Hardness as a basis of fruit choice in two sympatric primates

Fruit color and size are significant determinants of food choice in mammals and birds, but hardness, an important physical property of fruit and seeds, has generally been overlooked as a determinant of food choice in studies of mammalian foraging behavior. Two methods were used to determine fruit hardness during a field study of two sympatric primates, the black spider monkey (Ateles paniscus) and the bearded saki monkey (Chiropotes satanas) in Surinam. We measured both puncture resistance of fruit pericarp and crushing resistance of seeds. Puncture resistance of the pericarp of some fruit opened by Chiropotes was as much as 15 times greater than that of all fruit successfully opened by Ateles. In contrast, crushing resistance of species of seeds masticated by Chiropotes was significantly lower than that of seeds swallowed by Ateles. These data demonstrate that hardness of both fruit pericarp and seed may play a significant role in food choice among sympatric vertebrates. Measurements of both puncture resistance of the pericarp and crushing resistance of the seed are necessary for understanding the significance of fruit hardness in these primates.     

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.     

Fruit color and fruit size of bird-disseminated plants in Japan

Fruit color, fruit size and phenology of bird-disseminated plants were examined in different climatic zones of Japan and the relationships between the plants and frugivorous birds were disscussed.Black fruit was the most common in warm-temperate areas and red was the most common in cool-temperate and subarctic zones. Red was more dominant in the lower layer of the forests in all climatic zones. Bicolor fruits were frequent in trees and were not found in herbs. Both in warm- and cool-temperate zones conspicuous fruits which are red and bicolored display were more frequent in summer than in winter.The diameter of most fruits were 4–11 mm. Fruits in warm-temperate were somewhat bigger than those in cooltemperate zone. In forest strata the fruits of shrubs were smaller than those of trees and herbs in width. However I found no relationships between fruit size and fruit color.The frugivorous birds could have influenced not only the evolution of seasonal differences in the proportion of fruit color between warm-temperate and cool-temperate region, but also affect the fruit size.     

Fruit size in a tropical tree species: variation,preference by birds,and heritability

Ocotea tenera (Lauraceae), an understory bird-dispersed tree, produces single-seeded fruits that vary in diameter from 1.4 to 2.4 cm. Much of the variation within a population at Monteverde, Costa Rica occurred within individual trees. The relative size of fruits produced by different trees remained generally constant over an 11-year period despite slight differences between years in the average size of fruits produced by a given tree.Fruit-eating birds could thus express their preferences for particular fruit size characteristics by choosing among trees that have distinct distributions of fruit diameters, and between individually variable fruits within trees. In a field study of individually marked fruits, birds removed 46.2% of fruits; the rest of the fruits were destroyed by invertebrate (25.3%) and vertebrate (4.3%) pulp-feeders or aborted by the plant after remaining ripe but uneaten for as long as 100 days (24.2%). The four major avian seed dispersers of O. tenera each have gape widths exceeding all but the largest fruits. Birds preferred plants with greater-than-average-sized fruits; within trees, they favored larger fruits, apparently because net pulp mass increases with fruit diameter. Fruits that ripened early in the season were more likely to be removed and were removed more quickly than late-ripening fruits.Based on mother-offspring regressions of mean fruit size, the phenotypic variation in fruit diameter in O. tenera is highly heritable, indicating the potential for an evolutionary response to selection by birds. Nonetheless, directional selection on fruit size or shape is likely to be inconsistent, constrained by genetic correlations, and weak compared to selection on traits like fecundity or phenology.     

The scaling of eye size with body mass in birds

We developed a simple method that uses skulls to estimate the diameter, and hence the mass, of birds'' eyes. Allometric analysis demonstrated that, within five orders (parrots, pigeons, petrels, raptors and owls) and across 104 families of flying birds, eye mass is proportional to (body mass)^0.68 over a range of body masses (6 g to 11.3 kg). As expected from their habits and visual ecology, raptors and owls have enlarged eyes, with masses 1.4 and 2.2 times greater than average birds of the same weight. Taking existing relationships for flight speed on body mass, we find that resolution increases close to (flight speed)^1.333. Consequently, large birds resolve objects at a longer time to contact than small birds. Eye radius and skull size co-vary in strict proportion, suggesting common physiological, aerodynamic and mechanical constraints. Because eye mass scales close to brain mass, metabolic rate and information processing could also be limiting, but the precise factors determining the scaling of eye to body have not been identified.     

The effect of spatio-temporal variation in understanding the fruit crop size hypothesis

In order to evaluate the 'fruit crop size' hypothesis, we analyzed the effect of fruit availability on the number of visits by birds and on the proportion of removed fruits, and on how much of the variation in the proportion of removed fruits could be explained by spatio-temporal variability. Fieldwork was done on the coast of the state of Veracruz, Mexico, using the small tree Bursera fagaroides (Burseraceae) and its frugivorous feeding assemblage, on four hills during four years. The number of fruits produced, the number of visits by birds, and the proportion of removed fruits varied between years with more than half an order of magnitude. The number of available fruits was associated to both the number of visits by birds and the proportion of fruits removed from each plant individual, and supports the fruit crop size hypothesis. However, the hypothesis varies in strength depending on total fruit production by the population per year and per hill. The spatio-temporal variation of the system was the effect of variation in the intensity of fructification between years and hills; the inclusion of spatio-temporal variability helped to explain most of the variation found in our results. The latter approach may explain the explain the conflicting results found by other authors in studies done in only one year or at one site, where variation is greatly reduced. Considering the number of published reports, a meta-analysis seems to be in order to determine the existence of a general effect between fruit production, the number of visits by birds and the proportion of fruits removed. If this is possible, we hypothezise that the association between fruit production and the number of visits by birds should be of low intensity.     

ABA-deficiency results in reduced plant and fruit size in tomato

Abscisic acid (ABA) deficient mutants, such as notabilis and flacca, have helped elucidating the role of ABA during plant development and stress responses in tomato (Solanum lycopersicum L.). However, these mutants have only moderately decreased ABA levels. Here we report on plant and fruit development in the more strongly ABA-deficient notabilis/flacca (not/flc) double mutant. We observed that plant growth, leaf-surface area, drought-induced wilting and ABA-related gene expression in the different genotypes were strongly correlated with the ABA levels and thus most strongly affected in the not/flc double mutants. These mutants also had reduced fruit size that was caused by an overall smaller cell size. Lower ABA levels in fruits did not correlate with changes in auxin levels, but were accompanied by higher ethylene evolution rates. This suggests that in a wild-type background ABA stimulates cell enlargement during tomato fruit growth via a negative effect on ethylene synthesis.     

Time – size tradeoffs: a phylogenetic comparative study of flowering time, plant height and seed mass in a north-temperate flora

Parents face a timing problem as to when they should begin devoting resources from their own growth and survival to mating and offspring development. Seed mass and number, as well as maternal survival via plant size, are dependent on time for development. The time available in the favorable season will also affect the size of the developing juveniles and their survival through the unfavorable season. Flowering time may thus represent the outcome of such a time partitioning problem. We analyzed correlations between flowering onset time, seed mass, and plant height in a north-temperate flora, using both cross-species comparisons and phylogenetic comparative methods. Among perennial herbs, flowering onset time was negatively correlated with seed mass (i.e. plants with larger seeds started flowering earlier) while flowering onset time was positively correlated with plant height. Neither of these correlations was found among woody plants. Among annual plants, flowering onset time was positively correlated with seed mass. Cross-species and phylogenetically informed analyses largely agreed, except that flowering onset time was also positively correlated with plant height among annuals in the cross-species analysis. The different signs of the correlations between flowering onset time and seed mass (compar. gee regression coefficient=−7.8) and flowering onset time and plant height (compar. gee regression coefficient=+30.5) for perennial herbs, indicate that the duration of the growth season may underlie a tradeoff between maternal size and offspring size in perennial herbs, and we discuss how the partitioning of the season between parents and offspring may explain the association between early flowering and larger seed mass among these plants.     

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.     

Allometry of egg mass, clutch size and total clutch mass in dinosaurs: comparison with modern reptiles and birds

The author presents for the first time empirical allometrical equations corresponding the mass of dinosaurs with the mass of their eggs, clutch size and its total mass. Comparison of these equations with those that were proposed for modern taxa of reptiles and birds shows that dinosaurs can be characterized by intermediate value of allometry index.     

DNA amount, latitude, and crop plant distribution

Avdulov and Stebbins noted a tendency for species with large chromosomes in several angiosperm groups or families (including the Gramineae, Commelinaceae, Liliales, Polemoniales and the Leguminosae) to be localized in distribution to temperate latitudes. As chromosome size and DNA content are closely correlated, the distribution of species with large DNA amounts per chromosome, or per diploid genome, might expected to be similarly localized. This hypothesis was tested using samples of crop species with large ranges of DNA amounts from the Gramineae and the Leguminosae. For instance, the mean DNA amount per chromosome for the sample of cereal grain species showed about a 36-fold range from 0·033 picograms (pg) in Eragrostis tef to 1·186 pg in Secale cereale, while for the sample of pulse crops the range was about 70-fold from 0·032 pg in Lablab niger to 2·225 pg in Vicia faba. The results for cereal grain crops, cultivated pasture grasses and pulse crops show that cultivation of species with high DNA amounts per diploid genome tends to be localized in temperate latitudes, or to seasons and regions at lower latitudes where the conditions approximate to those normally found in temperate latitudes. Moreover, man has shown a strong tendency to choose species for cultivation with increasingly lower DNA amounts at successively lower latitudes. Thus, there is a cline for DNA amount and latitude. This cline is exhibited independently by both C₃ and C₄ crop species, and by both annuals and perennials and hence is independent of life cycle type and the taxonomic distribution of C₃ and C₄ photosynthesis. The cline is apparently a natural phenomenon which man has modified and exaggerated in agriculture. It is suggested, therefore, that interspecific variation in DNA amount between angiosperm species may have adaptive significance affecting the distribution of both crop and non-crop species. The cline might be caused either by variation in DNA amount per se, or by variation in some factor(s) correlated with DNA amount. The factor(s) causally responsible for the cline, and their mode of action should be investigated since they may have implications for agriculture and plant breeding.     

Lekking in birds: choice, competition and reproductive constraints

This paper discusses the importance of female choice and intrasexual competition in lek species. The importance of phenotypic differences between individuals is stressed. Reproductive constraints limit the possible behavioural strategies that can be used by males and females. I suggest that it is difficult to understand reproductive behaviour without a knowledge of these reproductive constraints.     

Trade-offs between flowering time,plant height,and seed size within and across 11 communities of a QingHai-Tibetan flora

Flowering timing is of fundamental biological importance for its tight association with pre-flower growth states and subsequent reproduction success. Here, we selected plant height and seed size to represent plant growth and reproduction states, respectively, and analyzed their associations with flowering time in 11 communities together representing a QingHai-Tibetan flora. Trait associations were examined using Pearson correlation analyses (TIPs) and phylogenetically independent contrasts (PICs) within individual communities and meta-analyses across all communities. The results of TIPs-based and PICs-based analyses were generally congruent, although fewer contrasts were significant with PICs, probably because of low statistical power. Overall, flowering time was negatively correlated with seed size and plant height (i.e., plants with larger seeds and stature started flowering earlier) in various woody communities, but correlations were neutral or positive in herbaceous communities. The seed size–flowering time relationship was negative for woody and herbaceous perennials but not for annual herbs in most communities. The relationship between plant height and flowering time was negative for woody but positive for herbaceous plants. Moreover, the lack of difference in time–size relationships between anemophilous and entomophilous plants suggests that pollination type may only be a secondary force in controlling flowering phenology. Our studies demonstrate that environmental conditions, community structure, and plant life history strategies may affect community flowering time singly or in combination.     

Incidence of healed fracture in the skeletons of birds, molluscs and primates

The incidences of healed fracture in the limb bones of birds and the shells of molluscs were estimated by the examination of samples of bones and shells. The results are compared to published data on fracture incidence in molluscs and in primates and other mammals. The relationship between observed incidence of healed fracture, costs of growth and use of the skeleton, and the costs associated with its failure are discussed in terms of a theory of factors of safety.     

Fruit characters as a basis of fruit choice and seed dispersal in a tropical forest vertebrate community

Summary Interactions between a large community of vertebrate frugivore-granivores (including 7 species of large canopy birds, 19 species of rodents, 7 species of ruminants, and 6 species of monkeys), and 122 fruit species they consume, were studied for a year in a tropical rainforest in Gabon.The results show how morphological characters of fruits are involved in the choice and partitioning of the available fruit spectrum among consumer taxa. Despite an outstanding lack of specificity between fruit and consumer species, consideration of simple morphological traits of fruits reveals broad character syndromes associated with different consumer taxa. Competition between distantly related taxa that feed at the same height is far more important than has been previously supposed. The results also suggest how fruit characters could have evolved under consumer pressure as a result of consumer roles as dispersers or seed predators. Our analyses of dispersal syndromes show that fruit species partitioning occurs more between mammal taxa than between mammals and birds. There is thus a bird-monkey syndrome and a ruminant-rodent-elephant syndrome. The bird-monkey syndrome includes fruit species on which there is no pre-dispersal seed predation. These fruits (berries and drupes) are brightly colored, have a succulent pulp or arillate seeds, and no protective seed cover. The ruminant-rodent-elephant syndrome includes species for which there is pre-dispersal predation. These fruits (all drupes) are large, dull-colored, and have a dry fibrous flesh and well-protected seeds.     

Fruit diet of Alouatta guariba and Brachyteles arachnoides in Southeastern Brazil: comparison of fruit type, color, and seed size

Fruit is an important food resource for neotropical primates. In this study I compare the fruit diet of sympatric brown howlers (Alouatta guariba) and southern muriquis (Brachyteles arachnoides). Feeding behavior was studied over 12 months and fruit species consumed were identified and assigned to the categories fruit type, fruit color, and seed size. Observed-fruit feeding records were compared with expected records determined from local availability of the fruit of the tree species. I also determined dietary overlap. Fruit consumption occupied 8 and 12% of the feeding time of A. guariba and B. arachnoides, respectively. Fruit from eight tree species were consumed by the former and fruit from twenty-two species by the latter. Patterns of fruit selection of A. guariba and B. arachnoides varied widely. Although howlers and muriquis converge behaviorally by selecting fruit with common attributes (fleshy/unprotected, violet and brown/black-colored), unlike A. guariba, B. arachnoides fed on immature seeds of fleshy/protected and dry fruit. Large seeds were ingested, and defecated intact, by B. arachnoides only. There was little overlap of fruit diet even within categories that had been selected by both, suggesting that dietary divergence is occurring at the interspecific level. Different resource exploitation probably mediates the coexistence of A. guariba and B. arachnoides in low diversity, semideciduous forests, where the environment imposes narrow limits on primate food choices.     

Climate,body condition and spleen size in birds

Climatic conditions may impact on the body condition of animals and thereby affect their survival prospects. However, climate may also impact directly on the survival prospects of animals by affecting the size of immune defence organs that are used for defence against parasites. We used a large long-term database on body condition and size of the spleen in birds to test for immediate and delayed relationships between climatic conditions as indexed by the North Atlantic Oscillation (NAO) and body condition and spleen mass, respectively. Across 14 species of birds, spleen mass was significantly positively correlated with the NAO index, while the delayed effect of NAO on spleen mass was not significant. Spleen mass was positively related to body condition, but body condition did not depend significantly on NAO or delayed NAO effects. Bird species with a strong positive effect of NAO on spleen mass tended to have small spleens for their body size, while species with a strong negative effect of NAO on spleen mass tended to have relatively large spleens. Since bird species with relatively large spleen have been shown to suffer more from the negative effects of parasites, we can infer that the effects of climate as indexed by NAO on the size of the spleen depends on the importance of parasite-mediated natural selection.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.