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 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.     

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.     

Effectiveness of Scat Detection Dogs for Detecting Forest Carnivores

Abstract: We assessed the detection and accuracy rates of detection dogs trained to locate scats from free-ranging black bears (Ursus americanus), fishers (Martes pennanti), and bobcats (Lynx rufus). During the summers of 2003-2004, 5 detection teams located 1,565 scats (747 putative black bear, 665 putative fisher, and 153 putative bobcat) at 168 survey sites throughout Vermont, USA. Of 347 scats genetically analyzed for species identification, 179 (51.6%) yielded a positive identification, 131 (37.8%) failed to yield DNA information, and 37 (10.7%) yielded DNA but provided no species confirmation. For 70 survey sites where confirmation of a putative target species' scat was not possible, we assessed the probability that ≤1 of the scats collected at the site was deposited by the target species (probability of correct identification; P_ID). Based on species confirmations or P_ID values, we detected bears at 57.1% (96) of sites, fishers at 61.3% (103) of sites, and bobcats at 12.5% (21) of sites. We estimated that the mean probability of detecting the target species (when present) during a single visit to a site was 0.86 for black bears, 0.95 for fishers, and 0.40 for bobcats. The probability of detecting black bears was largely unaffected by site- or visit-specific covariates, but the probability of detecting fishers varied by detection team. We found little or no effect of topographic ruggedness, vegetation density, or local weather (e.g., temp, humidity) on detection probability for fishers or black bears (data were insufficient for bobcat analyses). Detection dogs were highly effective at locating scats from forest carnivores and provided an efficient and accurate method for collecting detection-nondetection data on multiple species.     

Alternative seed-handling strategies in primates: seed-spitting by long-tailed macaques (Macaca fascicularis)

Summary The seeds in fruits consumed by primates may be chewed and digested, swallowed and defecated intact, or separated from the flesh and spat out. We show by a combination of close field observations and experiments with caged animals, that long-tailed macaques (Macaca fascicularis) have a remarkably low threshold of 3–4 mm for swallowing seeds and also that wild macaques rarely break them. The seeds of 69% of the ripe fruit species eaten are spat out intact or cleaned outside the mouth and dropped. Seed-spitting significantly reduces the swallowed food bulk and may lessen the risk of releasing seed toxins during mastication. However, it requires that even small fruits are processed in the mouth one or a few at a time. We suggest that fruit storage in the cheek pouches of cercopithecine monkeys allows them to spit seeds individually without excessively slowing fruit intake while feeding on patchily distributed fruit. In contrast, Apes and New World monkeys apparently swallow and defecate most ripe seeds in their diet and colobine monkeys break and digest them, detoxifying seed defenses by bacterial fermentation.     

Long-term trends in food habits of Asiatic black bears in the Misaka Mountains on the Pacific coast of central Japan

I did the food habits of the Asiatic black bear Ursus thibetanus from 1013 fecal samples collected between 1999 and 2005 in the Misaka Mountains on the Pacific coast of central Japan. The food habits of the bears showed clear seasonal changes, and I classified the food resources of the bears into three types. Staple foods were green vegetation in spring, soft mast (Prunus spp.) and insects in summer, and hard mast (Quercus spp.) in autumn. Alternative foods were green vegetation and other soft mast (Rubus spp.) in summer and Japanese chestnuts Castanea crenata and vine fruits in autumn. Foods of opportunity were hard mast (Quercus spp.) that had been shed in the previous autumn and were found in spring and other fruits in autumn. Seasonal food habits showed yearly variations: bears used alternative foods and foods of opportunity in response to the yearly variation in staple food amount, but the magnitude of variability of food habits differed among seasons, with large variability in autumn and small variability in summer and spring. The primary influence on the yearly variation in food habit is presumably the fluctuation in fruit production among years. Summer is probably the most difficult season in terms of the bear's food supply, because the number of fruiting species is limited and staple foods such as new green vegetation and fruits are less available. Long-term studies of the availability of the main food items and food habits of bears will be critical for further understanding these animals’ feeding ecology and for determining the factors that influence their behavior.     

Seed Dispersal by the Sloth Bear (Melursus ursinus) in South India1

Previous studies have shown that sloth bears are mainly myrmecophagous, but in this study, 39 and 83 percent (wet and dry season, respectively) of scats surveyed in South India contained fruits. Seeds from three of six plant species collected from scats germinated faster than seeds not passing through bears; germination percentage was not higher in any of the six species. These results suggest that the sloth bear may play an important role in the population dynamics of fleshy‐fruited species of the region.     

Morphology and phenology of seeds and whole fruit eaten by Milne-Edwards’ sifaka,Propithecus diadema edwardsi,in Ranomafana National Park,Madagascar

Although it is an anatomical folivore, the diet of the Milne-Edwards’ sifaka (Propithecus diadema edwardsiA. Grandidier, 1871) in Ranomafana National Park contained 35% seeds, 30% whole fruit, and 28% leaves. Plant species used as seed sources differed from those used as whole fruit sources in terms of temporal variation in consumption, taxonomic affiliation, morphology, and phenology. Although seeds were destroyed in both exploitation styles used by the sifakas—seed and whole fruit-eating—the gross morphology of species used as seed sources conformed to the complex of traits typical for fruits experiencing seed predation, while species used as whole fruit sources conformed to traits typical for fruits that do not experience predispersal predation. Many of the 19 plant species from which the seed was extracted and eaten contained a single seed with moderate testa thickness, and fruits containing this type of seed were medium-sized with dry or fibrous flesh, moderate skin thickness, and a dull color. In contrast, brightly colored, juicy fruits with minimally protected seeds were characteristic of the 38 plant species from which both pericarp and seed were eaten. Compared to transectwide measures of fruit availability or patterns restricted to whole fruit sources, fewer species of seed sources produced fruit per month and fruiting activity was more seasonal.     

Phenology of fleshy fruits in a wet sclerophyll forest in southeastern Australia: are birds an important influence?

Summary The hypothesis that seasonality in the production of fleshy fruits in temperate regions is the result of selection by avian seed dispersal agents or avian seed predators was tested in a temperate wet sclerophyll forest in south-eastern Australia. I determined whether ten common fleshy-fruited species produced fruits when potential avian seed dispersers were most abundant or avian seed predators were least abundant. The season of fruit production was not correlated with avian disperser abundance nor with seasonal changes in avian seed predators. Peak fruiting occurred during autumn but fruit-eating birds were equally abundant from spring through to autumn. Avian seed predators (parrots) did not show any seasonal variation in abundance. If dispersers are influencing fruiting seasonality in wet sclerophyll forest, it is likely that changes in social behaviour and feeding patterns of dispersers during autumn, rather than increases in abundance, will be an important influence on fruiting patterns in wet sclerophyll forest. However, environmental and life history factors may also influence phenology.     

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.     

Cicada nymphs dominate American black bear diet in a desert riparian area

American black bears are considered dependent on high‐elevation forests or other montane habitats in the drylands of western North America. Black bear sign, including that of cubs, was observed throughout the summers of 2015, 2016, and 2018 along a perennial desert river in the Sonoran Desert of Arizona. We analyzed the contents of 21 black bear scats, collected from May to October of 2016 and 2018. Apache cicada nymphs (Diceroprocta apache) were the dominant food item, occurring in 90% of scats and comprising an average of 59% of scat contents. In the process of excavating these nymphs, bears created large areas of turned‐over soil, a form of ecosystem engineering with potential implications for soils, vegetation, and fluvial geomorphology. Given that species distributions are shaped by physiological and ecological contexts, as well as anthropogenic legacies, it is possible that black bears once occurred more commonly in desert riparian systems prior to widespread agricultural development, hunting, and dewatering. Although more research is necessary, we suggest that desert riparian systems may be an alternative habitat for black bears. Better understanding the diet and habitat breadth of American black bears is important in the context of increasing landscape fragmentation and militarization in the U.S.‐Mexican borderlands.     

Fruit fate,frugivory, and fruit characteristics: a study of the hawthorn,Crataegus monogyna (Rosaceae)

Summary The fate of fruits from a population of European hawthorn (Crataegus monogyna) in western Oregon, USA, was examined over a two-year period. Only one frugivore, the American robin (Turdus migratorius) foraged on the C. monogyna fruits, making this an unusually straightforward fruit-frugivore system. Dispersal efficiency was low, with an average 21% of seeds being dispersed (carried away from parent plants) each year; the most common fate of fruits was to simply fall. Robins dropped 20% of the fruits that they picked, and defecated/regurgitated 40% of the fruits (seeds) that they swallowed, beneath parent plants. One trait, gruit abundance, strongly affected the probability of bush visitation by robins, bushes with larger fruit displays being preferred. Both absolute dispersal success (number of seeds) and dispersal efficiency (proportion of seeds; success per propagule) were also found to be correlated most strongly with initial fruit abundance. Individual plant fecundity and fruit quality were found to vary little between years; as a result, dispersal efficiencies for individual plants were also annully consistent. Larger (older) plants produced more fruits and therefore had higher fitness. These results suggest that the optimal fruiting strategy for C. monogyna is therefore to get as big as possible as quickly as possible by delaying fruiting until later in life.     

小兴安岭地区黑熊的食性分析

2004 年5 月至2005 年11 月,在黑熊主要分布区小兴安岭利用无线电遥测技术跟踪黑熊并判定黑熊取食生境,收集黑熊粪便51 堆,利用粪便组织学分析方法对黑熊食物组成成分以及食物的选择性进行分析。结果表明:春初、秋末黑熊觅食生境为海拔400 ～ 560 m 的针叶林、针阔混交林;春末、夏初觅食生境为阔叶林、针阔混交林;夏季、秋初觅食生境为阔叶林、针阔混交林、河岸杂木林等。黑熊的大宗食物为植物,即使是夏季食物种类丰富季节,食物中植物成分仍近70% 。黑熊食物表现出季节性变化,季节不同采食种类不同,采食植物性食物的部位也不同。春季黑熊的食物种类最少,食物多样性指数为2.317,食物均匀性指数为0.5923,夏季的食物种类最丰富,食物多样性指数2.628,食物均匀性指数0.6367,秋季食物种类比春季丰富,但没有夏季丰富,食物多样性指数为2.361,食物均匀性最小,仅为0 5173。黑熊对植物类食物具有选择性,对红松、蒙古栎、核桃楸等坚果和猕猴桃、山桃等浆果类食物表现为正选择性;而对木贼、禾本科、榆、宽叶苔草、色木、桦、杨、柳表现为负选择性。      

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     

The role of Japanese macaques (Macaca fuscata) as endozoochorous seed dispersers on Kinkazan Island, northern Japan

We studied the characteristics of seeds within faeces, an important aspect of endozoochorous seed dispersal, in Japanese macaques Macaca fuscata inhabiting Kinkazan Island, northern Japan. We intermittently collected faecal samples from 1999 to 2009 (N = 1294) and examined the rate of seed occurrence, species/life-form composition, number of seeds, and their intact rate. Seeds were found within faecal samples during every month, but their characteristics changed monthly: the rate of seed occurrence and the number of plant species within faecal samples were greater in summer and fall, and the intact rate and number of intact seeds observed within single faecal samples were also higher during these seasons than spring and winter. These results suggest that Japanese macaques on Kinkazan act as seed dispersers in summer and fall and that they disperse intact seeds into wider areas within the forest through defecation. During the study period, we observed seeds from a total of 35 plant species from 22 families in our samples. In addition to those of woody plants, we also observed seeds from as many as 12 herbaceous plants, for which sympatric sika deer (Cervus nippon) have historically been considered the sole seed dispersal agents. The intact rate of seeds was significantly negatively correlated with the seeds’ mean cubic diameter, and this relationship was strengthened for non-fleshy fruits. We also conducted regional comparisons of the characteristics of defecated seeds in order to address whether regional variations in the diet of the macaques affect their efficacy as seed dispersers, both in terms of quantity and quality. Macaques living in the natural habitats of Kinkazan and Yakushima dispersed more seeds of tall tree species than do macaques inhabiting the human-altered areas of in Shimokita and Kashima. The number of plant species represented within single faecal samples also varied geographically, being greater in Yakushima. This pattern likely resulted from Yakushima's warm temperate climate, as the other three study sites occur in the cool temperate region. Our results suggest that the composition of seeds dispersed by Japanese macaques is not rigid, but is determined instead by the vegetation found in a given habitat.     

Endangered globose cactus Melocactus lanssensianus P. J. Braun depends on lizards for effective seed dispersal in the Brazilian Caatinga

Effective seed dispersal is essential to plant reproductive success. In this study, we evaluated the fruiting phenology, fruit traits, and seed dispersal of the endangered globose cactus Melocactus lanssensianus in the Brazilian Caatinga over 1-year period. We carried out monthly phenological monitoring, focal observations, and germination experiments, to identify the effective seed dispersers of this cactus. M. lanssensianus exhibited a continuous, non-seasonal fruiting pattern, with peaks during both the dry and rainy seasons. We observed seed dispersal by Tropidurus semitaeniatus and T. hispidus lizards. In 116 h of focal observations, lizards made 76 visits during different times of day, with a mean dispersal distance of 5 m. Both lizard species showed more frugivory interactions in the dry season, with peak visits in water-stressed months. We collected 132 intact and viable seeds from 29 fecal samples, specifically from T. semitaeniatus (N?=?20 scats; 122 seeds) and from T. hispidus (N?=?9 scats; 10 seeds). Germination experiments with seeds consumed by T. semitaeniatus, washed seeds and control seeds revealed that 85% of seeds found in T. semitaeniatus feces germinated compared to 41% of the control seeds. Frequency, pattern of visits and germination rates indicate T. semitaeniatus is an effective seed disperser of M. lanssensianus. Continuous production of fleshy fruits and environmental conditions of the Caatinga ecosystem favor the close dependent mutualistic interaction reported here.

     

Composition and clumping of seeds deposited by frugivorous birds varies between forest microsites

More frequent deposition of seeds by frugivores beneath plants in fruit could impose spatial limits to the distribution of plants dispersed by animals and contribute to species coexistence. Also, differences in diet and use of microhabitats by seed dispersers could promote spatial variation in the combination of seed species deposited. We investigated patterns of seed deposition of Miconia fosteri and Miconia serrulata (Melastomataceae) by birds in the Amazon. The goal was to determine how distribution and abundance of fruiting plants, both con‐ and hetero‐specifics, affect the spatial variability in clumping and composition of multi‐specific seed deposition. We established two 9‐ha plots in undisturbed terra‐firme understory in the Ecuadorian Amazon. Seed rain was sampled with seed traps located in four microsites: below plants of the focal species, below Anthurium eminens (Araceae), and in randomly selected microsites. We examined seed deposition in these microsites in relation to habitat, fruiting neighborhood (fruit abundance, and distance to and density of plants of the target species), and crop size of M. fosteri or M. serrulata to determine if microsites differed in abundance and species composition of seeds. Seed traps below plants in fruit received more seeds than did randomly located traps. Seeds of the target species were, moreover, more commonly deposited below con‐ rather than hetero‐specific plants. Seed aggregation below fruiting plants increased in forest neighborhoods where the abundance of fruits and the combination of fruiting plant species contributed to the arrival of seeds. Microsites differed notably in the combination of seeds deposited by frugivores, and differences were less pronounced among microsites that received seeds of M. fosteri and M. serrulata than among all microsites where at least some seed species were deposited by birds. We demonstrate that two closely related, ecologically similar species possess many similarities in their patterns of seed deposition and in the factors that affect those patterns. The combination of seed species deposited below foci of dispersal depended on the fruiting plant species, and the spatial patterns of seed deposition varied with the location of the microsite and the combination of co‐dispersed species in the neighborhood. Similar species that share the same dispersers were confronted with different combinations of seeds depending on the microsite where they arrived, which could promote forest heterogeneity in the combination of plant species.     

Estimate of the seed shadow created by the Asiatic black bear Ursus thibetanus and its characteristics as a seed disperser in Japanese cool‐temperate forest

We estimated the seed shadow created by the Asiatic black bear Ursus thibetanus in order to evaluate the bears effectiveness as a seed disperser. We combined data from bear movements, determined by GPS telemetry, with data from gut retention time (GRT). We estimated plant seed shadows in two ways: from direct movement data to give the actual seed shadow (ASS), and from cumulative movement data to give the potential seed shadow (PSS). The purpose of this study was to answer the following questions: (1) does GRT differ between seasons or in the size of contents? (2) Does seed shadow vary among sex, seasons, estimation method (ASS or PSS), and years? (3) Does the masting affect seed shadows? There were no differences in median GRT among seasons or seed dimensions. Combining these data, the seed shadows produced by long GRT (median; 15.2–19.7 hours, maximum; 44.0 hours) and large daily movements suggest that the bears effectively move 40% of the seeds they consume to a distance greater than 500 m from the parent tree and can potentially move the seeds up to a maximum distance of more than 22 000 m from the parent tree. The results also indicate that bears make complex seed shadows caused by multiple defecations and long periods of daily movement. In summary, PSS did not differ between sexes, but PSS can be expected to be larger in autumn than in summer of each year. ASS, however, can be expected to be larger in males than females, and to be larger in autumn than in summer. ASS may become especially large during a poor masting year as compared to good masting years. These results indicate that bears are potentially more effective seed dispersers during years of poor fruit production in autumn. The bears have longer seed shadows than other seed disperser and consequently may play a unique role in the maintenance and renewal of forest ecosystem.     

Allometric allocation in fruit and seed packaging conditions the conflict among selective pressures on seed size

Selective pressures on seed size could vary among the different stages of plant life cycles, so no simple relation could explain a priori its evolution. Here, we determined the relationships between seed size and two fitness components—seed dispersal and survival from predation—in a bird-dispersed tree, Crataegus monogyna. We interpret these relationships in relation to the patterns of mass allocation to fruit and seed components. Selection patterns were assessed at two levels (1) selection pressures on the parent tree; comparing seed dispersal efficiency among individual plants and (2) selection pressures at the individual seed level; comparing seed size variation (i) before and after dispersal, and (ii) before and after postdispersal seed predation. Dispersal efficiency (percentage of seed crop dispersed) was positively correlated with fruit mass and fruit width. Differences in crop size did not offset this effect, and larger seeds were overrepresented in the seed rain relative to the seed pool before dispersal. However, the advantage of larger seeds during the dispersal stage was cancelled later by an opposite selection pressure exerted by seed predators. As a result, smaller seeds had a higher probability of surviving postdispersal seed predation, establishing an evolutionary conflict imposed by the need for dispersal and the danger of being predated. Birds and rodents preferentially selected highly profitable fruits and seeds in terms of the relative proportion of their components. Larger fruits had a higher pulp to seed proportion than smaller ones, and all seeds had the same proportion of coat relative to the embryo-plus-endosperm fraction. Hence, although predator pressures were stronger than disperser ones, larger seeds invested proportionally less in structural defense than in dispersal.     

Crop size,plant aggregation,and microhabitat type affect fruit removal by birds from individual melastome plants in the Upper Amazon

We studied the efficiency (proportion of the crop removed) and quantitative effectiveness (number of fruits removed) of dispersal of Miconia fosteri and M. serrulata (Melastomataceae) seeds by birds in lowland tropical wet forest of Ecuador. Specifically, we examined variation in fruit removal in order to reveal the spatial scale at which crop size influences seed dispersal outcome of individual plants, and to evaluate how the effect of crop size on plant dispersal success may be affected by conspecific fruit abundance and by the spatial distribution of frugivore abundance. We established two 9-ha plots in undisturbed terra-firme understory, where six manakin species (Pipridae) disperse most seeds of these two plant species. Mean levels of fruit removal were low for both species, with high variability among plants. In general, plants with larger crop sizes experienced greater efficiency and effectiveness of fruit removal than plants with smaller crops. Fruit removal, however, was also influenced by microhabitat, such as local topography and local neighborhood. Fruit-rich and disperser-rich patches overlapped spatially for M. fosteri but not M. serrulata, nonetheless fruit removal of M. serrulata was still much greater in fruit-rich patches. Fruit removal from individual plants did not decrease in patches with many fruiting conspecifics and, in fact, removal effectiveness was enhanced for M. fosteri with small crop sizes when such plants were in patches with more conspecifics. These results suggest that benefits of attracting dispersers to a patch balanced or outweighed the costs of competition for dispersers. Spatial pattern of fruit removal, a measure of plant fitness, depended on a complex interaction among plant traits, spatial patterns of plant distribution, and disperser behavior.