Flowering Ramets Research Articles

Floral distribution, clonal structure, and their effects on pollination success in a self-incompatible Convallaria keiskei population in northern Japan

In plant species, when clonal growth produces a patchy structure and flowering ramets are clustered, the amount of pollen contributing to reproductive success is often regulated by pollinator efficiency and geitonogamy. The spatial population structure may influence reproductive success. We examined the clonal structure, the spatial ramet distribution, and their combined effects on fruit set in a natural population of the insect-pollinated, self-incompatible clonal herb, Convallaria keiskei, in northern Japan. The number of shoots, flowers, and fruits in 1-m2 quadrats were counted at every 5 m grid point in an established 100 × 90-m study plot. From all the quadrats where shoots existed, leaf samples were collected for allozyme analysis. Using the two spatial parameters of flowering ramet densities and genotypes, we then constructed individual-based fruit-set models. A total of 236 quadrats contained shoots, and 135 contained flowering ramets, which indicated expanded distribution of this plant throughout the study plot, while shoots, flowers and fruits all showed clustering distributions. Allozyme analysis of 282 samples revealed 94 multilocus genotypes. The largest clone extended to more than 40 m, whereas 56 genotypes were detected in only one sample. Several large clones and many small clones were distributed close to each other. Fine-scale spatial modelling revealed that the neighbouring flower numbers of different genotypes, compared with local genet or flower diversity, more influenced fruit set, in which the range of the neighbour was 14.5 m. These findings indicate that the compatible pollen dispersed by insect pollinators has a significant effect on sexual reproduction, in this C. keiskei population. Consequently, the spatial structure, which includes both genet distribution and clonal expansion by ramets, had a significant effect on pollination success.

Comparison of size vs. life-state classification in demographic models for the terrestrial orchid Cleistes bifaria

Recent studies using capture–recapture modelling in terrestrial orchids have shown relationships among survival, life-state, climate and dormancy, but to date, there has been no rigorous study of the effects of size on demographic rates. Here we use multistate capture–recapture models to investigate the relationships between survival, ramet size, life-state, and propensity for extended dormancy of Cleistes bifaria in two populations in Florida and West Virginia. Using estimated leaf area as a measure of ramet size, we investigated relative fit to the data of models in which ramets were classified by life-state alone (dormant, vegetative, and flowering), size alone (dormant, small, and large), or by a combination of size and state (dormant, small vegetative, large vegetative, small flowering, and large flowering ramets). This scheme allowed us to compare the effects of a size versus state classification on survival and transition probabilities, including the propensity for dormancy. For survival rates, the size-classified model was preferable in terms of parsimony (AIC) to models classified either by state or by a combination of size and state. In C. bifaria, annual survival rate for large ramets was close to 1.0 and for small and dormant ramets, 0.91 and 0.76, respectively. This highlights the importance of protecting large plants. In contrast, a model combining life-state with ramet size was most parsimonious for explaining variation in transition rates. As the ‘size + state’ classification is convenient, holds more information, and seems more closely tied to fitness than classification by either size or life-state alone, it may be particularly useful in planning and assessing conservation management of orchids.

Heavy metals modify costs of reproduction and clonal growth in the stoloniferous herb Potentilla anserina

We examined costs of sexual reproduction and clonal propagation, and their consequences for resource allocation in the clonal stoloniferous herb, Potentilla anserina, a typical pioneer species in disturbed areas. We used heavy-metal treatment in soil to create unfavourable growing conditions, because costs of reproduction are more likely to be expressed when resources are limited. We also studied whether heavy metals affect the plasticity of clonal growth form that enables the plants to avoid poor growing conditions. Ramets collected from field were grown in a greenhouse under the heavy-metal treatment consisting of a control and two levels of heavy-metals added in soil. Clonal propagation was costly in terms of total biomass of flowering ramets. Also the costs of sexual reproduction were detected in flowering ramets. Contrary to our predictions, the costs of flower production were visible in the control but not in the heavy-metal contaminated plants. Only the flowering ramets were able to produce longer stolons under heavy-metal stress, but the stolon biomass was not affected by heavy metals. Results indicate that clonal propagation and sexual reproduction may be costly for P. anserina. However, the costs are modified by heavy-metal contamination.

Intraclonal variation in defence substances and palatability: a study on Carex and lemmings

Clonal sedges consist of integrated ramets at different development stages. Many of these sedges are important food for herbivores, yet differences in herbivore preferences and defence allocation between ramet development stages have not previously been evaluated. In this study we investigated intraclonal ramet variation in level of plant defence and nutrient compounds and intraclonal ramet preferences by lemmings (Lemmus trimucronatus) in field samples of a rhizomatous sedge (Carex stans). Plant defence was measured as the level of proteinase inhibitor activity (PIA) and the ratio of PIA to soluble plant proteins (SPP), whereas plant nutrients were measured as the level of soluble plant sugars (SPS) and SPP. Flowering ramets generally had a higher content of defence compared to vegetative ramets, which is consistent with the optimal defence theory predicting that defence compounds are allocated to the ramet stage of the highest fitness value. Compared to vegetative ramets, the flowering ramets had a lower content of SPP and a higher content of SPS. The lemmings showed preference differences between the ramet development stages, and to a large extent the ramet content of defence compounds and nutrient compounds covaried with these preferences in the predicted way. This study shows that defence allocation between ramet development stages of the clonal sedge Carex conforms to predictions of the optimal defence theory.

Effects of population spatial structure on the quantity and quality of seeds set byPrimula sieboldii(Primulaceae)

AbstractEffects of spatial population structure on the reproductive success ofPrimula sieboldiiE. Morren, an endangered heterostylous perennial, were studied through the analysis of quantity and quality of seeds in a natural habitat in central Japan. Seed set of individual flowering ramets varied significantly depending on the degrees of isolation from their potential mates. The flowering ramets, which have the opposite‐morph ramets within 5 m, set significantly higher mean seeds per flower (approx. 15) than that of more isolated ramets (approx. 5). The former produced a considerably variable number (0–100) of seeds per flower, while the latter set more or less uniform number of seeds per flower. Viability of seeds from the former ramets was also variable with significantly higher mean viability percentage than the latter. Early seedling survival was also significantly different between the maternal isolation classes, while survival and growth of the established seedlings in a greenhouse did not differ significantly between these classes. The level of allozyme heterozygosity of the surviving progenies was not significantly different between the classes differing in maternal isolation. The observation suggests that the isolated maternal plants produced fewer and less viable seeds, which may be a result of strong inbreeding depression that manifests in early life stages of the progenies. By the stage of seedling establishment, therefore, less fit homozygotes are purged while fitter heterozygotes are allowed to survive irrespective of maternal isolation.

Population Size and Reproduction inPhlox pilosa

Abstract:We analyzed the relationships between population size and reproductive characteristics in the perennial prairie forbPhlox pilosa, an obligate outcrossing butterfly‐pollinated species. We examined 27 populations ranging in size from 9 to over 75,000 flowering ramets in two regions of the state of Iowa (eastcentral and northwest) in 1993 and 1994. We collected flowers from each population and scored them for pollen arrival to stigmas and number of pollen tubes. We collected fruiting ramets from each population at the end of thePhloxgrowing season and scored them for height, biomass, and reproductive variables, including the number of flowers initiated and opened and the number of capsules initiated and matured. In both years, population size was significantly correlated with the number of capsules matured per ramet. Differences between populations in capsule production were set primarily at the pollination stage. In 1993, pollen arrival to stigmas was significantly lower than in 1994 and was correlated with population size in eastcentral Iowa populations, indicating that lower reproduction in small populations that year was at least partially due to inadequate amounts of pollen being moved. In 1993, weather conditions likely depressed pollinator activity, but absolute capsule formation was high because of high flower production per ramet and high population densities. In 1994, when pollen arrival to stigmas was relatively high and unrelated to population size, outcross pollen movement was greater in larger populations. Increased efficacy of outcross pollen movement in 1994 may have resulted from lower flower production and less dense populations forcing greater pollinator movement between ramets or from variation between years in fine‐scale spatial genetic substructuring of populations. Our results indicate that the viability ofPhlox pilosacan be best ensured by protecting and creating populations of at least 1000–2000 flowering ramets.

Early reproductive failure increases nectar production and pollination success of late flowers in south Andean Alstroemeria aurea.

Fertile ramets of bumblebee-pollinated Alstroemeria aurea, a clonal perennial native to the temperate forests of the southern Andes, produce single terminal inflorescences that may bear two or more temporally non-overlapping whorls of flowers. While fruit set is commonly high (>80%) among early-opening flowers, it is usually low (<20%) among late-opening flowers within ramets. Using flowering ramets with two whorls of flowers, we examined experimentally the following related hypotheses. First, late flowers act as a reserve of ovaries, increasing their likelihood of setting seed when early fruits abort due to either pollen or resource limitation. Second, where early fruit abortion has occurred, plants may actively ensure pollination of late flowers by increasing their attractants and rewards. In a natural population, we simulated (1) lack of pollen deposition in early flowers, by excising their stigmas just before receptivity, and (2) resource limitation, by removing all the leaves from an experimental flowering ramet. Treatments were applied to individual ramets according to a 2 × 2 factorial design. We found that when early flowers failed to set fruit due to stigma excision, nectar secretion and particularly pollen receipt strongly increased in late flowers. Higher pollen deposition contributed significantly to the observed five-fold increase in seed output of late flowers. Fruit and seed set from early flowers were more negatively affected by defoliation than that from late flowers. Defoliation did not interfere with a ramet's capacity to increase late reproductive output when early reproduction failed. These results support the assertion that late flowers act as a reserve of ovaries helping a plant to cope with an unpredictable environment. These results also suggest that plants may actively increase pollinator visitation by opportunistically increasing flower rewards.

The Effects of Population Size and Density on the Reproductive Output of Anemone canadensis L. (Ranunculaceae)

We studied the effects of population density and population size on stigma pollen load and fruit set in Anemone canadensis, a xenogamous self‐incompatible species. In 1993, 1994, and 1995, we examined 13–17 populations, with densities ranging from one to 39 flowering ramets per square meter and sizes ranging from 25 to 27,000 flowering ramets. In 1993, stigmas received fewer pollen grains than in 1994 or 1995. In 1993 and 1995, population size and fruit set were significantly and positively related, and in 1993, both population density and stigma pollen load were significantly and positively related to fruit set. Stigma pollen load was not significantly related to population density or size. Our results indicate that the effects of population density and population size on plant reproduction in A. canadensis represent a range of outcomes influenced by differences between years in the quality (self vs. outcross) of pollen moved. We hypothesize that small populations typically have poor fruit set because th...

Roles of succession, light, nutrients and disturbance on population vigor and maintenance of the rare plant Solidago shortii (Asteraceae)

Results of field and glasshouse experiments on Solidago shortii, and our observations on this species over many years, were used to construct a conceptual model of the roles of succession, light, soil nutrients and disturbance on population vigor and maintenance of this federal-endangered species. As cover of woody vegetation increased at a population site between 1986 and 1992, number of flowering ramets of S. shortii significantly decreased but number of vegetative ramets remained nearly constant. Adult plants transplanted into a redcedar thicket and those shaded in a glasshouse produced many fewer flowering ramets and capitula per flowering ramet and less biomass and had higher mortality than those in the open. Seedlings/juveniles shaded in a glasshouse had significantly less dry biomass; lower RGR, NAR, leaf area and root/shoot ratio and higher LAR, SLA and LWR than nonshaded ones. In a field site and glasshouse, fertilized plants (NPK) consistently had more flowering ramets and capitula per flowering ramet than nonfertilized ones. Hierarchy of dry weight of plants grown in a glasshouse in soils derived from five types of bedrock was phosphatic limestone > calcareous shale > sandstone > black shale = dolomite. Flowering and biomass production in the field-fertilizer and soil-type experiments were associated closely with levels of P. Number of flowering ramets significantly increased in plants transferred from shaded to nonshaded glasshouse conditions, but no such increase occurred after opening the canopy above plants in a thicket. Both high light and high nutrient levels apparently are necessary to maintain high vigor of S. shortii. In areas subject to invasion by woody plants, periodic high intensity disturbance may be required to prevent population extirpation.

Sex ratios, size distributions, and sexual dimorphism in the dioecious tree Ilex aquifolium (Aquifoliaceae)

Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain. Genet sex ratio was significantly male biased in one locality but not in the other. However, ramet and flowering ramet sex ratios were male biased at both study sites. Males had significantly thicker main trunks than females in one locality and produced more ramets in the other. Growth rate, estimated from mean width of annual rings, did not differ between localities, but males produced wider rings than females at both sites. Mean annual growth rates over the last 10, 20, and 30 yr were significantly higher for males. Measurements of chlorophyll fluorescence indicated that the efficiency of photosynthesis of leaves on nonfruiting branches of females was higher than for leaves on branches of male plants under low-light conditions, though not under saturating-light conditions. Efficiency of photosynthesis was significantly lower on fruiting branches of female plants than on nonfruiting branches. We discuss whether the observed between-sex differences are attributable to the higher cost of reproduction in females and/or to pollen competition.

Influence of local floral density and sex ratio on pollen receipt and seed output: empirical and experimental results in dichogamous Alstroemeria aurea (Alstroemeriaceae).

Local density and sexual composition are two aspects of floral neighborhoods thought to influence pollination and seed output of recipient plants. I characterized the floral neighborhood of 436 flowering ramets of Alstroemeria aurea, a southern Andean perennial, distributed among three sites. On each ramet, I measured total pollen receipt and seed output. The long-lived, bumblebee-pollinated flowers of A. aurea are synchronously protandrous with a given ramet being either all male or all female and thus incapable of self or geitonogamous pollination at the ramet level. Even though each ramet changes sex over time, A. aurea forms floral neighborhoods that remain stable with respect to density and sex ratio during the span of a focal ramet female phase. Contrary to expectation, under field conditions neither local density nor sexual identity explained significant amounts of variation in pollen receipt. Density of neighboring flowering ramets marginally affected pollen receipt in two of the three populations but in opposite directions. Despite the absence of strong effects of neighborhood sexual composition on pollen receipt, the sexual identity of neighbors affected seed output which suggests effects on the quality of pollination due to changes in patterns of pollen flow. I also compared pollen loads on the stigmas of artificially isolated ramets (6 m) with those on experimental focal ramets surrounded by six close neighbors (20 cm) that were either all male or all female. Here, pollen receipt by focal ramets in all-male neighborhoods was 1.3 times greater than in isolated ramets, and 3.8 times greater than in ramets in all-female neighborhoods. In these artificial neighborhoods, stigmatic pollen deposition increased significantly over time. In nature, rates of bumblebee visits were higher in female-biased (early-flowering) than in male-biased (late-flowering) co-occurring floral patches. Thus, spatio-temporal shifts in visitation frequencies associated with the sexual composition of floral neighborhoods might compensate for spatial variability in pollen availability within populations and explain the discrepancies between empirical and experimental results.

Surfgrass (Phyllospadix Torreyi) Reproduction: Reproductive Phenology, Resource Allocation, and Male Rarity

Little is known about the reproductive ecology of aquatic angiosperms, despite their wide distribution and ecological importance. Surfgrass (Phyllospadix torreyi) is a clonal marine angiosperm that lives on turbulent rocky shores. Surfgrass exhibits a strongly female—biased sex ratio in flowering shoots throughout its distribution along the Pacific coast of North America. The ecological causes for this biased sex ratio were examined over 3 yr in a surfgrass population off Catalina Island in southern California, USA. Abundances, biomass, and C:N content of male and female flowering ramets were measured, and the reproductive phenology, reproductive losses to abortions, herbivore damage to fruits and seeds, and clonal survival and growth were quantified. Each year, a quarter of the vegetative ramets reproduced sexually and seed production in the population was prolific. The population sex ratio was female biased across the entire depth distribution of surfgrass, but males were more abundant deeper in the bed. Despite male rarity, pollen was abundant in the population, and virtually all ovules were fertilized, with few losses to abortions or herbivory before seed release. Potential female fitness (seeds produced) was highest at shallow depths where light availability was greatest and abortions were reduced. The spatial segregation of the sexes was not due to environmental sex lability but to greater ramification of female vs. male clones in shallow depths. Female flowering shoots had significantly higher biomass than males across water depth, despite no obvious cost in terms of vegetative growth, or advantage in terms of plant size. If current theory on sex allocation than the sex ratio should be biased toward the gender with the lower reproductive cost is true for surfgrass, then surfgrass provides an example of how a subtle resource allocation difference can result in a dramatic population bias. An alternative explanation for the female bias in surfgrass population is greater male mortality due to significantly weaker attachment to the substratum. This study demonstrates the potential role hydrodynamics can play in aquatic plant reproduction and in structuring their population.

Effects of Rock Climbing on Cliff Goldenrod (Solidago sciaphila Steele) in Northwest Illinois

-Solidago sciaphila is an endemic goldenrod, restricted to dolomite or sandstone cliffs in and near the driftless region of the upper Midwest. A demographic study of 544 genets on currently climbed, previously climbed and unclimbed dolomitic cliffs in NW Illinois indicated that position on the cliff face was the most significant factor affecting growth. Seventy percent of all plants grew within 3 m of the cliff top, an area that comprised only 18% of the cliff face. Within the upper cliff zone, rock climbing significantly reduced Solidago density. Cliffs that were actively climbed had few genets in the upper 3 m, averaging 3.2/M2, while unclimbed cliffs and cliffs not climbed for 2 yr supported 14.2/M2 and 12.0/ i2, respectively. Basal area/M2 and flowering ramet production/m2 were significantly lower, and inflorescence length nonsignificantly lower, on currently climbed cliffs, due to the lower genet density. In the lower cliff zone (>3 m from the top) genet density was low (0.2-2.1/ m2) on all cliffs, regardless of climbing intensity. On climbed cliffs > 50% of flowering ramets were broken, significantly more than the 15% broken on unclimbed cliffs. Broken flowering ramets produced 22% of total inflorescence length on the currently climbed cliffs (compared to <5% on unclimbed and previously climbed cliffs), resulting in total inflorescence production statistically similar to, but lower than, that on unclimbed and previously climbed cliffs. Two years after cessation of climbing, Solidago in the upper zone of the previously climbed cliffs had similarly high density, basal area, ramet production and inflorescence production as on unclimbed cliffs. Climbing appeared to skew the population structure, favoring survival of large flowering genets and inhibiting survival of smaller nonflowering genets. This difference largely disappeared on cliffs unclimbed for 2 yr. To protect Solidago sciaphila, it is necessary to protect the entire cliff face, with highest priority given to the upper 3 m.

The effects of physical damage on seed production in flowering plants of Saponaria officinalis

Individual flowering ramets in a large riverbank stand of Saponaria officinalis, bouncingbet, were subjected to three damage treatments at anthesis: removal of most flowers, removal of all leaves, and bending of the stem just below the inflorescence. All seeds were collected from ripened capsules of treated plants as well as from a group shaded by a canopy of Convolvulus sepium and from an untreated control group. Seeds from the defloration treatment were significantly heavier than those from the other treatments. In the control, bent stem, and shaded treatments the seed masses were distributed in a bimodal manner, with most seeds forming a normal distribution around a midpoint of 1.5–1.7 mg and a cohort of heavy seeds having a mean mass of 2.5 mg. This heavy cohort (mode) was missing from the defoliation treatment. Of the total variation in seed mass, 36% was among individuals, 54% was among inflorescences within individuals, and only 10% was within inflorescences. This suggests that resources are allocated differentially between capsules at different positions on the inflorescence but almost uniformly within the individual capsule. Key words: defoliation, defloration, bouncingbet, seed production, Saponaria officinalis.

Importance of Queen Bumble Bees as Pollinators Facilitating Inter‐morph Crossing inPrimula sieboldii

AbstractFlower‐visiting insects, the distribution of pollen on an insect's body, and fruit and seed sets ofPrimula sieboldiiE. Morren were investigated in a maritime deciduous forest habitat of the Hidaka region in Hokkaido. Queens ofBombus diversus tersatusSmith (Hymenoptera: Apidae),Bombus schrencki albidopleuralisSkorikov, andBombus deuteronymus deuteronymusSchulz were observed to visit the flowers of the species. Bumblebee claw marks were found on the flower petals of 68% of the flowering ramets of the species. Scanning‐electronmicroscopy revealed that pin and thrum pollens ofP. sieboldiiwere deposited in different positions along the proboscis of aB. diversus tersatusqueen (n=38400 grains). On the glossa, all the observed pollen was of the pin type, while more than half of the pollen grains observed on the upper part of the proboscis, galea, stipes, and maxillary palpus were of the thrum type. In the field, high fruit and seed sets were recorded for both pin and thrum morphs, indicating the occurrence of sufficient legitimate pollination during the flowering season. In addition to the effectiveness of queen bumblebees as pollinators forP. sieboldiisuggested in this study, phenological and morphological matches, i.e., early spring flowering during the queen bee emergence season and the similar lengths of the corolla tube and the bee proboscis, also support the inference that queen bumble bees play an important role in legitimate pollination ofP. sieboldii.

Within- and between-population variation in ramet behaviour in the gynodioecious clonal herb, Glechoma hederacea (Labiatae)

Clones of the gynodioecious herb Glechoma hederacea L. produce ramets which flower and bear seed, ramets which flower but fail to bear seed, and sterile ramets. Performance and survivorship of these subsets of ramets were compared for hermaphrodite and male sterile clones in contrasting grassland and woodland habitats for 2 consecutive years. For all clones, ramet densities on given dates were comparable between years. Winter survival of ramets exceeded 95% and mortality during the growing season was exponential. No genet recruitment was recorded throughout the study. For all clones, flowering ramets were larger than nonflowering ramets. Both flowering and nonflowering ramets of hermaphrodite clones, from grassland and woodland, were significantly larger than corresponding types of ramets from male sterile clones. A higher proportion of ramets of hermaphrodite clones flowered and set seed than ramets of male sterile clones. Flowering ramets of hermaphrodite clones produced more flowers than flowering ramets of male sterile clones. For all clones, half-lives of subsets of ramets declined in the order: seed-bearing &gt; flowering but not seed-bearing &gt; nonflowering. Within the grassland habitat, ramet subsets from hermaphrodite clones had longer half-lives than corresponding subsets from the male sterile clones. In the absence of greater flowering and seed set by male sterile clones, self-incompatibility of hermaphrodite flowers, which has been reported previously for G. hederacea, is crucial for the maintenance of clones of both sexes in populations.

Paradioecy and Gender Ratios in Carex macrocephala (Cyperaceae)

Genets of Carex macrocephala, a species reported in the literature as dioecious, are monoecious with unisexual flowering ramets. In the two large populations on the coast of Washington that were censused, all genets had female-biased gender ratios. Differentiation of flower primordia is at least partially controlled by the presence of a vegetative ramet distal to the flowering ramets.

Spatial pattern, floral sex ratios, and fecundity in dioecious Aralia nudicaulis (Araliaceae)

Aralia nudicaulis L. (Araliaceae) is a perennial understory herb of the boreal forest which forms large clones by means of an extensive subterranean rhizome system. Populations are dioecious and pollinated primarily by bumble bees. To examine the relationships between the spatial pattern of sexual morphs and female fecundity, all flowering ramets were mapped in a 1-ha block of spruce–fir forest in central New Brunswick and the fecundity of females determined. Within the block, A. nudicaulis exhibited a 2.5:1 sex ratio of male/female flowering ramets. Ramets of the sexual morphs were negatively associated owing to cloning and a reduced likelihood of flowering in female ramets under dense canopy compared with males. Pattern analysis of the sex ratio of flowering ramets revealed a monotonic decline in variance with block size indicating that samples of sex ratio using small quadrats are likely to give misleading estimates for this species. The fecundity of females exhibited no systematic positional variation within the forest block. In most cases fecundity was not correlated with male and female flowering density, ramet sex ratio, and several subjectively estimated habitat variables. It is proposed that the long flight distances of pollinators, pollen carry-over, and the predominance of male flowers at the site interact to dampen out spatial effects on fecundity.

FLORAL SEX RATIOS AND LIFE HISTORY IN ARALIA NUDICAULIS (ARALIACEAE).

Darwin (1877) suggested that the resources allocated to reproduction differ between the sexes in certain species of dioecious flowering plants. Recent workers have postulated that differential expenditure on reproduction between sexes may account for the unequal sex ratios found in many dioecious species (Harris, 1958; Putwain and Harper, 1972; Lloyd, 1973; Lloyd and Webb, 1977; Melampy and Howe, 1977; Grant and Mitton, 1979; Hancock and Bringhurst, 1980). However, there is a lack of quantitative data concerning differences in reproductive effort of males and females under field conditions. It may seem intuitively obvious that females allocate greater amounts of resources to reproduction due to the requirements of fruit and seed development, but the extent and pattern of differences throughout the reproductive period have not been documented in natural populations. Although sex ratios of unity have been reported, deviations from this are frequently observed (Lloyd, 1973, 1974; Opler and Bawa, 1978; Hancock and Bringhurst, 1980; Webb and Lloyd, 1980). Lloyd (1973) has related biased sex ratios to life history, arguing that male-biased ratios tend to occur in iteroparous perennials of great longevity. Under the assumption that reproductive effort is greater in females, and that some limitation to energy expenditure exists, repeated flowering would restrict clonal propagation in females compared with males. This would result in an increase in the number of male relative to female inflorescences. Malebiased ratios, then, are explained as a consequence of repeated reproduction rather than as a result of direct selection. Aralia nudicaulis (wild sarsaparilla) is a rhizomatous perennial that occurs throughout the boreal forest zone of North America with extensions south into shaded woodlands of the U.S.A. Aralia nudicaulis is dioecious, possessing flowers of one sex only on a given individual. Rare flowering shoots contain perfect flowers (Scoggan, 1979) or separate male and female flowers. These floral types were found in less than 1% of the flowering shoots sampled for this study and are not considered further. In common with many of the herbaceous understory species of the boreal forest (e.g., Pteridium aquilinum, Clintonia borealis, Cornus canadensis), A. nudicaulis forms extensive clones which are probably of considerable age. Clonal growth in A. nudicaulis results from an extensive, subterranean rhizome system. Typically, clones (genets) are composed of scattered aerial shoots (ramets) which are either vegetative or reproductive. All ramets have a single, ternately compound leaf borne on a long petiole. In flowering ramets, this is subtended by a short naked scape terminated by a single umbellate inflorescence. The leaf and inflorescence are born on a short vertical shoot which arises from the underground rhizome. Fragmentation of underground parts as well as the complexity and extent of the rhizome system make identification of individual genets virtually impossible. Hence, in this study, all references to sex ratio refer to the sex ratio of flowering ramets. Field observation during 1978 indicated that a greater number of male than female flowering ramets occurred in forest sites of central New Brunswick, Canada. To extend these observations, surveys of ramet sex ratio in different habitats were made during 1979 and 1980. In order to compare