Spatial pattern of adult trees and the mammal-generated seed rain in the Iberian pear (original) (raw)

Seed Dispersal in the Iberian Pear, Pyrus bourgaeana : A Role for Infrequent Mutualists

Ecoscience, 2009

Seed dispersal by animals is a key interaction, with effects on the population ecology and evolution of many plant lineages. Despite the fact that infrequent seed dispersers can potentially provide important services to plant populations, little attention has been paid so far to scarce mutualists. We assessed different aspects of quantity and quality of seed dispersal from fruit removal to seed germination in the Iberian pear, Pyrus bourgaeana, finding that fruit consumers markedly differed in the nature of their interaction with the tree. Whereas the abundant rodents, rabbits, and deer damaged all seeds eaten, the uncommon carnivores badger and fox and the abundant boars dispersed a large fraction of ingested seeds as viable propagules, acting as legitimate seed dispersers. Despite low rates of visitation by badgers to fruiting trees, they transported more viable seeds than the abundant boars, due to better seed treatment and a higher feeding rate on pears. Seed dispersal by all 3 legitimate dispersers, especially the badger, enhanced post-dispersal P. bourgaeana seed survival, supporting the "escape" predation hypothesis. Pyrus bourgaeana showed relatively high frequencies of visits by a myriad of frugivores; however, it relied on the dispersal service provided by an infrequent carnivore, the badger, rather than on those provided by the abundant mammalian herbivores. Therefore, under some circumstances, uncommon animal counterparts play major roles in their mutualistic interactions with flowering plants.

Seed dispersal in the Iberian pear: a role for infrequent mutualists

Common seed dispersers contribute most to the persistence of a fleshy-fruited tree

Communications biology, 2023

Mutualistic interactions are by definition beneficial for each contributing partner. However, it is insufficiently understood how mutualistic interactions influence partners throughout their lives. Here, we used animal species-explicit, microhabitat-structured integral projection models to quantify the effect of seed dispersal by 20 animal species on the full life cycle of the tree Frangula alnus in Białowieża Forest, Eastern Poland. Our analysis showed that animal seed dispersal increased population growth by 2.5%. The effectiveness of animals as seed dispersers was strongly related to the interaction frequency but not the quality of seed dispersal. Consequently, the projected population decline due to simulated species extinction was driven by the loss of common rather than rare mutualist species. Our results support the notion that frequently interacting mutualists contribute most to the persistence of the populations of their partners, underscoring the role of common species for ecosystem functioning and nature conservation.

Animal-Plant Interaction: A Review On Terrestrial Vertebrate Seed Disperser Diversity And The Selectivity Pattern Based On The Size Of Fruits

The study was based on 107 studies and data concerning disperser species, plant species and family, fruit type and size, seed size plant life form and the habitat, were presented in matrix form. Data from this matrix were used in determining the disperser species diversity considering large taxonomic groups (mammals, birds and reptiles) and selection pattern based on the fruit and seed size. The diversity of mammals was high followed by birds and then reptiles with 65%, 30% and 5% respectively. Mammal taxonomic group dominated and was sub divided into primates, ungulates, carnivores, rodents and bat subgroups which accounted for 45%, 22%, 17%, 9% and 7% respectively confirming the dominance of primates. Simple correspondence analysis showed that ungulates dispersed very small fruits while carnivores, primates, bats and reptiles were categorized together for both small and medium sized fruits. Ungulates, birds and bats dispersed the smallest seeds while others dispersed both small and large sized seeds. The study revealed high diversity of mammals particularly primates therefore playing a huge role in structuring and restructuring terrestrial ecosystems, with a warning that the loss of ungulates may have catastrophic impacts on the structure and composition of small fruited and seeded plants.

Seed size is heterogeneously distributed among destination habitats in animal dispersed plants

Seed size is a central trait in plants, conditioning the probabilities of seed dispersal, predation, germination and seedling survival even within a single species. In wind-dispersed species, seed size is not homogeneously distributed in the seed shadow, and it is clear that this trait influences dispersal distances. However, in animal-dispersed species, it is poorly known how and why the process of seed dispersal determines, per se, the spatial distribution of seed size. We predict that frugivores may generate heterogeneous distributions of seed size on seed rain due to two mechanisms. First, frugivores differing in body size and post-feeding habitat selection may feed on a different array of seed sizes and deposit them in different destination habitats. Second, even feeding on a similar gradient of fruit sizes, frugivores may spend in different post-foraging times at different microhabitats, the more visited microhabitats receiving a larger proportion of small sized, longer-retained seeds. We analyzed the distribution of seed weights at destination microhabitats for three fleshy-fruited tree species, Taxus baccata, Ilex aquifolium and Crataegus monogyna, dispersed by a common guild of avian frugivores in a temperate secondary forest of N Spain. Mean seed weight varied among microhabitats for the two former species, with smaller average weight under the canopy of Taxus male trees. We discuss several alternative hypotheses and conclude the spatial segregation of seed weight to be a consequence of frugivore activity, probably related to size-related differences in seed retention time and longer visitation or permanency time in protective microhabitats.

Fruiting trees as dispersal foci in a semi-deciduous tropical forest

Oecologia, 2004

Quantification of seed rain patterns is an initial step toward explaining variation in plant recruitment, and consequently, organization of forest communities. Spatially contagious patterns of seed deposition, where seeds are patchily dispersed with some sites receiving relatively high densities and others receiving low densities of seeds, may be a common phenomenon for which we have very little knowledge. For example, prior feeding events by frugivores (monkeys and birds) combined with transport and dispersal of seeds to other fruiting trees may result in the contagious deposition of non-conspecific seeds below them. Here, we examined whether fruiting trees act as dispersal foci in the semi-deciduous tropical rainforest of the Dja Reserve, Cameroon. Seed rain was sampled below the canopies of nine tree species: three typically dispersed by large, frugivorous birds, three dispersed by monkeys, and three dispersed by wind. We found no evidence that monkeys generate spatially contagious patterns of seed rain under fruiting trees at which they feed. However, we found that rates of deposition of non-conspecific seeds and species richness of seeds delivered by birds (hornbills and turacos) were significantly greater during fruiting than non-fruiting periods, and significantly greater under fruiting individuals of bird-dispersed tree species than under fruiting individuals of monkey-or wind-dispersed tree species. Additionally, during fruiting periods, the composition of non-conspecific seed rain under birddispersed tree species was more similar to other birddispersed trees than to monkey-or wind-dispersed tree species. The contagious dispersal of non-conspecific seeds to fruiting, bird-dispersed trees leads to higher seed densities under fruiting trees than those caused by local seed production. Non-conspecific seeds deposited in high densities may experience increased seed mortality even far from parent trees if predators are generalists. Alternatively, in the absence of complete density-dependent mortality, contagious seed dispersal could result in associations among species dispersed by the same dispersal agent.

Dispersal of fleshy-fruited species: a matter of spatial scale?

Perspectives in Plant Ecology, Evolution and Systematics, 2000

The processes associated with the dispersal of fleshy-fruited species have been an important focus of ecological research during the last two decades. These processes include fruit removal, seed rain, seed predation, seed bank dynamics, germination and establishment. Some of them interfere with the mutualistic interaction of frugivorous birds and fleshy-fruited plants. We might expect such interference to be most pronounced where the intensity of the different processes has a spatial distribution similar to that of the original seed shadow. The central theme of this review is that the main processes associated with dispersal and recruitment act at different spatial scales. To investigate this idea, about 140 publications on dispersal of fleshy-fruited species from 1980 to 2000 were screened for the spatial scaling of these processes. Microhabitat, habitat, landscape, region and biome were the five spatial scales most commonly used. However, the representation of the different scales was not fully balanced; largescale studies were scarce and most publications considered only one scale. The review reveals some trends in scaling of the main processes of plant dispersal and recruitment. Seed dispersal by birds and seed predation by rodents are strongly determined at the habitat level, and several studies report negative results for contrasts between microhabitats. Germination and seedling establishment, on the other hand, appear to be mainly influenced by differences between microhabitats, though information on larger scales is scarce. Genetic differentiation and phenology of fruiting have mostly been investigated at the habitat, landscape and regional scale, whereas information on the abundance of frugivorous birds and patterns in plant distribution results are available across the full range of scales from the level of the microhabitat to the region and biome. Future research should be directed to the major gaps in our knowledge, i.e. regional and zonal comparisons of the processes associated with dispersal. They should also be more sensitive to scale issues and ideally should have a multi-scaled design.

Complementary roles of two resilient neotropical mammalian seed dispersers

Acta Oecologica

Capuchin monkeys (Cebus spp. and Sapajus spp.) and coatis (Nasua spp.) coexist in most neotropical forests, including small forest remnants. Both capuchins and coatis eat fruit and disperse seeds, but little is known about whether their roles in seed dispersal are redundant or complementary. We compiled 49 studies from the literature on feeding by capuchins and/or coatis, of which 19 were comprehensive enough for our analyses. We determined the relative importance of fruit eating to each species and compared their diets. Additionally, we analysed the structure of three fruit-frugivore networks built with both animal groups and the fruits they eat and evaluated whether fruit traits influenced the network topology. Fruits represented the largest part of capuchin and coati diets, even though coatis have been known for their opportunistic and generalist diets. Capuchins and coatis also exhibited similar general diet parameters (niche breadth and trophic diversity). The three networks exhibited high connectance values and variable niche overlap. A Multiple Correspondence Analysis, failed to detect any trait or trait combination related to food use. In conclusion, capuchins and coatis both have generalist diets; they feed on many different species of fruits and exhibit important complementarity as seed dispersers. Both are likely to be particularly important seed dispersers in disturbed and fragmented forests.

Spatial pattern of adult trees and the mammal-generated seed rain in the Iberian pear (original) (raw)

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