No effect of elevation and fragmentation on genetic diversity and structure in Polylepis australis trees from central Argentina

Phenological differences in flowering arising along elevational gradients may be caused by either local adaptation or phenotypic plasticity. Local adaptation can lead to reproductive isolation of populations at different elevational zones and thus produce elevational genetic structuring, while phenotypic plasticity does not produce elevational genetic structuring. In this study, we examined the effects of elevation and fragmentation on genetic diversity and structure of Polylepis australis populations, where individuals exhibit phenological differences in flowering along an elevational gradient. We assessed the polymorphism of amplified fragment length polymorphism markers in adults and saplings from one conserved and one fragmented forest covering elevations from 1600 to 2600 m asl. Over 98% of variation was found within populations, and we found very low and similar genetic differentiation along elevational gradients for adults and saplings in both continuous and fragmented forests. In addition, there was no significant relationship between genetic diversity and elevation. Results indicated that phenological differences along elevational gradients are more likely caused by phenotypic plasticity than local adaptation, and fragmentation does not appear to have affected genetic diversity and differentiation in the studied populations. Results therefore imply that if necessary, seeds for reforestation purposes may be collected from different elevations to the seeding or planting sites.     

Plasticity in functional traits in the context of climate change: a case study of the subalpine forb Boechera stricta (Brassicaceae)

Environmental variation often induces shifts in functional traits, yet we know little about whether plasticity will reduce extinction risks under climate change. As climate change proceeds, phenotypic plasticity could enable species with limited dispersal capacity to persist in situ, and migrating populations of other species to establish in new sites at higher elevations or latitudes. Alternatively, climate change could induce maladaptive plasticity, reducing fitness, and potentially stalling adaptation and migration. Here, we quantified plasticity in life history, foliar morphology, and ecophysiology in Boechera stricta (Brassicaceae), a perennial forb native to the Rocky Mountains. In this region, warming winters are reducing snowpack and warming springs are advancing the timing of snow melt. We hypothesized that traits that were historically advantageous in hot and dry, low‐elevation locations will be favored at higher elevation sites due to climate change. To test this hypothesis, we quantified trait variation in natural populations across an elevational gradient. We then estimated plasticity and genetic variation in common gardens at two elevations. Finally, we tested whether climatic manipulations induce plasticity, with the prediction that plants exposed to early snow removal would resemble individuals from lower elevation populations. In natural populations, foliar morphology and ecophysiology varied with elevation in the predicted directions. In the common gardens, trait plasticity was generally concordant with phenotypic clines from the natural populations. Experimental snow removal advanced flowering phenology by 7 days, which is similar in magnitude to flowering time shifts over 2–3 decades of climate change. Therefore, snow manipulations in this system can be used to predict eco‐evolutionary responses to global change. Snow removal also altered foliar morphology, but in unexpected ways. Extensive plasticity could buffer against immediate fitness declines due to changing climates.     

Distribution of bulbil- and seed-producing plants of Poa alpina (Poaceae) and their growth and reproduction in common gardens suggest adaptation to different elevations

• Premise of the study: The European Alps harbor a spatially heterogeneous environment. Plants can be adapted genetically to this heterogeneity but may also respond to it by phenotypic plasticity. We expected the important fodder grass Poa alpina to be adapted to elevation either genetically or plastically. • Methods: We investigated in three elevational common gardens whether growth and reproductive allocation of plants reproducing either by seeds or bulbils suggest adaptation to their elevation of origin and to what extent they can respond plastically to different elevations. Additionally, we analyzed genetic diversity using microsatellites and tested whether seeds are of sexual origin. • Key results: In the field, bulbil-producing plants occurred more often at higher elevations, whereas seed-producing plants occurred more often at lower elevations, but bulbil-producing plants were generally less vigorous in the common gardens. The response of plants to elevational transplantation was highly plastic, and vigor was always best at the highest location. The small genetic differences were not clinally related to elevation of origin, underlining the importance of phenotypic plasticity. Reproductive allocation was, however, independent of elevational treatments. Seed-producing plants had higher genetic diversity than the bulbil-producing plants even though we found that seed-producing plants were facultative apomicts mostly reproducing asexually. • Conclusions: Bulbil-producing P. alpina, showing a fitness cost at lower elevations compared with seed-producing plants, seem better adapted to higher elevations. By means of its two reproductive modes and the capacity to adjust plastically, P. alpina is able to occupy a broad ecological niche across a large elevational range.     

Intraspecific trait variation across elevation predicts a widespread tree species' climate niche and range limits

Global change is widely altering environmental conditions which makes accurately predicting species range limits across natural landscapes critical for conservation and management decisions. If climate pressures along elevation gradients influence the distribution of phenotypic and genetic variation of plant functional traits, then such trait variation may be informative of the selective mechanisms and adaptations that help define climatic niche limits. Using extensive field surveys along 16 elevation transects and a large common garden experiment, we tested whether functional trait variation could predict the climatic niche of a widespread tree species (Populus angustifolia) with a double quantile regression approach. We show that intraspecific variation in plant size, growth, and leaf morphology corresponds with the species' total climate range and certain climatic limits related to temperature and moisture extremes. Moreover, we find evidence of genetic clines and phenotypic plasticity at environmental boundaries, which we use to create geographic predictions of trait variation and maximum values due to climatic constraints across the western US. Overall, our findings show the utility of double quantile regressions for connecting species distributions and climate gradients through trait‐based mechanisms. We highlight how new approaches like ours that incorporate genetic variation in functional traits and their response to climate gradients will lead to a better understanding of plant distributions as well as identifying populations anticipated to be maladapted to future environments.     

Local adaptation to distinct elevational cores contributes to current elevational divergence of two Aquilegia vulgaris subspecies

Aims Phenotypic plasticity and local adaptation of populations at their distributional limits are crucial to understand species colonization and persistence in novel or marginal environments, as well as species divergence and niche width evolution. We assess the contribution of these processes to shape current elevational limits and determine elevational phenotypic divergence between two subspecies of Aquilegia vulgaris (subsp. vulgaris and nevadensis).Methods We conducted sowing and transplant experiments considering four elevations throughout the current elevational range of A. vulgaris in southern Iberian Peninsula. Experiments were designed to explore, on the one hand, local adaptation through three components of performance (germination, survival and growth) and, on the other hand, the phenotypic differentiation and/or plasticity associated to local adaptation. Four populations per subspecies (three from the elevational core and one from the elevational boundary) were used as seed sources. Patterns of local adaptation and phenotypic differentiation are examined in the context of the 'centre-periphery' hypothesis.Important findings Central populations of both subspecies performed better at their local elevations while marginal populations were maladapted, confirming the hypothesis and contributing to explain the current elevational segregation of these subspecies. Density of glandular pubescence and germination timing seem to be related to local adaptation, through phenotypic differentiation between subspecies or elevations. The widespread subsp. vulgaris showed signals of adaptive plasticity in the timing of germination while it was not the case in the endemic subsp. nevadensis .     

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient‐poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient‐poor grassland species.     

Contrasting patterns of genetic variation and structure in plant invasions of mountains

Aim To assess the population genetic consequences of the colonization of two species with contrasting mating systems, Solidago canadensis and Lactuca serriola, along altitudinal gradients in both their native and introduced ranges. Location Allegheny Mountains, West Virginia and Wallowa Mountains, Oregon, USA; Valais, southern Switzerland. Methods Leaf material was collected from populations along altitudinal gradients and genotyped at seven microsatellite loci for each species. Differences in variability between native and introduced areas and in relation to altitude were analysed using linear models. Differences in the genetic, geographical and altitudinal structure of populations between areas were analysed by AMOVA, cluster analysis and Mantel tests. Results Genetic variation within and across populations of S. canadensis was significantly reduced, while populations of L. serriola were significantly more variable, in the introduced area. Genetic diversity decreased significantly with altitude for S. canadensis but not L. serriola. Genetic structure of S. canadensis was similar in both areas, and populations were isolated by geographical but not altitudinal distance. By contrast, population structure of L. serriola was much weaker in the introduced area, and populations were not isolated by distance in either area. Main conclusions Solidago canadensis has experienced a strong genetic bottleneck on introduction to the Valais, but this has not prevented it from colonizing a wide altitudinal range. Variation in neutral markers is therefore not necessarily a good measure for judging the ecological behaviour of a species. By contrast, the greater variability of L. serriola in the introduced area, where it also occurs over a greater altitudinal range, can be explained by increased outcrossing among admixed populations. This suggests that the ecological amplitude of alien species might be enhanced after population admixture in the new range, especially for species with highly structured native populations. However, even genetically depauperate introduced populations can be expected to colonize the same environmental range that they occupy in the native area.     

Standing variation boosted by multiple sources of introduction contributes to the success of the introduced species, Lotus corniculatus

Although ecological differences between native and introduced ranges have been considered to drive rapid expansion of invasive species, recent studies suggest that rapid evolutionary responses of invasive species to local environments may also be common. Such expansion across heterogeneous environments by adaptation to local habitats requires genetic variation. In this study, we investigated the source and role of standing variation in successful invasion of heterogeneous abiotic environments in a self-incompatible species, Lotus corniculatus. We compared phenotypic and genetic variation among cultivars, natives, and introduced genotypes, and found substantial genetic variation within both native and introduced populations. Introduced populations possessed genotypes derived from both cultivars and native populations, and had lower population differentiation, indicating multiple sources of introduction and population admixture among the sources in the introduced range. Both cultivars and introduced populations had similarly outperforming phenotypes on average, with increased biomass and earlier flowering compared with native populations, but those phenotypes were within the range of the variation in phenotypes of the native populations. In addition, clinal variation within introduced populations was detected along a climatic gradient. Multiple introductions from different sources, including cultivars, may have contributed to pre-adaptive standing variation in the current introduced populations. We conclude that both introduction of cultivar genotypes and natural selection in local environments contributed to current patterns of genetic and phenotypic variation observed in the introduced populations.     

Staying in situ or shifting range under ongoing climate change: A case of an endemic herb in the Himalaya-Hengduan Mountains across elevational gradients

Aim

How species respond to ongoing climate change has been a hot research topic, especially with the controversy in shifting range (movement) or persisting in local habitat (in situ) as the primary response. Assessing the relative roles of range shifts, phenotypic plasticity and genetic adaptation helps us predict the evolutionary fate of species. We aim to explore the evolutionary strategies of plants under climate change from a keystone herb in alpine ecosystems, Mirabilis himalaica, along its elevational gradient.

Location

Himalaya-Hengduan Mountains, China.

Methods

We combined evidence from population genomics and ecological data in both space and time to investigate the state of “staying” or “moving”. We identified migration events by assessing historical and contemporary gene flow and changes in species distribution. Morphological variation was compared by measuring five traits using specimen data. Moreover, we explored climate-driven genetic variation and local selection regimes acting on populations in the alpine landscape along an elevational gradient.

Results

Our results argue that staying in situ by morphological variation and local genetic evolution rather than range shifting plays an important role in M. himalaica response to climate change. We first found trace evidence of upward or climatic-driven shifting along an elevational gradient, although asymmetric gene flow was restricted within microenvironments of mid-elevational populations. Furthermore, morphological variation comparisons revealed clinal variation, as resource allocation showed a declining pattern in vegetative growth but increased reproductive growth with increasing elevation. Outlier tests and environment association analyses indicated adaptative loci primarily related to thermal-driven selection and continuous adaptations to high elevation in the Himalaya-Hengduan Mountains.

Main Conclusions

Our findings show M. himalaica may persist in local habitats rather than shifting range under climate change, exhibiting a low risk of genomic vulnerability in current habitats. This study has important implications in improving our understanding of the evolutionary response in alpine plants to climate change.     

The quantitative genetic basis of clinal divergence in phenotypic plasticity

Phenotypic plasticity is thought to be an important mechanism for adapting to environmental heterogeneity. Nonetheless, the genetic basis of plasticity is still not well understood. In Drosophila melanogaster and D. simulans, body size and thermal stress resistance show clinal patterns along the east coast of Australia, and exhibit plastic responses to different developmental temperatures. The genetic basis of thermal plasticity, and whether the genetic effects underlying clinal variation in traits and their plasticity are similar, remains unknown. Here, we use line‐cross analyses between a tropical and temperate population of Drosophila melanogaster and D. simulans developed at three constant temperatures (18°C, 25°C, and 29°C) to investigate the quantitative genetic basis of clinal divergence in mean thermal response (elevation) and plasticity (slope and curvature) for thermal stress and body size traits. Generally, the genetic effects underlying divergence in mean response and plasticity differed, suggesting that different genetic models may be required to understand the evolution of trait means and plasticity. Furthermore, our results suggest that nonadditive genetic effects, in particular epistasis, may commonly underlie plastic responses, indicating that current models that ignore epistasis may be insufficient to understand and predict evolutionary responses to environmental change.     

Phenotypic differentiation of the Solidago virgaurea complex along an elevational gradient: Insights from a common garden experiment and population genetics

Plant species distributed along wide elevational or latitudinal gradients show phenotypic variation due to their heterogeneous habitats. This study investigated whether phenotypic variation in populations of the Solidago virgaurea complex along an elevational gradient is caused by genetic differentiation. A common garden experiment was based on seeds collected from nine populations of the S. virgaurea complex growing at elevations from 1,597 m to 2,779 m a.s.l. on Mt. Norikura in central Japan. Population genetic analyses with microsatellite markers were used to infer the genetic structure and levels of gene flow between populations. Leaf mass per area was lower, while leaf nitrogen and chlorophyll concentrations were greater for higher elevations at which seeds were originally collected. For reproductive traits, plants derived from higher elevations had larger flower heads on shorter stems and flowering started earlier. These elevational changes in morphology were consistent with the clines in the field, indicating that phenotypic variation along the elevational gradient would have been caused by genetic differentiation. However, population genetic analysis using 16 microsatellite loci suggested an extremely low level of genetic differentiation of neutral genes among the nine populations. Analysis of molecular variance also indicated that most genetic variation was partitioned into individuals within a population, and the genetic differentiation among the populations was not significant. This study suggests that genome regions responsible for adaptive traits may differ among the populations despite the existence of gene flow and that phenotypic variation of the S. virgaurea complex along the elevational gradient is maintained by strong selection pressure.     

Distance,elevation and environment as drivers of diversity and divergence in bumble bees across latitude and altitude

Identifying drivers of dispersal limitation and genetic differentiation is a key goal in biogeography. We examine patterns of population connectivity and genetic diversity using restriction site‐associated DNA sequencing (RADseq) in two bumble bee species, Bombus vosnesenskii and Bombus bifarius, across latitude and altitude in mountain ranges from California, Oregon and Washington, U.S.A. Bombus vosnesenskii, which occurs across a broader elevational range at most latitudes, exhibits little population structure while B. bifarius, which occupies a relatively narrow higher elevation niche across most latitudes, exhibits much stronger population differentiation, although gene flow in both species is best explained by isolation with environmental niche resistance. A relationship between elevational habitat breadth and genetic diversity is also apparent, with B. vosnesenskii exhibiting relatively consistent levels of genetic diversity across its range, while B. bifarius has reduced genetic diversity at low latitudes, where it is restricted to high‐elevation habitat. The results of this study highlight the importance of the intersect between elevational range and habitat suitability in influencing population connectivity and suggest that future climate warming will have a fragmenting effect even on populations that are presently well connected, as they track their thermal niches upward in montane systems.     

Rapid evolution in response to introduced predators II: the contribution of adaptive plasticity

Background  

Introductions of non-native species can significantly alter the selective environment for populations of native species, which can respond through phenotypic plasticity or genetic adaptation. We examined phenotypic and genetic responses of Daphnia populations to recent introductions of non-native fish to assess the relative roles of phenotypic plasticity versus genetic change in causing the observed patterns. The Daphnia community in alpine lakes throughout the Sierra Nevada of California (USA) is ideally suited for investigation of rapid adaptive evolution because there are multiple lakes with and without introduced fish predators. We conducted common-garden experiments involving presence or absence of chemical cues produced by fish and measured morphological and life-history traits in Daphnia melanica populations collected from lakes with contrasting fish stocking histories. The experiment allowed us to assess the degree of population differentiation due to fish predation and examine the contribution of adaptive plasticity in the response to predator introduction.     

Contrasting plant physiological adaptation to climate in the native and introduced range of Hypericum perforatum

How introduced plants, which may be locally adapted to specific climatic conditions in their native range, cope with the new abiotic conditions that they encounter as exotics is not well understood. In particular, it is unclear what role plasticity versus adaptive evolution plays in enabling exotics to persist under new environmental circumstances in the introduced range. We determined the extent to which native and introduced populations of St. John's Wort (Hypericum perforatum) are genetically differentiated with respect to leaf-level morphological and physiological traits that allow plants to tolerate different climatic conditions. In common gardens in Washington and Spain, and in a greenhouse, we examined clinal variation in percent leaf nitrogen and carbon, leaf delta(13)C values (as an integrative measure of water use efficiency), specific leaf area (SLA), root and shoot biomass, root/shoot ratio, total leaf area, and leaf area ratio (LAR). As well, we determined whether native European H. perforatum experienced directional selection on leaf-level traits in the introduced range and we compared, across gardens, levels of plasticity in these traits. In field gardens in both Washington and Spain, native populations formed latitudinal clines in percent leaf N. In the greenhouse, native populations formed latitudinal clines in root and shoot biomass and total leaf area, and in the Washington garden only, native populations also exhibited latitudinal clines in percent leaf C and leaf delta(13)C. Traits that failed to show consistent latitudinal clines instead exhibited significant phenotypic plasticity. Introduced St. John's Wort populations also formed significant or marginally significant latitudinal clines in percent leaf N in Washington and Spain, percent leaf C in Washington, and in root biomass and total leaf area in the greenhouse. In the Washington common garden, there was strong directional selection among European populations for higher percent leaf N and leaf delta(13)C, but no selection on any other measured trait. The presence of convergent, genetically based latitudinal clines between native and introduced H. perforatum, together with previously published molecular data, suggest that native and exotic genotypes have independently adapted to a broad-scale variation in climate that varies with latitude.     

Positive and negative biotic interactions and invasive Triadica sebifera tolerance to salinity: a cross‐continent comparative study

Exotic plant species may exhibit abiotic niche expansions that enable them to persist in a greater variety of habitat types in their introduced ranges than in their native ranges. This may reflect variation in limitation by different abiotic niche dimensions (realized niche shift) or phenotypic effects of biotic interactions that vary among ranges (realized niche expansion). Novel abiotic and biotic environments in the introduced range may also lead to genetic changes in exotic plant traits that enhance their abiotic stress tolerance (fundamental niche expansion). Here, we investigated how biotic interactions (aboveground herbivory and soil organisms) affect plant salinity tolerance using the invasive species Triadica sebifera from China (native range) and US (introduced range) populations grown in common gardens in both ranges. Simulated herbivory significantly reduced survival in saline treatments with reductions especially large at low salinity. Soil sterilization had a negative effect on survival at low salinity in China but had a positive effect on survival at low salinity in the US. Triadica survival and biomass were higher for US populations than for China populations, particularly in China but salinity tolerance did not depend on population origin. On average, arbuscular mycorrhizal (AM) colonization was higher for US populations, US soils and low salinity. These factors had a significant, positive, non‐additive interaction so that clipped seedlings from US populations in low saline US soils had high levels of AM colonization. Overall, our results show that phenotypic biotic interactions shape Triadica's salinity tolerance. Positive and negative biotic interactions together affected plant performance at intermediate stress levels. However, only aboveground damage consistently affected salinity tolerance, suggesting an important role for enemy release in expanding stress tolerance.     

Divergent selection along elevational gradients promotes genetic and phenotypic disparities among small mammal populations

Species distributed along mountain slopes, facing contrasting habitats in short geographic scale, are of particular interest to test how ecologically based divergent selection promotes phenotypic and genetic disparities as well as to assess isolation‐by‐environment mechanisms. Here, we conduct the first broad comparative study of phenotypic variation along elevational gradients, integrating a large array of ecological predictors and disentangling population genetic driver processes. The skull form of nine ecologically distinct species distributed over a large altitudinal range (100–4200 m) was compared to assess whether phenotypic divergence is a common phenomenon in small mammals and whether it shows parallel patterns. We also investigated the relative contribution of biotic (competition and predation) and abiotic parameters on phenotypic divergence via mixed models. Finally, we assessed the population genetic structure of a rodent species (Niviventer confucianus) via analysis of molecular variance and F_ST along three mountain slopes and tested the isolation‐by‐environment hypothesis using Mantel test and redundancy analysis. We found a consistent phenotypic divergence and marked genetic structure along elevational gradients; however, the species showed mixed patterns of size and skull shape trends across mountain zones. Individuals living at lower altitudes differed greatly in both phenotype and genotype from those living at high elevations, while middle‐elevation individuals showed more intermediate forms. The ecological parameters associated with phenotypic divergence along elevation gradients are partly related to species' ecological and evolutionary constraints. Fossorial and solitary animals are mainly affected by climatic factors, while terrestrial and more gregarious species are influenced by biotic and abiotic parameters. A novel finding of our study is that predator richness emerged as an important factor associated with the intraspecific diversification of the mammalian skull along elevational gradients, a previously overlooked parameter. Population genetic structure was mainly driven by environmental heterogeneity along mountain slopes, with no or a week spatial effect, fitting the isolation‐by‐environment scenario. Our study highlights the strong and multifaceted effects of heterogeneous steep habitats and ecologically based divergent selective forces in small mammal populations.     

Evolution of dispersal traits along an invasion route in the wind‐dispersed Senecio inaequidens (Asteraceae)

In introduced organisms, dispersal propensity is expected to increase during range expansion. This prediction is based on the assumption that phenotypic plasticity is low compared to genetic diversity, and an increase in dispersal can be counteracted by the Allee effect. Empirical evidence in support of these hypotheses is however lacking. The present study tested for evidence of differentiation in dispersal‐related traits and the Allee effect in the wind‐dispersed invasive Senecio inaequidens (Asteraceae). We collected capitula from individuals in ten field populations, along an invasion route including the original introduction site in southern France. In addition, we conducted a common garden experiment from field‐collected seeds and obtained capitula from individuals representing the same ten field populations. We analysed phenotypic variation in dispersal traits between field and common garden environments as a function of the distance between populations and the introduction site. Our results revealed low levels of phenotypic differentiation among populations. However, significant clinal variation in dispersal traits was demonstrated in common garden plants representing the invasion route. In field populations, similar trends in dispersal‐related traits and evidence of an Allee effect were not detected. In part, our results supported expectations of increased dispersal capacity with range expansion, and emphasized the contribution of phenotypic plasticity under natural conditions.     

Pre-adaptation or genetic shift after introduction in the invasive species Impatiens glandulifera?

Invasive exotic plants often grow fast, reproduce rapidly and display considerable phenotypic plasticity in their invasive range, which may be essential characteristics for successful invasion. However, it remains unclear whether these characteristics are already present in native populations (pre-adaptation hypothesis) or evolve after introduction (genetic shift hypothesis).To test these hypotheses we compared means and phenotypic plasticity of vegetative and reproductive traits between populations of Impatiens glandulifera collected from either the invasive (Norway) or native range (India). Seeds were sown and the resulting plants were exposed to different experimental environments in a glasshouse. We also tested whether trait means and reaction norms harbored genetic variation, as this may promote fitness in the novel environment.We did not find evidence that invasive populations of I. glandulifera grew more vigorously or produced more seeds than native populations. Phenotypic plasticity did not differ between the native and invasive range, except for the number of nodes which was more plastic in the invasive range. Genetic variation in the slope of reaction norms was absent, suggesting that the lack of change in phenotypic plasticity between native and invasive populations resulted from low genetic variation in phenotypic plasticity initially harbored by this species. Post-introduction evolution of traits thus probably did not boost the invasiveness of I. glandulifera. Instead, the species seems to be pre-adapted for invasion.We suggest that differences in habitat between the native and invasive range, more specifically the higher nutrient availability observed in the new environment, are the main factor driving the invasion of this species. Indeed, plants in the more nutrient-rich invasive range had greater seed mass, likely conferring a competitive advantage, while seed mass also responded strongly to nutrients in the glasshouse. Interactions between habitat productivity and herbivore defense may explain the lack of more vigorous growth in the new range.     

Native jewelweed,but not other native species,displays post‐invasion trait divergence

Invasive exotic plants reduce the diversity of native communities by displacing native species. According to the coexistence theory, native plants are able to coexist with invaders only when their fitness is not significantly smaller than that of the exotics or when they occupy a different niche. It has therefore been hypothesized that the survival of some native species at invaded sites is due to post‐invasion evolutionary changes in fitness and/or niche traits. In common garden experiments, we tested whether plants from invaded sites of two native species, Impatiens noli‐tangere and Galeopsis speciosa, outperform conspecifics from non‐invaded sites when grown in competition with the invader (Impatiens parviflora). We further examined whether the expected superior performance of the plants from the invaded sites is due to changes in the plant size (fitness proxy) and/or changes in the germination phenology and phenotypic plasticity (niche proxies). Invasion history did not influence the performance of any native species when grown with the exotic competitor. In I. noli‐tangere, however, we found significant trait divergence with regard to plant size, germination phenology and phenotypic plasticity. In the absence of a competitor, plants of I. noli‐tangere from invaded sites were larger than plants from non‐invaded sites. The former plants germinated earlier than inexperienced conspecifics or an exotic congener. Invasion experience was also associated with increased phenotypic plasticity and an improved shade‐avoidance syndrome. Although these changes indicate fitness and niche differentiation of I. noli‐tangere at invaded sites, future research should examine more closely the adaptive value of these changes and their genetic basis.     

Rapid differentiation of plasticity in life history and morphology during invasive range expansion and concurrent local adaptation in the horned beetle Onthophagus taurus

Understanding the interplay between genetic differentiation, ancestral plasticity, and the evolution of plasticity during adaptation to environmental variation is critical to predict populations’ responses to environmental change. However, the role of plasticity in rapid adaptation in nature remains poorly understood. We here use the invasion of the horned beetle Onthophagus taurus in the United States during the last half century to study the contribution of ancestral plasticity and post-invasion evolution of plastic responses in rapid population differentiation. We document latitudinal variation in life history and morphology, including genetic compensation in development time and body size, likely adaptive responses to seasonal constraints in the North. However, clinal variation in development time and size was strongly dependent on rearing temperature, suggesting that population differentiation in plasticity played a critical role in successful adaptation on ecological timescales. Clinal variation in wing shape was independent of ancestral plasticity, but correlated with derived plasticity, consistent with evolutionary interdependence. In contrast, clinal variation in tibia shape aligned poorly with thermal plasticity. Overall, this study suggests that post-invasion evolution of plasticity contributed to range expansions and concurrent adaptation to novel climatic conditions.