Limiting factors for seed production in Cynoglossum officinale

Summary Over three years of study, small plants of Cynoglossum officinale consistently produced more flowers per unit of dry weight than large plants. In contrast to earlier results, weight of all seeds tended to increase more than proportional to size. As a result a positive correlation existed between seed set per flower and plant size. The correlation between the mean number of pollinator visits per flower and size was positive but not significant. In a field experiment we found that resources rather than pollen were limiting seed set. Thus, it is unlikely that enhanced pollination of the largest plants causes the size-dependency of seed set per flower. Alternative hypotheses are discussed briefly.Publication of the Meijendel Comité, New Series No. 96     

Population fragmentation may reduce fertility to zero in Banksia goodii — a demonstration of the Allee effect

All individuals of all known populations of Banksia goodii were assessed for seed production. Small populations produced no or only a few seeds per unit canopy area. Effects of population size on seed production per unit area and seed production per plant were present over the whole range of population sizes, indicating that even in large populations seed production may still not be at its maximum. Resource differences could not explain this disproportionate decrease in seed production with decline in population size, because there were no differences in soil properties and understorey or overstorey cover between the small and large populations. Although plants in small and large populations were similar in size, seed production per plant was much lower in small populations. This was not because plants in small populations produced fewer cones but because the fraction of these cones that was fertile was much lower. Five of the nine smallest populations (<200 m²) produced no fertile cones over the last 10 years. The number of seeds per fertile cone did not depend on population size. The results are discussed in relation to pollination biology.     

Origins of variance in seed number and mass: interaction of sex expression and herbivory in Lomatium salmoniflorum

Summary As in many plant species, Lomatium salmoniflorum (Umbelliferae) individuals produce many flowers, only a subset of which produce mature seeds that escape seed parasitism and enter the seed bank. The interrelationships between the timing and number of flowers produced, sex expression, seed set, and seed parasitism were studied for their direct and indirect effects on the numbers and masses of viable seeds produced by individual plants. In a sample population of 369 plants that produced 161 386 flowers, 76% of the plants produced some hermaphroditic flowers. The percentage of hermaphroditic flowers increased significantly with the total number of flowers produced by a plant. Seed set was 65–90% in plants producing >600 flowers, but was highly variable in plants producing fewer flowers. Hand-pollinated plants showed the same pattern of seed set, suggesting that variable seed set in small plants may result from insufficient resources for seed development. The majority of schizocarps was produced by only 12% of the plants. Parasites killed 24.5% of the seeds prior to dispersal. Another 14.5% of the seeds lacked endosperm. Hence, the initial 161 386 flowers, which included 25874 hermaphroditic flowers each capable of producing two seeds, produced 42 468 seeds of which an estimated 25906 entered the seed bank as undamaged seeds with fully developed endosperm. Path analysis indicated that the number of hermaphroditic flowers on a plant and the percentage of seeds attacked by seed parasites had the greatest direct effects on the number of viable seeds entering the seed bank. The date at which a plant began flowering and the percentage of flowers setting seed had smaller or only indirect effects on viable seed production. Mean seed mass for plants was not significantly related to any of the factors that affected seed number, but little of the variance in seed mass occurred among plants. Masses of intact seeds in the population ranged 9-fold in both 1987 and 1988. Thirty-five percent of the variance was among seeds within umbels, 46% was among umbels within plants, and only 19% was among plants. The large variation among umbels within plants resulted from a seasonal pattern in which seeds from umbels produced late in the spring had lower mean seed masses than seeds from umbels produced early in the spring. Overall, the results indicate that both direct and indirect interactions between number of flowers, the date of initiation of flowering, seed set, and seed parasitism affect the number of viable seeds entering the seed bank. These interactions strongly bias viable seed output to a small minority of plants that produce many seeds with a wide range of masses over the growing season.     

Ecological genetics of vernalization response in Bromus tectorum L. (Poaceae)

BACKGROUND AND AIMS: Bromus tectorum (cheatgrass or downy brome) is an exotic annual grass that is dominant over large areas of former shrubland in western North America. To flower in time for seed production in early summer, B. tectorum plants generally require vernalization at winter temperatures, either as imbibed seeds or as established seedlings. METHODS: Variation in response to increasing periods of vernalization as seeds or seedlings for progeny of ten full-sib families from each of four B. tectorum populations from contrasting habitats was studied. KEY RESULTS: As vernalization was increased from 0 to 10 weeks, the proportion of plants flowering within 20 weeks increased, weeks to initiation of flowering decreased, and seed yield per plant increased, regardless of whether plants were vernalized as seeds or seedlings. Most of the variation was accounted for by differences among populations. Plants of the warm desert population flowered promptly even without vernalization, while those of the cold desert, foothill and montane populations showed incremental changes in response variables as a function of vernalization period. Populations differed in among-family variance, with the warm desert population generally showing the least variance and the cold desert population the most. Variation among populations and among families within populations decreased as vernalization period increased, whereas the non-genetic component of variance showed no such pattern. CONCLUSIONS: Variation in vernalization response was found to be adaptively significant and apparently represents the result of contrasting selection regimes on a range of founder genotypes.     

Size-dependent sex allocation in a monocarpic perennial herb, <Emphasis Type="Italic">Cardiocrinum cordatum</Emphasis> (Liliaceae)

The size-dependent sex allocation model predicts that the relative resource allocation to female function often increases with plant size in animal-pollinated plants. If size effects on reproductive success vary depending on the environmental conditions, however, the size dependency may differ among populations. We tried to detect site-specific variation in size-dependent sex allocation of a monocarpic hermaphrodite with reference to light availability. Multiple flowers and fruits were sampled from the individuals of Cardiocrinum cordatum, a monocarpic understory herb, and pollen, ovule and seed production were measured with reference to the plant size in two populations. Furthermore, frequency and foraging behavior of pollinator visitation was observed. Ovule production per flower increased with plant size in both populations, while pollen production per flower increased with size only in the population under sparse canopy. Therefore, proportional allocation to male function decreased with plant size in the population under closed canopy, but did not change in the population under sparse canopy. Pollinators usually visited only one flower per plant, indicating the negligible geitonogamous pollination in this species. Although seed production under closed canopy was lower than that under sparse canopy, seed-set rate per flower and seed mass per fruit were independent of plant size in either of the populations. Size-dependent sex allocation in this species was site-specific, suggesting that not only resource storage before reproduction (i.e., plant size) but also resource availability of environment throughout the reproductive process (i.e., light availability) affect reproductive performance in this species.     

COMPONENTS OF SEED AND POLLEN YIELD OF LOBELIA CARDINALIS: VARIATION AND CORRELATIONS

Plants from three Lobelia cardinalis populations were grown under common garden conditions to assess intra- and interplant variation in seed and pollen production. Seed number per flower and mean seed weight varied systematically with floral position on the inflorescence (lowest values were from terminal flowers) but pollen grain number per flower did not vary systematically with floral position. Most of the remaining variance in seed and pollen grain number per flower and mean seed weight was distributed among plants; clones produced very similar amounts of pollen and seed. Seed yield was positively correlated with seed production per flower and with total flower production, but not with mean seed weight; pollen yield was also positively correlated with pollen grain production per flower and total flower production. Seed and pollen yield were simple linear functions of plant size but only pollen yield was a simple linear function of flower production; seed yield was a quadratic function in which the second order term was negative. This quadratic relationship resulted from a negative correlation between seed number per flower and total flower production. This correlation, in addition to the wide variation among plants in pollen number per flower, accounts for the weak correlation of seed and pollen yield. I conclude from these data that it is unlikely that plants in natural L. cardinalis populations transmit genes to the population's seed crop equally through pollen and ovules—emphasizing the importance of measuring both male and female components of reproductive success.     

Size-dependent resource allocation among vegetative propagules and male and female functions in the forest herb Laportea bulbifera

Reproductive resource investment among vegetative propagules and male and female sexual function and their size-dependence were investigated in a perennial forest herb, Laportea bulbifera . A theoretical model based on fitness gain curves predicts that optimal investments in three reproductive modes will increase with plant size if fitness returns in all three modes increase but become saturated with investment. In a field population, large plants of L. bulbifera produced both male and female inflorescences with propagules, while small plants produced only vegetative propagules. Biomass of propagules, male inflorescences, and infructescences with achenes were all positively correlated with plant size. The increase in investment with plant size was larger for propagule production than for sexual reproduction. The relationship between propagule biomass and plant size was constant irrespective of year, while the relationship between the biomass of sexual reproductive organs and plant size differed between two successive years. Annual change of individual sex expression was investigated for 25 transplanted plants. Although each plant changed its sex expression variously among male, female and bisexual from year to year, 23 out of 25 plants produced both male and female inflorescences in at least one year. The number of viable (germinated and survived) offspring from seeds was not significantly different from the number from propagules. The production cost of a propagule was higher than that of a seed. Resource allocation theory does not seem to be applicable to size-dependent resource allocation, especially the allocation between seeds and propagules in this species.     

Size-dependent reproduction in Australian alpine Ranunculus

Abstract The effect of plant size on reproduction in four species of alpine Ranunculus (R. muelleri, R. dissectifolius, R. graniticola and R. niphophilus) was investigated in two sites over two seasons in the field on a total of 190 plants. The effects of plant size (number of leaves) and number of flowers on the number of anthers, ovules and seed per flower and per plant were determined. There was a positive relationship between several measures of reproduction and plant size in all four species, indicating that reproduction is size-dependent. All the results indicate that the main factor controlling the amount of seed produced by alpine Ranunculus is the size of the plant. Specifically, bigger plants produced more seed by producing more flowers, not by producing more ovules per flower, or higher seed set per flower. Correspondingly, bigger plants produced more anthers by producing more flowers, rather than by producing flowers with more anthers. The total number of seeds produced by a plant was directly proportional to plant size in the four species. Therefore, reproductive effort should not vary with plant size in the four species.     

Temporal patterns of seed set and decelerating fitness returns on female allocation in Zigadenus paniculatus (Liliaceae), an andromonoecious lily

I describe temporal patterns of seed production in the andromonoecious lily Zigadenus particulatus. Fruit set per flower and seed set per fruit declined through time within plants. Hand pollination experiments showed that this was not due to increasing pollen limitation. Nutrient supplementation had little effect on seed output, but leaf clipping reduced seed production, especially in late-blooming flowers, and removal of early-blooming flowers increased seed set by later flowers. Thus, the temporal pattern of seed output was due to declining availability of photosynthates. Plants with larger bulbs produced larger inflorescences, a greater proportion of hermaphrodite flowers, more fruits per hermaphrodite flower, and more seeds per fruit, but lost a greater fraction of their initial bulb mass as a consequence of fruiting. After controlling for the effects of bulb mass, plants with larger inflorescences produced a greater proportion of male flowers, and plants with more hermaphrodite flowers produced fewer fruits per hermaphrodite flower and fewer seeds per fruit. Thus, the female fitness gain curve was decelerating. The temporal decline in seed output provides a partial explanation for the parallel decline in allocation to pistils. However, a complete explanation for the pattern of gamete packaging requires an understanding of factors controlling male, as well as female, fitness.     

The role of the tolerance–fecundity trade‐off in maintaining intraspecific seed trait variation in a widespread dimorphic herb

Coexistence of species with different seed sizes is a long‐standing issue in community ecology, and a trade‐off between fecundity and stress tolerance has been proposed to explain co‐occurrence in heterogeneous environments. Here we tested an intraspecific extension of this model: whether such trade‐off also explains seed trait variation among populations of widespread plants under stress gradients. We collected seeds from 14 populations of Plantago coronopus along the Atlantic coast in North Africa and Europe. This herb presents seed dimorphism, producing large basal seeds with a mucilaginous coat that facilitates water absorption (more stress tolerant), and small apical seeds without coats (less stress tolerant). We analysed variation among populations in number, size and mucilage production of basal and apical seeds, and searched for relationships between local environment and plant size. Populations under higher stress (higher temperature, lower precipitation, lower soil organic matter) had fewer seeds per fruit, higher predominance of basal relative to apical seeds, and larger basal seeds with thicker mucilaginous coats. These results strongly suggest a trade‐off between tolerance and fecundity at the fruit level underpins variation in seed traits among P. coronopus populations. However, seed production per plant showed the opposite pattern to seed production per fruit, and seemed related to plant size and other life‐cycle components, as an additional strategy to cope with environmental variation across the range. The tolerance–fecundity model may constitute, under stress gradients, a broader ecological framework to explain trait variation than the classical seed size–number compromise, although several fecundity levels and traits should be considered to understand the diverse strategies of widespread plants to maximise fitness in each set of local conditions.     

Plant Parenthood in Milkweeds: A Direct Test of the Pollen Donation Hypothesis

Abstract For hermaphroditic plant species whose fruit production is limited by maternal resources, the "pollen donation hypothesis" views large floral displays as an adaptation to enhance the probability of fathering seeds on other plants. This hypothesis has frequently been used to describe the evolution of large floral displays in milkweeds ( Asclepias ). Most tests of the pollen donation hypothesis, however, have used indirect measures, such as flower production or pollen removal, to estimate male reproductive success. To test the pollen donation hypothesis directly, we performed a paternity analysis and determined the number of seeds sired by individual genotypes in a natural population of poke milkweed, A. exaltata , in southwestern Virginia. Seeds sired (male success) and seeds produced (female success) were significantly correlated with flower number per plant (for male success: r = 0.32, P < 0.05; for female success: r = 0.66, P < 0.0001). Functional gender of plants that reproduced both as males and females (N = 17) was not correlated with flower number per plant ( r = 0.35, P>0.05), indicating that plants with large floral displays did not reproduce primarily as males. Percent fruit-set and seed number per fruit were higher in 1986, when levels of pollinarium removal also were higher. Furthermore, several umbels that experienced high pollinator activity selectively matured fruits that contained many seeds. We argue that the evolution of large floral displays in milkweeds is the result of selection to increase overall reproductive success rather than male reproductive success alone.     

Plant size,geitonogamy and seed set in Ipomopsis aggregata

Summary We used powdered fluorescent dyes to estimate receipt of self vs. outcross pollen in the self-incompatible species Ipomopsis aggregata (Polemoniaceae). Flowers on small and large plants received equal amounts of outcross pollen, whereas flowers on large plants received more self pollen, so the proportion of self pollen delivered through geitonogamy increased with plant size. In natural populations emasculation of all flowers on a plant raised average seed set per flower from 5.19 to 6.99 and also raised fruit set, though not significantly. From these results one expects a negative correlation between plant size and seeds per flower. The opposite trend was observed in a sample of plants in the field, suggesting that deleterious effects of geitonogamy on female fecundity in large plants can be overruled by other factors such as size-related fruit or seed abortion. Results are discussed in relation to the evolution of gynodioecy.     

Solitary plants do as well as clumped ones in Silene uniflora (Caryophyllaceae)

Many studies have been done on seed production as a function of population density in wild plants Most of them show a higher seed-set per flower of densely growing plants In this study, in a gynodioecious Silene uniflora (Caryophyllaceae) population on the Baltic island of Oland, high plant density did not increase fruit-set or seed-set Instead, the total number of seeds set was slightly higher for widely scattered plants as a result of a somewhat lower number of ovules per flower in densely growing plants Individuals had nothing to gain by growing close together, because there was no reproductive parameter which could compensate for the low ovule number per flower of closely growing plants Plant size determined the total seed production of individuals, but did not correlate with any of the fitness components studied per flower basis The different gender morphs showed the same pattern, which is discussed as a comparison with pollen limitation in self-incompatible and self-incompatible plants     

Floral display size in comfrey, Symphytum officinale L. (Boraginaceae): relationships with visitation by three bumblebee species and subsequent seed set

The fecundity of insect-pollinated plants may not be linearly related to the number of flowers produced, since floral display will influence pollinator foraging patterns. We may expect more visits to plants with more flowers, but do these large plants receive more or fewer visits per flower than small plants? Do all pollinator species respond in the same way? We would also expect foragers to move less between plants when the number of flowers per plant are large, which may reduce cross-pollination compared to plants with few flowers. We examine the relationships between numbers of inflorescence per plant, bumblebee foraging behaviour and seed set in comfrey, Symphytum officinale, a self-incompatible perennial herb. Bumblebee species differed in their response to the size of floral display. More individuals of Bombus pratorum and the nectar-robbing B.?terrestris were attracted to plants with larger floral displays, but B. pascuorum exhibited no increase in recruitment according to display size. Once attracted, all bee species visited more inflorescences per plant on plants with more inflorescences. Overall the visitation rate per inflorescence and seed set per flower was independent of the number of inflorescences per plant. Variation in seed set was not explained by the numbers of bumblebees attracted or by the number of inflorescences they visited for any bee species. However, the mean seed set per flower (1.18) was far below the maximum possible (4 per flower). We suggest that in this system seed set is not limited by pollination but by other factors, possibly nutritional resources.     

From flowering to dispersal: reproductive ecology of an endemic plant,Astragalus australis var. olympicus (Fabaceae)

Astragalus australis var. olympicus is an endemic plant of the Olympic Mountains, Washington. It is considered a Species of Concern by the U.S. Fish and Wildlife Service. This study focused on the reproductive biology of the plant from flower production through seed germination to identify possible weak points that might contribute to its rarity and impede its conservation. Most plants produced a large mean number of flowers and ovules (314.8 and 4106, respectively), but relatively few of these formed fruits and seeds (25.8 and 3.8%, respectively). In decreasing importance, ovules in fruits were lost to predation, seed abortion, and lack of fertilization. The percentages of these fates differed among sites and years. Excluding pollinators by bagging flowers reduced fruit set by ∼50%, but seed set per fruit and seed mass were unaffected. Germination was affected by scarification, temperature, and moisture availability. About 11% of seeds damaged by predispersal seed predators (weevil larvae) remained viable and were released from dormancy. I hypothesize that predispersal seed predation (over 80% at one site) has a negative effect on population growth. Conservation of this species could benefit from improved fruit set and decreased seed predation.     

Reproduction of beetle‐pollinated Anaxagorea dolichocarpa (Annonaceae) is resilient to habitat disturbance in rainforest fragments

Strong evidence exists that fragmentation negatively affects pollination and plant reproduction, but little research has been conducted with regards to tropical trees. Specifically, effects of forest fragmentation on reproduction of plants with beetle‐pollinated flowers are poorly understood, and there are no data on the impact of fragmentation on reproduction in the structurally important tropical family Annonaceae. We examined the relationship between fragment size, pollinator abundance and seed set of beetle‐pollinated Anaxagorea dolichocarpa (Annonaceae) in a disturbed Brazilian Atlantic rainforest. Flower and fruit production and abundance of pollinators were quantified over ten months in three large (306–388 ha) and three small (6–14 ha) forest fragments. We recorded per flower pollinator abundance, resulting fruit set (fruits per flower) and seed set (monocarps per fruit) for a total of 209 individually marked flowers, and compared pollinator abundance in 186 flowers across all fragments. Flower and fruit production differed among fragments, but were similar for the combined large and small fragments. Between 64.8% (large fragments) and 66.3% (small fragments) of flowers received at least one pollinator. We found no significant difference in pollinator numbers between large and small fragments, and no correlation between pollinator abundance and fruit and seed set. A single visitor had a high probability of pollinating a flower. We conclude that 1) fragment size had no influence on pollinator number and plant reproductive success, and 2) generalist behavior of the pollinating beetles mitigate the risk of pollination failure for the reproductively specialized plant. However, further research may yet reveal genetic impoverishment of populations in small fragments due to restricted pollinator movements.     

Optimal resource allocation model for excessive flower production in a pollinating seed-predator mutualism

Many plants produce excessive flowers and several hypotheses have been proposed for adaptive significances of this behavior. Here, I develop a simple resource allocation model for plants in a mutualism with pollinating seed-predators to examine a novel hypothesis that excessive flower production can be favored to “dilute” seed predation by the pollinators. Pollinators visit flowers to deposit pollen and oviposit on them, and their offspring feed on a portion of the seeds, leaving the remainder intact. Further pollinator visits increase seed mortality by over-oviposition. Excessive flower production is favored if it decreases pollinator-visit frequency per flower, while it incurs decrease in seed production because of the resource trade-off. I examine three plant strategies: (1) no abortion, the plant allocates resource to all pollinated flowers to mature; (2) selective abortion, the plant aborts flowers depending on how many times they were visited by pollinators; and (3) random abortion, the plant indiscriminately aborts a fraction of pollinated flowers irrespective of how many times they were visited. I show that the random abortion strategy can perform much more effectively than the no-abortion strategy when the amount of resource is small, the production cost per flower is low, and the pollinator density is high, although the selective abortion strategy is always the best. This “predator dilution” effect has not been considered with regard to previous excessive flower production hypotheses.     

Consequences of variation in flowering phenology for seed head herbivory and reproductive success in Erigeron glaucus (Compositae)

Summary We examined the relationship between flowering phenology, reproductive success (seed production only), and seed head herbivory for 20 similarly sized clones of Erigeron glaucus growing at Bodega Bay Reserve, northern California, USA. Although clones tended to reach peak flowering on the same date, they differed in the proportion of their total flowers produced around that date (flowering synchrony). Clones also differed in the number and density of flower heads presented at any one time to pollinators and herbivores (floral display). Both of these characteristics had consequences for herbivory and plant reproductive success. The proportion of flower heads damaged by insect herbivores was greater for clones that concentrated flowering activity during the main flowering period for the population as a whole (high synchrony) compared to clones that spread flowering out temporally. The primary reason for this result was that clones with low flowering synchrony produced a significant proportion of their flower heads during the fall and therefore, escaped attack by the tephritid fly, Tephritis ovatipennis. Clones with intermediate synchrony had lower seed success (total number of viable seeds produced over the year) than clones with either low or high synchrony. The proportion of flower heads damaged by insect herbivores and number of tephritid flies reared from flower heads were both negatively correlated to floral display while seed head mass and germination rates were positively related to display. Thus, clones which produced dense floral displays were favored both in terms of reduced herbivory and increased successful seed production.     

海拔对青藏高原东部毛茛科植物繁殖特征和资源分配的影响

通过野外采样对青藏高原东部高寒草甸上两个海拔间3种常见毛茛科植物条裂银莲花(Anemone trullifo-liavar.linearis)、粗距翠雀花(Delphinium pachycentrumHemsl.)和钝裂银莲花(Anemone obtusiloba)的繁殖性状和资源分配进行了研究,并对植物在极端环境下采取的繁殖策略及繁殖模式进行了探讨.结果显示:(1)3个物种的株高都随着海拔的升高而降低;同一物种的花大小在不同海拔间均无显著差异;条裂银莲花单个种子重随海拔的升高而增加,但虫食数/株、结籽率和种子数/株均随着海拔的升高而减少;钝裂银莲花的繁殖分配、虫食数/株、种子数/株和单个种子重均随着海拔的升高而减小.(2)不同海拔条裂银莲花的个体大小与单花重、雄蕊重、虫食数/株均呈显著正相关,且回归斜率在海拔间有显著差异.粗距翠雀花花期的雄蕊重与个体大小呈显著正相关,但这种异速关系不受海拔和个体大小的影响;钝裂银莲花的个体大小与花期的所有繁殖特征以及果期的种子重/果实均呈显著正相关,不同海拔间个体大小与种子重/果实的斜率差异显著,且与花期各繁殖性状异速关系的截距差异显著.研究表明海拔对植物的个体大小以及种群间的繁殖对策和繁殖成功率有着重要的影响.     

Variation of seed heteromorphism in Chenopodium album and the effect of salinity stress on the descendants

Background and Aims

Chenopodium album is well-known as a serious weed and is a salt-tolerant species inhabiting semi-arid and light-saline environments in Xinjiang, China. It produces large amounts of heteromorphic (black and brown) seeds. The primary aims of the present study were to compare the germination characteristics of heteromorphic seeds, the diversity of plant growth and seed proliferation pattern of the resulting plants, and the correlation between NaCl stress and variation of seed heteromorphism.

Methods

The phenotypic characters of heteromorphic seeds, e.g. seed morphology, seed mass and total seed protein were determined. The effects of dry storage at room temperature on dormancy behaviour, the germination response of seeds to salinity stress, and the effect of salinity on growth and seed proliferation with plants derived from different seed types were investigated.

Key Results

Black and brown seeds differed in seed morphology, mass, total seed protein, dormancy behaviour and salinity tolerance. Brown seeds were large, non-dormant and more salt tolerant, and could germinate rapidly to a high percentage in a wider range of environments; black seeds were salt-sensitive, and a large proportion of seeds were dormant. These characteristics varied between two populations. There was little difference in growth characteristics and seed output of plants produced from the two seed morphs except when plants were subjected to high salinity stress. Plants that suffered higher salinity stress produced more brown (salt-tolerant) seeds.

Conclusions

The two seed morphs of C. album exhibited distinct diversity in germination characteristics. There was a significant difference in plant development and seed proliferation pattern from the two types of seeds only when the parent plants were treated with high salinity. In addition, seed heteromorphism of C. album varied between the two populations, and such variation may be attributed, at least in part, to the salinity.