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To avoid reaching lethal temperatures during periods of heat stress, plants may acclimate either their biochemical thermal tolerance or leaf morphological and physiological characteristics to reduce leaf temperature (Tleaf). While plants from warmer environments may have a greater capacity to regulate Tleaf, the extent of intraspecific variation and contribution of provenance is relatively unexplored. We tested whether upland and lowland provenances of four tropical tree species grown in a common garden differed in their thermal safety margins by measuring leaf thermal traits, midday leaf‐to‐air temperature differences (∆Tleaf) and critical leaf temperatures defined by chlorophyll fluorescence (Tcrit). Provenance variation was species‐ and trait‐specific. Higher ∆Tleaf and Tcrit were observed in the lowland provenance for Terminalia microcarpa, and in the upland provenance for Castanospermum australe, with no provenance effects in the other two species. Within‐species covariation of Tcrit and ∆Tleaf led to a convergence of thermal safety margins across provenances. While future studies should expand the number of provenances and species investigated, our findings suggest that lowland and upland provenances may not differ substantially in their vulnerability to heat stress, as determined by thermal safety margins, despite differences in operating temperatures and Tcrit. Summary statement: Plant populations originating from warmer environments could have adaptive variation to cope with heat stress. We found evidence of ecotypic variation in heat tolerance and thermoregulation in tropical rainforest trees. However, this did not translate to differences in thermal safety margins. [ABSTRACT FROM AUTHOR]

The ecological significance of Scots pine (Pinus sylvestris L.) in Europe, especially in areas devastated by bark beetles, has led to its consideration as a substitute for Norway spruce. This pioneering species boasts sun and drought tolerance, fast growth, and wood industry value. To gauge its potential, we examined two ecotypes across two test sites over two years, focusing on height and growth increment. Through statistical analysis employing R software and linear mixed models, we assessed heritability, genotype by environment interaction, and spatial correlations. Both ecotypes exhibited significant differences in height and increment, varying by year and site. Heritability was higher in the second year, with increment showing greater stability. Genetic correlations between sites were evident, suggesting stable increment ranking across locations. These findings underscore the role of ecotypic variation in Scots pine growth, advocating for its consideration in reforestation. Acknowledging such dynamics is vital for effective forest management and reforestation in Central Europe, promoting sustainability and informed decision-making. Further research will enhance this understanding of preserving and enhancing the region's tree populations.

ABSTRACT Due to climate change, drought frequencies and severities are predicted to increase across the United States. Plant responses and adaptation to stresses depend on plant genetic and environmental factors. Understanding the effect of those factors on plant performance is required to predict species’ responses to environmental change. We used reciprocal gardens planted with distinct regional ecotypes of the perennial grass Andropogon gerardii adapted to dry, mesic, and wet environments to characterize their rhizosphere communities using 16S rRNA metabarcode sequencing. Even though the local microbial pool was the main driver of these rhizosphere communities, the significant plant ecotypic effect highlighted active microbial recruitment in the rhizosphere, driven by ecotype or plant genetic background. Our data also suggest that ecotypes planted at their homesites were more successful in recruiting rhizosphere community members that were unique to the location. The link between the plants’ homesite and the specific local microbes supported the “home field advantage” hypothesis. The unique homesite microbes may represent microbial specialists that are linked to plant stress responses. Furthermore, our data support ecotypic variation in the recruitment of congeneric but distinct bacterial variants, highlighting the nuanced plant ecotype effects on rhizosphere microbiome recruitment. These results improve our understanding of the complex plant host–soil microbe interactions and should facilitate further studies focused on exploring the functional potential of recruited microbes. Our study has the potential to aid in predicting grassland ecosystem responses to climate change and impact restoration management practices to promote grassland sustainability. IMPORTANCE In this study, we used reciprocal gardens located across a steep precipitation gradient to characterize rhizosphere communities of distinct dry, mesic, and wet regional ecotypes of the perennial grass Andropogon gerardii. We used 16S rRNA amplicon sequencing and focused oligotyping analysis and showed that even though location was the main driver of the microbial communities, ecotypes could potentially recruit distinct bacterial populations. We showed that different A. gerardii ecotypes were more successful in overall community recruitment and recruitment of microbes unique to the “home” environment, when growing at their “home site.” We found evidence for “home-field advantage” interactions between the host and host–root-associated bacterial communities, and the capability of ecotypes to recruit specialized microbes that were potentially linked to plant stress responses. Our study aids in a better understanding of the factors that affect plant adaptation, improve management strategies, and predict grassland function under the changing climate.

Local adaptation is a fundamental phenomenon in evolutionary biology, with relevance to formation of ecotypes, and ultimately new species, and application to restoration and species' response to climate change. Reciprocal transplant gardens, a common garden in which ecotypes are planted among home and away habitats, are the gold standard to detect local adaptation in populations.This review focuses on reciprocal transplant gardens to detect local adaptation, especially in grassland species beginning with early seminal studies of grass ecotypes. Fast forward more than half a century, reciprocal gardens have moved into the genomic era, in which the genetic underpinnings of ecotypic variation can now be uncovered. Opportunities to combine genomic and reciprocal garden approaches offer great potential to shed light on genetic and environmental control of phenotypic variation. Our decadal study of adaptation in a dominant grass across the precipitation gradient of the US Great Plains combined genomic approaches and realistic community settings to shed light on controls over phenotype.Common gardens are not without limitations and challenges. A survey of recent studies indicated the modal study uses a tree species, three source sites and one growing site, focuses on one species growing in a monoculture, lasts 3 years, and does not use other experimental manipulations and rarely employs population genetic tools. Reciprocal transplant gardens are even more uncommon, accounting for only 39% of the studies in the literature survey with the rest occurring at a single common site. Reciprocal transplant gardens offer powerful windows into local adaptation when (a) placed across wide environmental gradients to encompass the species' range; (b) conducted across timespans adequate for detecting responses; (c) employing selection studies among competing ecotypes in community settings and (d) combined with measurements of form and function which ultimately determine success in home and away environments.Synthesis. Reciprocal transplant gardens have been one of the foundations in evolutionary biology for the study of adaptation for the last century, and even longer in Europe. Moving forward, reciprocal gardens of foundational non‐model species, combined with genomic analyses and incorporation of biotic factors, have the potential to further revolutionize evolutionary biology. These field experiments will help to predict and model response to climate change and inform restoration practices. [ABSTRACT FROM AUTHOR]

Abstract Background The highly polyphagous Queensland fruit fly (Bactrocera tryoni Froggatt) expanded its range substantially during the twentieth century and is now the most economically important insect pest of Australian horticulture, prompting intensive efforts to develop a Sterile Insect Technique (SIT) control program. Using a “common garden” approach, we have screened for natural genetic variation in key environmental fitness traits among populations from across the geographic range of this species and monitored changes in those traits induced during domestication. Results Significant variation was detected between the populations for heat, desiccation and starvation resistance and wing length (as a measure of body size). Desiccation resistance was correlated with both starvation resistance and wing length. Bioassay data for three resampled populations indicate that much of the variation in desiccation resistance reflects persistent, inherited differences among the populations. No latitudinal cline was detected for any of the traits and only weak correlations were found with climatic variables for heat resistance and wing length. All three stress resistance phenotypes and wing length changed significantly in certain populations with ongoing domestication but there was also a strong population by domestication interaction effect for each trait. Conclusions Ecotypic variation in heat, starvation and desiccation resistance was detected in Australian Qfly populations, and these stress resistances diminished rapidly during domestication. Our results indicate a need to select source populations for SIT strains which have relatively high climatic stress resistance and to minimise loss of that resistance during domestication.

Abstract Plant response to climate depends on a species’ adaptive potential. To address this, we used reciprocal gardens to detect genetic and environmental plasticity effects on phenotypic variation and combined with genetic analyses. Four reciprocal garden sites were planted with three regional ecotypes of Andropogon gerardii, a dominant Great Plains prairie grass, using dry, mesic, and wet ecotypes originating from western KS to Illinois that span 500–1,200 mm rainfall/year. We aimed to answer: (a) What is the relative role of genetic constraints and phenotypic plasticity in controlling phenotypes? (b) When planted in the homesite, is there a trait syndrome for each ecotype? (c) How are genotypes and phenotypes structured by climate? and (d) What are implications of these results for response to climate change and use of ecotypes for restoration? Surprisingly, we did not detect consistent local adaptation. Rather, we detected co‐gradient variation primarily for most vegetative responses. All ecotypes were stunted in western KS. Eastward, the wet ecotype was increasingly robust relative to other ecotypes. In contrast, fitness showed evidence for local adaptation in wet and dry ecotypes with wet and mesic ecotypes producing little seed in western KS. Earlier flowering time in the dry ecotype suggests adaptation to end of season drought. Considering ecotype traits in homesite, the dry ecotype was characterized by reduced canopy area and diameter, short plants, and low vegetative biomass and putatively adapted to water limitation. The wet ecotype was robust, tall with high biomass, and wide leaves putatively adapted for the highly competitive, light‐limited Eastern Great Plains. Ecotype differentiation was supported by random forest classification and PCA. We detected genetic differentiation and outlier genes associated with primarily precipitation. We identified candidate gene GA1 for which allele frequency associated with plant height. Sourcing of climate adapted ecotypes should be considered for restoration.

ABSTRACT Investigation of microbial communities has led to many advances in our understanding of ecosystem function, whether that ecosystem is a subglacial lake or the human gut. Within these communities, much emphasis has been placed on interspecific variation and between-species relationships. However, with current advances in sequencing technology resulting in both the reduction in sequencing costs and the rise of shotgun metagenomic sequencing, the importance of intraspecific variation and within-species relationships is becoming realized. Our group conducts multi-omic analyses to understand how spatial structure and resource availability influence diversification within a species and the potential for long-term coexistence of multiple ecotypes within a microbial community. Here, we present examples of ecotypic variation observed in the lab and in the wild, current challenges faced when investigating intraspecies diversity, and future developments that we expect to define the field over the next 5 years.

Plant response to climate depends on a species' adaptive potential. To address this, we used reciprocal gardens to detect genetic and environmental plasticity effects on phenotypic variation and combined with genetic analyses. Four reciprocal garden sites were planted with three regional ecotypes of Andropogon gerardii, a dominant Great Plains prairie grass, using dry, mesic, and wet ecotypes originating from western KS to Illinois that span 500–1,200 mm rainfall/year. We aimed to answer: (a) What is the relative role of genetic constraints and phenotypic plasticity in controlling phenotypes? (b) When planted in the homesite, is there a trait syndrome for each ecotype? (c) How are genotypes and phenotypes structured by climate? and (d) What are implications of these results for response to climate change and use of ecotypes for restoration? Surprisingly, we did not detect consistent local adaptation. Rather, we detected co‐gradient variation primarily for most vegetative responses. All ecotypes were stunted in western KS. Eastward, the wet ecotype was increasingly robust relative to other ecotypes. In contrast, fitness showed evidence for local adaptation in wet and dry ecotypes with wet and mesic ecotypes producing little seed in western KS. Earlier flowering time in the dry ecotype suggests adaptation to end of season drought. Considering ecotype traits in homesite, the dry ecotype was characterized by reduced canopy area and diameter, short plants, and low vegetative biomass and putatively adapted to water limitation. The wet ecotype was robust, tall with high biomass, and wide leaves putatively adapted for the highly competitive, light‐limited Eastern Great Plains. Ecotype differentiation was supported by random forest classification and PCA. We detected genetic differentiation and outlier genes associated with primarily precipitation. We identified candidate gene GA1 for which allele frequency associated with plant height. Sourcing of climate adapted ecotypes should be considered for restoration. [ABSTRACT FROM AUTHOR]

Aims: The study aimed at characterizing the patterns of natural variation in the tolerance and accumulation capacities for zinc (Zn), cadmium (Cd), and nickel (Ni) between and within edaphic ecotypes of the Zn/Cd/Ni hyperaccumulator, Noccaea caerulescens. Methods: Tolerance was assessed in a hydroponic 'sequential exposure' test, using the lowest concentration that completely arrested root growth as an end point. Accumulation was measured as the foliar metal concentration after six weeks of growth at 5 µM Zn, 2 µM Cd, or 1 µM Ni. Results: Zn and Cd tolerance were positively correlated, and highest in the calamine ecotype. Ni tolerance was without significant ecotypic variation. The ultramafic ecotype was as Zn-tolerant as the non-metallicolous one, but much more sensitive to Cd. The accumulation capacities for Zn, Cd and Ni were all positively correlated and without significant ecotypic variation. Zn hyperaccumulation capacity was species-wide, but Cd and Ni hyperaccumulation capacities were lacking in four populations (all calamine). Conclusions: There is considerable independent variation among populations regarding their Zn, Cd, and Ni accumulation capacities. This variation is most pronounced within the calamine ecotype, because some populations apparently had adopted an exclusion strategy for Zn or Cd hypertolerance, whereas others had not. [ABSTRACT FROM AUTHOR]

Premise: Evolutionary adaptation may enable plants to inhabit a broad range of environments. However, germination and early life‐history stages have seldom been considered in estimates of evolutionary adaptation. Moreover, whether soil microbial communities can influence evolutionary adaptation in plants remains little explored. Methods: We used reciprocal transplant experiments to investigate whether two populations of an invasive plant Solidago canadensis that occur in contrasting habitats of low versus high salinity expressed adaptation to the respective salinity levels. We germinated S. canadensis seeds collected from low‐and high‐salinity habitats under low‐ and high‐salt treatments. We also raised S. canadensis seedlings from the two salinity habitats under low‐ and high‐salt treatments and in the presence versus absence of microbial communities from the two habitats. Results: Genotypes from a low‐salinity habitat had higher germination rates under low‐salt treatment than genotypes from a high‐salinity habitat. However, both genotypes had similar germination rates under a high‐salt treatment. The two genotypes also had similar seedling survival and biomass responses to low‐ and high‐salt treatments. Nevertheless, seedling biomass was significantly higher under low salt treatment. Soil microbial communities did not influence biomass of S. canadensis under the two salt treatments. Conclusions: The results on germination rates suggest partial local adaptation to low salinity. However, there was no evidence of local adaptation to salinity at the seedling survival and growth stages. The finding that germination and seedling biomass responded to different salt treatments suggests that the two traits are important for salt tolerance. [ABSTRACT FROM AUTHOR]

Giant barrel sponges (GBSs) belong to a cryptic species complex (Xestospongia spp.) and are found on tropical reefs worldwide. Over their range, including most of the Caribbean, GBSs have a cylindrical shape, with variation in height, diameter and surface complexity. However, off the southwest coast of Barbados, GBSs mostly exhibit a clam shape or a tub shape, interspersed with a few that have the normal barrel morphotype, suggesting that this variation is not due to environmental factors. Haplotype identification (mtDNA-COI) of six clam and six normal sponges indicated no clear genetic differentiation based on morphotype; hence, this morphological variation remains unexplained.

Herein we studied the reproductive biology of a viviparous lizard (Mabuya dorsivittata) from the Wet Chaco region (northeastern Argentina) and compared the results with other populations from the Espinal (central Argentina) and the Atlantic Forest (southeastern Brazil), and with other Neotropical species of Mabuya to better understand the possible causes of its reproductive phenotype variation. Males and females of M. dorsivittata from the Wet Chaco exhibited associated, seasonal, and annual reproductive cycles. Spermatogenic activity related positively to a lengthening photoperiod reaching maximum activity in late spring (December). Females displayed an extended gestation period of 11 months, from mid-summer (February) to late spring or early summer (December) when births occur. Embryonic development was associated with temperature and historical rainfall. Litter size ranged from 3 to 8 (mean = 5.3 ± 1.3 SD) and increased with body size and body mass of females. Fat-body mass varied seasonally and was inversely correlated with spermatogenesis and to embryonic development. Females were larger in body size and interlimb length, and smaller in head length than males. We observed interpopulational differences in minimum body size, litter size, and timing of birth, probably as a result of phenotypic plasticity, genetic divergence or both.

The limiting effects of stressors like desiccation, light and salinity on seagrass growth and distribution are well-studied. However, little is known about their interactive effects, and whether such effects might differ among populations that are adapted to different local conditions. In two laboratory experiments we tested (a) if growth and development of intertidal, temperate Zostera noltii is affected by emergence time (experiment 1 and 2), and (b) how this is affected by an additional, second stressor, namely shading (experiment 1) or high salinity (25, 30 and 35, experiment 2). In addition, we tested (c) whether the effects of emergence time and salinity varied between three different European seagrass populations (Saint-Jacut/France, Oosterschelde/The Netherlands, and Sylt/Germany), which are likely adapted to different salinity levels (experiment 2). In both experiments, emergence of 8 h per tidal cycle (of 12 h) had a negative effect on seagrass relative growth rate (RGR), and aboveground biomass. Emergence furthermore reduced either rhizome length (experiment 1) or belowground biomass (experiment 2). Shading (experiment 1) resulted in lower RGR and a two-fold higher aboveground/belowground ratio. We found no interactive effects of emergence and shading stress. Salinity (experiment 2) did not affect seagrass growth or morphology of any of the three populations. The three tested populations differed greatly in morphology but showed no differential response to emergence or salinity level (experiment 2). Our results indicate that emergence time and shading show an additive negative effect (no synergistic or antagonistic effect), making the plants still vulnerable to such combination, a combination that may occur as a consequence of self-shading during emergence or resulting from algal cover. Emergence time likely determines the upper limit of Z. noltii and such shading will likely lower the upper limit. Shading resulted in higher aboveground/belowground ratios as is a general response in seagrass. Z. noltii of different populations originating fromsalinity 30 and 35 seem tolerant to variations in salinity within the tested range. Our results indicate that the three tested populations show morphotypic rather than ecotypic variation, at least regarding the salinity and emergence, as there were no interactive effects with origin. For restoration, this implies that the salinity regime of the donor and receptor site of Z. noltii is of no concern within the salinity range 25-35. [ABSTRACT FROM AUTHOR]

Patterns of morphological variation within the North American annual hemiparasite, Melampyrum lineare, are reexamined in this study of its four varieties: M. lineare var. americanum, M. lineare var. latifolium, M. lineare var. lineare, and M. lineare var. pectinatum. Data were collected from 248 herbarium specimens drawn from the species' geographic range in Canada and the United States and included 45 vegetative, reproductive, and ecological characters. Each variety was found to have a broader distribution than previously reported, which expanded the area of known sympatry among the varieties to include most of the species' range. Multivariate analysis of variance revealed statistically significant differences in morphology among the four varieties (p<0.001 in all cases). However, linear discriminant analysis of morphological data showed a continuum of variation and accurately identified the taxonomic variety of individual specimens only 44-75% of the time. Moreover, principal component analysis of continuous morphological variables failed to uncover partitions of the data that would support alternative circumscriptions of subspecific taxa. A chi-squared contingency test to determine if varietal determinations depended on soil-moisture level failed to find evidence supporting such a conclusion (p=0.121). Results show that morphological variation observed in this species cannot be divided into reliably diagnosable groups. While ecotypes are common in Eurasian Melampyrum species and are explained in part by seasonal variation, no common garden experiments to determine how abiotic and biotic conditions affect phenotype have been conducted using M. lineare. Ongoing molecular phylogeographic study of this species may provide alternative metrics for characterizing the diversity of this wide-ranging species. [ABSTRACT FROM AUTHOR]

Acclimatory adjustments of foliar vascular architecture, photosynthetic capacity, and transpiration rate in Arabidopsis thaliana ecotypes (Italian, Polish [Col-0], Swedish) were characterized in the context of habitat of origin. Temperatures of the habitat of origin decreased linearly with increasing habitat latitude, but habitat precipitation was greatest in Italy, lowest in Poland, and intermediate in Sweden. Plants of the three ecotypes raised under three different growth temperature regimes (low, moderate, and high) exhibited highest photosynthetic capacities, greatest leaf thickness, highest chlorophyll a/b ratio and levels of b-carotene, and greatest levels of wall ingrowths in phloem transfer cells, and, in the Col-0 and Swedish ecotypes, of phloem per minor vein in plants grown at the low temperature. In contrast, vein density and minor vein tracheary to sieve element ratio increased with increasing growth temperature - most strongly in Col-0 and least strongly in the Italian ecotype - and transpirational water loss correlated with vein density and number of tracheary elements per minor vein. Plotting of these vascular features as functions of climatic conditions in the habitat of origin suggested that temperatures during the evolutionary history of the ecotypes determined acclimatory responses of the foliar phloem and photosynthesis to temperature in this winter annual that upregulates photosynthesis in response to lower temperature, whereas the precipitation experienced during the evolutionary history of the ecotypes determined adjustment of foliar vein density, xylem, and transpiration to temperature. In particular, whereas photosynthetic capacity, leaf thickness, and foliar minor vein phloem features increased linearly with increasing latitude and decreasing temperature of the habitats of origin in response to experimental growth at low temperature, transpiration rate, foliar vein density, and minor vein tracheary element numbers and cross-sectional areas increased linearly with decreasing precipitation level in the habitats of origin in response to experimental growth at high temperature. This represents a situation where temperature acclimation of the apparent capacity for water flux through the xylem and transpiration rate in a winter annual responded differently from that of photosynthetic capacity, in contrast to previous reports of strong relationships between hydraulic conductance and photosynthesis in other studies. [ABSTRACT FROM AUTHOR]

A novel genetic screen was used to identify host factors in Arabidopsis thaliana that suppress mutations in the Cauliflower mosaic virus (CaMV) movement protein gene (gene I). A series of small mutations was made in gene I and the mutations were tested for their suitability in a suppressor screen. The first round of screening yielded only revertants or second-site mutations in gene I. A derivative of one of the second-site mutant viruses (N7) that was delayed in symptom production was used in a second round of screening for suppressor plants that accelerated symptom production. Two candidate suppressor plants were found that accelerated by 1 to 4 days the first appearance of symptoms caused by the mutant viruses. One of the suppressors (5-2), called asc1 (acceleration of symptoms by CaMV N7), was mapped to chromosome 1. Two additional loci that differentially affect N7 virus susceptibility in the parental Columbia and Ler ecotypes were mapped to chromosomes 3 and 4 by quantitative trait locus (QTL) analysis.

Identifying suitable genetic stock for restoration often employs a 'best guess' approach. Without adaptive variation studies, restoration may be misguided. We test the extent to which climate in central US grasslands exerts selection pressure on a foundation grass big bluestem ( Andropogon gerardii), widely used in restorations, and resulting in local adaptation. We seeded three regional ecotypes of A. gerardii in reciprocal transplant garden communities across 1150 km precipitation gradient. We measured ecological responses over several timescales (instantaneous gas exchange, medium-term chlorophyll absorbance, and long-term responses of establishment and cover) in response to climate and biotic factors and tested if ecotypes could expand range. The ecotype from the driest region exhibited greatest cover under low rainfall, suggesting local adaptation under abiotic stress. Unexpectedly, no evidence for cover differences between ecotypes exists at mesic sites where establishment and cover of all ecotypes were low, perhaps due to strong biotic pressures. Expression of adaptive differences is strongly environment specific. Given observed adaptive variation, the most conservative restoration strategy would be to plant the local ecotype, especially in drier locations. With superior performance of the most xeric ecotype under dry conditions and predicted drought, this ecotype may migrate eastward, naturally or with assistance in restorations. [ABSTRACT FROM AUTHOR]

Predicting how plants will respond to global warming necessitates understanding of local plant adaptation to temperature. Temperature may exert selective effects on plants directly, and also indirectly through environmental factors that covary with temperature, notably soil properties. However, studies on the interactive effects of temperature and soil properties on plant adaptation are rare, and the role of abiotic versus biotic soil properties in plant adaptation to temperature remains untested. We performed two growth chamber experiments using soils and Bistorta vivipara bulbil ecotypes from a subarctic elevational gradient (temperature range: ±3°C) in northern Sweden to disentangle effects of local ecotype, temperature, and biotic and abiotic properties of soil origin on plant growth. We found partial evidence for local adaption to temperature. Although soil origin affected plant growth, we did not find support for local adaptation to either abiotic or biotic soil properties, and there were no interactive effects of soil origin with ecotype or temperature. Our results indicate that ecotypic variation can be an important driver of plant responses to the direct effects of increasing temperature, while responses to covariation in soil properties are of a phenotypic, rather than adaptive, nature.

Two varieties of Aucuba japonica differ in ways that can be considered adaptive to differing geo-climatic conditions in their respective distribution ranges. Irrespective of growth stage, the mean leaf size of A. japonica var. japonica was significantly larger than A. japonica var. borealis. Smaller leaf size and ultimately smaller stature of A. japonica var. borealis are an advantage under the higher snow load and lower temperatures in the forests along the East Sea where the variety grows. Snow load also acted as an important driving force for structural modifications of A. japonica var. borealis from cellular level in leaves to the organization of branch extension growth. Global warming by changing snowfall patterns in Japan may lead to range shifts in the two varieties of A. japonica. [ABSTRACT FROM AUTHOR]

Background and Aims Summer dormancy is an adaptive trait in geophytes inhabiting regions with a Mediterranean climate, allowing their survival through the hot and dry summers. Summer dormancy in Poa bulbosa is induced by increasing day-length and temperature and decreasing water availability during spring. Populations from arid habitats became dormant earlier than those from mesic habitats. Relaxation of dormancy was promoted by the hot, dry summer conditions. Here we test the hypothesis that dormancy relaxation is also delayed in ecotypes of P. bulbosa inhabiting arid regions, as a cautious strategy related to the greater unpredictability of autumn rains associated with decreasing precipitation. Methods Ecotypes collected across a precipitation gradient (100–1200 mm year21) in the Mediterranean climate region were grown under similar conditions in a net-house in Israel. Differences among ecotypes in dormancy induction and dormancy relaxation were determined by measuring time to dormancy onset in spring, and time to sprouting after the first effective rain in autumn. Seasonal and ecotype variation in dormancy relaxation were assessed by measuring time to sprouting initiation, rate of sprouting and maximal sprouting of resting dry bulbs sampled in the net-house during late spring, and mid- and late summer, and planted in a wet substrate at temperatures promoting (10 8C) or limiting (20 8C) sprouting. Key Results Earlier dormancy in the spring and delayed sprouting in autumn were correlated with decreasing mean annual rainfall at the site of ecotype origin. Seasonal and ecotype differences in dormancy relaxation were expressed in bulbs planted at 20 8C. During the summer, time to sprouting decreased while rate of sprouting and maximal sprouting increased, indicating dormancy relaxation. Ecotypes from more arid sites across the rainfall gradient showed delayed onset of sprouting and lower maximal sprouting, but did not differ in rate of sprouting. Planting at 10 8C promoted sprouting and cancelled differences among ecotypes in dormancy relaxation. Conclusions Both the induction and the relaxation of summer dormancy in P. bulbosa are correlated with mean annual precipitation at the site of population origin. Ecotypes from arid habitats have earlier dormancy induction and delayed dormancy relaxation, compared with those from mesic habitats. [ABSTRACT FROM AUTHOR]

In species with widespread distribution, populations found in markedly different environments can show differences in developmental traits. This, in time, can have an effect on reproductive success. Sources of variation in developmental traits can be genetic or environmentally induced. I examined the relationship between environmental and genetic influences on juvenile development in populations of the colonial spider, Parawixia bistriata, located at sites with different moisture regimes and associated environmental variables (e.g., prey availability). It was expected that individuals from different populations would show differences in developmental traits and that those differences will be associated with lower reproductive success at dry sites. I recorded the phenology and developmental traits of native and transplanted individuals in the field and estimated reproductive success based on clutch size. Colonies from wet versus dry sites showed different phenologies, with individuals at dry sites maturing later. Transplant results suggest plasticity in instar duration caused by environmental effects. Despite differences in resources and spider phenology, clutch sizes of native dry and wet populations were similar. Transplanted individuals, however, were differentially affected. Transplants from wet to dry sites (WD) showed lower growth rates and smaller clutches, whereas transplants from dry to wet sites had larger clutch sizes than in native habitat. Delayed maturation and failure to reproduce in WD individuals is associated with a lower tendency to capture prey in groups and less aggressive interactions during prey capture. Thus, despite negative environmental effects on development, dry native individuals have evolved non-developmental traits that allow successful reproduction. [ABSTRACT FROM AUTHOR]

Abstract: Plant populations may adapt to environmental conditions over time by developing genetically based morphological or physiological characteristics. For tidal freshwater forested wetlands, we hypothesized that the conditions under which trees developed led to ecotypic difference in response of progeny to hydroperiod. Specifically, we looked for evidence of ecotypic adaptation for tidal flooding at different salinity regimes using growth and ecophysiological characteristics of two tidal and two non-tidal source collections of baldcypress (Taxodium distichum (L.) L.C. Rich) from the southeastern United States. Saplings were subjected to treatments of hydrology (permanent versus tidal flooding) and salinity (0 versus ∼2gl−1) for two and a half growing seasons in a greenhouse environment. Saplings from tidal sources maintained 21–41% lower overall growth and biomass accumulation than saplings from non-tidal sources, while saplings from non-tidal sources maintained 14–19% lower overall rates of net photosynthetic assimilation, leaf transpiration, and stomatal conductance than saplings from tidal sources. However, we found no evidence for growth or physiological enhancement of saplings from tidal sources to tide, or of saplings from non-tidal sources to no tide. All saplings growing under permanent flooding exhibited reduced growth and leaf gas exchange regardless of source, with little evidence for consistent salinity effects across hydroperiods. While we reject our original hypothesis, we suggest that adaptations of coastal baldcypress to broad (rather than narrow) environmental conditions may promote ecophysiological and growth enhancements under a range of global-change-induced stressors, perhaps reflecting a natural resilience to environmental change while precluding adaptations for specific flood regimes. [Copyright &y& Elsevier]

Populations of the terrestrial garter snake ( Thamnophis elegans) around Eagle Lake in California exhibit dramatic ecotypic differentiation in life history, colouration and morphology across distances as small as a few kilometres. We assayed the role of selection in ecotypic differentiation in T. elegans using FST- QST analysis and identified selective agents using direct and indirect observations. We extended the conventional implementation of the FST -QST approach by using three-level analyses of genetic and phenotypic variance to assess the role of selection in differentiating populations both within and between ecotypes. These results suggest that selection has driven differentiation between as well as within ecotypes, and in the presence of moderate to high gene flow. Our findings are discussed in the context of previous correlational selection analyses which revealed stabilizing and correlational selection for some of the traits examined. [ABSTRACT FROM AUTHOR]

• Three small populations of a dwarf ecotype of the forest tree Eucalyptus globulus are found on exposed granite headlands in south-eastern Australia. These populations are separated by at least 100 km. • Here, we used 12 nuclear microsatellites and a chloroplast DNA marker to investigate the genetic affinities of the dwarf populations to one another and to their nearest populations of tall E. globulus. Cape Tourville was studied in greater detail to assess the processes enabling the maintenance of distinct ecotypes in close geographical proximity. • The three dwarf populations were not related to one another and were more closely related to adjacent tall trees than to one another. At Cape Tourville the dwarf and tall ecotypes were significantly differentiated in microsatellites and in chloroplast DNA. The dwarf and tall populations differed in flowering time and no evidence of pollen dispersal from the more extensive tall to the dwarf population was found. • The three dwarf populations have evolved in parallel from the local tall ecotypes. This study shows that small marginal populations of eucalypts are capable of developing reproductive isolation from nearby larger populations through differences in flowering time and/or minor spatial separation, making parapatric speciation possible. [ABSTRACT FROM AUTHOR]

Globally, tidal marshes are found in small pockets or narrow bands totaling only approximately 45,000 square kilometers. The combination of salinity, low floristic and structural complexity, and regular tidal inundation, as well as unpredictable catastrophic flooding, provides a unique selective environment that shapes local adaptations, including those that are morphological, physiological, demographic, and behavioral. Although tidal marshes support a low diversity of nonaquatic vertebrate species, a high proportion of these inhabitants, at least along North American coastlines, are restricted to or have subspecies restricted to tidal marshes. Tidal marshes and their endemic fauna face broad threats from a variety of human-caused environmental changes. Future research should focus on global inventories, intercontinental comparative work, and investigation to determine why almost all presently described endemic taxa appear to be found in North America. [ABSTRACT FROM AUTHOR]

Octocorals, like many other colonial benthic invertebrates, exhibit remarkable levels of morphological variability. The basis for this variability has been largely unexplored.Plexaura flexuosaLamouroux, a common Caribbean octocoral, is found in virtually all reef habitats, and exhibits habitat-related differences in growth rates and fecundity. Population genetic structure and morphological variability in branch and sclerite characters were examined in nine populations from back reef, shallow forereef, and forereef habitats in the Florida Keys. Discriminant analysis of morphological characters correctly classified 89, 88, and 100% of samples from back, shallow fore, and forereef habitats, respectively. Analysis of randomly amplified polymorphic DNA profiles (RAPDs) showed no evidence of genetic differentiation between shallow back, shallow fore, and the majority of forereef colonies. However, there were two distinct genetic groups of forereef colonies. Much of the habitat-related morphological variability amongPlexaura flexuosais due to plasticity, which is likely an important feature contributing to the broad distribution of this species. However, there may be two genetic subgroups on forereefs. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that South Andean populations of the highly polymorphic and mostly Northern Hemisphere perennial forb Cerastium arvense L. show ecotypic variation along distinct habitats. We compared differences in morphology and flowering phenology among six natural populations occurring in different environments. Genetic differences were analyzed by a common-garden experiment and isozyme electrophoresis. Several of the morphological differences observed in the field were maintained after more than a year of cultivation in the common garden (e.g., plant height and leaf width). Mean tests and multivariate analyses on morphological traits generally distinguished high-elevation populations from the rest, and a similar grouping of populations was obtained from isozyme data at 10 loci. Cerastium arvense had genetic polymorphism levels of >50% in all populations and an average genetic diversity (H[sub T] = 0.254) of which approximately 20% was distributed among populations. These marked genetic differences are probably maintained by restricted gene flow due to variation in flowering time. Morphological and genetic differences suggest ecotypic variation in C. arvense in the southern Andes, which seems to have originated by disruptive selective pressures in different environments and the effect of genetic drift in response to the extreme climatic changes occurring during the Pleistocene.Key words: common-garden experiment, ecotypic variation, elevation and precipitation, genetic diversity, Patagonian Andes, phenology.L'herbe pérenne Cerastium arvense L. est hautement polymorphique et essentiellement répandue dans l'hémisphère nord. Dans ce travail, nous avons testé l'hypothèse que les populations sud andines montrent une variation écotypique en fonction d'habitats distincts. Nous avons comparé des différences de morphologie et de phénologie de la floraison entre six populations naturelles provenant d'environnements différents. Les différences génétiques ont été analysées par culture sur un même site et par électrophorèse isoenzymatiques. Plusieurs différences morphologiques observées en conditions naturelles se sont maintenues après plus d'un an de culture sur le même site expérimental (e.g., hauteur des plants et largeur des feuilles). Des comparaisons de moyenne et des analyses multivariables sur les traits morphologiques permettent generalmente de distinguer les populations de haute altitude des autres populations, ce qui est confirmé par les données isoenzymatiques sur 10 loci. Le C. arvense présente un polymorphisme génétique élevé >50 % dans chaque population et une diversité génétique moyenne (H[sub T] = 0.254), dont environ 20 % se distribue entre les différentes populations. Ces différences génétiques marquées sont probablement maintenues par un flux de gènes restreint et associées à des variations dans les dates de floraison. Ces différences morphologiques et génétiques chez le C. arvense dans le sud des Andes suggèrent une variation écotypique, qui semble résulter de pressions sélectives différentes dans différents environnements et d'un effet de dérive génétique en réponse à des changements climatiques survenus pendant le Pléistocène.Mots clés : culture expérimentale, variation écotypique, altitude et précipitation, diversité génétique, Andes patagoniennes, phénologie. [ABSTRACT FROM AUTHOR]

Giant barrel sponges (GBSs) belong to a cryptic species complex (Xestospongia spp.) and are found on tropical reefs worldwide. Over their range, including most of the Caribbean, GBSs have a cylindrical shape, with variation in height, diameter and surface complexity. However, off the southwest coast of Barbados, GBSs mostly exhibit a clam shape or a tub shape, interspersed with a few that have the normal barrel morphotype, suggesting that this variation is not due to environmental factors. Haplotype identification (mtDNA-COI) of six clam and six normal sponges indicated no clear genetic differentiation based on morphotype; hence, this morphological variation remains unexplained. [ABSTRACT FROM AUTHOR]

Fresh seed derived from a Mediterranean population of non-radiate Senecio vulgaris L. showed strong innate dormancy over a wide temperature range. In contrast, fresh seed of British S. vulgaris exhibited > 80% germination at 20 °C. Dormancy in Mediterranean seed was overcome by: prolonged storage at 15 °C and above; a short stratification treatment (2 wk at 4 °C); prolonged leaching with water; treatment with gibberellic acid (GA3) alone (and with kinetin); and to a lesser extent, by wounding (i.e. removal of a small portion of the fruit and seed coat). A petroleum ether extract from fresh Mediterranean seed strongly inhibited the germination of previously non-dormant seed (of British origin). This implies that dormancy may be caused by an inhibitor present in the embryo or seed coat which might act by preventing the synthesis or liberation of gibberellins required for germination. The innate dormancy exhibited by seed of non-radiate Mediterranean S. vulgaris, enables the species to adopt a winter annual life cycle which is typical of Mediterranean ephemerals. [ABSTRACT FROM AUTHOR]

An algorithm of automatic classification is proposed and applied to a large collection of perennial ryegrass wild populations from France. This method is based on an ascendant hierarchical clustering using the Euclidian distance from the principal components extracted from the variance-covariance matrix between 28 agronomic traits. A contiguity constraint is imposed: only those pairs of populations which are defined as contiguous are grouped together into a cluster. The definition of contiguity is based on a geostatistical parameter: the range of the variogramme, i.e. the largest distance above which the variance between pairs of population no longer increases. This method yields clusters that are generally more compact than those obtained without constraint. In most cases the contours of these clusters fit well with known ecogeographic regions, namely, for macroclimatic homogeneous conditions. This suggests that selective factors exert a major influence in the genetic differentiation of ryegrass populations for quantitatively inherited adaptive traits. It is proposed that such a method could provide useful genetic and ecogeographic bases for sampling a core collection in widespread wild species such as forage grasses. [ABSTRACT FROM AUTHOR]

Ecotypic variations in leaf conductance, soil-to-leaf hydraulic conductance, components of tissue water potential, hydraulic architecture parameters and xylem embolism were examined in greenhouse-grown two-year-old Aleppo pine (Pinus halepensis Mill.) seedlings from six origins representing the geographic range of the species in Italy. Cortical resin composition of the seedlings was also determined. Measurements were made on well-watered seedlings and on seedlings subjected to recurring severe drought. Drought-stressed seedlings had lower mean leaf conductances, transpiration rates and soil-to-leaf hydraulic conductances than well-watered seedlings. They also exhibited more negative osmotic potentials, higher relative water deficit at incipient plasmolysis, but a similar maximum modulus of elasticity. Drought-stressed seedlings showed a higher degree of xylem embolism, a lower Huber value, lower leaf specific conductivity and lower specific conductivity than well-watered seedlings. [ABSTRACT FROM PUBLISHER]

Investigation of microbial communities has led to many advances in our understanding of ecosystem function, whether that ecosystem is a subglacial lake or the human gut. Within these communities, much emphasis has been placed on interspecific variation and between-species relationships. However, with current advances in sequencing technology resulting in both the reduction in sequencing costs and the rise of shotgun metagenomic sequencing, the importance of intraspecific variation and within-species relationships is becoming realized. Our group conducts multi-omic analyses to understand how spatial structure and resource availability influence diversification within a species and the potential for long-term coexistence of multiple ecotypes within a microbial community. Here, we present examples of ecotypic variation observed in the lab and in the wild, current challenges faced when investigating intraspecies diversity, and future developments that we expect to define the field over the next 5 years.

Five ecotypes of Arabidopsis thaliana, from widely dispersed origins, were grown under combinations of ambient and elevated atmospheric CO concentrations and ambient and elevated temperatures within solardomes. Total above-ground plant biomass was measured when the majority of plants across all ecotypes and treatments had formed seed pods. There were substantial differences in biomass between the ecotypes across all treatments. Temperature had no effect on biomass whilst CO had a significant effect both alone and in interaction with ecotype. The CO x ecotype interaction was mostly due to the enhancement of a single ecotype from the Cape Verde Islands. [ABSTRACT FROM AUTHOR]