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1.
Heather M. Love Christine A. Maggs Tomás E. Murray Jim Provan 《Annals of botany》2013,112(9):1743-1750
Background and Aims
Riparian systems are prone to invasion by alien plant species. The spread of invasive riparian plants may be facilitated by hydrochory, the transport of seeds by water, but while ecological studies have highlighted the possible role of upstream source populations in the establishment and persistence of stands of invasive riparian plant species, population genetic studies have as yet not fully addressed the potential role of hydrochoric dispersal in such systems.Methods
A population genetics approach based on a replicated bifurcate sampling design is used to test hypotheses consistent with patterns of unidirectional, linear gene flow expected under hydrochoric dispersal of the invasive riparian plant Impatiens glandulifera in two contrasting river systems.Key results
A significant increase in levels of genetic diversity downstream was observed, consistent with the accumulation of propagules from upstream source populations, and strong evidence was found for organization of this diversity between different tributaries, reflecting the dendritic organization of the river systems studied.Conclusions
These findings indicate that hydrochory, rather than anthropogenic dispersal, is primarily responsible for the spread of I. glandulifera in these river systems, and this is relevant to potential approaches to the control of invasive riparian plant species. 相似文献2.
Background and Aims
In habitat mosaics, plant populations face environmental heterogeneity over short geographical distances. Such steep environmental gradients can induce ecological divergence. Lowland rainforests of the Guiana Shield are characterized by sharp, short-distance environmental variations related to topography and soil characteristics (from waterlogged bottomlands on hydromorphic soils to well-drained terra firme on ferralitic soils). Continuous plant populations distributed along such gradients are an interesting system to study intrapopulation divergence at highly local scales. This study tested (1) whether conspecific populations growing in different habitats diverge at functional traits, and (2) whether they diverge in the same way as congeneric species having different habitat preferences.Methods
Phenotypic differentiation was studied within continuous populations occupying different habitats for two congeneric, sympatric, and ecologically divergent tree species (Eperua falcata and E. grandiflora, Fabaceae). Over 3000 seeds collected from three habitats were germinated and grown in a common garden experiment, and 23 morphological, biomass, resource allocation and physiological traits were measured.Key Results
In both species, seedling populations native of different habitats displayed phenotypic divergence for several traits (including seedling growth, biomass allocation, leaf chemistry, photosynthesis and carbon isotope composition). This may occur through heritable genetic variation or other maternally inherited effects. For a sub-set of traits, the intraspecific divergence associated with environmental variation coincided with interspecific divergence.Conclusions
The results indicate that mother trees from different habitats transmit divergent trait values to their progeny, and suggest that local environmental variation selects for different trait optima even at a very local spatial scale. Traits for which differentiation within species follows the same pattern as differentiation between species indicate that the same ecological processes underlie intra- and interspecific variation. 相似文献3.
Tenna Riis Carla Lambertini Birgit Olesen John S. Clayton Hans Brix Brian K. Sorrell 《Annals of botany》2010,106(5):813-822
Background and Aims
The successful spread of invasive plants in new environments is often linked to multiple introductions and a diverse gene pool that facilitates local adaptation to variable environmental conditions. For clonal plants, however, phenotypic plasticity may be equally important. Here the primary adaptive strategy in three non-native, clonally reproducing macrophytes (Egeria densa, Elodea canadensis and Lagarosiphon major) in New Zealand freshwaters were examined and an attempt was made to link observed differences in plant morphology to local variation in habitat conditions.Methods
Field populations with a large phenotypic variety were sampled in a range of lakes and streams with different chemical and physical properties. The phenotypic plasticity of the species before and after cultivation was studied in a common garden growth experiment, and the genetic diversity of these same populations was also quantified.Key Results
For all three species, greater variation in plant characteristics was found before they were grown in standardized conditions. Moreover, field populations displayed remarkably little genetic variation and there was little interaction between habitat conditions and plant morphological characteristics.Conclusions
The results indicate that at the current stage of spread into New Zealand, the primary adaptive strategy of these three invasive macrophytes is phenotypic plasticity. However, while limited, the possibility that genetic diversity between populations may facilitate ecotypic differentiation in the future cannot be excluded. These results thus indicate that invasive clonal aquatic plants adapt to new introduced areas by phenotypic plasticity. Inorganic carbon, nitrogen and phosphorous were important in controlling plant size of E. canadensis and L. major, but no other relationships between plant characteristics and habitat conditions were apparent. This implies that within-species differences in plant size can be explained by local nutrient conditions. All together this strongly suggests that invasive clonal aquatic plants adapt to a wide range of habitats in introduced areas by phenotypic plasticity rather than local adaptation. 相似文献4.
Background and Aims
Invasiveness of some alien plants is associated with their traits, plastic responses to environmental conditions and interpopulation differentiation. To obtain insights into the role of these processes in contributing to variation in performance, we compared congeneric species of Impatiens (Balsaminaceae) with different origin and invasion status that occur in central Europe.Methods
Native I. noli-tangere and three alien species (highly invasive I. glandulifera, less invasive I. parviflora and potentially invasive I. capensis) were studied and their responses to simulated canopy shading and different nutrient and moisture levels were determined in terms of survival and seedling traits.Key Results and Conclusions
Impatiens glandulifera produced high biomass in all the treatments and the control, exhibiting the ‘Jack-and-master’ strategy that makes it a strong competitor from germination onwards. The results suggest that plasticity and differentiation occurred in all the species tested and that along the continuum from plasticity to differentiation, the species at the plasticity end is the better invader. The most invasive species I. glandulifera appears to be highly plastic, whereas the other two less invasive species, I. parviflora and I. capensis, exhibited lower plasticity but rather strong population differentiation. The invasive Impatiens species were taller and exhibited higher plasticity and differentiation than native I. noli-tangere. This suggests that even within one genus, the relative importance of the phenomena contributing to invasiveness appears to be species''specific. 相似文献5.
Background and Aims
Hygrochasy is a capsule-opening mechanism predominantly associated with plants in arid habitats, where it facilitates spatially and temporally restricted dispersal. Recently, hygrochastic capsules were described in detail for the first time in alpine Veronica in New Zealand. The aim of the present study was to investigate whether hygrochastic capsules are an adaptation of alpine Veronica to achieve directed dispersal to safe sites. We expect that by limiting dispersal to rainfall events, distances travelled by seeds are short and confine them to small habitat patches where both seedlings and adults have a greater chance of survival.Methods
Dispersal distances of five hygrochastic Veronica were measured under laboratory and field conditions and the seed shadow was analysed. Habitat patch size of hygrochastic Veronica and related non-hygrochastic species were estimated and compared.Key Results
Dispersal distances achieved by dispersal with raindrops did not exceed 1 m but weather conditions could influence the even distribution of seeds around the parent plant. Compared with related Veronica species, hygrochastic Veronica mostly grow in small, restricted habitat patches surrounded by distinctly different habitats. These habitat patches provide safe sites for seeds due to their microtopography and occurrence of adult cushion plants. Non-hygrochastic Veronica can be predominantly found in large habitats without clearly defined borders and can be spread over long distances along rivers.Conclusions
The results suggest that hygrochasy is a very effective mechanism of restricting seed dispersal to rainfall events and ensuring short-distance dispersal within a small habitat patch. It appears that it is an adaptation for directed dispersal to safe sites that only exist within the parent habitat. 相似文献6.
Background and Aims
Despite the intense interest in phenological adaptation to environmental change, the fundamental character of natural variation in germination is almost entirely unknown. Specifically, it is not known whether different genotypes within a species are germination specialists to particular conditions, nor is it known what physiological mechanisms of germination regulation vary in natural populations and how they are associated with responses to particular environmental factors.Methods
We used a set of recombinant inbred genotypes of Arabidopsis thaliana, in which linkage disequilibrium has been disrupted over seven generations, to test for genetic variation and covariation in germination responses to distinct environmental factors. We then examined physiological mechanisms associated with those responses, including seed-coat permeability and sensitivity to the phytohormones gibberellic acid (GA) and abscisic acid (ABA).Key Results
Genetic variation for germination was environment-dependent, but no evidence for specialization of germination to different conditions was found. Hormonal sensitivities also exhibited significant genetic variation, but seed-coat properties did not. GA sensitivity was associated with germination responses to multiple environmental factors, but seed-coat permeability and ABA sensitivity were associated with specific germination responses, suggesting that an evolutionary change in GA sensitivity could affect germination in multiple environments, but that of ABA sensitivity may affect germination under more restricted conditions.Conclusions
The physiological mechanisms of germination responses to specific environmental factors therefore can influence the ability to adapt to diverse seasonal environments encountered during colonization of new habitats or with future predicted climate change. 相似文献7.
De Frenne P Graae BJ Brunet J Shevtsova A De Schrijver A Chabrerie O Cousins SA Decocq G Diekmann M Hermy M Heinken T Kolb A Nilsson C Stanton S Verheyen K 《Annals of botany》2012,109(5):1037-1046
Background and Aims
The response of forest herb regeneration from seed to temperature variations across latitudes was experimentally assessed in order to forecast the likely response of understorey community dynamics to climate warming.Methods
Seeds of two characteristic forest plants (Anemone nemorosa and Milium effusum) were collected in natural populations along a latitudinal gradient from northern France to northern Sweden and exposed to three temperature regimes in growth chambers (first experiment). To test the importance of local adaptation, reciprocal transplants were also made of adult individuals that originated from the same populations in three common gardens located in southern, central and northern sites along the same gradient, and the resulting seeds were germinated (second experiment). Seedling establishment was quantified by measuring the timing and percentage of seedling emergence, and seedling biomass in both experiments.Key Results
Spring warming increased emergence rates and seedling growth in the early-flowering forb A. nemorosa. Seedlings of the summer-flowering grass M. effusum originating from northern populations responded more strongly in terms of biomass growth to temperature than southern populations. The above-ground biomass of the seedlings of both species decreased with increasing latitude of origin, irrespective of whether seeds were collected from natural populations or from the common gardens. The emergence percentage decreased with increasing home-away distance in seeds from the transplant experiment, suggesting that the maternal plants were locally adapted.Conclusions
Decreasing seedling emergence and growth were found from the centre to the northern edge of the distribution range for both species. Stronger responses to temperature variation in seedling growth of the grass M. effusum in the north may offer a way to cope with environmental change. The results further suggest that climate warming might differentially affect seedling establishment of understorey plants across their distribution range and thus alter future understorey plant dynamics. 相似文献8.
Pérez-Ortega S Fernández-Mendoza F Raggio J Vivas M Ascaso C Sancho LG Printzen C de Los Ríos A 《Annals of botany》2012,109(6):1133-1148
Background and Aims
Phenotypic variability is a successful strategy in lichens for colonizing different habitats. Vagrancy has been reported as a specific adaptation for lichens living in steppe habitats around the world. Among the facultatively vagrant species, the cosmopolitan Cetraria aculeata apparently forms extremely modified vagrant thalli in steppe habitats of Central Spain. The aim of this study was to investigate whether these changes are phenotypic plasticity (a single genotype producing different phenotypes), by characterizing the anatomical and ultrastructural changes observed in vagrant morphs, and measuring differences in ecophysiological performance.Methods
Specimens of vagrant and attached populations of C. aculeata were collected on the steppes of Central Spain. The fungal internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GPD) and the large sub-unit of the mitochondrial ribosomal DNA (mtLSUm), and the algal ITS and actin were studied within a population genetics framework. Semi-thin and ultrathin sections were analysed by means of optical, scanning electron and transmission electron microscopy. Gas exchange and chlorophyll fluorescence were used to compare the physiological performance of both morphs.Key Results and Conclusions
Vagrant and attached morphs share multilocus haplotypes which may indicate that they belong to the same species in spite of their completely different anatomy. However, differentiation tests suggested that vagrant specimens do not represent a random sub-set of the surrounding population. The morphological differences were related to anatomical and ultrastructural differences. Large intercalary growth rates of thalli after the loss of the basal–apical thallus polarity may be the cause of the increased growth shown by vagrant specimens. The anatomical and morphological changes lead to greater duration of ecophysiological activity in vagrant specimens. Although the anatomical and physiological changes could be chance effects, the genetic differentiation between vagrant and attached sub-populations and the higher biomass of the former show fitness effects and adaptation to dry environmental conditions in steppe habitats. 相似文献9.
Jonathan R. De Long Nigel D. Swarts Kingsley W. Dixon Louise M. Egerton-Warburton 《Annals of botany》2013,111(3):409-418
Background and Aims
Mycorrhizal specialization has been shown to limit recruitment capacity in orchids, but an increasing number of orchids are being documented as invasive or weed-like. The reasons for this proliferation were examined by investigating mycorrhizal fungi and edaphic correlates of Microtis media, an Australian terrestrial orchid that is an aggressive ecosystem and horticultural weed.Methods
Molecular identification of fungi cultivated from M. media pelotons, symbiotic in vitro M. media seed germination assays, ex situ fungal baiting of M. media and co-occurring orchid taxa (Caladenia arenicola, Pterostylis sanguinea and Diuris magnifica) and soil physical and chemical analyses were undertaken.Key Results
It was found that: (1) M. media associates with a broad taxonomic spectrum of mycobionts including Piriformospora indica, Sebacina vermifera, Tulasnella calospora and Ceratobasidium sp.; (2) germination efficacy of mycorrhizal isolates was greater for fungi isolated from plants in disturbed than in natural habitats; (3) a higher percentage of M. media seeds germinate than D. magnifica, P. sanguinea or C. arenicola seeds when incubated with soil from M. media roots; and (4) M. media–mycorrhizal fungal associations show an unusual breadth of habitat tolerance, especially for soil phosphorus (P) fertility.Conclusions
The findings in M. media support the idea that invasive terrestrial orchids may associate with a diversity of fungi that are widespread and common, enhance seed germination in the host plant but not co-occurring orchid species and tolerate a range of habitats. These traits may provide the weedy orchid with a competitive advantage over co-occurring orchid species. If so, invasive orchids are likely to become more broadly distributed and increasingly colonize novel habitats. 相似文献10.
Background and Aims
Functional traits are indicators of plant interactions with their environment and the resource-use strategies of species can be defined through some key functional traits. The importance of genetic variability and phenotypic plasticity in trait variations in response to a common environmental change was investigated in two subalpine species.Methods
Two species with contrasted resource-use strategies, Dactylis glomerata and Festuca paniculata, were grown along a productivity gradient in a greenhouse experiment. Functional traits of different genotypes were measured to estimate the relative roles of phenotypic plasticity and genetic variability, and to compare their levels of phenotypic plasticity.Key Results
Trait variability in the field for the two species is more likely to be the result of phenotypic plasticity rather than of genetic differentiation between populations. The exploitative species D. glomerata expressed an overall higher level of phenotypic plasticity compared with the conservative species F. paniculata. In addition to different amplitudes of phenotypic plasticity, the two species differed in their pattern of response for three functional traits relevant to resource use (specific leaf area, leaf dry matter content and leaf nitrogen content).Conclusions
Functional trait variability was mainly the result of phenotypic plasticity, with the exploitative species showing greater variability. In addition to average trait values, two species with different resource-use strategies differed in their plastic responses to productivity. 相似文献11.
Background and Aims
Low soil fertility limits growth and productivity in many natural and agricultural systems, where the ability to sense and respond to nutrient limitation is important for success. Helianthus anomalus is an annual sunflower of hybrid origin that is adapted to desert sand-dune substrates with lower fertility than its parental species, H. annuus and H. petiolaris. Previous studies have shown that H. anomalus has traits generally associated with adaptation to low-fertility habitats, including a lower inherent relative growth rate and longer leaf lifetime.Methods
Here, a cDNA microarray is used to identify gene expression differences that potentially contribute to increased tolerance of low fertility of the hybrid species by comparing the nitrogen stress response of all three species with high- and low-nutrient treatments.Key Results
Relative to the set of genes on the microarray, the genes showing differential expression in the hybrid species compared with its parents are enriched in stress-response genes, developmental genes, and genes involved in responses to biotic or abiotic stimuli. After a correction for multiple comparisons, five unique genes show a significantly different response to nitrogen limitation in H. anomalus compared with H. petiolaris and H. annuus. The Arabidopsis thaliana homologue of one of the five genes, catalase 1, has been shown to affect the timing of leaf senescence, and thus leaf lifespan.Conclusions
The five genes identified in this analysis will be examined further as candidate genes for the adaptive stress response in H. anomalus. Genes that improve growth and productivity under nutrient stress could be used to improve crops for lower soil fertility which is common in marginal agricultural settings. 相似文献12.
Jean-Michel Leong Pock Tsy Roselyne Lumaret Elodie Flaven-Noguier Mathieu Sauve Marie-Pierre Dubois Pascal Danthu 《Annals of botany》2013,112(9):1759-1773
Background and Aims Adansonia
comprises nine species, six of which are endemic to Madagascar. Genetic relationships between the Malagasy species remain unresolved due to conflicting results between nuclear and plastid DNA variation. Morphologically intermediate individuals between distinct species have been identified, indicative of interspecific hybridization. In this paper, microsatellite data are used to identify potential cases of hybridization and to provide insights into the evolutionary history of the genus on Madagascar.Methods
Eleven microsatellites amplified with new primers developed for Adansonia rubrostipa were used to analyse 672 individuals collected at 27 sites for the six Malagasy species and morphologically intermediate individuals. Rates of individual admixture were examined using three Bayesian clustering programs, STRUCTURE, BAPS and NewHybrids, with no a priori species assignment.Key Results
Population differentiation was coherent, with recognized species boundaries. In the four Malagasy species of section Longitubae, 8·0, 9·0 and 9·5 % of individuals with mixed genotypes were identified by BAPS, NewHybrids and STRUCTURE, respectively. At sites with sympatric populations of A. rubrostipa and A. za, NewHybrids indicated these individuals to be F2 and, predominantly, backcrosses with both parental species. In northern Madagascar, two populations of trees combining A. za and A. perrieri morphology and microsatellite alleles were identified in the current absence of the parental species.Conclusions
The clear genetic differentiation observed between the six species may reflect their adaptation to different assortments of climate regimes and habitats during the colonization of the island. Microsatellite variation reveals that hybridization probably occurred in secondary contact between species of section Longitubae. This type of hybridization may also have been involved in the differentiation of a local new stabilized entity showing specific microsatellite alleles and morphological characters, suggesting a potential role of hybridization in the recent history of diversification on Madagascar. 相似文献13.
Background and Aims
The gametophytes of most homosporous ferns are cordate–thalloid in shape. Some are strap- or ribbon-shaped and have been assumed to have evolved from terrestrial cordate shapes as an adaptation to epiphytic habitats. The aim of the present study was to clarify the morphological evolution of the strap-shaped gametophyte of microsoroids (Polypodiaceae) by precise analysis of their development.Methods
Spores of Colysis decurrens collected in Kagoshima, Japan, were cultured and observed microscopically. Epi-illuminated micrographs of growing gametophytes were captured every 24 h, allowing analysis of the cell lineage of meristems. Light microscopy of resin-sections and scanning electron microscopy were also used.Key Results
Contrary to previous assumptions that strap-shaped Colysis gametophytes have no organized meristem, three different types of meristems are formed during development: (1) apical-cell based – responsible for early growth; (2) marginal – further growth, including gametophyte branching; and (3) multicellular – formation of cushions with archegonia. The cushion is two or three layers thick and intermittent. The apical-cell and multicellular meristems are similar to those of cordate gametophytes of other ferns, but the marginal meristem is unique to the strap-shaped gametophyte of this fern.Conclusions
The strap-shaped gametophytes of C. decurrens may have evolved from ancestors with a cordate shape by insertion of the marginal meristem phase between the first apical-cell-based meristem and subsequent multicellular meristem phases. Repeated retrieval of the marginal meristem at the multicellular meristem phase would result in indefinite prolongation of gametophyte growth, an ecological adaptation to epiphytic habitats. 相似文献14.
15.
Background and Aims
The Senecio hybrid zone on Mt Etna, Sicily, is characterized by steep altitudinal clines in quantitative traits and genetic variation. Such clines are thought to be maintained by a combination of ‘endogenous’ selection arising from genetic incompatibilities and environment-dependent ‘exogenous’ selection leading to local adaptation. Here, the hypothesis was tested that local adaptation to the altitudinal temperature gradient contributes to maintaining divergence between the parental species, S. chrysanthemifolius and S. aethnensis.Methods
Intra- and inter-population crosses were performed between five populations from across the hybrid zone and the germination and early seedling growth of the progeny were assessed.Key Results
Seedlings from higher-altitude populations germinated better under low temperatures (9–13 °C) than those from lower altitude populations. Seedlings from higher-altitude populations had lower survival rates under warm conditions (25/15 °C) than those from lower altitude populations, but also attained greater biomass. There was no altitudinal variation in growth or survival under cold conditions (15/5 °C). Population-level plasticity increased with altitude. Germination, growth and survival of natural hybrids and experimentally generated F1s generally exceeded the worse-performing parent.Conclusions
Limited evidence was found for endogenous selection against hybrids but relatively clear evidence was found for divergence in seed and seedling traits, which is probably adaptive. The combination of low-temperature germination and faster growth in warm conditions might enable high-altitude S. aethnensis to maximize its growth during a shorter growing season, while the slower growth of S. chrysanthemifolius may be an adaptation to drought stress at low altitudes. This study indicates that temperature gradients are likely to be an important environmental factor generating and maintaining adaptive divergence across the Senecio hybrid zone on Mt Etna. 相似文献16.
Lucia Muggia Sergio Pérez-Ortega Theodora Kopun Günther Zellnig Martin Grube 《Annals of botany》2014,114(3):463-475
Background and Aims
The integrity and evolution of lichen symbioses depend on a fine-tuned combination of algal and fungal genotypes. Geographically widespread species complexes of lichenized fungi can occur in habitats with slightly varying ecological conditions, and it remains unclear how this variation correlates with symbiont selectivity patterns in lichens. In an attempt to address this question, >300 samples were taken of the globally distributed and ecologically variable lichen-forming species complex Tephromela atra, together with closely allied species, in order to study genetic diversity and the selectivity patterns of their photobionts.Methods
Lichen thalli of T. atra and of closely related species T. grumosa, T. nashii and T. atrocaesia were collected from six continents, across 24 countries and 62 localities representing a wide range of habitats. Analyses of genetic diversity and phylogenetic relationships were carried out both for photobionts amplified directly from the lichen thalli and from those isolated in axenic cultures. Morphological and anatomical traits were studied with light and transmission electron microscopy in the isolated algal strains.Key Results
Tephromela fungal species were found to associate with 12 lineages of Trebouxia. Five new clades demonstrate the still-unrecognized genetic diversity of lichen algae. Culturable, undescribed lineages were also characterized by phenotypic traits. Strong selectivity of the mycobionts for the photobionts was observed in six monophyletic Tephromela clades. Seven Trebouxia lineages were detected in the poorly resolved lineage T. atra sensu lato, where co-occurrence of multiple photobiont lineages in single thalli was repeatedly observed.Conclusions
Low selectivity apparently allows widespread lichen-forming fungi to establish successful symbioses with locally adapted photobionts in a broader range of habitats. This flexibility might correlate with both lower phylogenetic resolution and evolutionary divergence in species complexes of crustose lichen-forming fungi. 相似文献17.
Eduardo Fernández-Pascual Borja Jiménez-Alfaro Juli Caujapé-Castells Ruth Jaén-Molina Tomás Emilio Díaz 《Annals of botany》2013,112(5):937-945
Background and Aims
Seed dormancy varies within species in response to climate, both in the long term (through ecotypes or clines) and in the short term (through the influence of the seed maturation environment). Disentangling both processes is crucial to understand plant adaptation to environmental changes. In this study, the local patterns of seed dormancy were investigated in a narrow endemic species, Centaurium somedanum, in order to determine the influence of the seed maturation environment, population genetic composition and climate.Methods
Laboratory germination experiments were performed to measure dormancy in (1) seeds collected from different wild populations along a local altitudinal gradient and (2) seeds of a subsequent generation produced in a common garden. The genetic composition of the original populations was characterized using intersimple sequence repeat (ISSR) PCR and principal co-ordinate analysis (PCoA), and its correlation with the dormancy patterns of both generations was analysed. The effect of the local climate on dormancy was also modelled.Key Results
An altitudinal dormancy cline was found in the wild populations, which was maintained by the plants grown in the common garden. However, seeds from the common garden responded better to stratification, and their release from dormancy was more intense. The patterns of dormancy variation were correlated with genetic composition, whereas lower temperature and summer precipitation at the population sites predicted higher dormancy in the seeds of both generations.Conclusions
The dormancy cline in C. somedanum is related to a local climatic gradient and also corresponds to genetic differentiation among populations. This cline is further affected by the weather conditions during seed maturation, which influence the receptiveness to dormancy-breaking factors. These results show that dormancy is influenced by both long-and short-term climatic variation. Such processes at such a reduced spatial scale highlight the potential of plants to adapt to fast environmental changes. 相似文献18.
Background and Aims
Tolerance and defence against herbivory are among the many mechanisms attributed to the success of invasive plants in their novel ranges. Because tolerance and defence against herbivory differ with the ontogeny of a plant, the effects of herbivore damage on plant fitness vary with ontogenetic stage and are compounded throughout a plant''s lifetime. Environmental stresses such as light and nutrient limitations can further influence the response of the plant. Much is known about the response of plants in the seedling and reproductive adult stages, but less attention has been given to the pre-reproductive juvenile stage.Methods
Juvenile plants of the North American invasive Lonicera maackii were exposed to simulated herbivory under high and low light and nitrogen availability and growth, allocation patterns and foliar defensive chemistry were measured. In a second experiment, complete nutrient availability and damage type (generalist caterpillar or simulated) were manipulated.Key Results
Juvenile plants receiving 50 % defoliation had lower total biomass and a higher root^:^shoot ratio than controls for all treatment combinations except low nitrogen/low light. Low light and defoliation increased root^:^shoot ratio. Light, fertilization and defoliation had little impact on foliar defensive chemistry. In the second experiment, there was a reduction in total biomass when caterpillar damage was applied. The root^:^shoot ratio increased under low soil fertility and was not affected by defoliation. Stem-diameter growth rates and specific leaf area did not vary by damage type or fertilization. Foliar protein increased through time, and more strongly in defoliated plants than in controls, while peroxidase activity and total flavonoids decreased with time. Overall, resource limitations were more influential than damage in the growth of juvenile L. maackii plants.Conclusions
The findings illustrate that even when resources are limited, the tolerance and defence against herbivory of a woody invasive plant in the juvenile stage may contribute to the establishment and persistence of some species in a variety of habitats. 相似文献19.
Background
Soil biota effects are increasingly accepted as an important driver of the abundance and distribution of plants. While biogeographical studies on alien invasive plant species have indicated coevolution with soil biota in their native distribution range, it is unknown whether adaptation to soil biota varies among populations within the native distribution range. The question of local adaptation between plants and their soil biota has important implications for conservation of biodiversity and may justify the use of seed material from local provenances in restoration campaigns.Methodology/Principal Findings
We studied soil biota effects in ten populations of the steppe grass Stipa capillata from two distinct regions, Europe and Asia. We tested for local adaptation at two different scales, both within (ca. 10–80 km) and between (ca. 3300 km) regions, using a reciprocal inoculation experiment in the greenhouse for nine months. Generally, negative soil biota effects were consistent. However, we did not find evidence for local adaptation: both within and between regions, growth of plants in their ‘home soil’ was not significantly larger relative to that in soil from other, more distant, populations.Conclusions/Significance
Our study suggests that negative soil biota effects can prevail in different parts of a plant species'' range. Absence of local adaptation points to the possibility of similar rhizosphere biota composition across populations and regions, sufficient gene flow to prevent coevolution, selection in favor of plasticity, or functional redundancy among different soil biota. From the point of view of plant - soil biota interactions, our findings indicate that the current practice of using seeds exclusively from local provenances in ecosystem restoration campaigns may not be justified. 相似文献20.