Fruit removal and postdispersal survivorship in the tropical dry forest shrub Erythroxylum havanense: ecological and evolutionary implications

We studied the relationship between the removal rate and the spatiotemporal availability of ripe fruits of the tropical deciduous shrub Erythroxylum havanense in western Mexico. We also evaluated the effects of dispersal on seed survival during the first stages of establishment. Fast and early dispersal should be favored in E. havanense, since propagules have more time to grow and accumulate resources before the beginning of the severe dry season. In general, high rates of fruit removal imply faster and earlier dispersal. Thus, plants producing large crops should benefit from high removal rates, which will increase the probability of successful establishment by their progeny. To characterize both individual and population fruiting patterns, we made daily counts of fruits on 51 plants arranged in six clumps of different sizes. The daily number of fruits removed per plant was higher for plants with larger initial crop sizes and larger numbers of ripe fruits on a given day, but decreased as clump size increased. Additionally, we monitored postdispersal survival and germination in an experiment manipulating seed density, distance from adult plants, and seed predation. Early establishment was independent of density or distance, and vertebrate seed predation was the main agent of seed mortality. Our results indicate that the critical variable with respect to fruit removal is the number of fruits a plant produces, large plants having higher dispersal rates. Large plants are also more likely to have more seeds escaping postdispersal seed predation.     

BIRD-DISPERSAL OF PHYTOLACCA AMERICANA L. AND THE INFLUENCE OF FRUIT REMOVAL ON SUBSEQUENT FRUIT DEVELOPMENT

Characteristics of fruits, seeds, and ripening of Phytolacca americana were studied in New Jersey, USA to assess their importance in the dispersal strategy of this species. Removal by birds was directly related to the percent of ripe fruits available on a raceme. Fruit removal from a raceme resulted in lower fruit pulp and seed weights for fruits developing on the same raceme, but these differences probably do not influence probability for dispersal by birds. We demonstrate that characteristics of the fruit pulp may decrease seed availability for the primary seed predator, Peromyscus leucopus, and increase the time fruits are available for dispersal. We speculate on the significance of the sequential fruiting in Phytolacca and the relationship to availability of dispersal agents and high-lipid fruits. Sequential ripening and protection from predation result in seed dispersal from late August to early December.     

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     

Phenological variation in fruit characteristics in vertebrate-dispersed plants

Summary We investigated inter-specific variation in fruit characteristics — fruit size, seed number per fruit, seed weight, nutritional content, fruit persistence, and fruit synchronization — in relation to flowering and fruiting phenology in 34 species of fleshy fruited plants. Except for aspects of fruit synchrony and persistence, the results in general were inconsistent with previous suggestions about adaptive variation in phenologically related fruit traits. The main results were as follows: (1) Late flowering, late fruiting, lengthy development time from flower to fruit, and highly persistent fruits constitute a complex of correlated characteristics among the species. (2) Synchronization of fruiting within individuals increased from early ripening fruits to late ripening fruits. Fruiting synchrony was more pronounced in species with a small crop size than in species with a large fruit crop, whereas synchrony was not significantly related to flowering synchronization, nor to life form. (3) Nitrogen and carbohydrate content of fruit pulp did not vary in relation to phenology, whereas lipid content decreased from early to late ripening fruits. (4) No seasonal trends were found for variation in seed size or seed number per fruit. (5) Interactions with flowering phenology and developmental constraints are important in phenological fruiting patterns. Temporal variation in start of fruiting was partly (36%) explained by variation in flowering time. Seed weight variation explained 17% of variation in development time from flower to fruit. (6) Despite constraints from flowering and seed development, some adaptive adjustment in fruiting phenology is likely to be allowed for among the investigated species. Such an adaptive variation in fruiting phenology was suggested by intra-generic comparisons of Prunus and Vaccinium species.     

A field test of the directed deterrence hypothesis in two species of wild chili

The directed deterrence hypothesis posits that secondary metabolites in ripe fruit function to deter fruit consumption by vertebrates that do not disperse seeds, while not impacting consumption by those that do. We tested this hypothesis in two species of wild chilies (Capsicum spp.). Both produce fruits that contain capsaicinoids, the compounds responsible for the pungency of chilies. Previous work suggests seed-dispersing birds but not seed-destroying rodents consume chili fruits, presumably because rodents are deterred by capsaicin. However, fruit removal from chili plants by rodents and other mammals has not been previously explored. Because laboratory rodents can develop a preference for capsaicin, it is quite possible that wild rodents are natural consumers of chili fruits. We monitored the fate of 125 marked fruits of Capsicum chacoense and 291 fruits of Capsicum annuum. For both species, essentially all fruit removal occurred during the day, when rodents are inactive. Video monitoring revealed fruit removal only by birds, mostly by species known to disperse chili seeds in viable condition. Furthermore, these species are from taxonomic groups that tend to specialize on lipid-rich fruits. Both species of chili produce fruits that are unusually high in lipids (35% in C. chacoense, 24% in C. annuum). These results support the directed deterrence hypothesis and suggest that fruiting plants distinguish between seed predators and seed dispersers by producing fruits that repel the former and attract the latter.     

Factors affecting seed rain beneath fleshy-fruited plants

We investigated factors affecting seed rain beneath nine fleshy-fruited fruiting plant species growing in a 1-ha plot of planted Pinus thunbergii in central Japan. We tested whether the numbers of seeds and seed species dropped by birds beneath fruiting plants were correlated with the number of fruits removed by birds from the plants. Most of fruiting plant species with high fruit removal had significantly high seed rain. Both the numbers of seeds and seed species dropped were significantly, positively correlated with the number of fruits removed across for all fruiting plant species. Therefore, fruit removal predicted the difference among heterospecific fruiting plants in seed rain. We also tested whether the number of fruits removed from fruiting plants by birds was related with fruit crop size, fruit size, and height of the plants, and the numbers of fruits and fruit species of neighboring plants near the plants. Most of fruiting plant species with high fruit crop size had significantly high fruit removal. The number of fruits removed was significantly, positively correlated with both the fruit crop size and the number of neighboring fruits across the nine fruiting plant species. However, the effect of the neighboring fruit density on fruit removal was lower remarkably than that of fruit crop size. Therefore, fruit crop size best predicted the differences among heterospecific fruiting plants in fruit removal. We suggest that fruiting plant species with high fruit crop size and high fruit removal contribute to intensive seed rain beneath them. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fruit characteristics and factors affecting fruit removal in a Panamanian community of strangler figs

We describe fruiting characteristics for 12 species in a community of strangler figs (Moraceae: Urostigma) studied in Panama. We quantify diurnal and nocturnal removal rates and proportions of fruits removed, and relate them to the activities of the main dispersers of the figs: bats and birds. These results combined with previous studies show that there are clear differences between fig species with fruit that ripen red and those with fruit that remain green(ish). In the red-fruited species, the fruit are small, ripen asynchronously over relatively long periods, produce little scent, and are mainly taken during the day by birds. In contrast, in the green(ish)-fruited species, the fruits are larger, span a range of sizes, ripen relatively synchronously, produce very distinctive aromas, and are mainly taken at night by bats. This dichotomy in fruiting characteristics suggests coadaptive links between groups of dispersers and different species within the genus Ficus. All fig species produce a range of fruit crop sizes (10–155 fuits/m² canopy area) of which a high proportion were removed by seed dispersers (>80%). Removal rates (fruit removed per day) were positively correlated with crop size, suggesting that trees with large crop size attract more frugivores. Removal rates of green-fruited figs were significantly lower and persistence and abortion of ripe fruit were significant higher around full moon, apparently due to the reduced activity of bats. We further estimate the number of bats that are sustained by a tree fruit crop and account for the observed fruit removal. We then discuss the evidence for coadaptation between different groups of figs and their seed dispersers, Finally, we consider the conservation implications for figs as keystone resources in tropical forests. Received: 26 April 1999 / Accepted: 10 January 2000     

Does attraction to frugivores or defense against pathogens shape fruit pulp composition?

Fruit traits evolve in response to an evolutionary triad between plants, seed dispersers, and antagonists that consume fruits but do not disperse seeds. The defense trade-off hypothesis predicts that the composition of nutrients and of secondary compounds in fruit pulp is shaped by a trade-off between defense against antagonists and attraction to seed dispersers. The removal rate model of this hypothesis predicts a negative relationship between nutrients and secondary compounds, whereas the toxin-titration model predicts a positive relationship. To test these alternative models, we evaluated whether the contents of nutrients and secondary compounds can be used to predict fruit removal by mutualists and pathogens in 14 bird-dispersed plants on a subtropical island in São Paulo state, southeastern Brazil. We selected eight to ten individuals of each species and prevented fruit removal by covering four branches with a net and left fruits on four other branches available to both, vertebrate fruit consumers and pathogens. The persistence of ripe fruits was drastically different among species for bagged and open fruits, and all fruit species persisted longer when protected against seed dispersers. We found that those fruits that are quickly removed by vertebrates are nutrient-rich, but although the attack rate of pathogens is also high, these fruits have low contents of quantitative defenses such as tannins and phenols. Thus, we suggest that the fruit removal rate by seed dispersers is the primary factor selecting the levels of fruit defense. Likewise, nutrient-poor fruits have low removal of seed dispersers and low probability of attack by pathogens. These species retain ripe fruits in an intact condition for a prolonged period because they are highly defended by secondary compounds, which reduce overall attractiveness. However, this strategy might be advantageous for plants that depend on rare or unreliable dispersers.     

Influence of between-year variation in the density of Rhus <Emphasis Type="Italic">trichocarpa</Emphasis> fruits on the removal of fruit by birds

The fruiting phenology and fruit removal patterns of Rhus trichocarpa Miq. (Anacardiaceae) were investigated in a warm-temperate secondary forest in Japan. Mature fruits of this species are dispersed by birds. Effects of fruit display size and canopy openness on fruit removal were investigated in years with different fruit densities (i.e., masting and non-masting years). Moreover, effects of increased canopy openness during winter on fruit removal were also investigated. Seasonal patterns of fruit removal were quite different between masting and non- masting years. In the non-mast year, fruits were removed by birds soon after maturation in the summer. In contrast, in the mast year, fruits were removed gradually by birds from summer to winter. Moreover, the rate of fruit removal was greater for trees with a larger display size in the non-mast year, whereas that was greater for trees with greater canopy openness in the mast year. Canopy openness increased in winter, and fruit removal in winter was enhanced in trees with a more open canopy only in the non-mast year. These observations strongly suggest that avian dispersers became satiated in the mast year, whereas fruit removal was enhanced in the non-mast year. In the mast year, although many fruits were not dispersed until winter, they were neither depredated nor rotten, and the long period of fruit removal by birds may have enhanced fruit dispersal. The large abundance of seedlings and saplings of this species in Japanese secondary forests suggests that this fruiting strategy is beneficial.     

Impact of habitat structure and fruit abundance on avian seed dispersal and fruit predation

So far, it is poorly understood how differential responses of avian seed dispersers and fruit predators to changes in habitat structure and fruit abundance along land-use gradients may translate into consequences for the seed dispersal of associated plants. We selected a gradient of habitat modification (forest, semi-natural, and rural habitat) characterized by decreasing tree cover and a high variation in local fruit availability. Along this gradient we quantified fruit removal by avian seed dispersers and fruit predators from 18 Sorbus aucuparia trees. We analyzed the relative importance of tree cover and fruit abundance in explaining species richness, abundance and fruit removal rates of both guilds from S. aucuparia trees. Species richness and abundance of seed dispersers decreased with decreasing tree cover, whereas fruit removal by seed dispersers decreased with decreasing fruit abundance independent of tree cover. Both variables had no effect on species richness, abundance and fruit removal by fruit predators. Consequently, seed dispersers dominated relative fruit removal in fruit-rich sites but the dispersal/predation ratio shifted in favor of predation in fruit-poor habitat patches. Our study demonstrates that variation in local habitat structure and fruit abundance can cause guild-specific responses. Such responses may result in a shift in fruit removal regimes and might affect the dispersal ability of dependent fruiting plants. Future studies should aim at possible consequences for plant recruitment and guild-specific responses of frugivores to disturbance gradients on the level of entire plant–frugivore associations.     

Maturation characteristics of Rubus pennsylvanicus fruit: are black and red the same?

Summary Fruit of the blackberry, Rubus pennsylvanicus Poir. (Rosaceae), were examined to determine variation in maturation characteristics. Maturation timing and rate varied greatly among individual fruits, resulting in a bi-colored fruiting display comprised largely of two maturation stages, pre-ripe (salmon and scarlet) and ripe (dark brown and black). While ripe fruit were generally larger and heavier than pre-ripe fruit, exhibiting greater fresh and dry fruit weight, diameter, water content, and total seed weight, no significant differences were found in energy content, i.e. numbers of calories per gram pulp, or in pulp:seed ratio. The differences between ripe and pre-ripe fruit appear to be due largely to an increase in water content and seed weight with maturity. The fact that little energetic benefit accrues to the preferential selection of ripe fruit suggests that bi-colored Rubus displays may be considered to be unicolored.     

脊椎动物传播植物肉质果中的次生物质及其生态作用

在种子植物-动物的互惠关系中,植物果实成熟后需要吸引种子传播者取食果实,传播其种子至适宜萌发的生境,同时又要防御种子捕食者过度消耗种子。果实内的次生物质(如:配糖生物碱、大黄素、辣椒素)在此过程中起到重要的调控作用。依赖脊椎动物传播的肉质果中往往含有与植物茎、叶内相同的次生物质,其种类繁多,主要分为含氮化合物、酚类化合物和萜类化合物。未成熟果实内富含次生物质(如:单宁、大黄素),主要保护未成熟种子不被潜在的捕食者和食果动物取食,这些次生物质的含量通常随果实成熟而降低;其它次生物质(如:脱辅基类胡萝卜素)的含量随果实成熟而增多,可能起到吸引食果动物的作用。在对脊椎动物捕食的抵御中,果实内不同类型的次生物质促使成熟果实对所有脊椎动物都有毒性(专毒性)或者仅对种子捕食者有毒性(泛毒性)。肉质果内的次生物质对植物-食果动物相互关系的调控作用,还可以通过调节动物取食频次和数量、抑制和促进种子萌发、改变种子在肠道的滞留时间、吸引传播者等生态作用而实现。某种次生物质往往集多种生态作用于一身。目前对肉质果内次生物质与脊椎动物相互关系的探讨还不够深入。未来研究需要综合考虑植物次生物质与果实生理生化、形态学等特征对食果者的综合调控机理;次生物质在种子传播后的调控作用对植物种群或群落结构和分布格局的影响;从动植物协同进化角度探讨植物次生物质的产生、防御和吸引策略与脊椎动物对果实的选择和消费之间的关系等。开展脊椎动物传播肉质果实中次生物质的研究,对完善种子传播机制、植物繁殖和更新格局,丰富动植物相互作用、协同进化理论具有重要的意义。     

The effect of unripe fruits on ripe fruit removal by birds in Pistacia terebinthus: flag or handicap?

The shrub Pistacia terebinthus produces crowded infructescences with up to several hundred fruits, which are bright red when unripe and turn green when ripe. Most fruits contain an empty seed and never reach maturity. More ripe fruits were removed by birds from experimental bicolored fruit displays (consisting of infructescences with ten ripe fruits and stripped of unripe fruits, paired with infructescences with only unripe fruits) than from monocolored ones (single infructescences with ten ripe fruits and stripped of unripe fruits). Thus, the presence of unripe fruits seems to increase the conspicuousness or attractiveness of fruit displays to fruit-eating birds. A second experiment compared ripe fruit removal from experimental infructescences having only ripe fruits, with that from control infructescences containing both ripe fruits and natural numbers of unripe fruits, all on P. terebinthus plants. Unlike the first experiment, each bicolored display in this case consisted of a single infructescence with both unripe and ripe fruits. A higher proportion of ripe fruits was removed by birds from infructescences free of unripe fruits. This result suggests that the presence of unripe fruits reduces the accessibility of ripe fruits for fruit-eating birds. This is further supported by field observations of bird foraging behavior.     

Oviposition pattern and within-season spatial and temporal variation of pre-dispersal seed predation in a population of Mimosa bimucronata trees

Spatial and temporal variation of pre-dispersal seed predation was investigated in a population of Mimosa bimucronata trees located in the south-east region of Brazil. Three main hypotheses were addressed: (1) that the life stages of the seed predator Acanthoscelides schrankiae are synchronised with the reproductive stages of its host plant; (2) that seed predation levels vary spatially as a result of differences in fruiting phenology synchrony and fruit production among trees; and (3) that predation levels should be affected by the proximity of trees, showing a spatial structure. Also investigated was the oviposition pattern of A. schrankiae among seeds and fruits. Twenty spatially referenced trees were monitored throughout a year to examine tree phenology and egg laying and adult emergence. The bruchine’s life stages were synchronised with the reproductive stages of M. bimucronata trees. Egg distribution among seeds and fruits was aggregated. Infestation rates of adult bruchines were not spatially related to fruiting phenology and there is evidence that seed predation is a spatially density-independent process, because the relationship between infestation rates and fruit production was not significant. Finally, it was observed that the distribution of adult bruchines was spatially structured, because similar levels of infestation were found among nearby trees.     

应用结构方程模型解析影响黄连木果实产量 和种子命运的因素

果实(种子)产量和质量是影响植物种群更新的重要因素。为了探明影响黄连木果实产量和种子命运的因素以及这些影响因素之间的相互作用, 作者于2009年对河南省济源市45株黄连木(Pistacia chinensis)结果样树的植株特征、果实特征、果实产量和种子命运等进行了测定, 并用结构方程模型进行综合分析。结果表明: (1)黄连木果实产量与树高、树冠面积和果序大小等特征成正相关, 但与胸径、果实大小相关性不显著; (2)与捕食者饱和假说的预测不一致, 单株果实产量对黄连木广肩小蜂(Eurytoma plotnikovi)的种子捕食率(即虫蛀率)无显著直接负向效应; (3)树高和果实大小对虫蛀率为显著直接正向效应, 胸径对虫蛀率为显著直接负向效应, 显示黄连木广肩小蜂对植株特征和果实特征有一定的选择能力; (4)空壳率与虫蛀率成显著负相关, 空壳果实越多, 越易逃避黄连木广肩小蜂的寄生, 空壳果实的存在对完好种子起到了一定保护作用, 可能是黄连木防御昆虫寄生的重要机制; (5)空壳率和虫蛀率对种子完好率有显著直接负向效应, 而胸径、果序大小和果实产量对完好率为间接正向效应, 树高和果实大小为间接负向效应。可见, 黄连木植株特征和果实特征均不同程度地影响其果实产量和昆虫寄生, 从而影响黄连木的种子质量和种群更新。     

Effects of fruit thinning on fruit and seed features of <Emphasis Type="Italic">Cistus ladanifer</Emphasis>

Fruit and seed features are the result of reproductive allocation decisions which ultimately depend on both plant availability of resources and total number of developing fruits. In this study, we manipulated fruit load in Cistus ladanifer plants by removing 0, 25 or 75% of developing fruits. Fruit features (total fruit weight, fruit-wall weight, total seed weight per fruit and seed number per fruit) were unaffected by fruit thinning, nevertheless mean seed weight increased in treated plants independently of thinning intensity. This reduced compensation was unrelated to plant size and had no consequences on fruit predation by insects. From these results it could be suggested that not only availability of resources but also morphological constraints could affect seed size in Cistus ladanifer. On the other hand, this change in seed weight could have important consequences since in this species heavy seeds perform better after fire events but light ones are advantageous in between fire recruitments.     

Crop Size and Fruit Neighborhood Effects on Bird Visitation to Fruiting Schefflera morototoni Trees in Puerto Rico1

Studies of zoochorous seed dispersal systems often consider crop size, yet seldom consider the kinds and amounts of fruits surrounding parent plants (the fruit neighborhood) when attempting to explain among‐plant variation in fruit removal. We studied avian frugivory at 24 Schefflera morototoni trees from February to May 1998 in central Puerto Rico. The number of fruits removed by avian seed dispersers per visit was similar among focal trees (typically 2–4). In contrast, visitation rate was highly variable (range: 0–71 visits per 4 h). We used multiple regression analyses to evaluate the relative roles of crop size (focal tree ripe fruit abundance) and fruit neighborhood variables (measured within 30 m of focal trees) in affecting visitation to focal trees by avian frugivores. Visitation rate was positively related to crop size (although this variable was only significant in one of four regression models considered) and negatively related to the presence or abundance of conspecific fruits, suggesting that trees competed intraspecifically for dispersers. Relationships between visitation and heterospecific fruits were mixed—some kinds of fruits appeared to enhance visitation to focal trees, while others seemed to reduce visitation. In most regression models, neighborhood variables had larger effects on visitation than focal tree fruit crop size. Our results highlight the important effects of local fruiting environments on the ability of individual plants to attract seed dispersers.     

Factors Affecting Nesting Site Choice in Chimpanzees at Tshibati,Kahuzi-Biega National Park: Influence of Sympatric Gorillas

We recorded 310 fresh chimpanzee night nests at 72 nest sites to determine their choice of tree and site for nesting vis-à-vis the effects of sympatric gorillas. Chimpanzees did not use trees for nesting according to their abundance, but instead tended to nest in fruit trees that they used as food sources. Nesting patterns of chimpanzees may vary with nesting group size, the type of vegetation, and fruit species eaten or not eaten by gorillas. When chimpanzees lodged as a small group in the secondary forest, they nested more frequently in trees bearing ripe fruits eaten only by themselves than in those with fruit eaten also by gorillas. When they lodged as a large group in the primary forest, they nested more frequently in trees bearing ripe fruits eaten by both apes. Nest group size is positively correlated with the availability of preferred ripe fruits in secondary forest. These findings not only reflect the larger foraging groups at the larger fruiting trees but also suggest that chimpanzees may have tended to occupy fruiting trees effectively by nesting in them and by forming large nest groups when the fruits attracted gorillas. Competition over fruits between gorillas and chimpanzees, due to their low productivity in the montane forest of Kahuzi, may have promoted the chimpanzee tactics.     

Facultative ripening in Hamelia patens (Rubiaceae): effects of fruit removal and rotting

Summary In Costa Rica individual Hamelia patens trees produce fruit throughout the year and experience dramatic changes in rates of fruit removal and rotting. During some moths, most fruits rot because they are not removed. Rotting fruits increase the probability that other fruits on the same infructescence will rot. When removal rates are high, fruits are taken as soon as their seeds become viable but before the fruit is completely ripe. Experimental removal of fruits produced significantly higher ripening rates than on control infructescences. This response allows Hamelia to ripen more fruit and increase the number of fruits taken when dispersers are abundant (e.g., during migration). The proximate mechanism of this response probably includes reallocation of energy conserved when partially ripe fruits are removed. Responding to fluctuating disperser populations likely increases dispersal success and may function as the ultimate cause.     

Compensatory response of two dune annuals to simulated browsing and fruit predation

Abstract. Greenhouse and field studies were conducted to determine the effects of artificial fruit removal and clipping (simulated deer browsing) on components of reproduction of two indeterminate dune annuals: Cakile edentula var. lacustris (Bigel.) Hook and Corispermum hyssopifolium L. The results showed that both species were able to partially or completely compensate or even overcompensate for low to moderate levels of clipping or fruit removal only if the damage occurred in the early stages of fruit development. The indeterminate habit of growth of both species facilitated their compensatory ability. The removal of fruits and clipping of plants which mimick browsing by white tailed deer along Lake Huron resulted in a significant increase in their period of flowering and fruiting, especially in the early stages of fruit development. The plants compensated for fruit loss by increasing the number of fruits per plant. A delay in fruit removal or clipping to later stages of fruit maturation of both species drastically reduced reproduction. Similar experiments in the field revealed that, although the critical periods during which the plants were most susceptible were the same, the plants had lower compensatory ability. Fruit damage and clipping generally did not affect the seed mass of both species.