Non-clonal Plants Research Articles

Simulating life history trade-offs of clonal plants in drought

This study investigates responses of clonal plants and non-clonal plants to drought and their competition results using a spatial simulator based on clonal and nonclonal life history strategies. The clonal and non-clonal plants are designed as two phenotypes of one generic species with facultative clonal growth. Therefore, both phenotypes share the same life histories beside their allocation to aboveground and belowground growth, resulting in differences in leaf biomass, underground storage, and seed reproduction. Clonal plants tend to store biomass underground which would boost survival in the long-term, while non-clonal plants invest towards aboveground growth and thus more seed reproduction in the short-term. It is shown that allocation to storage in clonal plants provide them with an advantage when faced with severe drought since they can resprout from belowground. In comparison, non-clonal plants do better when there is no drought as they allocate more to aboveground growth and seeds. The simulations results have demonstrated how clonal life histories might impact plant population dynamics under drought, which might increase in frequency and extent as anthropogenic climate change continues. It also can be easily parameterized to investigate other species of interest under other environmental conditions.

Incorporating clonality into the plant ecology research agenda.

A longstanding research divide exists in plant ecology: either focusing on plant clonality, with no ambition to address nonclonal plants, or focusing on all plants, ignoring that many ecological processes can be affected by the fact that some plants are clonal while others are not. This gap cascades into a lack of distinction and knowledge about the similarities and differences between clonal and nonclonal plants. Here we aim to bridge this gap by identifying areas that would benefit from the incorporation of clonal growth into one integrated research platform: namely, response to productivity and disturbance, biotic interactions, and population dynamics. We are convinced that this will provide a roadmap to gain valuable insights into the ecoevolutionary dynamics relevant to all plants.

Frequency of flower visitors and achene production increase with rising population size in the self-incompatible herb Centaurea scabiosa (Asteraceae)

Self-incompatible, non-clonal plant species are especially dependent on the activity of flower visitors for seed production. Therefore, populations of these plants are vulnerable to a reduced flower visitation rates, but also to increased isolation by extinction of local populations. To study how local populations of Centaurea scabiosa, a self-incompatible, bee-pollinated herb species changed over time in the region of Bonn, we collected historical population records in the area and investigated their current status. We found that more than half of the subpopulations mentioned in the literature between 1950 and 2012 (38 of 65) have since disappeared. Small populations were most vulnerable, whereas medium to large populations increased in size. In a second step, we studied visitation frequencies and achene production and weight across 14 extant populations. We found that both flower visitation frequency and achene production were positively related to population size. Achene weight was neither related to the frequency of flower visitors nor to achene production. These results clearly indicate that reduced pollen transfer and lower pollination rates may contribute to local extinction in small populations of Centaurea scabiosa. Overall our results call for an intensified monitoring of the populations of self-incompatible plant species.

Young clonal and non-clonal herbs differ in growth strategy but not in aboveground biomass compensation after disturbance.

Clonal plants have more traits enabling individual persistence (larger belowground storage of buds and assimilates), whereas non-clonal plants have more traits enabling population persistence (a higher reliance on regeneration from seeds). This difference presumably makes those groups respond differently to disturbance. We asked whether this difference is already expressed in the first year of the plant's life. In a pot experiment with 17 congeneric pairs of clonal and non-clonal herbs, we investigated response to a disturbance at the individual level. We were interested whether the leaf C/N ratio (a proxy reflecting active growth and photosynthetic efficiency), the R/S ratio (a proxy for belowground storage) and the amount of compensated biomass differ between clonal and non-clonal herbs. Moreover, we asked whether compensation for the loss of aboveground biomass after disturbance can be predicted by the R/S ratio or explained by the leaf C/N ratio. We found that clonal herbs have higher leaf C/N and R/S ratios than non-clonal herbs. Under disturbance, the leaf C/N and R/S ratios decreased in the clonal herbs and increased in the non-clonal herbs. However, the clonal and non-clonal plants did not differ in biomass compensation ability. Neither the R/S ratio nor the leaf C/N ratio explained the compensation abilities of the herbs. These results show that even though the growth strategies of clonal and non-clonal plants and their reactions to disturbance are different, the groups are similarly capable of compensating for the loss of aboveground biomass. Clonal plants do not have an advantage over non-clonal plants under disturbance during their first year of life.

Response of clonal versus non-clonal herbs to disturbance: Different strategies revealed

Disturbance is an omnipresent selective factor that shapes plant strategies. While annual species that rely on rapid generative reproduction dominate in habitats frequently affected by severe disturbance, long-lived woody species occupy habitats where the effects of disturbance are weak. These are, however, the extremes in the disturbance gradient. Habitats under intermediate disturbance are occupied by the whole spectrum of plant strategies. In this study, we hypothesized that clonal herbs are better adapted to intermediate disturbance than non-clonal herbs because the characteristics of their bud bank and related belowground carbohydrate storage promote vegetative regeneration. In a greenhouse experiment, we tested the effects of disturbance on the survival and performance of 17 congeneric pairs of clonal and non-clonal herbs cultivated from seed. In addition to a non-disturbed control, we applied five disturbance treatments: biomass removal 2 cm above the soil surface, removal of 70 % of the aboveground biomass, late spring frost, flooding, and belowground injury. Mortality was negligible except the flooding treatment, where it was higher for non-clonal than for clonal plants. Total biomass was reduced more by the disturbance treatments for clonal than for non-clonal plants, suggesting that clonal species suffer more than non-clonal species. On the other hand, clonal plants had significantly greater total belowground biomass and R:S ratios than non-clonal plants, suggesting a strong investment in belowground organs by clonal plants. In response to disturbance, the SLA and SRL values increased in clonal plants but decreased in non-clonal plants, indicating that clonal and non-clonal plants differ in how they cope with disturbance. Although clonality is considered to be an adaptation to disturbance, our results indicate that, during the first year of life, clonal herbs are more sensitive to disturbance than non-clonal herbs, likely due to preferential investment in belowground biomass.

Reaching similar goals by different means – Differences in life-history strategies of clonal and non-clonal plants

Clonality is a largely underexplored plant life-history trait with possibly profound effects on plant demography. Clonal growth constitutes an alternative reproductive pathway, which should provide clonal species with an advantage over non-clonal ones under disturbance regimes unfavourable to regeneration from seeds.We investigated how clonal and non-clonal species differ in their life histories (other than clonality) and how this relates to disturbance regimes where the studied species occur. Further, we focused on the contribution of clonality to fluctuations in the populations of species and the importance of clonality for the life cycle of a species in relation to its other life-history characteristics. We achieved this through phylogenetically informed analyses of the matrix population models available from the COMPADRE database coupled with information on species clonality from the CLO-PLA database.The phylogenetic principal component analysis revealed that plant life-history characteristics could be aligned along two gradients. The gradient of generation time and individual turnover in populations was more important and corresponded to the frequency of habitat disturbance. Clonal species on average had populations with lower overall rates of individual turnover and disturbance frequencies. The second gradient was correlated with disturbance severity and plant ability to regenerate after the loss of biomass. The importance of clonal growth for the life cycle of a clonal species increased with more severe disturbance events. The fluctuation of population growth rates depended on the life-history characteristics of a species but not on clonality. The net effect of clonal growth on the fluctuations of the populations of a species was positive.In general, clonality seems to provide an important alternative for adjusting plant life history to the disturbance regime and other site conditions allowing a plant to circumvent its morphological or developmental constraints. Clonal growth turned out to be mainly a mechanism that enables population expansion under favourable conditions rather than a mechanism that buffers the effects of adverse conditions.

The Description of Rubber Farmer Management in Sibiru Biru Sub-district, Deli Serdang Regency, North Sumatra and Its Response to the Introduction of Tapping Technology

Production of smallholder rubber in Indonesia is still very low, in the range of 600 - 900 kg of dry rubber/ha/year. Many factors influence it, such as non-clonal plants still being managed. Other factors such as agronomic aspects which include efforts to shorten the TBM period either through agronomic technology (canopy management, fertilization, or ground water management) are still ignored by smallholder rubber farmers, due to the limited access, capital, and even the perception that rubber plant production will not experience significant increase through tapping systems. The main and first approach that must be taken at this time on smallholder rubber is a new technology in tapping and management. This activity was carried out by four meetings and training in the garden of one of the trainees. Trainees consisted of rubber farmers in Sari Laba Jahe Hamlet, which also included rubber farmers from Peria Ria Hamlet - Sibiru Biru Sub-district (Deli Serdang Regency, North Sumatra). The package of tapping technology introduction consists of 3 main elements, namely: 1) tapping starts from the upper left to the lower right in each tapping field, 2) the application of 2.5% stimulant concentration is carried out in the tapping groove every 4 tapping times and 3) tapping in a month can be combined with tapping 1/S to the top using a pacekung tapping knife. Thus, in a month done 4 times of double cut tapping, namely 1/2S (in the lower tapping area using an ordinary tapping knife, downward: pull method) + 1 / 4S (upward using a pacekung tapping knife: shearing method). The results of this activity show that it can increase the production, thereby increasing the volume of sap sold. This activity also shows that the dominant farmers manage 1 hectare of land, and with the planting year and planting material that have the potential to be increased in production through tapping systems. The survey results show that general knowledge about rubber cultivation is dominantly obtained from this activity.

Plasticity in the growth habit prolongs survival at no physiological cost in a monocarpic perennial at high altitudes.

Monocarpic plants are those that flower, produce seeds and then die. Although most monocarpic plants are annual or biennial, some of them are perennial. However, relatively little is known regarding the biology of monocarpic perennials. Pyrenean saxifrage (Saxifraga longifolia) is a monocarpic perennial that is well adapted to high-mountain ecosystems. Here, we evaluated altitudinal changes in clonality in various populations growing in their natural habitat with particular emphasis on the physiological costs of clonal growth. We assessed the percentage of clonal plants in nine populations growing in their natural habitat, as well as the plant stress response of clonal and non-clonal plants, in terms of photoprotection and accumulation of stress-related phytohormones, in a 3-year study at Las Blancas (2100 m a.s.l.). We also evaluated the influence of plant size on the activation of defensive responses to biotic and abiotic stresses. We found that 12 % of Pyrenean saxifrage plants growing at the highest altitudes (2100 m a.s.l.) produced lateral rosettes which survived the flowering of the main rosette and shared the same axonomorphic root, thus escaping monocarpic senescence. This clonal growth did not worsen the physiological performance of plants growing at this altitude. Furthermore, increased plant size did not negatively affect the physiology of plants, despite adjustments in endogenous stress-related phytohormones. In contrast, maturity led to rapid physiological deterioration of the rosette, which was associated with monocarpic senescence. This study shows that the evolution of clonality has allowed Pyrenean saxifrage to survive harsh environmental conditions and it provides evidence that harsh environments push plant species to their limits in terms of life form and longevity.

Large-scale environmental niche variation between clonal and non-clonal plant species: Roles of clonal growth organs and ecoregions

Clonal plant species can produce genetically identical and potentially independent offspring, and dominate a variety of habitats. The divergent evolutionary mechanisms between clonal and non-clonal plants are interesting areas of ecological research. A number of studies have shown that the environmental niche theory can support the mechanisms of evolution across plant species clades at large scales. However, few studies have explored large-scale environmental niche variation between clonal and non-clonal plant species. Here, we used principal component analysis to quantify the environmental niche of 137 plant species belonging to 13 genera, including 87 clonal species and 50 non-clonal species. We then used a standardized effect size to assess environmental niche variation between clonal and non-clonal plant species within each genus, based on types of clonal growth organs and ecoregions. Our study provided the first evidence that there were significant environmental niche differences between clonal and non-clonal plant species at large scales. Such differences varied depending on the types of clonal growth organs and ecoregions. Clonal plants with different growth organs (i.e., epigeogenous stems, hypogeogenous stems, root-splitters, and adventitious buds on roots) contributed greatly to differences in climatic niches between clonal and non-clonal plants. Differences in environmental niches between clonal and non-clonal plant species also depended on ecoregion types. Specifically, the ecoregions of temperate broadleaf and mixed forests can lead to environmental niche variation between clonal and non-clonal plant species. Our results provide new insights into the evolutionary divergence between clonal and non-clonal plant species.

Effect of clonal reproduction on quantitative indices and component composition of essential oil of peppermint varieties

Quantitative and qualitative composition of essential oils of peppermint breeds Lebedinaya Pesnya, Lubenchanka, Lidiya, Ukrainskaya Perechnaya, Mama, Chornolista was investigated before and after clonal microreproduction by the method of isolated tissues and bodies culture in vitro. Methods of essential oil steam distillation, capillary gas chromatography and statistical analysis were used in the research. It is established that increase in essential oil quantity was observed for peppermint breeds on which reproduction and improvement іn vіtro technology was applied. As a result of clonal microreproduction of peppermint plants in culture іn vіtro on nutrient medium Murasige and Skug, in which the growth regulators 0.75 mg/l of 6-benzylaminopurine, 0.1 mg/l of adenine, 0.05 mg/l of indolil-3-acetic acid and 0.5 mg/l of gibberellins acid were added and virocide Ribavirin in concentration 10 mg/l, improvement was obtained in comparison with vegetatively reproduced plants; increase in essential oil quantity per hectare was established for the following breeds; Chornolista by 54.2%, Lebedinaya pesnya by 38.2%, Ukrainskaya Perechnaya by 36.7%, Mama by 28.5%, Lubenchanka by 17.1% and Lidiya by 11.6%. For oil content the highest indices were noted for Lubenchanka, Mama and Lebedinaya Pesnya peppermint breeds with product yield 4.02%, 3.98% and 3.84% respectively. It was established that the essential oil component composition in non-clonal peppermint plants raw materials and plants-regenerants after culture in vitro is variable depending on breed. Limonene, cineole, menthone, menthofuran, iso-menthone, menthyl acetate, β-caryophyllene, iso-menthol, menthol, pulegone, germacren, piperitone, carvone were identified in peppermint essential oil. High content of menthol, low content of carvone, piperitone, pulegone (except for Chornolista, Ukrainskaya Perechnaya breeds) and menthofuran (except for Chornolista, Ukrainskaya Perechnaya and Lubenchanka breeds) are characteristic for Ukrainian selection peppermint investigated breeds. A clear tendency to menthol and menthone content ratio increase is observed in plants which were improved in conditions іn vіtro. Pulegone was not detected in essential oil samples of Lebedinaya Pesnya, Lidiya and Mama breeds. Biochemical markers of Lebedinaya Pesnya, Lubenchanka, Mama breeds, which differentiate them within the group of investigated breeds, are higher limonene, piperitone and menthol pool; for Ukrainskaya Perechnaya and Chornolista breeds – pulegone, cineole and menthone; for Lidiya breed – iso-menthone.

Phenotypic plasticity and specialization in clonal versus non-clonal plants: A data synthesis

Reproductive strategies can be associated with ecological specialization and generalization. Clonal plants produce lineages adapted to the maternal habitat that can lead to specialization. However, clonal plants frequently display high phenotypic plasticity (e.g. clonal foraging for resources), factors linked to ecological generalization. Alternately, sexual reproduction can be associated with generalization via increasing genetic variation or specialization through rapid adaptive evolution. Moreover, specializing to high or low quality habitats can determine how phenotypic plasticity is expressed in plants. The specialization hypothesis predicts that specialization to good environments results in high performance trait plasticity and specialization to bad environments results in low performance trait plasticity. The interplay between reproductive strategies, phenotypic plasticity, and ecological specialization is important for understanding how plants adapt to variable environments. However, we currently have a poor understanding of these relationships. In this study, we addressed following questions: 1) Is there a relationship between phenotypic plasticity, specialization, and reproductive strategies in plants? 2) Do good habitat specialists express greater performance trait plasticity than bad habitat specialists? We searched the literature for studies examining plasticity for performance traits and functional traits in clonal and non-clonal plant species from different habitat types. We found that non-clonal (obligate sexual) plants expressed greater performance trait plasticity and functional trait plasticity than clonal plants. That is, non-clonal plants exhibited a specialist strategy where they perform well only in a limited range of habitats. Clonal plants expressed less performance loss across habitats and a more generalist strategy. In addition, specialization to good habitats did not result in greater performance trait plasticity. This result was contrary to the predictions of the specialization hypothesis. Overall, reproductive strategies are associated with ecological specialization or generalization through phenotypic plasticity. While specialization is common in plant populations, the evolution of specialization does not control the nature of phenotypic plasticity as predicted under the specialization hypothesis.

Enforced Clonality Confers a Fitness Advantage.

In largely clonal plants, splitting of a maternal plant into potentially independent plants (ramets) is usually spontaneous; however, such fragmentation also occurs in otherwise non-clonal species due to application of external force. This process might play an important yet largely overlooked role for otherwise non-clonal plants by providing a mechanism to regenerate after disturbance. Here, in a 5-year garden experiment on two short-lived, otherwise non-clonal species, Barbarea vulgaris and Barbarea stricta, we compared the fitness of plants fragmented by simulated disturbance (“enforced ramets”) both with plants that contemporaneously originate in seed and with individuals unscathed by the disturbance event. Because the ability to regrow from fragments is related to plant age and stored reserves, we compared the effects of disturbance applied during three different ontogenetic stages of the plants. In B. vulgaris, enforced ramet fitness was higher than the measured fitness values of both uninjured plants and plants established from seed after the disturbance. This advantage decreased with increasing plant age at the time of fragmentation. In B. stricta, enforced ramet fitness was lower than or similar to fitness of uninjured plants and plants grown from seed. Our results likely reflect the habitat preferences of the study species, as B. vulgaris occurs in anthropogenic, disturbed habitats where body fragmentation is more probable and enforced clonality thus more advantageous than in the more natural habitats preferred by B. stricta. Generalizing from our results, we see that increased fitness yielded by enforced clonality would confer an evolutionary advantage in the face of disturbance, especially in habitats where a seed bank has not been formed, e.g., during invasion or colonization. Our results thus imply that enforced clonality should be taken into account when studying population dynamics and life strategies of otherwise non-clonal species in disturbed habitats.

Age of maturity in alpine herbaceous perennials in the northwest Caucasus

Sod transplantation experiment was carried out for 24 years in alpine communities, Teberda Reserve, the North-West Caucasus, Russia. Age of maturity (AOM) was estimated as a period between first registra- tion of a species on.a permanent plot and flowering shoot appearance. Mean species AOM varied from 2.3 years (Antennaria dioica with clonal propagation) to 13.7 years for Taraxacum stevenii (non-clonal plant). General gradient of alpine plant traits and population strategies was determined. It represents a continuum ranging from ruderal--stress-tolerants (shorter AOM, clonality, shorter leaf life span, low rate of mycorrhizal infection, low regrowth ability, low generative shoot number, low specific leaf area and leaf nitrogen content) to competitor--stress-tolerants (longer AOM, longer leaf life span, higher rate of mycorrhizal infection, higher regrowth ability, high generative shoot number, high specific leaf area and leaf nitrogen content).

Population genetic structure and clonal diversity of Allium oleraceum (Amaryllidaceae), a polyploid geophyte with common asexual but variable sexual reproduction

Clonal plants are, on average, considered to be as genetically diverse as nonclonal plants. However, the behaviour of clonal plants ranges between multiclonality and uniclonality, depending on environmental conditions and life history traits. Allozyme electrophoresis of band phenotypes was used to examine the genetic structure of 13 cytotype-uniform and 17 cytotype-mixed populations of polyploid Allium oleraceum (2n = 4x, 5x, 6x), a clonal bulbous geophyte that has been considered seed-sterile and completely reliant on vegetative reproduction through aerial bulbils and daughter bulbs. The genetic structure was dominated by low within-population variation whereas genetic differentiation was high among populations. Eighty-five distinct multilocus genotypes were found among 756 sampled individuals, but populations generally exhibited a low level of clonal diversity. Tetra- and pentaploids showed twofold higher total and within-population diversity, but also had more genetically differentiated populations in comparison with hexaploids. Tetraploids formed two separate groups in the cluster analysis, and this finding most likely suggests their different origin. Pentaploids were grouped in a separate cluster and frequently intermixed with tetra- and hexaploids sampled at cytotype-mixed sites. Such a pattern suggests gene flow between cytotypes. Most hexaploids were genetically similar and clustered separately from the other cytotypes, suggesting their similar origin and absence of gene flow to and from other cytotypes. Identical band phenotypes found in coexisting cytotypes within certain mixed-ploidy populations might indicate in situ neopolyploidization. Collectively, the pattern of genetic structure and diversity observed in A. oleraceum is typical of clonal plants with the dominance of vegetative offspring and scarce recruitment of sexual offspring. The low and spatially unstructured genetic variation observed in hexaploids, in contrast with higher and spatially structured genetic variation in tetra- and pentaploids, seems to be related to different levels of sexual fertility, ecological amplitude and colonization abilities of the cytotypes. It provides evidence for the existence of both primary and secondary contact zones of cytotypes in A. oleraceum.

Spatial patterning and floral synchrony among trillium populations with contrasting histories of herbivory.

We investigated the spatial patterning and floral synchrony within and among populations of a non-clonal, forest understory herb, Trillium catesbaei. Two populations of T. catesbaei within Great Smoky Mountains National Park were monitored for five years: Cades Cove (high deer abundance) and Whiteoak Sink (low deer abundance). All individuals within each population were mapped during year one and five. Only flowering and single-leaf juveniles were mapped during intervening years. Greater distances between flowering plants (plants currently in flower) and substantially lower population densities and smaller patch sizes were observed at Cades Cove versus Whiteoak Sink. However, with the exception of flowering plants, contrasting histories of herbivory did not appear to fundamentally alter the spatial patterning of the T. catesbaei population at Cades Cove, an area with a long and well-documented history of deer overabundance. Regardless of browse history, non-flowering life stages were significantly clustered at all spatial scales examined. Flowering plants were clustered in all years at Whiteoak Sink, but more often randomly distributed at Cades Cove, possibly as a result of their lower abundance. Between years, however, there was a positive spatial association between the locations of flowering plants at both sites. Flowering rate was synchronous between sites, but lagged a year behind favorable spring growing conditions, which likely allowed plants to allocate photosynthate from a favorable year towards flowering the subsequent year. Collectively, our results suggest that chronically high levels of herbivory may be associated with spatial patterning of flowering within populations of a non-clonal plant. They also highlight the persistence of underlying spatial patterns, as evidenced by high levels of spatial clustering among non-flowering individuals, and the pervasive, although muted in a population subjected to chronic herbivory, influence of precipitation and temperature on flowering in long-lived forest herbs.

Perennial roots to immortality.

Maximum lifespan greatly varies among species, and it is not strictly determined; it can change with species evolution. Clonal growth is a major factor governing maximum lifespan. In the plant kingdom, the maximum lifespans described for clonal and nonclonal plants vary by an order of magnitude, with 43,600 and 5,062 years for Lomatia tasmanica and Pinus longaeva, respectively. Nonclonal perennial plants (those plants exclusively using sexual reproduction) also present a huge diversity in maximum lifespans (from a few to thousands of years) and even more interestingly, contrasting differences in aging patterns. Some plants show a clear physiological deterioration with aging, whereas others do not. Indeed, some plants can even improve their physiological performance as they age (a phenomenon called negative senescence). This diversity in aging patterns responds to species-specific life history traits and mechanisms evolved by each species to adapt to its habitat. Particularities of roots in perennial plants, such as meristem indeterminacy, modular growth, stress resistance, and patterns of senescence, are crucial in establishing perenniality and understanding adaptation of perennial plants to their habitats. Here, the key role of roots for perennial plant longevity will be discussed, taking into account current knowledge and highlighting additional aspects that still require investigation.

Testing a growth efficiency hypothesis with continental-scale phenological variations of common and cloned plants

Variation in the timing of plant phenology caused by phenotypic plasticity is a sensitive measure of how organisms respond to weather and climate variability. Although continental-scale gradients in climate and consequential patterns in plant phenology are well recognized, the contribution of underlying genotypic difference to the geography of phenology is less well understood. We hypothesize that different temperate plant genotypes require varying amount of heat energy for resuming annual growth and reproduction as a result of adaptation and other ecological and evolutionary processes along climatic gradients. In particular, at least for some species, the growing degree days (GDD) needed to trigger the same spring phenology events (e.g., budburst and flower bloom) may be less for individuals originated from colder climates than those from warmer climates. This variable intrinsic heat energy requirement in plants can be characterized by the term growth efficiency and is quantitatively reflected in the timing of phenophases-earlier timing indicates higher efficiency (i.e., less heat energy needed to trigger phenophase transitions) and vice versa compared to a standard reference (i.e., either a uniform climate or a uniform genotype). In this study, we tested our hypothesis by comparing variations of budburst and bloom timing of two widely documented plants from the USA National Phenology Network (i.e., red maple-Acer rubrum and forsythia-Forsythia spp.) with cloned indicator plants (lilac-Syringa x chinensis 'Red Rothomagensis') at multiple eastern US sites. Our results indicate that across the accumulated temperature gradient, the two non-clonal plants showed significantly more gradual changes than the cloned plants, manifested by earlier phenology in colder climates and later phenology in warmer climates relative to the baseline clone phenological response. This finding provides initial evidence supporting the growth efficiency hypothesis, and suggests more work is warranted. More studies investigating genotype-determined phenological variations will be useful for better understanding and prediction of the continental-scale patterns of biospheric responses to climate change.

Clonal growth forms in Arctic plants and their habitat preferences: a study from Petuniabukta, Spitsbergen

Abstract The ability to grow clonally is generally considered important for plants in Arctic regions but analyses of clonal characteristics are lacking for entire plant communities. To fill this gap, we assessed the clonal growth of 78 plant species in the Petuniabukta region, central Spitsbergen (Svalbard), and analyzed the clonal and other life-history traits in the re- gional flora and plant communities with respect to environmental gradients. We distin- guished five categories of clonal growth organs: perennial main roots produced by non- clonal plants, epigeogenous rhizomes, hypogeogenous rhizomes, bulbils, and stolons. Clonal growth differed among communities of the Petuniabukta region: non-clonal plants prevailed in open, early-successional communities, but clonal plants prevailed in wetlands. While the occurrence of plants with epigeogenous rhizomes was unrelated to stoniness or slope, the occurrence of plants with hypogeogenous rhizomes diminished with increasing stoniness of the substratum. Although the overall proportion of clonal plants in the flora of the Petuniabukta region was comparable to that of central Europe, the flora of the Petunia- bukta region had fewer types of clonal growth organs, a slower rate of lateral spread, and a different proportion of the two types of rhizomes.

A review of adaptive strategies of clonal plants to interspecific competition

Clonal plants have many advantages over non-clonal plants, such as longevity, spatial mobility and two modes of reproduction. Therefore, clonal plants are dominant or constructive species in many natural ecosystems. We re- view the adaptive strategies of clonal plants to interspecific competition and elaborate the differences of competi- tive ability. It accounts for the responses to interspecific competition from those aspects, including modular mor- phology, clonal architecture, reproductive strategy and the relationship between physiological integration and in- terspecific competition. Those factors lead to different results, such as diversities of experimental materials, con- ditions of habitat, design of experiments and dynamic spatial changes of morphology and physiology of clonal plants. Key issues that need research are proposed, including clonal plants and interspecific competition under global change and its molecular ecological mechanism.

Are clonal plants more frequent in cold environments than elsewhere?

In stressful environments, clonality provides plants with reproductive insurance and conservation of limiting nutrients. Hence, clonal growth is expected to be more frequent in floras of cold environments, such as the alpine and arctic regions, than in temperate regions. Evidence for this is largely based on comparisons of the ratio of clonal to non-clonal vascular plant species in local floras, as it is difficult to obtain reliable data that assess the extent of clonality in plant communities. Here we review, to the best of our knowledge, the most comprehensive dataset on the proportion of clonal vascular plant species in regional floras of cold environments/regions. Contrary to our expectations, the results do not show a higher proportion of clonal species in cold environments than in the reference regions. The results rather show regional differences explicable by different species pools and/or climates. More data, which take into account environmental gradients, habitat diversity and different modes of clonal growth, the relative dominance (abundance) of clonal plants, are necessary to test the hypothesis that the ratio of clonal to non-clonal vascular plants in cold environments/regions is higher than elsewhere.