Intraspecific competition and light effect on reproduction of Ligularia virgaurea,an invasive native alpine grassland clonal herb

The relationship between sexual reproduction and clonal growth in clonal plants often shows up at the ramet level. However, only a few studies focus on the relationship at the genet level, which could finally account for evolution. The sexual reproduction and clonal growth of Ligularia virgaurea, a perennial herb widely distributed in the alpine grasslands of the Qinghai‐Tibetan Plateau of China, were studied under different competition intensities and light conditions at the genet level through a potted experiment. The results showed that: (1) sexual reproduction did not depend on density or light, and increasing clonal growth with decreasing density and increasing light intensity indicated that intraspecific competition and light intensity may affect the clonal life history of L. virgaurea; (2) both sexual reproduction and clonal growth show a positive linear relationship with genet size under different densities and light conditions; (3) a threshold size is required for sexual reproduction and no evidence of a threshold size for clonal growth under different densities and light conditions; (4) light level affected the allocation of total biomass to clonal and sexual structures, with less allocation to clonal structures and more allocation to sexual structures in full sunlight than in shade; (5) light determined the onset of sexual reproduction, and the genets in the shade required a smaller threshold size for sexual reproduction to occur than the plants in full sunlight; and (6) no evidence was found of trade‐offs between clonal growth and sexual reproduction under different densities and light conditions at the genet level, and the positive correlation between two reproductive modes indicated that these are two integrated processes. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.     

Infertile times: response to damage in genets of the clonal sedge Carex bigelowii

Tolerance to grazing is a plant trait that can be adaptive in systems where plants are subjected to a diversity of herbivore attack types. To test the tolerance ability of the clonal sedge Carex bigelowii, which is food plant to several herbivores in alpine and arctic areas, and the potential fitness costs of this tolerance, replicated units of genets were subjected to three levels of damage throughout three consecutive seasons. The three levels of treatment were no damage, light damage and heavy damage, and the damage was conducted by tearing off all plant material at 3 and 0 cm above-ground respectively. The genets had no tolerance under damage in terms of sexual reproduction. In terms of clonal reproduction the genets showed tolerance under light damage but not under heavy damage. However, no fitness cost was found for this tolerance ability, i.e. genets had higher reproduction and growth under no damage. The average ramet weight had a similar decrease under both a low and high damage treatment. Changed partitioning of biomass between plant parts and reduced concentration of total non-structural carbohydrates (TNC) in storage organs are possible mechanisms for the ability to uphold clonal reproduction in response to damage. There were no significant indications that tolerance ability or its fitness cost differed between genets. Our results suggest that when subjected to heavy damage genets will only reproduce vegetatively. Consequently, it seems C. bigelowii has evolved to allocate resources to the survival of an already successful genet rather than to a potential new genet of unknown success.     

Vegetative multiplication and patch colonisation of Asarum europaeum subsp. europaeum L. (Aristolochiaceae) inferred by a combined morphological and molecular study

Asarum europaeum subsp. europaeum (Aristolochiaceae) is a rhizomatous herb forming distinct patches in calcareous broadleaved forests. Within natural stands, patches were mapped. In two regions, at least four patches were dug out, and connections between leaf modules through rhizomatous spacers were checked for signs of clonal reproduction (decay, breaking). Modules were sampled for amplified fragment length polymorphism (AFLP) fingerprinting to test whether they represent unique genets or are merigenets of a larger genet (split up by clonal reproduction), respectively.Morphologically, merigenet-relationships were only revealed in few cases with disrupted spacers between modules. With the obtained AFLP profiles for two primer combinations, the samples could be assigned to genets; clonal descendants of the same genet were readily identified. In one patch analysed in detail, 18 samples from 17 unconnected “plants” belonged to only two genets, which were morphologically divided into two and 15 merigenets, respectively. These two genets probably belonged to different maternal lineages and came into contact after lateral spread from the established clones. They showed divergent affinities to samples from adjacent patches (which all represented unique genets).The findings support the suitability of the combined morpho-ecological and molecular approach: compared to either method alone, it allows a more detailed analysis and interpretation of the fine-scale clonal structure, patch colonisation and especially of vegetative multiplication (with morpho-ecological studies to discern clonal growth and clonal reproduction and AFLP fingerprinting for genet and merigenet identification, respectively).     

Local forest environment largely affects below-ground growth, clonal diversity and fine-scale spatial genetic structure in the temperate deciduous forest herb Paris quadrifolia

Paris quadrifolia (herb Paris) is a long-lived, clonal woodland herb that shows strong differences in local population size and shoot density along an environmental gradient of soil and light conditions. This environmentally based structuring may be mediated by differences in clonal growth and seedling recruitment through sexual reproduction. To study the interrelationship between environmental conditions and spatial patterns of clonal growth, the spatial genetic structure of four P. quadrifolia populations growing in strongly contrasting sites was determined. In the first place, plant excavations were performed in order to (i) determine differences in below-ground growth of genets, (ii) investigate connectedness of ramets and (iii) determine total genet size. Although no differences in internode length were found among sites, clones in moist sites were much smaller (genets usually consisted of 1-3 interconnected shoots, most of them flowering) than genets in dry sites, which consisted of up to 15 interconnected shoots, the majority of which were vegetative. Further, amplified fragment length polymorphism (AFLP) markers were used. Clonal diversity was higher in populations located in moist and productive ash-poplar forests compared to those found in drier and less productive mixed forest sites (G/N: 0.27 and 0.14 and Simpson's D: 0.84 and 0.75, respectively). Patterns of spatial population genetic structure under dry conditions revealed several large clones dominating the entire population, whereas in moist sites many small genets were observed. Nevertheless, strong spatial genetic structure of the genet population was observed. Our results clearly demonstrate that patterns of clonal diversity and growth form of P. quadrifolia differ among environments. Limited seedling recruitment and large clone sizes due to higher connectedness of ramets explain the low clonal diversity in dry sites. In moist sites, higher levels of clonal diversity and small clone sizes indicate repeated seedling recruitment, whereas strong spatial genetic structure suggests limited seed dispersal within populations.     

Clonal spread of invasive Ludwigia hexapetala and L. grandiflora in freshwater wetlands of California

Ludwigia hexapetala and L. grandiflora are recent, aggressive invaders of freshwater wetlands in California. To assess the relative role of sexual versus clonal reproduction in invasive spread, we used AFLP markers to genotype 794 ramets of L. hexapetala sampled from 27 populations in three watersheds of California, and 150 ramets of L. grandiflora from five populations in a fourth watershed. We then used two analytical methods, similarity thresholds and character incompatibilities, to distinguish genotypic variation within genets (clones) from variation between genets. Our analyses revealed extremely limited genotypic and genet variation in invasive L. hexapetala and L. grandiflora within California. Within L. hexapetala, 95% of the ramets analyzed represented a single genet. The genet was the only one detected in 20 populations. The remaining seven populations contained two to nine genets. Within L. grandiflora, all ramets were of only one genotype. Thus, invasive spread within and between populations, and across watersheds, appears to be almost exclusively clonal and brought about by the dispersal of vegetative propagules. The extremely low seedling recruitment indicates that management should target vegetative dispersal and growth.     

Clonal Diversity in Differently-Aged Populations of the Pseudo-Annual Clonal Plant Circaea lutetiana L.

Abstract: In many clonal plant species seedling recruitment is restricted to short colonization episodes early in the development of the population, and clonal diversity (i.e., genet diversity) in the population is expected to decrease with increasing population age. In established populations of the pseudo-annual Circaea lutetiana seedling recruitment has previously not been observed. Therefore, we expected established populations to have low clonal diversities. We analysed number and frequency of genets and spatial distribution of genets in six differently-aged C. lutetiana populations with the use of four informative RAPD primers. We found relatively low clonal diversities in young populations but very high clonal diversities in established populations. Therefore, the hypothesis was rejected that seedling recruitment does not occur in established populations. Moreover, we did not find large genet size asymmetries in established populations. Genet size differences can be caused by stochastic processes or by fitness related traits, such as differences in vegetative reproduction. Because vegetative propagation of ramets is dependent on ramet size, and the number of ramets and the size of each ramet determine genet size, we expected that large genets produced, on average, large ramets. However, this was not the case, suggesting that stochastic processes caused genet size differences. Genet size may also be bounded if spatial distribution of genets is affected by micro-habitat differences. For this we expected to find a clumped spatial distribution of ramets of the same genet. However, ramets of large genets were always found intermingled with ramets belonging to other genets.     

Demographic response to shading and defoliation in two woodland orchids

Many woodland herbs are long-lived, clonal geophytes that have evolved life histories favoring survival over reproduction. We examined the life history responses of natural populations of two woodland orchid species,Cypripedium calceolus andCephalanthera longifolia to defoliation and heavy shading conducted early in the growing seasons of 2002 and 2003. We asked whether, in view of the importance of growth for the survival of geophytes, treated plants were more likely to exhibit reduced flowering than reduced vegetative growth in the seasons following treatment. We also asked whether plants would suffer reduced ramet performance. Both treatments led to significant declines in flower number per ramet, number of leaves per ramet, and mean ramet height relative to controls inCypripedium. However, inCephalanthera, only shaded plants exhibited significant declines in flower number per ramet, and only defoliated plants exhibited declines in mean ramet height. The number of ramets per plant did not decline relative to controls in either species. Thus, these orchids, especiallyCypripedium, appeared to allocate resources preferentially to vegetative growth functions over sexual reproduction. Per-plant variation in leaf and flower number per ramet, as well as in mean ramet height, consistently declined in response to treatment, significantly so in the case of mean ramet height, suggesting that ramets became more similar within genets. These results suggest both similarities and differences in the ways in whichCephalanthera andCypripedium mobilize resources in response to stress.     

The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites

Using highly polymorphic microsatellite markers, we assessed clonal structure and paternity in a population of the bryophyte species Polytrichum formosum. Identical multilocus genotypes of individual shoots were almost never observed in spatially separated cushions, but were found to be highly clustered within moss cushions. Therefore, asexual reproduction through dispersal of gametophyte fragments is not very important in P. formosum. However, asexual reproduction on a very localized scale through vegetative growth of genets (branching of gametophytes via clonal growth of rhizomes) is very extensive. The patchy spatial distribution of genets and the absence of intermingling among genets suggest that this species follows a 'phalanx' clonal growth strategy. Vegetative proliferation of genets will increase their size, and, consequently, will have considerable fitness consequences for individuals in terms of increased genet longevity and reproductive output. Although paternity analysis of sporophytes confirmed male genet size, i.e. gamete production, to be an important determinant of male reproductive fitness, it also showed that the spatial distance to female genets is the predominant factor that governs male reproductive success. Moreover, we showed that male gamete dispersal distances in P. formosum are much further than generally assumed, and are in the order of metres rather than centimetres. Combining the findings, we conclude that the high genotypic diversity observed for this facultatively clonal species is most likely explained by a preponderance of sexual reproduction over clonal reproduction.     

Sexual reproduction and clonal growth in Reinhardtia gracilis (Palmae), an understory tropical palm

Patterns of sexual reproduction and clonal growth were investigated in the understory palm Reinhardtia gracilis var. gracilior over a 3-yr period. R. gracilis is a very abundant clonal palm in the tropical rain forest of Los Tuxtlas, Veracruz, México. Because ramets form clumps, genets are easily identified in the field. Genets were monitored in a 0.5-ha area, and classified by size according to the number of ramets they possessed. In contrast to clonal growth, sexual reproduction was highly dependent on genet size. The probability of reproduction, the number of inflorescences, and the number of fruits produced were positively correlated with genet size. However, neither the probability of producing a ramet, nor the number of ramets produced per genet were correlated with genet size. Over the 3 yr of study, 55% of the genet population had at least one ramet with reproductive structures, while <1% (a single genet in one year) had six ramets with flowers. Thirty-two percent of the mature genets reproduced during each of three consecutive years. In contrast, 58% of the genets produced no new ramets during these 3 yr. No evidence was found of a trade-off between clonal growth and sexual reproduction. Ramet production increases genet size and this in turn increases genet reproductive performance. Clonal growth in this species may be viewed as a growth strategy that tends to maximize genet fitness.     

Dynamics of distribution and performance of ramets constructing genets: a demographic�Cgenetic study in a clonal plant, Convallaria keiskei

Background and Aims

In clonal plants producing vegetative offspring, performance at the genet level as well as at the ramet level should be investigated in order to understand the entire picture of the population dynamics and the life history characteristics. In this study, demography, including reproduction and survival, the growth patterns and the spatial distributions of ramets within genets of the clonal herb Convallaria keiskei were explored.

Methods

Vegetative growth, flowering and survival of shoots whose genets were identified using microsatellite markers were monitored in four study plots for 3 years (2003–2005). The size structures of ramets in genets and their temporal shifts were then analysed. Their spatial distributions were also examined.

Key Results

During the census, 274 and 149 ramets were mapped in two 1 × 2 m plots, and 83 and 94 ramets in two 2 × 2 m quadrats. Thirty-eight genotypes were identified from 580 samples. Each plot included 5–18 genets, and most ramets belonged to the predominant genet(s) in each plot. Shoots foliated yearly for several years, but flowering ramets did not have an inflorescence the next year. A considerable number of new clonal offspring persistently appeared, forming a bell-shaped curve of the size structure of ramets in each genet. Comparing the structures modelled by the normal distributions suggested variation among ramets belonging to a single genet and variation among genets. Furthermore, spatial analyses revealed clumped and distant distributions of ramet pairs in a genet, in which the distant patterns corresponded to the linearly elongating clonal growth pattern of this species.

Conclusion

Characteristics of ramet performances such as flowering and recruitment of clonal offspring, in addition to growth, played a large part in the regulation of genet dynamics and distribution, which were different among the studied genets. These might be characteristics particularly relevant to clonal life histories.Key words: Clonal plant, Convallaria keiskei, demography, genet, genetic identification, growth pattern, life history, ramet, spatial distribution     

不同养分条件下和不同生境类型中根茎草本黄帚橐吾的克隆生长

 对多年生植物黄帚橐吾(Ligularia virgaurea)在不同氮肥梯度和不同生境类型中的克隆生长行为进行研究。结果表明：1)资源水平与群落性质影响着间隔子(Spacer)长度的变化,氮肥处理使之明显变短;自然群落中的间隔子长度远远长于人工群落,说明黄帚橐吾间隔子具有很强的形态可塑性,能对资源水平和生境优劣作出反应。2)分枝强度(Branching intensity)具有随资源水平的增高而上升的趋势,表明无性系分株(Ramet)的形成和生长受环境资源状况和源株(Genet)生长状况的影响;3)黄帚橐吾的分枝角度为0˚或180˚,资源水平与环境差异对其影响不大,可塑性低;4)环境资源贫乏或植株比较拥挤时,黄帚橐吾个体根系资源分配比例加大,说明黄帚橐吾的资源分配(Resource allocation)模式更多地受环境资源条件和群落性质的影响。     

不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明：（1）在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。（2）黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量（TB）大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60 d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比（R/S）大于小种子幼苗。（3）黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率（RGR）较大于大种子幼苗,但叶面积比率（LAR）、叶面积干质量比（SLA）、叶干质量（LWR）差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

Effects of intraspecific competition on size variation and reproductive allocation in a clonal plant

Clonal plants grow in diameter rather than height, and therefore competition among genets is likely to be symmetric and to result in smaller variation in size of genets than in non-clonal plants. Moreover, clonal plants can reproduce both sexually and vegetatively. We studied the effects of density on the size of rosettes and of clones, variation in the size of rosettes and of clones, and allocation to sexual and vegetative reproduction in the clonal herb Ranunculus reptans . We grew plants from an artificial population of R. reptans in 32 trays at two densities. After four months, differences in density were still apparent, although clones in the low-density treatment had on average 155% more rosettes and 227% more rooted rosettes than clones in the high-density treatment. The coefficient of variation of these measures of clone size was 15% and 83% higher, respectively, in the low-density treatment. This indicates that intraspecific competition among clones of R. reptans is symmetric and increases the effective population size. Rooted rosettes were larger and varied more in size in the low-density treatment. The relative allocation of the populations to sexual and to vegetative reproduction was 19% and 13% higher, respectively, in the high-density treatment. Moreover, seeds produced in the high-density treatment had a 24% higher mass and a 7% higher germination percentage. This suggests that with increasing density, allocation to sexual reproduction increases more than allocation to vegetative reproduction in R. reptans , which corresponds to the response of some other species with a spreading growth form but not of species with a compact growth form. We conclude that intraspecific competition is an important factor in the life-history evolution of R. reptans because intraspecific competition affects its clonal life-history traits and may affect evolutionary processes such as genetic drift and selection through its effect on the effective population size.     

SEXUAL DIMORPHISM IN BIOMASS ALLOCATION AND CLONAL GROWTH OF XANTHOXYLUM AMERICANUM

Reproduction can have a high resource cost. It has been suggested that greater investments in sexual reproduction by female dioecious plants leads to a lower rate of vegetative growth in females than in males. In this study, we investigated sexual dimorphism in biomass allocation and genet growth of the dioecious clonal shrub, northern prickly ash (Xanthoxylum americanum). The allocation of biomass over the course of one growing season to reproductive tissue, leaves, and growth of aboveground first-year wood, was compared in 18 clones growing in fields and six clones in woods in southeastern Wisconsin during 1985 and 1986. In addition, the number of shoots per clone, and weight of nonfirst-year wood (accumulated biomass) above- and below-ground were estimated. In open field sites, male clones allocated more biomass to new wood and less to reproduction than females, although males allocated more to flowers alone. Accordingly, male clones had significantly more shoots and more accumulated biomass both above- and below-ground than female clones. In the woods, where fruit set was near zero, there were few significant differences between male and female clones in either biomass allocation or accumulated biomass. These results support the hypothesis that the high resource investment in fruit production by females reduces their vegetative growth relative to males.     

Density-dependent reproductive and vegetative allocation in the aquatic plant Pistia stratiotes (Araceae)

Pistia stratiotes is an aquatic macrophyte that grows in temporary-ponds in the southern Pantanal, Brazil. It reproduces both sexually and asexually and is usually observed forming dense mats on the water surface, a condition favored by the plant's vegetative reproduction coupled with an ability for rapid growth. In this study we examined the effect of densely crowded conditions on the production of reproductive and vegetative structures. In addition, we verified whether there is a trade-off between clonal growth and investment in sexual reproductive structures, and whether there is an allocation pattern with plant size. Individual plant biomass and the number of the rosettes producing sexual reproductive structures and vegetative growth structures both increased with density. Increase in plant size resulted in increased proportional allocation to sexual reproductive structures and vegetative growth structures. Allocation of biomass to reproduction did not occur at the expense of clonal growth. Thus, the density response appears as a increase of rosettes producing sexual reproductive structures and vegetative growth structures. Therefore, long leaves and stolons may be adaptive under densely crowded conditions where competition for light is intense. An important aspect in the study of trade-offs is the size-dependency of the allocation patterns .Usually, larger plants produce more biomass. Therefore, larger plants can allocate more biomass to both vegetative and sexual reproduction than smaller plants and thus show a positive correlation between both traits rather than the expected negative one.     

Clonal reproduction, vegetative multiplication and habitat colonisation in Tussilago farfara (Asteraceae): A combined morpho-ecological and molecular study

Using a combined morpho-ecological and molecular (amplified fragment length polymorphism (AFLP) fingerprinting) approach, clonal growth, clonal reproduction and the resulting vegetative multiplication were examined in the pioneer species Tussilago farfara (Asteraceae).

In two forest plots in Berlin (Germany), all modules and spacers of the plant were mapped and dug out. The plants showed intense clonal growth with leaf modules connected through long branched rhizomes. The rhizomes were brittle and regularly exhibited rotting zones and breaks. This clonal reproduction can occur rather fast; in a submersed stand in Lanke (Brandenburg, Germany), rhizomes showed signs of disintegration only a few weeks after the modules developed. As a consequence, modules become separated and genets fragment into merigenets.

Using AFLP fingerprints, the relationships of samples from the two dug out plots were assessed: 15 and 18 analysed samples (representing 13 and 16 merigenets) belonged to only two and three distinct genets, respectively. Each of these genets was split into at least two to eleven morphologically independent merigenets, indicating frequent and effective clonal reproduction.

The study highlights the relevance of vegetative multiplication in T. farfara, achieved rapidly through repeated clonal growth and subsequent clonal reproduction. The typical strategy of habitat colonisation and maintenance is described and illustrated for this pioneer species.     

Female and male fitness consequences of clonal growth in a dwarf bamboo population with a high degree of clonal intermingling

Background and Aims

Although many studies have reported that clonal growth interferes with sexual reproduction as a result of geitonogamous self-pollination and inbreeding depression, the mating costs of clonal growth are expected to be reduced when genets are spatially intermingled with others. This study examined how clonal growth affects both female and male reproductive success by studying a population of a mass-flowering plant, Sasa veitchii var. hirsuta, with a high degree of clonal intermingling.

Methods

In a 10 × 10 m plot, genets were discriminated based on the multilocus genotypes of 11 nuclear microsatellite loci. The relationships between genet size and the components of reproductive success were then investigated. Male siring success and female and male selfing rates were assessed using paternity analysis.

Key Results

A total of 111 genets were spatially well intermingled with others. In contrast to previous studies with species forming distinct monoclonal patches, seed production linearly increased with genet size. While male siring success was a decelerating function of genet size, selfing rates were relatively low and not related to genet size.

Conclusions

The results, in conjunction with previous studies, emphasize the role of the spatial arrangement of genets on both the quantity and quality of offpsring, and suggest that an intermingled distribution of genets can reduce the mating costs of clonal growth and enhance overall fitness, particularly female fitness.     

Optimal allocation of resources in response to shading and neighbours in the heteroblastic species, Acacia implexa

BACKGROUND AND AIMS: Heteroblasty is an encompassing term referring to ontogenetic changes in the plant shoot. A shaded environment is known to affect the process of heteroblastic development; however, it is not known whether crowded or high density growing conditions can also alter heteroblasty. Compound leaves of the shade-intolerant Acacia implexa allocate less biomass per unit photosynthetic area than transitional leaves or phyllodes and it is hypothesized that this trait will convey an advantage in a crowded environment. Compound leaves also have larger photosynthetic capture area - a trait known to be advantageous in shade. This studied tested the hypothesis that more compound leaves will be developed under shade and crowded environments. Furthermore, this species should undergo optimal allocation of biomass to shoots and roots given shaded and crowded environments. METHODS: A full factorial design of irradiance (high and low) and density levels (high, medium and low) on three populations sourced from varying rainfall regions (high, medium and low) was established under controlled glasshouse conditions. Traits measured include the number of nodes expressing a compound leaf, biomass allocation to shoots and roots, and growth traits. Key Results A higher number of nodes expressed a compound leaf under low irradiance and in high density treatments; however, there were no significant interactions across treatments. Phenotypes strongly associated with the shade avoidance syndrome were developed under low irradiance; however, this was not observed under high density. There was no significant difference in relative growth rates across light treatments, but growth was significantly slower in a crowded environment. Conclusions Heteroblastic development in Acacia can be altered by shade and crowded environments. In this experiment, light was clearly the most limiting factor to growth in a shaded environment; however, in a crowded environment there were additional limiting resources to growth.     

Short‐term fitness benefits of physiological integration in the clonal herb Hydrocotyle peduncularis

Abstract We test whether physiological integration enhances the short‐term fitness of the clonal herb Hydrocotyle peduncularis (Apiaceae, R. Brown ex A. Richards) subjected to spatial variation in water availability. Our measures of fitness and costs and benefits are based on the relative growth rate of fragmented genets. Physiological integration over a gradient in soil moisture resulted in a highly significant net benefit to genet growth of 0.015 g g^?1 day^?1. This net benefit represents a significant enhancement of the average fitness of fragmented genets spanning the moisture gradient relative to the average of those growing in homogeneous moist or dry conditions. Sections of genet fragments growing in dry conditions in spatially heterogeneous treatments had significantly higher growth than the sections they were connected to that were growing in moist conditions. Within fragments, older (parent) sections growing in moist conditions experienced significant costs from connection to younger (offspring) sections growing in dry conditions. In contrast, offspring sections with ample water did not experience any costs when connected to parent sections growing in dry conditions. However, the net benefit of physiological integration was similar for parent and offspring sections, suggesting that parent and offspring sections contributed equally to the net benefit of physiological integration to genet growth and short‐term fitness.     

Spatial genet dynamics of a dwarf bamboo: Clonal expansion into shaded forest understory contributes to regeneration after an episodic die-off

The ability of clonal plants to spread horizontally and to share resources within genets has long been considered advantageous in spatially heterogeneous environments, yet our understanding of how such traits relate to its widespread success and dominance is still limited. Using a dwarf bamboo, Sasa kurilensis, that often dominates cool-temperate forest understorys, we investigated how population recovery over 20 years after an episodic die-off may be augmented by clonal expansion via rhizomes. Previous analyses on genet demography using 9-m² plots showed that more productive genets were more likely to survive, spread laterally, and replace less productive ones. In this study, we examined whether the recovery of biomass in lower light microsites, where biomass recovery was initially slower, was supported by the spread of productive genets at larger scales, from surrounding higher-light microsites. We found that the biomass recovery in lower-light plots was more supported by genets that spread clonally into the plots. Such genets that spread from outside plots produced larger culms than those that had originally germinated there. Whereas genets that contributed much to the biomass of the low-light plots spread extensively from higher-light microsites, the spatial extent of genets that originally germinated in these plots was quite limited, so that the patterns of clonal expansion appeared to be unidirectional along the light gradient. Our findings suggest that clonal expansion of productive genets from higher-light into shaded microsites may be important for S. kurilensis to proliferate across heterogeneous light environments.