Fruit abortion and the regulation of fruit number in Yucca whipplei

Summary Flowering and fruiting patterns of Yucca whipplei (Agavaceae), a monocarpic perennial of the southern California chaparral, were studied to determine the role of fruit abortion in the regulation of seed yield. Data on reproductive expenditure, fruit abortion and fruit maturation were obtained for 108 flowering individuals at two sites. The proportion of flowers maturing fruits was less than 10% at both sites. Inflorescences produced an average of 2,045±111 and 1,743±77 flowers at the two sites, initiated an average of 439±48 and 304±21 fruits, and matured an average of 194±16 and 162±10 fruits, respectively. Overall, 51% of the fruits which initiated development were aborted and abscized in an early stage of development.The hypothesis that fruit abortion serves to regulate seed yeild, matching fruit production to the available resources, yields three predictions which are borne out by our findings: (1) the proportion of initiated fruits which abort is an increasing function of the number of fruits initiated, (2) the number of fruits matured is an increasing function of estimates of the amount of resources available to support fruits, and (3) on any inflorescence, fruits initiated early have a lower probability of aborting than fruits initiated late.These results suggest that low fruit set in Yucca whipplei is caused by shortage of resources to support developing fruits, rather than by a shortage of pollinators. Possible explanations of the adaptive significance of regulating maternal investment via fruit abortion are mentioned, but further experimentation is required before any conclusions can be drawn.     

Selective seed abortion affects the performance of the offspring in Bauhinia ungulata

BACKGROUND AND AIMS: Under the microgametophytic competition hypothesis, a non-random pattern of seed abortion is expected, in which only the most vigorous seeds reach maturity. In a previous study, it was found that Bauhinia ungulata (Fabaceae) exhibits a pattern of seed abortion dependent on the position of the ovule within the ovary; ovules located in the stylar half of the fruit, close to the point of entry of pollen tubes to the ovary, have a low probability of seed abortion, whereas ovules in the basal half of the fruit are aborted with a high probability. METHODS: A series of experimental fruits was generated, in which ovules from either the stylar (treatments 1 and 2) or the basal (treatments 3 and 4) half of fruits were destroyed, to evaluate whether these patterns of selective seed abortion have an effect on the vigour of the offspring in B. ungulata. KEY RESULTS: Only 53 % of the seed from control fruits germinated. Seed set in fruits from treatments 1 and 2 showed a significantly lower (33-43 %) percentage of germination; the germination of seeds from fruits in treatments 3 and 4 (49-51 %) did not differ from control seeds. In addition, it was found that the differences in vigour of the offspring are not random with respect to the position of the ovule in the pod. CONCLUSIONS: The overall performance of the seeds correlated with their likelihood of maturation. Seeds located at the basal half of the treatment fruits showed lower values of vigour than seeds located on the stylar half. The differences were more marked for early measures of fitness.     

The effects of pollen load size and donor diversity on pollen performance, selective abortion, and progeny vigor in Mirabilis jalapa

The influence of pollen competitive environment on pollen performance (pollen germination, stigmatic penetration, and pollen tube growth rate), the maturation or abortion of initiated fruit, seed size, and seedling vigor was explored by manipulating the size and diversity of stigmatic pollen loads on Mirabilis jalapa. All aspects of pollen performance significantly increased with the number of pollen grains on a stigma or pollen tubes in a style, but was not influenced by the diversity of pollen donors. Plants tended to mature single-ovulate fruits that came from flowers where pollen load size and diversity were greatest and aborted those where these were lowest. No plants from seeds resulting from pollinations with a single pollen grain survived, but other fitness measures were mostly determined by maternal plant. The data suggest that pollen performance is influenced by pollen competitive environment, and both the genetic diversity of the pollen load and number of competing pollen tubes are important determinants of seed/fruit abortion.     

EFFECTS OF NONRANDOM SEED ABORTION ON PROGENY PERFORMANCE IN PHASEOLUS COCCINEUS L

In this study, we sought to determine if Phaseolus coccineus normally aborts potentially viable seeds, and whether seed abortion is nonrandom with respect to progeny vigor. The ovaries of Phaseolus coccineus typically have six linearly arranged ovules. The three ovule positions at the stylar end are more likely to mature seeds than the three ovules at the basal end of the ovary. When we destroyed the developing ovules at the stylar end of the fruit after fertilization but before seed abortion, there was a significant increase in the probability that the ovules in the three basal positions would produce a mature seed. The probability of seed maturation in control fruits (no ovules destroyed) ranged from 38.3 to 42.7% over the three field seasons, whereas in the experimental fruits it ranged from 64.3 to 79.7% (similar to that of ovules at the stylar end in control fruits). We did not find any significant change in the probability of seed production in the three ovule positions in the stylar end of the ovary (the positions with high probability of seed maturation) when the basal ovules were experimentally destroyed. These results indicate that potentially viable seeds are regularly aborted in P. coccineus, with seed abortion more frequent in the basal ovule positions than at the stylar positions. In two greenhouse studies and one field study, we compared the vigor of progeny produced in the control fruits with the vigor of progeny produced in fruits where three ovules (either stylar or basal end) were destroyed. We found that the performance of the progeny from the three positions at the stylar end of the control fruits did not differ from the performance of the progeny from experimental fruits in which the three basal ovule positions were destroyed. In contrast, the progeny from the basal positions of the control fruits outperformed the progeny from the experimental fruits when the seeds were produced in the three basal ovules (stylar ovules destroyed). Our findings indicate that when the experimental treatment increased the probability of seed maturation, there was a significant decrease in the average vigor of the progeny in the remaining (basal) ovule positions.     

Fruit mass variability in Vaccinium myrtillus as a response to altitude,simulated herbivory and nutrient availability

Variability in fruit mass may respond to environmental conditions, in addition to the genetic effect that has been reported in several reproductive features. We first analyzed fruit traits in 15 localities along an altitudinal gradient (300–2000 m a.s.l.) in the berries of Vaccinium myrtillus. We then tested whether changes in natural conditions, such as nutrient availability and herbivory by ungulates, affected fruit features in this species. Therefore, nitrogen (N) addition and clipping were applied in plots situated in six of the 15 localities. In these plots, we later collected fruits in two consecutive years in order to obtain fruit mass, seed number and initial number of ovules per flower ovary. Data along the altitudinal gradient showed that fruit mass was determined by both ovule number and seed number, although these factors only explained approximately half of the variation. Fruit mass and number of ovules and seeds followed a similar pattern with altitude, increasing until reaching a maximum at around 1700 m. Regarding the effect of the experimental treatments, fertilized non-clipped plants produced the heaviest fruits but clipping alone had no significant effect on fruit mass. Moreover, high soil pH had a positive influence on fruit mass. In addition, whereas the original number of ovules per ovary was not affected by the experimental treatments, the number of seeds per fruit increased and the abortion rate decreased in fertilized non-clipped plots, which means that the effect of simulated herbivory on these fruit traits depended on N addition. In conclusion, fruit mass was clearly affected by nutrient availability and this effect is attributed to an increase in the production of seeds rather than to an increase in module size and number of ovules per ovary. This outcome suggests that fruit mass is a plastic trait influenced by environmental factors like nutrient availability.     

文冠果花粉供体的多样性对果实产出的影响

很多植物的花,其柱头上接受的花粉供体多样性数量通常与果实成熟和种子产出有关。关于提高花粉多样性能否增加植物的生殖产出问题,文献中时常有相互矛盾的结论。本研究通过对自交不亲和性植物文冠果(Xanthoceras sorbifolium)进行1、2、3、4种花粉供体传粉实验,调查了不同花粉供体数量对文冠果雌性生殖的影响。结果表明,增加亲和花粉供体的多样性,一定程度上提高了花序上果实的坐果数量,同时也增加了果实中种子的数量及单粒种子重量。对文冠果授以4种亲和性花粉供体后,花序上成熟果实的平均数最多;3种亲和性花粉供体传粉后,每个果实中的种子数最多,单粒种子也最重。如果混合花粉中含有自交花粉,那么果实将败育。除花粉多样性影响雌性生殖产出外,母本基因型也具有重要影响,即增加文冠果种植品系的多样性,将有助于提高果实和种子产量。本研究还讨论了花粉遗传多样性效应、母本交配选择及果实选择性败育假说。     

Changes in Baboon Feeding Behavior: Maturity-dependent Fruit and Seed Size Selection within a Food Plant Species

Despite considerable inter- and intraindividual variation in fruit and seed size in many plant species, researchers have given little attention to the relevance of the traits for primate fruit choice within a food plant species and its implications for tree regeneration. We studied feeding behavior and selectivity of olive baboons (Papio anubis) in the African locust bean (Parkia biglobosa, Mimosaceae), via direct observations of habituated groups and indirect evidence from leftovers of pods after feeding events. Olive baboons acted as both seed predators and dispersers for Parkia biglobosa. They fed on and destroyed unripe seeds, and swallowed intact ripe seeds when consuming mature fruit pulp. Predation rate was high, and only 10% of the seeds were dispersed. Predation and dispersal of seeds is linked to seed number and size. Digestible unripe seeds accounted for 10% of the unripe fruit mass, while indigestible ripe seeds made up 28% of the mature fruit mass. With these constraints, olive baboons increased food gain per fruit by selecting unripe pods containing a high number of large and heavy seeds. Consequently, only pods with fewer and smaller seeds remained for maturation. Thereafter, baboons fed on mature pods containing the smallest seeds, and exploited pods with more seeds to a greater extent than those with fewer seeds. Thus, fruits with small seeds and an intermediate seed number contributed the most to dispersal by baboons.     

Effects of Seed Number on Competition and Dominance among Fruits in Capsicum annuum L.

The effects of seed number on set, development and growth ofa fruit, and on inhibition of later-developed fruits were studiedby varying the pollen load on the stigma of sweet pepper flowers(Capsicum annuum L.). Despite much variation, a linear increasein individual fruit weight with seed number could be observed.Seed number affected the growth rate rather than the growingperiod of fruit. When seed numbers were low, the probabilityof fruit setting was positively related to seed number. However,a relatively low seed number (50–100 seeds/fruit: 20–30%of the maximum seed number) was sufficient for maximal fruitset. An increase in seed number increased the inhibitory effect ofa fruit on set and growth of later-developing fruits. As a result,when pollination treatments were applied to all the flowersof a plant, results could be quite different to those obtainedwhen only a limited number of flowers were treated. Fruit setof the second fruit was reduced by the application of a highpollen load to the first flower, even when the first fruit abortedbefore it had accumulated much dry matter. Our results suggestthat growth inhibition of the second fruit by seed number ofthe first fruit is controlled both by competition for limitedassimilates, as well as by dominance due to the production ofplant growth regulators by the developing fruit. Sweet pepper; Capsicum annuum L.; pollination; fruit set; abortion; abscission; fruit growth; first-fruit dominance; sink strength     

Fruit size and shape: Allometry at different taxonomic levels in bird-dispersed plants

Summary The likelihood that a plant's seeds will be dispersed by fruit-eating birds may depend upon the size and shape of its fruits. Assuming that elongate fruits can be swallowed more easily than spherical fruits of equal volume and that plant fitness is enhanced by seed dispersal by many individuals and species of birds, natural selection should favour increasing fruit elongation with increasing fruit size in bird-dispersed plants. According to this view, this allometric pattern would be adaptive. Alternatively, fruit shape in bird-dispersed plants may be constrained by development or phylogeny. To determine whether there was any evidence to support the adaptive allometry hypothesis, we examined allometric relationships between length and diameter in fruits and seeds in a group of neotropical bird-dispersed plant species. Using the major axis technique, we regressed ln(diameter) on ln(length) for fruits and seeds at various taxonomic levels: (1) within individual trees ofOcotea tenera (Lauraceae) (2) among 19 trees within a population ofO. tenera, as well as among pooled fruits from multiple trees within 20 other species in the Lauraceae, (3) among 25 sympatric species within a plant family (Lauraceae) and (4) among 167 species representing 63 angiosperm families within a plant community in Monteverde, Costa Rica. At most taxonomic levels, a tendency for fruit length to increase more rapidly than fruit diameter among fruits (negative allometry) occurred more frequently than expected by chance. Estimated slopes of the regressions of fruit length on fruit diameter were < 1 within 15 of the 19 individualO. tenera trees, among tree means withinO. tenera, among pooled fruits within 16 of the 20 other species in the Lauraceae, among species means within the Lauraceae and among means of all bird-dispersed species in the lower montane forests of Monteverde. Seed allometry showed similar patterns, although for both fruits and seeds the broad confidence intervals of the slopes estimated by major axis regression overlapped 1 in many cases. Among the 63 Monteverde family means, fruit length and diameter scaled isometrically. Based on measurements of ontogenetic changes in fruit shape in a single species,O. viridifolia, we found no evidence that negative allometry in fruit shape within the Lauraceae was an inevitable consequence of developmental constraints. Instead, increasing elongation of fruits and seeds in certain plant taxa is consistent with adaptation to gape-limited avian seed dispersers. Contrary results from vertebrate-dispersed species from Malawi and Spain may reflect differences between the New and Old World in plant taxa, seed dispersers or evolutionary history.     

Fruit removal efficiency and success: influence of crop size in a neotropical treelet

The reproductive success of animal-dispersed plants is closely linked to the number of seeds that they are able to disperse. The fruit crop size hypothesis states that a plant with large fruit crop size will attract more dispersers than a plant with a smaller fruit crop, which may result in more seeds being dispersed from the foremost. In this study, we experimentally examined the effect of crop size and other factors on primary seed dispersal in a neotropical shrub/tree, Casearia corymbosa (Flacourtiaceae). We used two predictive variables of reproductive success, which produce an accurate picture of seed dispersal ratio: fruit removal efficiency (proportion of a fruit crop removed by frugivores) and fruit removal success (relative contribution of each individual tree to the number of fruits removed in the population). We established two levels of fruit crop size at the C. corymbosa individuals, using plants with large (150 fruits) and small crops (50 fruits). We found that individual plants with larger crops had significantly higher values of fruit removal efficiency (92.6%) and success (5%) than plants with smaller crops (69.3% and 1.3%, respectively). Fruit removal efficiency was related to vegetation type, plant height and fruit width, but the variance explained by these variables was low ( < 8%). Fruit removal success was significantly related to crop size ( > 90% of the variance explained). These results suggest that fruit removal efficiency and success are strongly related to fruit crop size of C. corymbosa plants.     

Fruit size preference in the New Zealand pigeon (Hemiphaga novaeseelandiae)

Abstract We investigated whether the New Zealand pigeon Hemiphaga novaeseelandiae (Columbidae) exhibits size‐based preferences for fruits. We tested the hypothesis that in small‐fruited species, pigeons would prefer larger fruits, but in larger‐fruited species, this preference would reverse as the pigeons become increasingly limited by their gape size. We collected undispersed fruits and bird‐dispersed seeds of 10 plant species, some over several sites or years (13 datasets in total). We estimated the fruit size of dispersed seeds by fitting regressions of fruit diameter to seed diameter in intact fruits. We were able to predict fruit diameter from seed diameter in 12 of the 13 populations, although the relationship was stronger in single‐seeded species than in multi‐seeded species. Seven of the 12 populations tested showed a significant difference in seed diameter among undispersed and dispersed seeds. However, our results showed no consistent pattern in fruit size preference by the New Zealand pigeon and did not support our hypothesis. The large‐bodied New Zealand pigeon is generally not gape limited and fruit size preferences appear to be independent of mean fruit size.     

FLOWER,FRUIT AND SEED ABORTION IN TROPICAL FOREST TREES: IMPLICATIONS FOR THE EVOLUTION OF PATERNAL AND MATERNAL REPRODUCTIVE PATTERNS

Flower, fruit and immature seed abortion was studied in seven self-incompatible species of trees in a tropical lowland semideciduous forest. The species showed considerable variability in fruit and seed set and the rate at which flowers and fruits were aborted. The amount of flower and fruit abortion also varied over time within species. Small samples of open-pollinated flowers in three species showed adequate amounts of pollen on the stigma, but it could not be determined whether the pollen was compatible or incompatible. In a species with multiseeded fruits, the aborted fruits contained significantly fewer seeds than those retained on the plant. Position of fruit within the inflorescence and of seed within the ovary also had a marked effect on abortion: fruits and seeds at certain positions had a higher probability of abortion than those at other positions. Experiments to test the effect of pollen source on abortion were inconclusive. The factors underlying abortions were evaluated in the context of three mutually non-exclusive hypotheses. It is concluded that selection for increased pollen dispersal and uncertainty in paternity of the zygotes are major factors underlying abortions.     

Fruit phenology of Prunus jamasakura and the feeding habit of the Asiatic black bear as a seed disperser

We investigated the relationship between the fruit phenology of Prunus jamasakura and the fruit-feeding period of the Asiatic black bear (Ursus thibetanus). The purposes of this study were to determine (1) when bears feed on the fruit of P. jamasakura in relation to phenology; (2) whether ingestion damages seeds; and (3) how ingestion influences seed germination. We assessed the relationship between the phenology of fruit maturation (size, sugar concentration, color, persistence, and germination percentage) and the feeding period of bears in the field, as judged from bear shelves and claw marks. We also compared the germination percentage of seeds ingested by captive bears with that of uningested. Bears fed on the fruit from days 50 to 66 after flowering, when most of the fruits were on the tree and became large, the germination percentage of seeds increased, and the sugar concentration became high. Bears fed only on mature fruits and so obtained high-quality nutrients. Germination tests showed that ingestion of fruits by the bears caused no physical damage to the seeds. Ingested seeds did not show a significant difference in germination percentage from seeds, whose pulp was artificially removed. These results indicate that bears are potentially effective dispersers from a qualitative perspective and, to some extent, from a quantitative perspective.     

Fruit production in Sorbus aucuparia L. (Rosaceae) and pre-dispersal seed predation by the apple fruit moth (Argyresthia conjugella Zell.)

Variation in fruit production and pre-dispersal seed predation by Argyresthia conjugella was studied in␣four populations of Sorbus aucuparia in northern Sweden.␣The number of infructescences, fruits per infructescence, consumed seeds and developed unattacked seeds per fruit were scored in marked trees from 1984 to 1990. The results showed that the number of fruits produced in each population determined the number of seed predators occurring in the host population, as the yearly number of seed predators was significantly and positively correlated with yearly number of fruits, in all but one population. The seed predators showed a delay in response to variation in number of fruits produced. This lag in response resulted in a large proportion of fruits being attacked and seeds consumed in a bad fruiting year that followed a good fruiting year, and vice versa. The proportion of fruits attacked and seeds consumed was largest in the population showing the greatest between-year variation in fruit production and lowest in the population showing the lowest between-year variation in fruit production. Furthermore, the individuals within the former population were synchronised, while they were not in the latter population. These results contradict one of the possible explanations of mast-seeding, where large synchronised between-year variation is supposed to reduce pre-dispersal seed predation. Instead, differences in attraction of the seed predator to differences in fruit crop size could explain the observed difference in seed predation between the two populations with opposite fruiting patterns. Within each population, irrespective of year, the proportion of fruits attacked and seeds consumed was independent of a tree's fruiting display. Therefore, trees with high fruit production, despite harbouring the largest number of seed predators, produced the largest number of developed seeds in absolute numbers, compared to trees that produced few fruits. Received: 25 February 1996 / Accepted: 30 November 1996     

Seed size selection by olive baboons

Seed size is an important plant fitness trait that can influence several steps between fruiting and the establishment of a plant’s offspring. Seed size varies considerably within many plant species, yet the relevance of the trait for intra-specific fruit choice by primates has received little attention. Primates may select certain seed sizes within a species for a number of reasons, e.g. to decrease indigestible seed load or increase pulp intake per fruit. Olive baboons (Papio anubis, Cercopithecidae) are known to select seed size in unripe and mature pods of Parkia biglobosa (Mimosaceae) differentially, so that pods with small seeds, and an intermediate seed number, contribute most to dispersal by baboons. We tested whether olive baboons likewise select for smaller ripe seeds within each of nine additional fruit species whose fruit pulp baboons commonly consume, and for larger seeds in one species in which baboons feed on the seeds. Species differed in fruit type and seed number per fruit. For five of these species, baboons dispersed seeds that were significantly smaller than seeds extracted manually from randomly collected fresh fruits. In contrast, for three species, baboons swallowed seeds that were significantly longer and/or wider than seeds from fresh fruits. In two species, sizes of ingested seeds and seeds from fresh fruits did not differ significantly. Baboons frequently spat out seeds of Drypetes floribunda (Euphorbiaceae) but not those of other plant species having seeds of equal size. Oral processing of D. floribunda seeds depended on seed size: seeds that were spat out were significantly larger and swallowed seeds smaller, than seeds from randomly collected fresh fruits. We argue that seed size selection in baboons is influenced, among other traits, by the amount of pulp rewarded per fruit relative to seed load, which is likely to vary with fruit and seed shape.     

Effect of ovule position within the pod on the probability of seed production in Bauhinia ungulata (Fabaceae)

BACKGROUND AND AIMS: It has been claimed that ovules linearly ordered within a fruit differ in their probabilities of reaching maturity. This was investigated by studying the effect the position of an ovule within the pod has on seed abortion and seed production in Bauhinia ungulata. METHODS: Fruits collected during the dry seasons of 1999, 2000 and 2001 were opened, and the number, position and status of each ovule within the fruit were recorded. A GLM model was used to assess the effects of population, tree identity and ovule position within the pod on ovule fertilization, seed abortion, seed damage and seed maturation in two populations of B. ungulata. KEY RESULTS: Nearly 30% of the ovules were not fertilized in 1999; this percentage dropped to 5% the following two years. Seed abortion (50%) and seed damage (15%) were the same every year during the study period. Only 15% of the initial ovules developed into mature seeds in 1999; this value increased to 35% in 2000 and 2001. However, seed survivorship was dependent on the position of the ovule within the pod; non-fertilized and early aborted ovules were found more often near the basal end of the ovary. The frequency of seed damage was not affected by position. Mature seeds were found mainly in the stylar half of fruits, where ovules are likely to be fertilized by fast pollen tubes. CONCLUSIONS: The pattern of seed production in B. ungulata is non-random but is dependent upon the position of the ovule within the pod. The results suggest that the seeds produced within a fruit might differ in their vigour.     

Persistent, non-seed-size maternal effects on life-history traits in the progeny generation in squash, Cucurbita pepo

Maternal-environmental effects on subsequent progeny life-history traits were evaluated in squash ( Cucurbita pepo L.) in terms of the amount of time available for seed development, and the timing of fruit production. Progeny arising from three kinds of fruit were compared. Plants from which fruits were removed 3 d post-pollination throughout the growing season developed only 'late' fruits (during 10–15 d) at the end of the growing season; on control plants both 'early' and 'late' fruits developed (both types allowed to ripen fully). Seed from each type of fruit was weighed individually and categorized into three size classes, then germinated and raised to maturity, including regular harvesting of all fruits 3 d post-pollination. Maternal effects were evident for both vegetative and reproductive traits and carried over to later stages. In contrast, effects due simply to seed size disappeared by day 30 for leaf variables and day 60 for male flower production. Within a seed-size class, progeny arising from fruit of treated plants produced significantly more leaves, with greater size, and more male flowers than those arising from fruit of control plants, while the reverse was true for fruit number and fruit mass. This result is discussed in terms of possible gibberellic acid involvement. In control plants, progeny arising from seeds in the large, fully mature 'early' fruits produced significantly more, and larger leaves by day 30 than did those from late fruits (suggesting differential provisioning in seeds during development). Male flower production had a highly significant positive correlation with vegetative mass and a significant negative correlation with fruit production.     

WIND DISPERSAL OF FRUITS WITH VARIABLE SEED NUMBER IN A TROPICAL TREE (LONCHOCARPUS PENTAPHYLLUS: LEGUMINOSAE)

The tropical tree, Lonchocarpus pentaphyllus (Poir.) DC. (Leguminosae-Papilionoideae), matures indehiscent wind-dispersed fruits containing 0–4 seeds. Most fruits are one-seeded (82%) while less than 2% are three-seeded. An increase in seed number per fruit correlates with increases in four characteristics expected to affect dispersal distance under field conditions: fruit weight, fruit area, square root of wing-loading, and rate of descent in still air. The dry weight of a seed decreases with an increase in seed number per fruit. Under field conditions nearly 40% of the mature fruits fall within the radius of the tree crown. Fruits with more intact seeds are dispersed shorter distances; fruits with no developed seeds travel the farthest. Among one-seeded fruits dispersed beyond the crown radius, dispersal distance is inversely proportional to the square root of wing-loading. The weight of seed in these one-seeded fruits, however, is independent of dispersal distance. Fruits with more seeds have a higher proportion of underdeveloped seeds. However, a greater proportion of two- and three-seeded fruits have at least one intact mature seed than do one-seeded fruits. This comparative study illustrates that changes in fruit morphology and weight associated with different numbers of seeds per fruit affect dispersal properties as well. A decrease in seed number per fruit increases both seed weight and dispersal distance, but it decreases the probability that a given dispersal event results in movement of an intact seed.