Non-serpentine Populations Research Articles

Early lateral root formation in response to calcium and nickel shows variation within disjunct populations of Arabidopsis lyrata spp. lyrata

Root architecture is important in nutrient uptake and avoidance of toxic compounds within the soil. Arabidopsis lyrata spp. lyrata has widespread distribution in disjunct environments that encounter unique stressors starting at germination. Five populations of A. lyrata spp. lyrata show local adaptation to Nickel (Ni) but cross-tolerance to variations in Calcium (Ca) concentration within the soil. Differentiation among the populations begins early in development and appears to impact timing of lateral root formation; therefore the purpose of the study was to understand changes in root architecture and root exploration in response to Ca and Ni within the first three weeks of growth. Lateral root formation was first characterized under one concentration of Ca and Ni. Lateral root formation and tap root length were reduced in all five populations in response to Ni compared to Ca, with the least reduction in the three serpentine populations. When the populations were exposed to a gradient (either Ca or Ni) there were differences in population response based on the nature of the gradient. Start side was the greatest determinant of root exploration and lateral root formation under a Ca gradient, while population was the greatest determinant of root exploration and lateral root formation under a Ni gradient. All populations exhibited about the same frequency of root exploration under a Ca gradient, while the serpentine populations exhibited much higher levels of root exploration under a Ni gradient compared to the two non-serpentine populations. Differences among populations in response to Ca and Ni demonstrate the importance of stress responses early in development, particularly in species that have widespread distribution among disparate habitats.

Diversity of Ni growth response and accumulation in Central-Eastern Mediterranean Odontarrhena (Brassicaceae) populations on and off serpentine sites

Nickel response and accumulation were analyzed in 12 populations from seven Central-Eastern Mediterranean Odontarrhena taxa on and off serpentine sites to test the presence of metal-induced growth stimulation and its relationship with tolerance and plant Ni concentration. Seedlings were cultivated in hydroponics with increasing NiSO4 concentrations to obtain dose-response curves and to evaluate Ni levels in roots and shoots. In all the accessions, a metal stimulatory effect on growth was present in the low-dose zone and significantly fitted the Brain-Cousens hormetic model. Accessions showed broad variation in tolerance, with the most tolerant plants requiring the highest Ni concentrations in the culture medium for optimal growth. Significant differences were also detected in plant Ni concentrations and a positive relationship was found between tolerance and accumulation. The serpentine and non-serpentine populations of O. chalcidica were similarly capable of hyperaccumulation, suggesting this ability to a be a species-wide trait. In the case of O. muralis, a species that preferentially avoids serpentine soils, the two populations from non-serpentine sites showed the same Ni-enhanced growth of the serpentine accessions of the other species investigated here, but only at the lowest concentration, and reached shoot Ni amounts approaching the Ni hyperaccumulation threshold. Therefore, in Odontarrhena the capacity to tolerate and accumulate Ni could be considered a specieswide trait in all the serpentine taxa, both endemic and facultative. Regarding the metal concentration showed by the accessions in nature, neither Ni levels in the field-collected plants nor those in their natural soils of origin were related to Ni tolerance. On the other hand, Ni accumulation capacity appeared as the main driving factor for the metal concentration in the plants in their native habitats.

Intraspecific trait variability and genetic diversity in the adaptive strategies of serpentine and non-serpentine populations of Silene paradoxa L.

AimsWe investigated whether individuals of Silene paradoxa L., grown in serpentine and non-serpentine soils, displayed variation in functional traits and adaptive strategies together with a differentiation of the gene pool. We hypothesised that individuals growing in serpentine sites may be exposed to a higher degree of stress, resulting in measurable differences in leaf traits and adaptive strategies, and as well that the differences in the soil type were associated with a genetic process of differentiation.MethodsWe analysed a specific set of leaf functional traits of populations of S. paradoxa grown on serpentine and non-serpentine soils. Furthermore, DNA-fingerprinting techniques were used to further dissect the emergence of genetic processes of differentiation linked to the different soil types.ResultsWe detected a relevant intraspecific trait variation in S. paradoxa, with the populations from serpentine sites significantly polarised towards the stress-tolerant adaptive strategy. This polarisation came with a shift in gene pool selection, even if we did not detect quantitative differences in the genetic diversity or evidence of genetic drift.ConclusionsThe results indicate that particular edaphic conditions acted on the selection of some regions of the species’ genome, independently of the site, with various portions of the genome being exclusive to or prevalent in the serpentine or non-serpentine populations.

A study of functional traits reveals serpentinomorphoses and new taxa in populations of Mediterranean Genista (Fabaceae)

In this work we try to determine whether the modifications in the functional traits of a plant species, both morphological and phenological, and caused by the adaptive serpentinomorphoses syndrome are enough to differentiate a new taxon. For this purpose, Genista hirsuta subsp. lanuginosa, a western Mediterranean serpentinophyte (subserpentinophyte) with populations both on serpentines and outside them was selected. The study of functional types (functional traits, which link morphology with adaptations, and phenological reproductive and vegetative phases) was performed in both populations. The results showed that there were statistically significant differences between the two types of populations (serpentine and non-serpentine) with respect to some of the quantitative functional characters studied (plant height, crown diameter, Specific leaf area (SLA), and length of photosynthetic stems). Moreover, other differences were detected with respect to semi-quantitative and qualitative traits: location of renewal buds, branch type, morphology of aerial part, bark consistency, leaf tomentosity, morphology of the root system, and organ redness. Some of them are consistent with serpentinomorphoses syndrome, such as the existence of dwarfism (height of plants), cushion habit, macro-rooted plants and lower SLA (stenophylly) in serpentine populations, besides the presence of redness, which could be a character also linked to serpentinomorphoses. However, neither glaucescent organs nor glabrescence were observed (on the contrary, there is a greater general tomentosity in the plants of the serpentine population). In addition, phenological differences were detected, consisting of a generalized shortening of the phenophases and a certain delay in the reproductive phenophases in the serpentine populations, a characteristic trait in serpentine flora, and differences in sequencing phenophases. These facts lead to propose the use of phenology, in combination with functional traits, to detect serpentinomorphoses syndrome. The detected differences are enough to separate taxonomically the two populations of Genista hirsuta subsp. lanuginosa, proposing for the non-serpentine populations a new variety: var. silicicola nov.

Major QTL controls adaptation to serpentine soils in Mimulus guttatus.

Spatially varying selection is a critical driver of adaptive differentiation. Yet, there are few examples where the fitness effects of naturally segregating variants that contribute to local adaptation have been measured in the field. Plant adaptation to harsh soil habitats provides an ideal study system for investigating the genetic basis of local adaptation. The work presented here identifies a major locus underlying adaptation to serpentine soils in Mimulus guttatus and estimates the strength of selection on this locus in native field sites. Reciprocal transplant and common-garden studies show that serpentine and nonserpentine populations of M.guttatus differ in their ability to survive on serpentine soils. We directly mapped these field survival differences by performing a bulk segregant analysis with F2 survivors from a field transplant study and identify a single QTL where individuals that are homozygous for the nonserpentine allele do not survive on serpentine soils. Genotyping the survivors from an independent mapping population reveals that this same QTL controls serpentine tolerance in a second, geographically distant population. Finally, we show that this QTL controls tolerance to soil properties, as opposed to some other aspect of the field sites that may differ, by performing a laboratory-based common-garden experiment in native serpentine soils that replicates the survival differences observed in the field. These results indicate that despite the myriad chemical and physical challenges plants face in serpentine habitats, adaptation to these soils in M.guttatus has a simple genetic basis.

Phylogeographic testing of alternative histories of single-origin versus parallel evolution of early flowering serpentine populations of Picris hieracioides L. (Asteraceae) in Japan

Serpentine, a chemically extreme substrate with a discontinuous distribution, supports a high proportion of endemic plant species. The evolutionary pathway of edaphic endemics in isolated areas may be of parallel origin (convergence), but this can be difficult to detect due to similar sets of phenotypic traits repeatedly selected for by the extreme conditions of serpentine environments. Testing the alternative histories of single origin vs. parallel evolution in serpentine plant populations provides insight into the ability of plants to adapt to extreme serpentine environments and to disperse between isolated serpentine areas. In this study, we focused on the herb Picris hieracioides L. (Asteraceae), which includes early-flowering serpentine populations surrounded by later flowering, non-serpentine populations on Hokkaido Island, Japan. We performed population genetic analysis based on genome-wide SNPs markers and quantified temporal overlap of flowering times under natural conditions. Phylogeographic analysis confirmed the occurrence of two genetic groups, corresponding to the serpentine and non-serpentine races. Although the two races were found to occur in close parapatry over multiple paired soil sites, little evidence for hybridization was detected. The flowering times of the two races showed significant divergence, with flowering peaks separated by more than 1 month. Overall, this study supported the single origin of serpentine Picris populations, and showed the role of divergent flowering time as a strong prezygotic barrier to maintain the edaphic races over short spatial distances.

Simultaneous evaluation of the effects of geographic, environmental and temporal isolation in ecotypic populations of Solidago virgaurea.

Early stages of ecological speciation can create populations with an ecology and reproduction timing distinct from those of related populations. Landscape genetic models incorporating environmental heterogeneity and population-specific reproductive traits enable the processes of population genetic differentiation to be inferred. We investigated genome-wide genetic variation in ecotypic populations of Solidago virgaurea sensu lato, a herbaceous plant inhabiting a wide range of habitats (woodlands, serpentine barrens and alpine grasslands) and displaying remarkable variation in flowering time. Simultaneous evaluation of environmental factors revealed an overwhelming effect of soil type differences on neutral genetic differentiation, compared with elevational differences. This result probably reflects the abrupt environmental changes generated by geological boundaries, whereas mountain slopes exhibit clinal changes, facilitating gene exchange between neighbouring populations. Temporal isolation was positively associated with genetic differentiation, with some early-flowering serpentine populations having allele frequencies distinct from adjacent nonserpentine populations. Overall, this study highlights the importance of ecological processes and of evolution of flowering time to promote genetic differentiation of S.virgaurea populations in a complex landscape.

Drought Response Strategies ofClarkia gracilis(Onagraceae) Populations from Serpentine and Nonserpentine Soils

Premise of research. The serpentine grassland system provides the opportunity to examine whether drought response traits may have contributed to differentiation in the stress-tolerant genus Clarkia. Commonly utilized drought responses might be indicative of traits important to species diversification in stressful environments.Methodology. We examined the drought response strategies of populations of Clarkia gracilis (Onagraceae) from both serpentine and nonserpentine soils. Physiological, morphological, and biomass data were collected under controlled greenhouse conditions.Pivotal results. Serpentine-derived plants exhibited faster growth and germination rates and larger leaf size than nonserpentine-derived plants under increasing water stress, indicating drought escape strategies. However, serpentine-derived plants also employed dehydration avoidance by increasing their water-use efficiency (decreased transpiration rate) under drought stress. In terms of biomass, serpentine-derived plants had a higher fitness potential than nonserpentine-derived plants. Nonserpentine-derived plants tended toward dehydration avoidance through decreased growth rate, decreased transpiration, and smaller leaf size.Conclusions. Our data support transpiration rate as a trait important to stress tolerance. Moreover, serpentine-derived plants avoid drought with drought escape strategies more than nonserpentine plants and may have a higher fitness potential, particularly in water-limiting conditions. Thus, serpentine populations may be competitively superior to nonserpentine populations under drought stress conditions.

Serpentine populations of Arabidopsis lyrata ssp. lyrata show evidence for local adaptation in response to nickel exposure at germination and during juvenile growth

Evolutionary divergence among disjunct populations that encounter different stressful conditions may be rapid due to limited gene flow. Arabidopsis lyrata ssp. lyrata (L.) O’Kane & Al-Shehbaz grows throughout the mid-Atlantic region in a variety of fragmented and stressful environments, including serpentine soils. The purpose of this study was to investigate the differential responses to heavy metals (particularly nickel and chromium, naturally occurring in serpentine soils) among three serpentine populations compared to two non-serpentine populations of A. l. ssp. lyrata, as evidence of local adaptation. The five populations were exposed to a nickel, chromium or control treatment during germination and juvenile growth. None of the populations had a negative growth response to chromium. All five populations had reductions in growth when exposed to nickel. The greatest reductions were found in the two non-serpentine populations, which had reductions of 97–99% compared to the control. In contrast, the three serpentine populations had reductions of 23–83%, with most reduction in one of the serpentine populations (Robert E. Lee). Compared to the non-serpentine populations and the least tolerant serpentine population, the two most tolerant serpentine populations (Pilot and Soldiers Delight) had early lateral root formation, accumulated less nickel in their shoots and roots, and had high shoot phenolics. All three serpentine populations had increased serine levels in response to nickel and chromium. The tolerance mechanisms we found in the most tolerant serpentine populations serve as evidence for local adaptation to nickel stress in the non-hyperaccumulator A. l ssp. lyrata.

Nickel effect on root-meristem cell division in Plantago lanceolata (Plantaginaceae) seedlings

The toxic effect of nickel (Ni) on cell division on root-meristem cells in seedlings of Plantago lanceolata L. was studied and compared. Seed material was collected from serpentine and non-serpentine populations of the species distributed in the Rhodope Mountains, Bulgaria. The root-tip meristem cells of germinated seeds were treated with different solutions of 0.01, 0.025, 0.05, 0.1 mM Ni as NiSO4 6H2O with distilled water for 24 h and 48 h respectively. The mitotic index decreased when Ni concentrations and exposure time increased in both type of samples. Significant differences in the mitotic indexes were found between the controls and the roots treated with Ni. The mitotic index was higher in root-meristem cells of serpentine seedlings. C-mitosis, anaphase bridges, chromosome stickiness, laggards and extrusion of nuclear material into the cytoplasm were observed in the root-tip cells treated with Ni. The percentage of aberrations generally increased in a concentration- and time-dependent manner. The percentage of the extruded nuclei was higher in cells treated with 0.05 and 0.1 mM Ni. It can be concluded that P. lanceolata seedlings on serpentine can tolerate higher Ni concentrations than can non-serpentine seedlings.

Effect of nickel on pollen germination and pollen tube length in Arabis alpina (Brassicaceae)

In this work we studied and compared the toxic effect of nickel (Ni) on pollen germination and pollen tube length in Arabis alpina L. collected from serpentine and non-serpentine populations distributed in the Rila mountains, Bulgaria. Pollen grains were treated with prepared standard solutions of 100, 300, 500, and 700 μM Ni as NiCl2 in distilled water. A nutritional medium was also used to assess pollen germination. Nickel inhibited pollen germination and pollen tube elongation in both serpentine and non-serpentine plants. The percentage of germinated pollen in serpentine plants treated with Ni was higher than in non-serpentine plants but there was no difference in pollen tube elongation between groups. However, pollen tubes showed abnormalities such as coiling and swelling of the tip, or burst, and varied considerably among the samples. A complete break of pollen tube elongation is due to such abnormalities. Also, decreased pollen fertility in both populations was found. The plants from serpentines were less sensitive to (i.e. more tolerant of) elevated Ni concentrations commonly found in serpentine soils.

Root sprouting in Knautia arvensis (Dipsacaceae): effects of polyploidy, soil origin and nutrient availability

Plants able to resprout from roots have a potential bud bank that gets initiated after injury to overcome meristem limitation after loss of all stem parts and to facilitate regeneration. Knautia arvensis is reportedly able to sprout from its roots on arable land, but information is missing regarding such ability in serpentine populations or how it might differ between diploids and tetraploids. We hypothesized that (1) 'ruderal' non-serpentine populations better tolerate severe disturbance than relic, serpentine ones; (2) tetraploid populations resprout more readily than diploids due to enhanced growth of higher ploidy levels; and (3) plants of different ploidy levels from serpentine soils are, for evolutionary reasons, more similar in their response to disturbances than plants from non-serpentine soils. To test these hypotheses, we conducted a pot experiment. Its results do not support our hypothesis that the ability to sprout from roots is a factor driving the spread of new weedy taxa into central Europe or the hypothesis that it is related to polyploidization in the genus Knautia. Both tetraploids and plants from non-serpentine populations regenerated less vigorously than diploids and plants from serpentine populations. However, the genetically closer populations of serpentine origin were more similar in their response to experimental manipula- tions than their genetically distinct non-serpentine counterparts. The success of non-serpentine taxa in disturbed habitats of central Europe might be related to traits other than the ability to resprout.

Growth and nickel uptake by serpentine and non-serpentine populations of Fimbristylis ovata (Cyperaceae) from Sri Lanka

Compared with serpentine floras of Southeast Asia, the serpentine vegetation of Sri Lanka is impoverished in regard to serpentine endemics and nickel hyperaccumulators. All species so far documented from the serpentine outcrops of Sri Lanka also have non-serpentine populations; it is unclear whether the serpentine populations are physiologically distinct and deserve ecotypic recognition. We conducted a preliminary study to examine whether serpentine and non-serpentine populations of Fimbristylis ovata represent locally adapted ecotypes by investigating their growth and potential for nickel uptake and tolerance under greenhouse conditions. Although both populations of F. ovata showed a similar growth pattern in serpentine soil during short-term exposure (21 days), the non-serpentine population was unable to survive in serpentine soil under long-term exposure (4 months). Both populations were able to uptake nickel from serpentine soil during short-term exposure (21 days). The serpentine population, however, translocated significantly more nickel from its roots to shoots (translocation factor 0.43) than the non-serpentine population (translocation factor 0.29). Our preliminary investigations suggest that the serpentine and non-serpentine populations of F. ovata may be locally adapted to their respective soils. However, additional studies are required to determine whether the populations deserve ecotypic recognition.

Essential and toxic element concentrations in Hypericum perforatum

The herb Hypericum perforatum L. – otherwise known as St John’s Wort – that grows on serpentine and non-serpentine sites is widely used in traditional medicine in Bulgaria. Plant aerial parts (Hiperici herba) as well as methanol/water (1 : 1) and water extracts prepared from eight populations growing on and off serpentine were analysed for essential (Fe, Mn, Cr, Co, Cu, Zn) and toxic (Ni, Cd, Pb) elemental concentration using inductively plasma optical emission spectrometry and electro thermal atomic absorption spectrometry. The results showed that metal concentrations varied across sites. Non-serpentine populations were well separated based on their total metal concentrations. The plant is Ni tolerant, but has the potential to accumulate trace elements at toxic levels. The transfer of elements from the herb material to an extract was solvent and metal dependent. The highest mobility, e.g. percentages of extraction, was found for Cu, Zn and Ni in all extracts. The amount of Cd, Ni and Cr was above the permissible limits in dry plant material and both types of extracts. The element concentrations found in this medicinal plant show that people should be careful when collecting it from serpentine sites and using it for medication.

Climatic niche shifts in the serpentine soil flora of California

Question Soil properties are known to have a profound effect on the geographic distribution of plants. Unusual soils seem to allow species to occur outside their ‘typical’ (realized) climatic niche. However, the generality of this pattern, and the mechanisms that drive it, are poorly known. Here, we focus on the tendency for some plant species to occur at unusually low elevations on infertile substrates, especially serpentine soils. We ask whether there is a flora-wide trend in the state of California toward lower elevations and warmer thermal limits on infertile serpentine soils than on other soils. Location State of California, USA. Methods We used herbarium data from 19 institutions. We only used species collected from both serpentine and non-serpentine soils. To focus on plant response to recent climate, we discarded records from before 1979. Finally, we discarded records that did not report latitude and longitude. The final data set consisted of 36 045 specimens representing 814 species. Latitude and longitude were used to infer elevation, temperature and soil type. We then developed a simulation modelling approach to test for significant differences in elevational and thermal distribution between serpentine and non-serpentine soils. Results Serpentine populations are found at lower elevations than non-serpentine populations, at both the low and high ends of elevation distributions (two tailed t-test, P < 0.01). This pattern is partially matched by temperature: both high and low temperature data indicate that serpentine populations are limited to less extreme temperatures than non-serpentine populations (two tailed t-test, P < 0.01). Conclusions We show that there is a flora-wide trend toward lower elevation limits on serpentine soils in the state of California. Temperature data suggest a slightly different pattern, with serpentine plants occupying more moderate temperatures. We suggest that this difference may be due to a decoupling of elevation and temperature in some parts of California. Overall, our results are consistent with two mechanisms of plant range limitation: (1) a biotic mechanism at lower elevations (high temperatures), where serpentine provides a refuge from competition; and (2) an abiotic limit at upper elevations (low temperatures), where the effect of cold is exacerbated by the infertility of serpentine.

Nickel tolerance of serpentine and non-serpentine Knautia arvensis plants as affected by arbuscular mycorrhizal symbiosis

Serpentine soils have naturally elevated concentrations of certain heavy metals, including nickel. This study addressed the role of plant origin (serpentine vs. non-serpentine) and symbiosis with arbuscular mycorrhizal fungi (AMF) in plant Ni tolerance. A semi-hydroponic experiment involving three levels of Ni and serpentine and non-serpentine AMF isolates and populations of a model plant species (Knautia arvensis) revealed considerable negative effects of elevated Ni availability on both plant and fungal performance. Plant growth response to Ni was independent of edaphic origin; however, higher Ni tolerance of serpentine plants was indicated by a smaller decline in the concentrations of photosynthetic pigments and restricted root-to-shoot Ni translocation. Serpentine plants also retained relatively more Mg in their roots, resulting in a higher shoot Ca/Mg ratio. AMF inoculation, especially with the non-serpentine isolate, further aggravated Ni toxicity to host plants. Therefore, AMF do not appear to be involved in Ni tolerance of serpentine K. arvensis plants.

EFFECTS OF CALCIUM/MAGNESIUM QUOTIENTS AND NICKEL IN THE GROWTH MEDIUM ON GROWTH AND NICKEL ACCUMULATION IN PISTACIA ATLANTICA

We selected two serpentine (ultramafic) and non-serpentine populations of P. atlantica and a cultivar of P. vera cv. ‘Badami’, to compare their responses to two growth limiting factors of serpentine soils: low calcium (Ca)/ magnesium (Mg) quotients and high concentrations of nickel (Ni). A solution culture system using perlite as a neutral substrate was used for growing the plants. Growth and elemental composition of plants then were analyzed. All populations/species proved to be excluders of Ni but, interestingly the excluding ability of P. vera to prevent translocation of Ni from root to shoot was higher than that of both populations of P. atlantica. The plants of serpentine population of P. atlantica were more resistant to lower Ca/Mg quotients and higher concentrations of Ni. We suggest that the growth and exclusion responses of the tested plants to Ca/Mg quotients and Ni result from adaptations to their natural substrates, ultramafic or saline soils.

Soil nutritional status, not inoculum identity, primarily determines the effect of arbuscular mycorrhizal fungi on the growth of Knautia arvensis plants

Arbuscular mycorrhizal (AM) symbiosis is among the factors contributing to plant survival in serpentine soils characterised by unfavourable physicochemical properties. However, AM fungi show a considerable functional diversity, which is further modified by host plant identity and edaphic conditions. To determine the variability among serpentine AM fungal isolates in their effects on plant growth and nutrition, a greenhouse experiment was conducted involving two serpentine and two non-serpentine populations of Knautia arvensis plants grown in their native substrates. The plants were inoculated with one of the four serpentine AM fungal isolates or with a complex AM fungal community native to the respective plant population. At harvest after 6-month cultivation, intraradical fungal development was assessed, AM fungal taxa established from native fungal communities were determined and plant growth and element uptake evaluated. AM symbiosis significantly improved the performance of all the K. arvensis populations. The extent of mycorrhizal growth promotion was mainly governed by nutritional status of the substrate, while the effect of AM fungal identity was negligible. Inoculation with the native AM fungal communities was not more efficient than inoculation with single AM fungal isolates in any plant population. Contrary to the growth effects, a certain variation among AM fungal isolates was revealed in terms of their effects on plant nutrient uptake, especially P, Mg and Ca, with none of the AM fungi being generally superior in this respect. Regardless of AM symbiosis, K. arvensis populations significantly differed in their relative nutrient accumulation ratios, clearly showing the plant's ability to adapt to nutrient deficiency/excess.

Arbuscular mycorrhizal symbiosis on serpentine soils: the effect of native fungal communities on different Knautia arvensis ecotypes

Serpentine soils represent a unique environment that imposes multiple stresses on vegetation (low Ca/Mg ratios, macronutrient deficiencies, elevated heavy metal concentrations and drought). Under these conditions, a substantial role of arbuscular mycorrhizal (AM) symbiosis can be anticipated due to its importance for plant nutrition and stress alleviation. We tested whether serpentine and non-serpentine populations of Knautia arvensis (Dipsacaceae) differ in the benefits derived from native AM fungal communities. Four serpentine and four non-serpentine populations were characterised in terms of mycorrhizal colonisation and soil characteristics. The serpentine populations showed significantly lower mycorrhizal colonisation than their non-serpentine counterparts. The mycorrhizal colonisation positively correlated with soil pH, Ca and K concentrations and Ca/Mg ratio. Seedlings from each population were then grown for 3 months in their sterilised native substrates, either uninoculated or reinoculated with native AM fungi. Two serpentine and two non-serpentine populations responded positively to mycorrhizal inoculation, while no significant change in plant growth was observed in the remaining populations. Contrary to our hypothesis, serpentine populations of K. arvensis did not show higher mycorrhizal growth dependence than non-serpentine populations when grown in their native soils and inoculated with native AM fungi.

Distribution and Ecotypic Variation of the Invasive Annual Barb Goatgrass (Aegilops triuncialis) on Serpentine Soil

AbstractSuccessful colonization of newly introduced species is driven by a multitude of factors and is highly dependent on the species. It has long been hypothesized that preadaptation and postestablishment natural selection of introduced species can facilitate their invasion; however, to date, limited research has been dedicated to these theories. In addition, although the correlation between establishment of invasive species and disturbance has been noted and widely studied, the susceptibility of undisturbed habitats to invasion remains unclear. In California, serpentine habitats are severe edaphic environments that have been relatively free of anthropogenic disturbance and nonindigenous species invasions. In this study, we documented the occurrence of the nonindigenous barb goatgrass on serpentine and nonserpentine grasslands in the California Northern Interior Coast Range and the western foothills of the Sierra Nevada Mountains and conducted greenhouse and field experiments to assess the species' degree of adaptation to serpentine soils. Reconnaissance of serpentine intrusions and yearly monitoring suggest that barb goatgrass may grow preferentially on serpentine soil, particularly disturbed serpentine sites. In the greenhouse, for most measures of performance, serpentine populations performed better than nonserpentine populations when grown on serpentine soil. Particularly noteworthy was that serpentine populations had higher root-mass ratios than nonserpentine populations when grown on serpentine soil. In contrast to the greenhouse study, field-grown populations from serpentine and nonserpentine sources performed equally well on nonserpentine; alluvial, disturbed serpentine; and shallow, undisturbed serpentine, although the overall species' performance was diminished on severe serpentine soils. Alarmingly, even in the absence of previous exposure to serpentine, barb goatgrass was capable of establishing and spreading into minimally disturbed sites with strong serpentinitic characteristics.