the relationships among phenology, fitness, and environmental drivers of selection. Despite widely documented advancements in phenology with warming climate, we lack empirical estimates of how selection on phenology varies in response to continuous climate drivers or how phenological shifts in response to warming conditions affect fitness. We leverage an unusual long-term dataset with repeated, individual measurements of phenology and reproduction in a long-lived alpine plant. We analyze phenotypic plasticity in flowering phenology in relation to two climate drivers, snowmelt timing and growing degree days (GDDs). Plants flower earlier with increased GDDs and earlier snowmelt, and directional selection also favors earlier flowering under these conditions. However, reproduction still declines with warming and early snowmelt, even when flowering is early. Furthermore, the steepness of this reproductive decline increases dramatically with warming conditions, resulting in very little fruit production regardless of flowering time once GDDs exceed approximately 225 degree days or snowmelt occurs before May 15. Even though advancing phenology confers a fitness advantage relative to stasis, these shifts are insufficient to maintain reproduction under warming, highlighting limits to the potential benefits of phenological plasticity under climate change.

Spatial variability in herbaceous plant phenology is mostly explained by variability in temperature but also by photoperiod and functional traits

Whereas temporal variability of plant phenology in response to climate change has already been well studied, the spatial variability of phenology is not well understood. Given that phenological shifts may affect biotic interactions, there is a need to investigate how the variability in environmental factors relates to the spatial variability in herbaceous species' phenology by at the same time considering their functional traits to predict their general and species-specific responses to future climate change. In this project, we analysed phenology records of 148 herbaceous species, which were observed for a single year by the PhenObs network in 15 botanical gardens. For each species, we characterised the spatial variability in six different phenological stages across gardens. We used boosted regression trees to link these variabilities in phenology to the variability in environmental parameters (temperature, latitude and local habitat conditions) as well as species traits (seed mass, vegetative height, specific leaf area and temporal niche) hypothesised to be related to phenology variability. We found that spatial variability in the phenology of herbaceous species was mainly driven by the variability in temperature but also photoperiod was an important driving factor for some phenological stages. In addition, we found that early-flowering and less competitive species characterised by small specific leaf area and vegetative height were more variable in their phenology. Our findings contribute to the field of phenology by showing that besides temperature, photoperiod and functional traits are important to be included when spatial variability of herbaceous species is investigated.

Sparse modeling for climate variable selection across trophic levels

Understanding how populations respond to climate is fundamentally important to many questions in ecology, evolution, and conservation biology. Climate is complex and multifaceted, with aspects affecting populations in different and sometimes unexpected ways. Thus, when measuring the changing climate it is important to consider the complexity of the phenomenon and the number of ways it can be characterized through different metrics. We used a Bayesian sparse modeling approach to select among 80 metrics of climate and applied the approach to 19 datasets of bird, insect, and plant population responses to abiotic conditions as case studies of how the method can be applied for climate variable selection in a time series context. For phenological datasets, mean spring temperature was frequently selected as an important climate driver, while selected predictors were more diverse for population metrics such as abundance or reproductive success. The climate variable selection approach presented here can help to identify potential climate metrics when there is limited physiological or mechanistic information to make an a priori variable selection, and is broadly applicable across studies on population responses to climate.

Topography-mediated light environment regulates intra-specific seasonal and diurnal patterns of photosynthetic plasticity and plant ecophysiological adaptation strategies

Due to substantial topographic variations in the Himalaya, incident solar radiation in the forest canopy is highly unequal. This results in significant environmental differences at finer scales and may lead to considerable differences in photosynthetic productivity in montane forests. Therefore, local-scale ecophysiological investigations, may be more effective and instructive than landscape-level inventories and models. We investigated leaf ecophysiological differences and related adaptations between two Quercus semecarpifolia forests in aspect-mediated, significantly varying light regimes in the same mountain catchment. Seasonal and diurnal rates of photosynthesis (A) were significantly higher in south aspect (S) than the north (N). Although temperature was a key contributor to seasonal fluctuations in photosynthetic physiology, photoperiod significantly determined intraspecific variations in seasonal and diurnal plasticity of leaf ecophysiological traits between the two topography-mediated light environments. The regression model for A as a function of stomatal conductivity (gsw) explained the critical role of gsw in triggering photosynthetic plasticity as an adaptive function against varying environmental stresses due to seasonal solar differences. We also examined, modifications in chlorophyll content between the two light regimes across seasons to determine the chlorophyll adaptation strategy. The N aspect had higher leaf chl a, b, and chl a + b and a lower chl-allocation ratio (a/b) than S, which helped to optimize the required light reception in the photoreaction centers for improved photosynthetic performance. The leaf light response curves for A and gsw were observed against varying incident photosynthetic photon flux densities (0-2000 mol.m2 s-1 PPFD) for both aspects. We found that the same species developed significantly distinct light response strategies and photosynthetic capacities in S than in N for the given magnitudes of PPFD. Such acquired ecophysiological adaptations owing to varying light environments may provide significant clues for understanding the impact of future climate change on Himalayan tree species.

Seasonal variation in dragonfly assemblage colouration suggests a link between thermal melanism and phenology

Phenology, the seasonal timing of life events, is an essential component of diversity patterns. However, the mechanisms involved are complex and understudied. Body colour may be an important factor, because dark-bodied species absorb more solar radiation, which is predicted by the Thermal Melanism Hypothesis to enable them to thermoregulate successfully in cooler temperatures. Here we show that colour lightness of dragonfly assemblages varies in response to seasonal changes in solar radiation, with darker early- and late-season assemblages and lighter mid-season assemblages. This finding suggests a link between colour-based thermoregulation and insect phenology. We also show that the phenological pattern of dragonfly colour lightness advanced over the last decades. We suggest that changing seasonal temperature patterns due to global warming together with the static nature of solar radiation may drive dragonfly flight periods to suboptimal seasonal conditions. Our findings open a research avenue for a more mechanistic understanding of phenology and spatio-phenological impacts of climate warming on insects.

Survival tactics of an endangered species Withania coagulans (Stocks) Dunal to arid environments

Withania coagulans is a valuable medicinal plant with high demand, but its wild growth and local usage pose a threat to its natural habitat. This study aims to understand the plant's growth, anatomy, and physiology in different environmental conditions to aid in conservation and re-vegetation efforts. Fifteen differently adapted populations of Withania coagulans were collected from diverse ecological regions, viz., (i) along the roadside, (ii) hilly areas, (iii) barren land, and (iv) wasteland to unravel the adaptive mechanisms that are responsible for their ecological success across heterogenic environments of Punjab, Pakistan. The roadside populations had high values of photosynthetic pigments, total soluble proteins, root endodermis thickness, stem and leaf cortical thickness, and its cell area. The populations growing in hilly areas showed better growth performance such as vigorous growth and biomass production. Additionally, there was enhanced accumulation of organic osmolytes (glycine betaine and proline), chlorophyll content (chl a/b), and enlarged epidermal cells, cortical cells, vascular bundles, metaxylem vessels, and phloem region in roots. In case of stem area, epidermal thickness, cortical thickness, vascular bundle, and pith area showed improved growth. However, the barren land population showed significant increase in carotenoid contents, vascular bundle area, and metaxylem area in roots, and xylem vessels and phloem area in stems and leaves. The wasteland population surpassed the rest of the populations in having greater root dry weight, higher shoot ionic contents, increased root area, thick cortical, and vascular bundle area in roots. Likewise, cortical thickness and its cell area, and pith area in stems, whereas large vascular bundles, phloem region, and high stomatal density were recorded in leaves. Subsequently, natural populations showed the utmost behavior related to tissue organization and physiology in response to varied environmental conditions that would increase the distribution and survival of species.

Differences in individual flowering time change pollen limitation and seed set in three montane wildflowers

PREMISE

Changes to flowering time caused by climate change could affects plant fecundity, but studies that compare the individual-level responses of phenologically distinct, co-occurring species are lacking. We assessed how variation in floral phenology affects the fecundity of individuals from three montane species with different seasonal flowering times, including in snowmelt acceleration treatments to increase variability in phenology.

METHODS

We collected floral phenology and seed set data for individuals of three montane plant species (Mertensia fusiformis, Delphinium nuttallianum, Potentilla pulcherrima). To examine the drivers of seed set, we measured conspecific floral density and conducted pollen limitation experiments to isolate pollination function. We advanced the phenology of plant communities in a controlled large-scale snowmelt acceleration experiment.

RESULTS

Differences in individual phenology relative to the rest of the population affected fecundity in our focal species, but effects were species-specific. For our early-season species, individuals that bloomed later than the population peak bloom had increased fecundity, while for our midseason species, simply blooming before or after the population peak increased individual fecundity. For our late-season species, blooming earlier than the population peak increased fecundity. The early and midseason species were pollen-limited, and conspecific density affected seed set only for our early-season species.

CONCLUSIONS

Our study shows that variation in individual phenology affects fecundity in three phenologically distinct montane species, and that pollen limitation may be more influential than conspecific density. Our results suggest that individual-level changes in phenology are important to consider for understanding plant reproductive success.

Disorder or a new order: How climate change affects phenological variability

Advancing spring phenology is a well documented consequence of anthropogenic climate change, but it is not well understood how climate change will affect the variability of phenology year to year. Species' phenological timings reflect the adaptation to a broad suite of abiotic needs (e.g., thermal energy) and biotic interactions (e.g., predation and pollination), and changes in patterns of variability may disrupt those adaptations and interactions. Here, we present a geographically and taxonomically broad analysis of phenological shifts, temperature sensitivity, and changes in interannual variability encompassing nearly 10,000 long-term phenology time series representing more than 1000 species across much of the Northern Hemisphere. We show that the timings of leaf-out, flowering, insect first-occurrence, and bird arrival were the most sensitive to temperature variation and have advanced at the fastest pace for early-season species in colder and less seasonal regions. We did not find evidence for changing variability in warmer years in any phenophase groups, although leaf-out and flower phenology have become moderately but significantly less variable over time. Our findings suggest that climate change has not to this point fundamentally altered the patterns of interannual phenological variability.

On the hidden temporal dynamics of plant adaptation

Adaptation to a wide range of environments is a major driver of plant diversity. It is now possible to catalog millions of potential adaptive genomic differences segregating between environments within a plant species in a single experiment. Understanding which of these changes contributes to adaptive phenotypic divergence between plant populations is a major goal of evolutionary biologists and crop breeders. In this review, we briefly highlight the approaches frequently used to understand the genetic basis of adaptive phenotypes in plants, and we discuss some of the limitations of these methods. We propose that direct observation of the process of adaptation using multigenerational studies and whole genome sequencing is a crucial missing component of recent studies of plant adaptation because it complements several shortcomings of sampling-based techniques.

Water and nutrient availability exert selection on reproductive phenology

PREMISE

Global change has changed resource availability to plants, which could shift the adaptive landscape. We hypothesize that novel water and nutrient availability combinations alter patterns of natural selection on reproductive phenology in Boechera stricta (Brassicaceae) and influence the evolution of local adaptation.

METHODS

We conducted a multifactorial greenhouse study using 35 accessions of B. stricta sourced from a broad elevational gradient in the Rocky Mountains. We exposed full siblings to three soil water and two nutrient availability treatment levels, reflecting current and projected future conditions. In addition, we quantified fitness (seed count) and four phenological traits: the timing of first flowering, the duration of flowering, and height and leaf number at flowering.

RESULTS

Selection favored early flowering and longer duration of flowering, and the genetic correlation between these traits accorded with the direction of selection. In most treatments, we found selection for increased height, but selection on leaf number depended on water availability, with selection favoring more leaves in well-watered conditions and fewer leaves under severe drought. Low-elevation genotypes had the greatest fitness under drought stress, consistent with local adaptation.

CONCLUSIONS

We found evidence of strong selection on these heritable traits. Furthermore, the direction and strength of selection on size at flowering depended on the variable measured (height vs. leaf number). Finally, selection often favored both early flowering and a longer duration of flowering. Selection on these two components of phenology can be difficult to disentangle due to tight genetic correlations.

Genetic variation in reproductive timing in a long-lived herbaceous perennial

PREMISE

Reproductive fitness of individual plants depends on the timing of flowering, especially in mate-limited populations, such as those in fragmented habitats. When flowering time traits are associated with differential reproductive success, the narrow-sense heritability (h² ) of traits will determine how rapidly trait means evolve in response to selection. Heritability of flowering time is documented in many annual plants. However, estimating h² of flowering time in perennials presents additional methodological challenges, often including paternity assignment and trait expression over multiple years.

METHODS

We evaluated the h² of onset and duration of flowering using offspring-midparent regressions and restricted maximum likelihood methods in an experimental population of an iterocarpic, perennial, herbaceous plant, Echinacea angustifolia, growing in natural conditions. We assessed the flowering time of the parental cohort in 2005 and 2006; the offspring in 2014 through 2017. We also examined the effects of the paternity assignment from Cervus and MasterBayes on estimates of h² .

RESULTS

We found substantial h² for onset and duration of flowering. We also observed variation in estimates among years. The most reliable estimates for both traits fell in the range of 0.1-0.17. We found evidence of a genotype by year interaction for onset of flowering and strong evidence that genotypes are consistent in their duration of flowering across years.

CONCLUSIONS

Substantial heritabilities in this population imply the capacity for a response to natural selection, while also suggesting the potential for differential contributions to adaptive evolution among seasons.

The Boechera model system for evolutionary ecology

Model systems in biology expand the research capacity of individuals and the community. Closely related to Arabidopsis, the genus Boechera has emerged as an important ecological model owing to the ability to integrate across molecular, functional, and eco-evolutionary approaches. Boechera species are broadly distributed in relatively undisturbed habitats predominantly in western North America and provide one of the few experimental systems for identification of ecologically important genes through genome-wide association studies and investigations of selection with plants in their native habitats. The ecologically, evolutionarily, and agriculturally important trait of apomixis (asexual reproduction via seeds) is common in the genus, and field experiments suggest that abiotic and biotic environments shape the evolution of sex. To date, population genetic studies have focused on the widespread species B. stricta, detailing population divergence and demographic history. Molecular and ecological studies show that balancing selection maintains genetic variation in ~10% of the genome, and ecological trade-offs contribute to complex trait variation for herbivore resistance, flowering phenology, and drought tolerance. Microbiome analyses have shown that host genotypes influence leaf and root microbiome composition, and the soil microbiome influences flowering phenology and natural selection. Furthermore, Boechera offers numerous opportunities for investigating biological responses to global change. In B. stricta, climate change has induced a shift of >2 weeks in the timing of first flowering since the 1970s, altered patterns of natural selection, generated maladaptation in previously locally-adapted populations, and disrupted life history trade-offs. Here we review resources and results for this eco-evolutionary model system and discuss future research directions.

New directions in tropical phenology

Earth's most speciose biomes are in the tropics, yet tropical plant phenology remains poorly understood. Tropical phenological data are comparatively scarce and viewed through the lens of a 'temperate phenological paradigm' expecting phenological traits to respond to strong, predictably annual shifts in climate (e.g., between subfreezing and frost-free periods). Digitized herbarium data greatly expand existing phenological data for tropical plants; and circular data, statistics, and models are more appropriate for analyzing tropical (and temperate) phenological datasets. Phylogenetic information, which remains seldom applied in phenological investigations, provides new insights into phenological responses of large groups of related species to climate. Consistent combined use of herbarium data, circular statistical distributions, and robust phylogenies will rapidly advance our understanding of tropical - and temperate - phenology.

Functional plasticity of Capsicum annuum var. glabriusculum through multiple traits

The diversity of functional traits still has not been studied enough in model plant species, even less so in little-known species. This experiment was carried out under the extreme heat of Sonoran Desert, using shading nets and under conditions where the availability of water and nutrients was not a stress factor. We evaluated how the low, intermediate and high sunlight regimes impact survival and promote multiple alterations on phenological and ecophysiological response of cultivated Capsicum annuum var. glabriusculum plants. Extremely warm temperatures promoted a high heat sum in degrees days throughout plants development. Most plants grown in high sunlight regimes did not survive; under intermediate sunlight regimes survival was high and plants developed vegetative and reproductively; but under low sunlight regimes plants survival was high; however, they developed just vegetatively. Photosynthetic response to light suggests that plants are physiologically acclimated to low and intermediate irradiance, whereas the CO₂ assimilation curves suggest contrasting photosynthetic capacity traits. Under the intermediate sunlight regimes, plants strengthened their performance through multiple functional traits (e.g. CO₂ and water diffusion traits, photosynthetic capacity, respiration, among others). Consequently, their biomass gain was faster and proportionally higher by 76 % with an investment of 14 % in fruits development. The principal components analysis extracted the main explanatory functional traits: photosynthetic nitrogen allocation, stomatal limitation, mesophyll conductance, Rubisco maximum carboxylation velocity, among others. In conclusion, phenological response and multiple functional traits determine plants acclimation to sunlight regimes and extremely warm temperatures in short term.

Plastid genomes reveal evolutionary shifts in elevational range and flowering time of Osmanthus (Oleaceae)

Species of Osmanthus are economically important ornamental trees, yet information regarding their plastid genomes (plastomes) have rarely been reported, thus hindering taxonomic and evolutionary studies of this small but enigmatic genus. Here, we performed comparative genomics and evolutionary analyses on plastomes of 16 of the 28 currently accepted species, with 11 plastomes newly sequenced. Phylogenetic studies identified four main lineages within the genus that are here designated the: "Caucasian Osmanthus" (corresponding to O. decorus), "Siphosmanthus" (corresponding to O. sect. Siphosmanthus), "O. serrulatus + O. yunnanensis," and "Core Osmanthus: (corresponding to O. sect. Osmanthus + O. sect. Linocieroides). Molecular clock analysis suggested that Osmanthus split from its sister clade c. 15.83 Ma. The estimated crown ages of the lineages were the following: genus Osmanthus at 12.66 Ma; "Siphosmanthus" clade at 5.85 Ma; "O. serrulatus + O. yunnanensis" at 4.89 Ma; and "Core Osmanthus: clade at 6.2 Ma. Ancestral state reconstructions and trait mapping showed that ancestors of Osmanthus were spring flowering and originated at lower elevations. Phylogenetic principal component analysis clearly distinguished spring-flowering species from autumn-flowering species, suggesting that flowering time differentiation is related to the difference in ecological niches. Nucleotide substitution rates of 80 common genes showed slow evolutionary pace and low nucleotide variations, all genes being subjected to purifying selection.

MeadoWatch: a long-term community-science database of wildflower phenology in Mount Rainier National Park

We present a long-term and high-resolution phenological dataset from 17 wildflower species collected in Mt. Rainier National Park, as part of the MeadoWatch (MW) community science project. Since 2013, 457 unique volunteers and scientists have gathered data on the timing of four key reproductive phenophases (budding, flowering, fruiting, and seeding) in 28 plots over two elevational gradients alongside popular park trails. Trained volunteers (87.2%) and University of  Washington scientists (12.8%) collected data 3–9 times/week during the growing season, using a standardized method. Taxonomic assessments were highly consistent between scientists and volunteers, with high accuracy and specificity across phenophases and species. Sensitivity, on the other hand, was lower than accuracy and specificity, suggesting that a few species might be challenging to reliably identify in community-science projects. Up to date, the MW database includes 42,000+ individual phenological observations from 17 species, between 2013 and 2019. However, MW is a living dataset that will be updated through continued contributions by volunteers, and made available for its use by the wider ecological community.

Measurement(s)	Timing of four key reproductive phenophases of wildflowers
Technology Type(s)	Field observations

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.

Earlier snow melt and reduced summer precipitation alter floral traits important to pollination

Climate change can cause changes in expression of organismal traits that influence fitness. In flowering plants, floral traits can respond to drought, and that phenotypic plasticity has the potential to affect pollination and plant reproductive success. Global climate change is leading to earlier snow melt in snow-dominated ecosystems as well as affecting precipitation during the growing season, but the effects of snow melt timing on floral morphology and rewards remain unknown. We conducted crossed manipulations of spring snow melt timing (early vs. control) and summer monsoon precipitation (addition, control, and reduction) that mimicked recent natural variation, and examined plastic responses in floral traits of Ipomopsis aggregata over 3 years in the Rocky Mountains. We tested whether increased summer precipitation compensated for earlier snow melt, and if plasticity was associated with changes in soil moisture and/or leaf gas exchange. Lower summer precipitation decreased corolla length, style length, corolla width, sepal width, and nectar production, and increased nectar concentration. Earlier snow melt (taking into account natural and experimental variation) had the same effects on those traits and decreased inflorescence height. The effect of reduced summer precipitation was stronger in earlier snow melt years for corolla length and sepal width. Trait reductions were explained by drier soil during the flowering period, but this effect was only partially explained by how drier soils affected plant water stress, as measured by leaf gas exchange. We predicted the effects of plastic trait changes on pollinator visitation rates, pollination success, and seed production using prior studies on I. aggregata. The largest predicted effect of drier soil on relative fitness components via plasticity was a decrease in male fitness caused by reduced pollinator rewards (nectar production). Early snow melt and reduced precipitation are strong drivers of phenotypic plasticity, and both should be considered when predicting effects of climate change on plant traits in snow-dominated ecosystems.

Uncertainty, Complexity and Constraints: How Do We Robustly Assess Biological Responses under a Rapidly Changing Climate?

How robust is our assessment of impacts to ecosystems and species from a rapidly changing climate during the 21st century? We examine the challenges of uncertainty, complexity and constraints associated with applying climate projections to understanding future biological responses. This includes an evaluation of how to incorporate the uncertainty associated with different greenhouse gas emissions scenarios and climate models, and constraints of spatiotemporal scales and resolution of climate data into impact assessments. We describe the challenges of identifying relevant climate metrics for biological impact assessments and evaluate the usefulness and limitations of different methodologies of applying climate change to both quantitative and qualitative assessments. We discuss the importance of incorporating extreme climate events and their stochastic tendencies in assessing ecological impacts and transformation, and provide recommendations for better integration of complex climate–ecological interactions at relevant spatiotemporal scales. We further recognize the compounding nature of uncertainty when accounting for our limited understanding of the interactions between climate and biological processes. Given the inherent complexity in ecological processes and their interactions with climate, we recommend integrating quantitative modeling with expert elicitation from diverse disciplines and experiential understanding of recent climate-driven ecological processes to develop a more robust understanding of ecological responses under different scenarios of future climate change. Inherently complex interactions between climate and biological systems also provide an opportunity to develop wide-ranging strategies that resource managers can employ to prepare for the future.

Variation in seasonal timing traits and life history along a latitudinal transect in Mimulus ringens

Seasonal timing traits are commonly under recurrent, spatially variable selection, and are therefore predicted to exhibit clinal variation. Temperate perennial plants often require vernalization to prompt growth and reproduction; however, little is known about whether vernalization requirements change across the range of a broadly distributed species. We performed a critical vernalization duration study in Mimulus ringens, coupled with population genomic analysis. Plants from eight populations spanning the latitudinal range were exposed to varying durations of 4°C vernalization between 0 and 56 days, and flowering response was assessed. RADSeq was also performed to generate 1179 polymorphic SNPs, which were used to examine population structure. We found unexpected life history variation, with some populations lacking vernalization requirement. Population genomic analyses show that these life history variants are highly divergent from perennials, potentially revealing a cryptic species. For perennial populations, minimum vernalization time was surprisingly consistent. However, once vernalized, northern populations flowered almost 3 weeks faster than southern. Furthermore, southern populations exhibited sensitivity to vernalization times beyond flowering competency, suggesting an ability to respond adaptively to different lengths of winter. Mimulus ringens, therefore, reveals evidence of clinal variation, and provides opportunities for future studies addressing mechanistic and ecological hypotheses both within and between incipient species.

How phenological tracking shapes species and communities in non-stationary environments

Climate change alters the environments of all species. Predicting species responses requires understanding how species track environmental change, and how such tracking shapes communities. Growing empirical evidence suggests that how species track phenologically - how an organism shifts the timing of major biological events in response to the environment - is linked to species performance and community structure. Such research tantalizingly suggests a potential framework to predict the winners and losers of climate change, and the future communities we can expect. But developing this framework requires far greater efforts to ground empirical studies of phenological tracking in relevant ecological theory. Here we review the concept of phenological tracking in empirical studies and through the lens of coexistence theory to show why a community-level perspective is critical to accurate predictions with climate change. While much current theory for tracking ignores the importance of a multi-species context, basic community assembly theory predicts that competition will drive variation in tracking and trade-offs with other traits. We highlight how existing community assembly theory can help understand tracking in stationary and non-stationary systems. But major advances in predicting the species- and community-level consequences of climate change will require advances in theoretical and empirical studies. We outline a path forward built on greater efforts to integrate priority effects into modern coexistence theory, improved empirical estimates of multivariate environmental change, and clearly defined estimates of phenological tracking and its underlying environmental cues.

Chronic selection for early reproductive phenology in an annual plant across a steep, elevational gradient of growing season length

Colonization along ubiquitous gradients of growing season length should require adaptation of phenological traits, driven by natural selection. Although phenology often varies with season length and genetic differentiation in phenological traits sometimes seems adaptive, few studies test whether natural selection is responsible for these patterns. The annual plant Rhinanthus minor is genetically differentiated for phenology across a 1000-m elevational gradient of growing season length in the Canadian Rocky Mountains. We estimated phenotypic selection on five phenological traits for three generations of naturally occurring individuals at 12 sites (n = 10,112), and two generations of genetically and phenotypically more variable transplanted populations at nine of these sites (n = 24,611). Selection was weak for most traits, but consistently favored early flowering across the gradient rather than only under short seasons. There was no evidence that apparent selection favoring early reproduction arose from failure to consider all components of fitness, or variation in other correlated phenological traits. Instead, selection for earlier flowering may be balanced by selection for strong cogradient phenological plasticity that indirectly favors later flowering. However, this probably does not explain the consistency of selection on flowering time across this steep, elevational gradient of growing season length.

Genetic architecture and adaptation of flowering time among environments

The genetic basis of flowering time changes across environments, and pleiotropy may limit adaptive evolution of populations in response to local conditions. However, little information is known about how genetic architecture changes among environments. We used genome-wide association studies (GWAS) in Boechera stricta (Graham) Al-Shehbaz, a relative of Arabidopsis, to examine flowering variation among environments and associations with climate conditions in home environments. Also, we used molecular population genetics to search for evidence of historical natural selection. GWAS found 47 significant quantitative trait loci (QTLs) that influence flowering time in one or more environments, control plastic changes in phenology between experiments, or show associations with climate in sites of origin. Genetic architecture of flowering varied substantially among environments. We found that some pairs of QTLs showed similar patterns of pleiotropy across environments. A large-effect QTL showed molecular signatures of adaptive evolution and is associated with climate in home environments. The derived allele at this locus causes later flowering and predominates in sites with greater water availability. This work shows that GWAS of climate associations and ecologically important traits across diverse environments can be combined with molecular signatures of natural selection to elucidate ecological genetics of adaptive evolution.

Review: Plant eco-evolutionary responses to climate change: Emerging directions

Contemporary climate change is exposing plant populations to novel combinations of temperatures, drought stress, [CO₂] and other abiotic and biotic conditions. These changes are rapidly disrupting the evolutionary dynamics of plants. Despite the multifactorial nature of climate change, most studies typically manipulate only one climatic factor. In this opinion piece, we explore how climate change factors interact with each other and with biotic pressures to alter evolutionary processes. We evaluate the ramifications of climate change across life history stages,and examine how mating system variation influences population persistence under rapid environmental change. Furthermore, we discuss how spatial and temporal mismatches between plants and their mutualists and antagonists could affect adaptive responses to climate change. For example, plant-virus interactions vary from highly pathogenic to mildly facilitative, and are partly mediated by temperature, moisture availability and [CO₂]. Will host plants exposed to novel, stressful abiotic conditions be more susceptible to viral pathogens? Finally, we propose novel experimental approaches that could illuminate how plants will cope with unprecedented global change, such as resurrection studies combined with experimental evolution, genomics or epigenetics.

Bulbous perennials precisely detect the length of winter and adjust flowering dates

In order to identify the most relevant environmental parameters that regulate flowering time of bulbous perennials, first flowering dates of 329 taxa over 33 yr are correlated with monthly and daily mean values of 16 environmental parameters (such as insolation, precipitation, temperature, soil water content, etc.) spanning at least 1 yr back from flowering. A machine learning algorithm is deployed to identify the best explanatory parameters because the problem is strongly prone to overfitting for traditional methods: if the number of parameters is the same or greater than the number of observations, then a linear model can perfectly fit the dependent variable (observations). Surprisingly, the best proxy of flowering date fluctuations is the daily snow depth anomaly, which cannot be a signal itself, however it should be related to some integrated temperature signal. Moreover, daily snow depth anomaly as proxy performs much better than mean soil temperature preceding the flowering, the best monthly explanatory parameter. Our findings support the existence of complicated temperature sensing mechanisms operating on different timescales, which is a prerequisite to precisely observe the length and severity of the winter season and translate for example, 'lack of snow' information to meaningful internal signals related to phenophases.

Gene flow between diploid and tetraploid junipers - two contrasting evolutionary pathways in two Juniperus populations

BACKGROUND

Gene flow and polyploidy have been found to be important in Juniperus evolution. However, little evidence has been published elucidating the association of both phenomena in juniper taxa in the wild. Two main areas were studied in Spain (Eastern Iberian Range and Sierra de Baza) with both diploid and tetraploid taxa present in sympatry. Gene flow and ploidy level were assessed for these taxa and the resulted offspring.

RESULTS

Twenty-two allo-triploid hybrids between J. sabina var. sabina and J. thurifera were found in the Eastern Iberian Range population. However, in the Sierra de Baza population no triploids were found. Instead, 18 allo-tetraploid hybrids between two tetraploid taxa: J. sabina var. balkanensis and J. thurifera were discovered. High genetic diversity was exhibited among the tetraploid hybrids at Sierra de Baza, in contrast to the genetically identical triploid hybrids at the Eastern Iberian Range; this suggests meiotic difficulties within the triploid hybrids. In addition, unidirectional gene flow was observed in both studied areas.

CONCLUSION

Polyploidy and hybridization can be complementary partners in the evolution of Juniperus taxa in sympatric occurrences. Juniperus was shown to be an ideal coniferous model to study these two phenomena, independently or in concert.

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.

Phenological responses of temperate and boreal trees to warming depend on ambient spring temperatures, leaf habit, and geographic range

Changes in plant phenology associated with climate change have been observed globally. What is poorly known is whether and how phenological responses to climate warming will differ from year to year, season to season, habitat to habitat, or species to species. Here, we present 5 y of phenological responses to experimental warming for 10 subboreal tree species. Research took place in the open-air B4WarmED experiment in Minnesota. The design is a two habitat (understory and open) × three warming treatments (ambient, +1.7 °C, +3.4 °C) factorial at two sites. Phenology was measured twice weekly during the growing seasons of 2009 through 2013. We found significant interannual variation in the effect of warming and differences among species in response to warming that relate to geographic origin and plant functional group. Moreover, responses to experimental temperature variation were similar to responses to natural temperature variation. Warming advanced the date of budburst more in early compared to late springs, suggesting that to simulate interannual variability in climate sensitivity of phenology, models should employ process-based or continuous development approaches. Differences among species in timing of budburst were also greater in early compared to late springs. Our results suggest that climate change-which will make most springs relatively "early"-could lead to a future with more variable phenology among years and among species, with consequences including greater risk of inappropriately early leafing and altered interactions among species.

Low-cost observations and experiments return a high value in plant phenology research

Plant ecologists in the Anthropocene are tasked with documenting, interpreting, and predicting how plants respond to environmental change. Phenology, the timing of seasonal biological events including leaf-out, flowering, fruiting, and leaf senescence, is among the most visible and oft-recorded facets of plant ecology. Climate-driven shifts in plant phenology can alter reproductive success, interspecific competition, and trophic interactions. Low-cost phenology research, including observational records and experimental manipulations, is fundamental to our understanding of both the mechanisms and effects of phenological change in plant populations, species, and communities. Traditions of local-scale botanical phenology observations and data leveraged from written records and natural history collections provide the historical context for recent observations of changing phenologies. New technology facilitates expanding the spatial, taxonomic, and human interest in this research by combining contemporary field observations by researchers and open access community science (e.g., USA National Phenology Network) and available climate data. Established experimental techniques, such as twig cutting and common garden experiments, are low-cost methods for studying the mechanisms and drivers of plant phenology, enabling researchers to observe phenological responses under novel environmental conditions. We discuss the strengths, limitations, potential hidden costs (i.e., volunteer and student labor), and promise of each of these methods for addressing emerging questions in plant phenology research. Applied thoughtfully, economically, and creatively, many low-cost approaches offer novel opportunities to fill gaps in our geographic, taxonomic, and mechanistic understanding of plant phenology worldwide.

Small spaces, big impacts: contributions of micro-environmental variation to population persistence under climate change

Individuals within natural populations can experience very different abiotic and biotic conditions across small spatial scales owing to microtopography and other micro-environmental gradients. Ecological and evolutionary studies often ignore the effects of micro-environment on plant population and community dynamics. Here, we explore the extent to which fine-grained variation in abiotic and biotic conditions contributes to within-population variation in trait expression and genetic diversity in natural plant populations. Furthermore, we consider whether benign microhabitats could buffer local populations of some plant species from abiotic stresses imposed by rapid anthropogenic climate change. If microrefugia sustain local populations and communities in the short term, other eco-evolutionary processes, such as gene flow and adaptation, could enhance population stability in the longer term. We caution, however, that local populations may still decline in size as they contract into rare microhabitats and microrefugia. We encourage future research that explicitly examines the role of the micro-environment in maintaining genetic variation within local populations, favouring the evolution of phenotypic plasticity at local scales and enhancing population persistence under global change.

Native bees of high Andes of Central Chile (Hymenoptera: Apoidea): biodiversity, phenology and the description of a new species of Xeromelissa Cockerell (Hymenoptera: Colletidae: Xeromelissinae)

High-altitude ecosystems are found in mountain chains and plateaus worldwide. These areas tend to be underrepresented in insect biodiversity assessments because of the challenges related to systematic survey at these elevations, such as extreme climatic and geographic conditions. Nonetheless, high-altitude ecosystems are of paramount importance because they have been seen to be species pumps for other geographic areas, such as adjacent locations, functioning as buffers for population declines. Moreover, these ecosystems and their biodiversity have been proposed to be fast-responding indicators of the impacts caused by global climate change. Bees have been highlighted among the insect groups that have been affected by these problems. This work used bees as a proxy to demonstrate and reinforce the importance of systematic surveys of high-altitude ecosystems. Here, field collections were undertaken and an updated review was conducted for the native bee biodiversity of the high-altitude ecosystem found at the Andes system of central Chile, including the phenological trends of these insects during the flowering season. Of the 58 species that have been described for this location, we were able to confirm the occurrence of 46 of these species as a result of our sampling. In addition, thanks to these recent collections, a new species of Xeromelissa Cockerell is described in the present work. These findings highlight the need for further high-altitude insect surveys of this biome, which include both temporal and spatial complexity in their design, to allow for accurate assessment of bee species diversity and compositional changes in these mountain regions.

Microclimate predicts frost hardiness of alpine Arabidopsis thaliana populations better than elevation

In mountain regions, topological differences on the microscale can strongly affect microclimate and may counteract the average effects of elevation, such as decreasing temperatures. While these interactions are well understood, their effect on plant adaptation is understudied. We investigated winter frost hardiness of Arabidopsis thaliana accessions originating from 13 sites along altitudinal gradients in the Southern Alps during three winters on an experimental field station on the Swabian Jura and compared levels of frost damage with the observed number of frost days and the lowest temperature in eight collection sites. We found that frost hardiness increased with elevation in a log-linear fashion. This is consistent with adaptation to a higher frequency of frost conditions, but also indicates a decreasing rate of change in frost hardiness with increasing elevation. Moreover, the number of frost days measured with temperature loggers at the collection sites correlated much better with frost hardiness than the elevation of collection sites, suggesting that populations were adapted to their local microclimate. Notably, the variance in frost days across sites increased exponentially with elevation. Together, our results suggest that strong microclimate heterogeneity of high alpine environments can preserve functional genetic diversity among small populations. Synthesis: Here, we tested how plant populations differed in their adaptation to frost exposure along an elevation gradient and whether microsite temperatures improve the prediction of frost hardiness. We found that local temperatures, particularly the number of frost days, are a better predictor of the frost hardiness of plants than elevation. This reflects a substantial variance in frost frequency between sites at similar high elevations. We conclude that high mountain regions harbor microsites that differ in their local microclimate and thereby can preserve a high functional genetic diversity among them. Therefore, high mountain regions have the potential to function as a refugium in times of global change.

Environmental heterogeneity generates intrapopulation variation in life-history traits in an annual plant

Environmental variation affects a plant's life cycle by influencing the timing of germination and flowering, and the duration of the growing season. Yet we know little information about how environmental heterogeneity generates variation in germination schedules and the consequences for growth and fecundity through genetic and plastic responses. We use an annual population of Mimulus guttatus in which, in nature, seeds germinate in both fall and spring. We investigate whether there is a genetic basis to the timing of germination, the effect of germination timing on fecundity, and if growth and flowering respond plastically to compensate for different season lengths. Using sibling families grown in simulated seasonal conditions, we find that families do not differ in their propensity to germinate between seasons. However, the germination season affects subsequent growth and flowering time, with significant genotype-by-environment interactions (G × E). Most G × E is due to unequal variance between seasons, because the spring cohort harbours little genetic variance. Despite their different season lengths, the cohorts do not differ in flower number (fecundity). Heterogeneous environments with unpredictable risks may maintain promiscuous germination, which then affects flowering time. Therefore, if selection at particular life stages changes with climate change, there may be consequences for the entire life cycle.

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.

Climate change shifts natural selection and the adaptive potential of the perennial forb Boechera stricta in the Rocky Mountains

Heritable genetic variation is necessary for populations to evolve in response to anthropogenic climate change. However, antagonistic genetic correlations among traits may constrain the rate of adaptation, even if substantial genetic variation exists. We examine potential genetic responses to selection by comparing multivariate genetic variance-covariances of traits and fitness (multivariate Robertson-Price identities) across different environments in a reciprocal transplant experiment of the forb Boechera stricta in the Rocky Mountains. By transplanting populations into four common gardens arrayed along an elevational gradient, and exposing populations to control and snow removal treatments, we simulated future and current climates and snowmelt regimes. Genetic variation in flowering and germination phenology declined in plants moved downslope to warmer, drier sites, suggesting that these traits may have a limited ability to evolve under future climates. Simulated climate change via snow removal altered the strength of selection on flowering traits, but we found little evidence that genetic correlations among traits are likely to affect the rate of adaptation to climate change. Overall, our results suggest that climate change may alter the evolutionary potential of B. stricta, but reduced expression of genetic variation may be a larger impediment to adaptation than constraints imposed by antagonistic genetic correlations.

Pleiotropy in developmental regulation by flowering-pathway genes: is it an evolutionary constraint?

Pleiotropy occurs when one gene influences more than one trait, contributing to genetic correlations among traits. Consequently, it is considered a constraint on the evolution of adaptive phenotypes because of potential antagonistic selection on correlated traits, or, alternatively, preservation of functional trait combinations. Such evolutionary constraints may be mitigated by the evolution of different functions of pleiotropic genes in their regulation of different traits. Arabidopsis thaliana flowering-time genes, and the pathways in which they operate, are among the most thoroughly studied regarding molecular functions, phenotypic effects, and adaptive significance. Many of them show strong pleiotropic effects. Here, we review examples of pleiotropy of flowering-time genes and highlight those that also influence seed germination. Some genes appear to operate in the same genetic pathways when regulating both traits, whereas others show diversity of function in their regulation, either interacting with the same genetic partners but in different ways or potentially interacting with different partners. We discuss how functional diversification of pleiotropic genes in the regulation of different traits across the life cycle may mitigate evolutionary constraints of pleiotropy, permitting traits to respond more independently to environmental cues, and how it may even contribute to the evolutionary divergence of gene function across taxa.