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.     

Production of male flowers does not decrease with plant size in insect-pollinated Sagittaria trifolia, contrary to predictions of size-dependent sex allocation

It has been proposed that relative allocation to female function increases with plant size in animalpollinated species.Previous investigations in several monoecious Sagittaria species seem to run contrary to the prediction of size-dependent sex allocation (SDS),throwing doubt on the generalization of SDS.Plant size,phenotypic gender,and flower production were measured in experimental populations of an aquatic,insect-pollinated herb Sagittaria trifolia (Alismataceae) under highly different densities.The comparison of ramets produced clonally can reduce confounding effects from genetic and environmental factors.In the high-density population,48％ of ramets were male without female flowers,but in the low-density population all ramets were monoecious.We observed allometric growth in reproductive allocation with ramet size,as evident in biomass of reproductive structures and number of flowers.However,within both populations female and male flower production were isometric with ramet size,in contrast to an allometric growth in femaleness as predicted by SDS.Phenotypic gender was not related to ramet size in either population.The results indicated that large plants may increase both female and male function even in animal-pollinated plants,pointing towards further studies to test the hypothesis of size-dependent sex allocation using different allocation currencies.     

Production of male flowers does not decrease with plant size in insect‐pollinated Sagittaria trifolia,contrary to predictions of size‐dependent sex allocation

Abstract It has been proposed that relative allocation to female function increases with plant size in animal‐pollinated species. Previous investigations in several monoecious Sagittaria species seem to run contrary to the prediction of size‐dependent sex allocation (SDS), throwing doubt on the generalization of SDS. Plant size, phenotypic gender, and flower production were measured in experimental populations of an aquatic, insect‐pollinated herb Sagittaria trifolia (Alismataceae) under highly different densities. The comparison of ramets produced clonally can reduce confounding effects from genetic and environmental factors. In the high‐density population, 48% of ramets were male without female flowers, but in the low‐density population all ramets were monoecious. We observed allometric growth in reproductive allocation with ramet size, as evident in biomass of reproductive structures and number of flowers. However, within both populations female and male flower production were isometric with ramet size, in contrast to an allometric growth in femaleness as predicted by SDS. Phenotypic gender was not related to ramet size in either population. The results indicated that large plants may increase both female and male function even in animal‐pollinated plants, pointing towards further studies to test the hypothesis of size‐dependent sex allocation using different allocation currencies.     

Classifying clonal growth forms based on vegetative mobility and ramet longevity: a whole community analysis

We measured rhizome branching, clonal mobility, and ramet longevity of 98 meadow plant species. A cluster analysis applied to this dataset revealed nine clonal growth types that differ mainly by the ramet lifespan and vegetative mobility. Then we compared the abundance of these groups of clonal species between the three following plant communities: (1) open, (2) restored and (3) overgrown wooded meadows in the Laelatu-Nehatu-Puhtu Nature Reserve, Estonia. This is the first study where the quantitative values of belowground clonal traits have been measured for all species of a species-rich community. We show that species with annual ramets and with a low vegetative mobility were most abundant in open grasslands. The relative abundance of perennial species with annual ramets was positively correlated with shoot density and species diversity, indicating that high ramet turnover rates combined with a high genet longevity can positively affect species coexistence in meadow communities. Hence, this study provides evidence for the fact that the average values of clonal life-history parameters differ between these communities. Herb communities under forest canopy consist, in average, of species with ramets that live longer and are clonally more mobile than in the communities of open sites.     

Factors controlling the population dynamics of the clonal helophyte Ranunculus lingua

Abstract. Two marginal and two central populations of the pseudo-annual aquatic plant Ranunculus lingua were studied over four years. The main purpose was to quantify potentially influential abiotic and biotic factors and to derive predictions about life-history differences between the populations. Variation in abundance and height of R. lingua ramets at different depths were related to water-level fluctuations, to abundance of other helophyes (emergent macrophytes), and to the occurrence of invertebrate grazing and fungal pathogens. Clear differences between marginal and central populations were shown in the depth distribution of ramet numbers and ramet heights, as well as in the dynamic patterns, where marginal populations had a higher flux of ramets. These patterns and regression analyses indicated that abiotic factors have a greater influence in marginal populations, whereas biotic factors are more important in central populations. It is suggested that marginal habitats for R. lingua would favour life-histories with a high reproductive capacity, whereas a large size of ramet would be the most important life-history feature in central habitats. This was supported by the fact that ramets in marginal populations, in spite of their smaller size, produced higher number of rhizomes than ramets in central populations. Variation in regional abundance was finally related to differences in demographic processes and dispersal potential between the populations.     

Life-history monographs of Japanese plants 14: Cardamine leucantha (Tausch) O. E. Schulz (Brassicaceae)

The life-history characteristics of Cardamine leucantha (Tausch) O. E. Schulz (Brassicaceae) are described. The species is an herbaceous perennial that favors open but relatively moist habitats. It is distributed from Kyushu to Hokkaido in Japan but also occurs in Korea, Mongolia, China and the Russian Far East. In southwestern Japan, shoots start sprouting from mid- to late April, reaching approximately 30–70 cm in height, with 5–10 compound leaves. Ramets simultaneously produce one or more stoloniferous rhizomes that elongate until new ramets are formed at the tips. Cardamine leucantha has a pseudo-annual life cycle, in which mother ramets wither at the end of each season and only daughter ramets appear aboveground in the next year. As a result, ramet positions change annually. In a study population, the number of flowers averaged 23.9 ± 21.0 per ramet and fruit set was 44.2 ± 24.8% (10.4 ± 10.1 fruits per ramet). Ramets produced 3.8 ± 2.3 rhizomes that were 22.0 ± 15.6 cm long. The species sometimes forms large populations. A single genet develops into a group of disconnected ramets spreading via clonal growth. Reproductive characteristics (e.g., fruit set and numbers of flowers and rhizomes) vary among populations, resulting in interpopulation differences in genet structure. Because the reference genome became available recently, established molecular tools will be applied effectively for the investigations of C. leucantha as a model clonal plant.     

Fitness and evolution in clonal plants: the impact of clonal growth

Seeds have often been emphasized in estimates of plant fitness because they are the units that carry genes to the next generation, disperse, and found new populations. We contend that clonal growth also needs to be considered when estimating fitness in clonal plants, regardless of whether fitness is measured from a genet or ramet perspective. Clonal growth affects genet fitness through both genet persistence and seed production. It affects ramet fitness through new ramet production, because both seeds and clonal propagants are considered offspring. The differential production of clonal propagants will contribute to fitness differences among individuals which may result in population-level changes in allele frequencies (i.e. microevolution). We describe a form of selection unique to clonal organisms, genotypic selection, that can result in evolution. Genotypic selection occurs when genotypically based traits are associated with differences in the rate of ramet production. It can lead to evolutionary change in quantitative trait means both directly and indirectly. It leads directly to change in the ramet population by increasing the proportion of ramets with more advantageous trait values. From the genet perspective, it leads indirectly to evolution within and among populations whenever significant portions of the genetic effect on a trait are inherited through seed. We argue that under most conditions, clonal growth will play a major role in the microevolution of clonal plants.     

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.     

Habitat and sex specific differences in the dioecious weed Acetosella vulgaris (Polygonaceae)

Abstract Patterns of resource allocation, numbers of reproductive structures and sex ratios of flowering populations of the dioecious weed Acetosella vulgaris (Fourr.) were examined in the Kosciuszko alpine region of Australia. Specifically, the sex‐specific response of ramets was compared between a disturbed alpine habitat, in which weeds such as A. vulgaris are common (disturbed roadside/path‐edge), and a native alpine habitat in which weeds appear to have a limited capacity to germinate, grow and reproduce (undisturbed tall alpine herbfield). The disturbed habitat was generally more favourable for growth of A. vulgaris. Ramets of both sexes had greater total and vegetative biomass than ramets in native habitats. Although reproductive biomass was also greater in disturbed habitats, females had less reproductive biomass than males, which was not as predicted. Reproductive effort was not affected by habitat or gender. The disturbed habitat also favoured increased numbers of inflorescences per ramet and flowers per ramet, as expected. Whereas the gender of the ramet also influenced numbers of reproductive structures, again, this was not as predicted. Females had more flowers per ramet and more flowers per inflorescence than males. This may be because of factors associated with wind pollination. Females were taller in native habitats but there was no difference between the sexes in disturbed habitats. Sex ratios varied from all male populations to nearly all female populations among the 25 sites sampled irrespective of habitat. Factors such as time since last disturbance may have contributed to variation in the sex ratios of alpine populations of A. vulgaris in Australia.     

Species-specific sprouting pattern in two dioecious Lindera shrubs: The role of physiological integration

Sprouting is recognized as an important genet persistence strategy for clonal woody plants, but the role of sprouting may differ between species and between sexes, depending on physiological integration. We tested the effect of physiological integration on the mortality, recruitment and growth of the sprouting male and female ramets of two closely related dioecious shrubs of Lindera, in a field experiment using girdling manipulation. Although between-sex differences observed were obscure, we found between-species differences in the sprouting patterns. The rates of ramet mortality and recruitment were significantly lower for L. praecox than L. triloba. In L. praecox genets, the ramet production was low, and the main ramets might actively translocate assimilates towards the small sprouted ramets, which then facilitates high ramet growth and survival (sprout-nursing strategy). Meanwhile, in L. triloba genets, although many ramets were recruited, assimilate translocation from the main ramets to the sprouted ramets might be less abundant, which causes high ramet mortality (sprout-turnover strategy). For a more general knowledge of the various sprouting strategies in clonal plants, our study demonstrated that inter-specific comparisons using girdling experiments at the whole-plant level could reveal the role of physiological integration on the link between the sprouting pattern and above-ground structures of clonal plants.     

Genet structure and determinants of clonal structure in a temperate deciduous woodland herb, Uvularia perfoliata

1 We used isozyme variation to examine the genet structure of Uvularia perfoliata patches in gap and closed canopy habitats in a temperate deciduous forest in Maryland, USA.
2 A large patch in a gap habitat was composed of a small number of widely spread genets with many ramets, and a large number of genets with more restricted distribution and few ramets. Genets with many ramets were patchily distributed at a metre scale. Analysis of genet structure on a scale of square centimetres, however, revealed that the genets were highly intermingled with no clear boundaries between them. The presence at both scales of sampling of many genets with unique multilocus genotypes indicated continuing genet recruitment within the population.
3 In the closed canopy habitat, the patches examined were each composed of a single unique multilocus genotype, suggesting that each had developed by asexual propagation following the establishment of a single genet.
4 The clonal structure of U. perfoliata patches in both gap and closed canopy habitats therefore appears to depend on recruitment patterns of genets. Populations in closed canopy habitats are characterized by a 'waiting' strategy, in which asexual ramet production maintains populations until genet recruitment by seed production can occur under the more optimal conditions associated with canopy gaps. Extended sampling suggests that the genetic diversity of U. perfoliata populations is primarily controlled by the disturbance regime of the forest canopy.     

Breeding durations as estimators of adult sex ratios and population size

Adult sex ratios (ASRs) and population size are two of the most fundamental parameters in population biology, as they are the main determinants of genetic and demographic viability, and vulnerability of a population to stochastic events. Underpinning the application of population viability analysis for predicting the extinction risk of populations is the need to accurately estimate parameters that determine the viability of populations (i.e. the ASR and population size). Here we demonstrate that a lack of temporal information can confound estimation of both parameters. Using acoustic telemetry, we compared differences in breeding durations of both sexes for a giant Australian cuttlefish Sepia apama breeding aggregation to the strongly male-biased operational sex ratio (4:1), in order to estimate the population ASR. The ratio of breeding durations between sexes was equal to the operational sex ratio, suggesting that the ASR is not strongly male-biased, but balanced. Furthermore, the short residence times of individuals at the breeding aggregation suggests that previous density-based abundance estimates have significantly underestimated population size. With the current wide application of population viability analysis for predicting the extinction risk of populations, tools to improve the accuracy of such predictions are vital. Here we provide a new approach to estimating the fundamental ASR parameter, and call for temporal considerations when estimating population size.     

Sex-specific pattern of spatial genetic structure in dioecious and clonal tree species, <Emphasis Type="Italic">Populus alba</Emphasis> L.

Fine-scale spatial genetic structure (SGS) has profound ecological and genetic consequences for plant populations, and some studies indicate that clonal reproduction may significantly enhance SGS. Clonality is widespread among dioecious species, but little is known about the relationship between clonal reproduction and SGS in the frame of sexual dimorphism. We asked the following questions: (1) Is there a sexually dependent pattern of SGS in white poplar population? (2) What is the relationship between clonal reproduction and SGS? and (3) Does this relationship have a sex-specific component? Using 16 microsatellite markers, genetic structure including fine-scale SGS and clonality of females and males of white poplar were investigated. Significant SGS was noted for both sexes at the ramet and genet levels. At the genet level, males had 2.7-fold higher SGS than that of females. Clonality significantly contributed to SGS only in females. A sibship structure revealed with pedigree analysis and clustering-based methods among males was likely the major factor of the observed SGS. The sexes differed in their clonal growth strategies. Spatial positioning of ramets in female clones suggested foraging behavior and/or avoidance of competition, while for male clones it indicated more expansion and space colonization. The obtained results led us to conclude that sexual dimorphism in life history traits may affect the course and rate of demo-genetic processes acting in natural populations of dioecious species. To our knowledge, this is the first study demonstrating a sex-specific pattern of SGS in natural populations of dioecious species.     

EFFECTS OF FIRE ON CLONAL GROWTH AND DYNAMICS OF PITYOPSIS GRAMINIFOLIA (ASTERACEAE)

The rhizomatous perennial Pityopsis graminifolia was studied in a Florida sandhill community in an annually burned site, a periodically burned site, and a site that has been protected from fire since 1965. These different fire regimes significantly affected the demography and life histories of both plants and plant parts in this clonal species. Fires resulted in reductions in ramet biomass and height, and an increase in the (root + rhizome)/shoot biomass ratio. Burning also decreased the total number of flower heads and new rhizomes produced per ramet. However, the survivorship of initiated rhizomes was greater in burned sites and resulted in a larger number of established daughter ramets per clone. As a result, in burned sites there was a shift in clone structure toward larger numbers of smaller ramets, but there were no significant reductions in seed or rhizome production on a per genet basis. The results showed that the responses to fire in P. graminifolia are different when measured at the genet vs. ramet level and that the effects of fire on clones can be explained by demographic responses of plant parts. Population regeneration in the study sites was dependent on successful clonal ramet production because no seedling recruitment was observed. This suggests that disturbances other than fire are important for new genet recruitment in these clonal populations.     

Sex expression, skewed sex ratios, and microhabitat distribution in the dioecious desert moss Syntrichia caninervis (Pottiaceae)

The moss Syntrichia caninervis is the dominant soil bryophyte in a blackbrush (Coleogyne ramosissima) community in the southern Nevada Mojave Desert, with a mean cover of 6.3%. A survey of the 10-ha study site revealed an expressed ramet sex ratio of 14♀ : 1♂ (N = 890), with 85% of ramets not expressing sex over their life span, and an expressed population sex ratio of 40♀ : 2♂ : 1♀♂ (female : male : mixed-sex, N = 89), with 52% of populations not expressing sex. A greater incidence of sex expression was associated with shaded microsites, higher soil moisture content, and taller ramets. Shaded microsites had higher surface soil moisture levels than exposed microsites. In the exposed microhabitat, surface soil moisture was positively correlated with ramet height but not with sex expression. Male ramets and populations were restricted to shaded microhabitats, whereas female ramets and populations were found in both shaded and exposed microhabitats, suggesting gender specialization. The rarity of mature sporophytes, found in 0% of the ramets sampled and in only 3% of the populations, is probably due to the rarity of mixed-sex populations. We hypothesize that mixed-sex populations are rare because of factors relating to male rarity and that the differential cost of sex expression reduces the clonal growth capacity of male individuals.     

Influences of the genetic neighborhood on ramet reproductive success in a clonal desert cactus

Clonal structure in clonal plants can affect sexual reproduction. Individual ramets can decrease reproduction if their neighbors are ramets of the same genet due to inbreeding depression or self-incompatibility. We assessed ramet reproductive success in the partial self-incompatible Ferocactus robustus (Cactaceae) as a function of floral display size in focal ramets and floral display size and clonal structure of their reproductive neighborhoods. Ramets were labeled, sized in number of stems, mapped and genetically identified through RAPD markers in one population. A pollen dispersal area of 15-m radius was established for each ramet to determine the clonal diversity in the neighborhoods. Flower production and fruit set were counted on a monthly basis during one reproductive season as a surrogate of ramet fitness. We expected a decrease in individual ramet reproductive success as a function of the number of reproductive ramets of the same genet in the neighborhood. A total of 272 sampled ramets revealed 116 multilocus genotypes, showing high clonal diversity in the population (G/N = 0.43, D = 0.98). Clonal diversity of neighborhoods ranged from 0.06 to 1 and fruit set varied from 0 to 76.9%. Individual ramet reproductive success was influenced by (1) mate availability, (2) floral display size of a genet within the reproductive neighborhood, and (3) the proportion of distinguishable genotypes. Floral display size of genets and ramets coupled with the genetic diversity within the reproductive neighborhood determines the low sexual reproduction in F. robustus.     

Comparison of clonal diversity in mountain and Piedmont populations of Trillium cuneatum (Melanthiaceae-Trilliaceae), a forest understory species

The balance between clonal and sexual reproduction can vary widely among plant populations, and the extent of clonality may be influenced by the combined effects of historical land use and variation in environmental conditions. We investigated patterns of clonal spread in five Trillium cuneatum populations, two in the Appalachian Mountains characterized by mesic, cooler conditions, and three at lower elevations experiencing warmer, drier conditions and greater disturbance. Using a new measure of the genet effective number and innovative orthogonal contrast methods, we quantified genet structure, contrasting clonal growth in the mountains with that in the Piedmont. Asexual propagation was more common in the Piedmont, where 25% of the sampled ramets were clonally derived, but was much less frequent in the mountains (7% clonal replicates). Hierarchical partitioning of variation in genet diversity showed that the majority (75.8%) of the variation resulted from more vegetative replication in the Piedmont. Most of the remaining variation (21.6%) was attributable to differences between urban and rural Piedmont populations, and a small, statistically nonsignificant fraction of the variation (2.6%) was due to interpopulation differences within the mountains. Higher frequency of cloning may enhance both genetic and demographic population viability in fragmented Piedmont habitats.     

RAMET DYNAMICS FOR THE CLONAL SEAWEED PTEROCLADIELLA CAPILLACEA (RHODOPHYTA): A COMPARISON WITH CHONDRUS CRISPUS AND WITH MAZZAELLA CORNUCOPIAE (GIGARTINALES)

Little is known about the dynamics and the ecological interactions among ramets (fronds) from populations of clonal red seaweeds. Small ramets are very difficult to tag, so their growth cannot be monitored directly. The temporal variation of the relationship between stand biomass and ramet density offers information on ramet performance. We calculated this relationship for an intertidal population of Pterocladiella capillacea (Gmelin) Santelices et Hommersand (Gelidiales) from Baja California, Mexico. Biomass and density were positively correlated on an annual basis, indicating that biomass accumulated without involving self-thinning among ramets. This contrasts with nonclonal seaweeds, for which self-thinning among individuals occurs during growth, but agrees with other clonal red seaweeds, such as Chondrus crispus Stackhouse and Mazzaella cornucopiae (Postels et Ruprecht) Hommersand (both Gigartinales). The growth pattern for these members of the Gelidiales and of the Gigartinales holds despite differences in holdfast morphology and ramet branching degree and despite differences in the capacity of coalescence during early stages, known only for the Gigartinales. The positive slope for the dynamic biomass–density relationship, on a bilogarithmic scale, was statistically steeper for M. cornucopiae than for P. capillacea and for C. crispus. This suggests that the addition of new ramets during the growth season may be relatively more beneficial for biomass accumulation rates for M. cornucopiae. This would be expected for high-intertidal species subjected to strong abiotic stress, for which ramet crowding constitutes a key protection. Pterocladiella capillacea occurs at the mid-intertidal zone and C. crispus at the subtidal zone, so ramets would be relatively less important in that respect.     

Clonal genetic structure and diversity in populations of an aquatic plant with combined vs. separate sexes

Clonality is often implicated in models of the evolution of dioecy, but few studies have explicitly compared clonal structure between plant sexual systems, or between the sexes in dioecious populations. Here, we exploit the occurrence of monoecy and dioecy in clonal Sagittaria latifola (Alismataceae) to evaluate two main hypotheses: (i) clone sizes are smaller in monoecious than dioecious populations, because of constraints imposed on clone size by costs associated with geitonogamy; (ii) in dioecious populations, male clones are larger and flower more often than female clones because of sex‐differential reproductive costs. Differences in clone size and flowering could result in discordance between ramet‐ and genet‐based sex ratios. We used spatially explicit sampling to address these hypotheses in 10 monoecious and 11 dioecious populations of S. latifolia at the northern range limit in Eastern North America. In contrast to our predictions, monoecious clones were significantly larger than dioecious clones, probably due to their higher rates of vegetative growth and corm production, and in dioecious populations, there was no difference in clone size between females and males; ramet‐ and genet‐based sex ratios were therefore highly correlated. Genotypic diversity declined with latitude for both sexual systems, but monoecious populations exhibited lower genotypic richness. Differences in life history between the sexual systems of S. latifolia appear to be the most important determinants of clonal structure and diversity.     

Sex expression and sex dimorphism in sporophytic populations of the desert moss Syntrichia caninervis

Ten sporophytic populations of Syntrichiacaninervis contained an average of 22 individualscm^–2, with a sex ratio of 7.9 Female:1 Male: 3.1 Nonexpressing(N = 300). In each of the populations, female individuals outnumberedmale individuals. A representative population size of 50 × 25cm was estimated to contain 27,250 organically distinct individualplants. Given the wide disparity in reproductive investment in this dioeciousspecies, sex-specific traits were investigated at the level of the individualinbiomass, total stem length, number of ramets, number of branches, length ofannual growth interval, length of longest ramet, age, number of inflorescences,number of ramets expressing sex, and consecutive seasons of sex expression. Theonly significant sex dimorphism recorded was in consecutive seasons of sexexpression, with nonsporophytic female individuals exhibiting a higherfrequencythan males. However, nonexpressing individuals had lower biomass, shorter totalstem length, fewer branches, and shorter ramets than males and females, andfewer ramets than female individuals. When the biomass of female and maleindividuals was controlled for inflorescence number, no significant differencesbetween the sexes in biomass were found. There appears to be a threshold sizefor sex expression, with all individuals above 2.0 mg dry weightexpressing sex (N = 108). Biomass and total stem length are strongpositive correlates (r = 0.88), and individual biomass is a betterpredictor of the number of inflorescences produced per individual than is stemlength (r = 0.85 vs. r = 0.69, respectively). Independent of stemlength, individual biomass had a positive and significant relationship withinflorescence number; however, independent of individual biomass, stem lengthwas not associated with inflorescence number. Overall sex expression was 0.74(individual level) and 0.65 (ramet level). The functional sex ratio wasassessedat the inflorescence level, and ranged from 9.7:1, to14.9:1 over the most recent four years. Fertilization frequencywas 0.69 (individual level) and 0.34 (perichaetial level). Over the last threeyears, 63% of all fertilized perichaetia resulted in an abortivesporophyte.