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Understanding the quality of seed dispersal effectiveness of frugivorous species can elucidate how endozoochory structures tropical forests. Large seeds, containing more resources for growth, and gut passage by frugivores, which remove seed pulp, both typically enhance the speed and probability of germination of tropical seeds. However, the interaction of seed size and gut passage has not been well studied. We assessed the role of two species of toucans (Ramphastos spp.) in seed germination of the tropical tree Eugenia uniflora , which produces seeds that vary considerably in size (3.7–14.3 mm), using 151 control and 137 regurgitated seeds in germination trials. We found that toucan regurgitation did not increase germination success, although 93.4% germinated compared to 76.8% of control seeds; however, larger seeds germinated more often at faster rates. Although only marginally significant, germination rates were 3.6× faster when seeds were both large and regurgitated by toucans, demonstrating that toucan regurgitation can disproportionally benefit larger E. uniflora seeds. As tropical forests are increasingly disturbed and fragmented by human activities, the ability of toucans to continue providing seed dispersal services to degraded habitats may be vital to the persistence of many tropical plants that contain larger seeds and depend on larger dispersers. [ABSTRACT FROM AUTHOR]

Large herbivores can disperse seeds over long distances through endozoochory. The Korean water deer (Hydropotes inermis argyropus), an internationally vulnerable species but locally considered a vermin, is a potential endozoochorous seed dispersal vector. In this study, feeding experiments were conducted to test the efficiency of seed dispersal through gut ingestion by the Korean water deer, its temporal pattern and the effect of gut passage on seed recovery and germination rate. Eight plant species, including species that formerly germinated from its faeces, were used to feed three Korean water deer. Once the deer had consumed all the provided seeds, their faeces were collected after 24, 48, 72 and 96 h. The collected faeces were air-dried, and the number of seeds retrieved from the faeces was counted every 24 h (0–24, 24–48, 48–72 and 72–96 h). Among the eight plant species, six species were retrieved with intact seeds. Panicum bisulcatum had the highest recovery rate of 33.7%, followed by Amaranthus mangostanus (24.5%) and Chenopodium album (14.4%). Most of the seeds were recovered within the 24–48 h time interval. Germination tests were conducted on the ingested and uningested seeds for the four species which had a sufficient recovery rate. The effects of gut passage on seed germination differed according to plant species. The germination rate substantially decreased after gut passage. The results suggest that the Korean water deer can disperse seeds, potentially over long distances albeit at a high cost of low seed recovery and germination rate. [ABSTRACT FROM AUTHOR]

For endozoochorous species, the quality component of seed dispersal effectiveness depends in part on the treatment seeds receive in the animal's gut. Covering a variety of taxa, diet, digestion system and body size of Prosopis flexuosa seed dispersers, we analysed differences among species in (1) mean retention time of ingested seeds, (2) recovery of viable seeds, (3) seed germination in comparison with seeds collected from trees and (4) germination of seeds after two different periods of retention in the gut. Feeding experiments were conducted with captive individuals of Dolichotis patagonum, Lycalopex gymnocercus, Rhea americana, Chelonoidis chilensis and Lama guanicoe. On the first day, we provided them with fruits containing controlled amounts of seed, and on the subsequent days, we collected faeces in order to recover seeds. We performed germination and viability tests on seeds coming from faeces and collected from trees. The results showed differences among species in the mean retention time of seeds. Chelonoidis chilensis had the longest mean retention time, but its effect on seed recovery and germination was similar to that of the other species, except for L. guanicoe, which showed the lowest seed recovery. When scarification and promotion of seed germination were considered, herbivorous mammals and tortoises (L. guanicoe, D. patagonum and C. chilensis) were the ones increasing germinability, whereas R. americana and L. gymnocercus did not significantly increase final seed germination percentage, which was similar to that for seeds collected from trees. P. flexuosa seeds receive a variety of treatments from endozoochorous dispersers, which might result in an overall fitness benefit for a plant living in unpredictable environments. [ABSTRACT FROM AUTHOR]

Large animals tend to disperse seeds over long distances via ingestion and defecation due to their large home range and capacity to move among different habitats for feeding. The aim of this study was to investigate the potential of endozoochorous seed dispersal by five herbivores: Ovis vignei , Capra aegagrus , Gazella subgutturosa , Cervus elaphus , Capreolus capreolus and two omnivores: Sus Scrofa and Ursus arctos in the Golestan National Park, northeast of Iran, by a greenhouse germination experiment. A total of 3107 seedlings belonging to 154 different plant taxa were germinated from 655 dung samples collected in three different habitats. Plant families that most frequently germinated were Poaceae and Brassicaceae. Urtica dioica was the most abundant germinating seed, accounting for 20% of all the seedlings recorded in our dung samples, whereas the most frequently observed species was Portulaca oleracea , which occurred in 24% of our samples. We showed that 54% of the seeds germinating were dispersed by only one of the mammals studied. Herbs and graminoids were the most frequently dispersed growth forms by the herbivores and the wild boar, whereas brown bears mostly dispersed shrubs. The seedling composition in the dung samples was strongly correlated with the local flora especially for non-selective feeders, like red deer. The differences observed in the number of plants and frequency of different growth forms dispersed among the studied mammals reflect their body size, digestive physiology, and dietary and habitat preferences. Our findings highlight the different and complementary roles of large herbivores and omnivores as long-distance seed dispersal vectors. [ABSTRACT FROM AUTHOR]

Madagascar is one of the most threatened biodiversity hotspots, and protection of its biodiversity is becoming increasingly urgent as deforestation of the island continues. For the long-term success of conservation efforts it is essential that key ecological processes, such as seed dispersal, are protected and restored. Therefore, the identification of ecological gaps is a vital task. For Madagascar, only little is known about plant–animal interactions, and traditional methods of ecological research are too time-consuming to provide crucial information about breakdowns in these interactions. To identify likely dispersal gaps we therefore used a theoretical approach to analyse plant–disperser interactions in Madagascar. We used data science tools to impute missing data on relevant plant traits to subsequently predict the most likely dispersal agents for each of Madagascar's endemic plant species. We found that 38% of the endemic species (N = 8,784) are endozoochorous, and among these 26–41% display a primate syndrome and 17–19% a bird syndrome (depending on the definition of syndromes). This lower percentage of endozoochorous species and higher percentage of species with a primate syndrome in Madagascar compared to other tropical areas reflects the unusual disperser guild on the island. Only five bird species but 20 lemur species are frugivorous, and 16 of those lemur species are currently threatened with extinction. The disappearance of frugivorous lemurs would significantly change the vegetation dynamics of Madagascar's ecosystems, and a high proportion of Madagascar's endemic plants would enter an extinction vortex. [ABSTRACT FROM AUTHOR]

Balanites maughamii appears to be an obligate elephant-dispersed species. Its fruits are strongly scented and produce a large range of volatiles, particularly aliphatic acids such as hexanoic and isovaleric acid. The seed coat can resist a compression force of >1.5 kN. Seeds removed from the seed coat, and those from compressed seeds or from elephant dung, have better germination than seeds enclosed by undamaged seed-coats, which largely failed to germinate over a 2-mo period. Mastication by elephants may be necessary to split the seed coat to allow germination and the germinant to emerge from the seed coat. We identify four traits of elephant-dispersed fruits; they are dull-coloured, presented on the ground, strongly scented and have exceptionally strong seed coats. [ABSTRACT FROM PUBLISHER]

Apes are important long-distance dispersers of large seeds in African tropical forests. Seed size and shape are likely to affect the ease of swallowing for an animal species. If an endozoochorous seed is larger than the digestive tract of an animal, the seed cannot be swallowed, and a round seed is more difficult to swallow than an elongated seed of the same length. In order to test if such a correlation exists between the seed size and its shape, we investigated the length and width of chimpanzee-dispersed seeds at the Mahale Mountains National Park, Tanzania. Among the 14 species of seeds, longer seeds had significantly narrower relative widths, and thus, they were more ovoid. Since the chimpanzee is the largest arboreal frugivore at Mahale, their food selection might have influenced the shape of larger seeds. The chimpanzee's selective consumption of such fruits with longer, elongated seeds may have facilitated the selective dispersal of such plant species in that area. [ABSTRACT FROM PUBLISHER]

Mimosa luisana is functionally important in the Tehuacán-Cuicatlán Valley, Mexico, since it is able to create favourable microsites for the establishment of other plant species. The endozoochory of M. luisana seeds by goats was evaluated in terms of excrement deposition pattern, seed survival and germination. The excrement deposition pattern was evaluated by collecting pellets in four plots of 25 × 2 m randomly placed in a grazing area and recording the microhabitat where pellets were found. Seed survival and germination were evaluated by feeding the goats with seeds and collecting dung pellets at 8-h intervals for 80 h. Seeds from goat pellets (treatment) and seeds collected from pods (control) were placed in a germination chamber for 24 d. Goats mainly deposited M. luisana seeds in viable sites (open areas) for growth. Mimosa luisana seeds survived the goat digestive treatment (5.91% ± 2.86%) and most of them (67% ± 25.9%) were recovered 8–32 h after ingestion. Goat gut treatment increased M. luisana final germination (47.5% ingested, 5.83% control) and shortened initial and mean time of germination. Our results indicate that goats may be an efficient disperser of M. luisana seeds. [ABSTRACT FROM PUBLISHER]

Fossilized hackberry (Celtis) seeds were found within the shells of two Stylemys individuals excavated from Oligocene sediments from South Dakota. The presence of in situ skeletal elements indicates that the tortoises were buried without extensive disarticulation. Abiotic transport of the seeds into the carcasses is unlikely given the anatomically correct placement of both skeletal elements and seeds and the comparative settling velocities of the encasing sediment versus modern Celtis seeds. Ecological evidence from modern Celtis and Stylemys analogues suggests that tortoises are commonly seed dispersal agents. The fossils are therefore interpreted as enterolites, providing the oldest reliable evidence of tortoise frugivory. [ABSTRACT FROM PUBLISHER]

Conceptual gaps and imprecise terms and definitions may obscure the breadth of plant-animal dispersal relationships involved in directed dispersal. The term 'directed' indicates predictable delivery to favourable microsites. However, directed dispersal was initially considered uncommon in diffuse mutualisms (i.e. those involving many species), partly because plants rarely influence post-removal propagule fate without specialized adaptations. This rationale implies that donor plants play an active role in directed dispersal by manipulating vector behaviour after propagule removal. However, even in most classic examples of directed dispersal, participating plants do not influence animal behaviour after propagule removal. Instead, such plants may take advantage of vector attraction to favourable plant microsites, indicating a need to expand upon current interpretations of directed dispersal. We contend that directed dispersal can emerge whenever propagules are disproportionately delivered to favourable microsites as a result of predictably skewed vector behaviour. Thus, we propose distinguishing active and passive forms of directed dispersal. In active directed dispersal, the donor plant achieves disproportionate arrival to favourable microsites by influencing vector behaviour after propagule removal. By contrast, passive directed dispersal occurs when the donor plant takes advantage of vector behaviour to arrive at favourable microsites. Whereas predictable post-removal vector behaviour is dictated by characteristics of the donor plant in active directed dispersal, characteristics of the destination dictate predictable post-removal vector behaviour in passive directed dispersal. Importantly, this passive form of directed dispersal may emerge in more plant-animal dispersal relationships because specialized adaptations in donor plants that influence post-removal vector behaviour are not required. We explore the occurrence and consequences of passive directed dispersal using the unifying generalized gravity model of dispersal. This model successfully describes vectored dispersal by incorporating the influence of the environment (i.e. attractiveness of microsites) on vector movement. When applying gravity models to dispersal, the three components of Newton's gravity equation (i.e. gravitational force, object mass, and distance between centres of mass) become analogous to propagules moving towards a location based on characteristics of the donor plant, the destination, and relocation processes. The generalized gravity model predicts passive directed dispersal in plant-animal dispersal relationships when (i) animal vectors are predictably attracted to specific destinations, (ii) animal vectors disproportionately disperse propagules to those destinations, and (iii) those destinations are also favourable microsites for the dispersed plants. Our literature search produced evidence for these three conditions broadly, and we identified 13 distinct scenarios where passive directed dispersal likely occurs because vector behaviour is predictably skewed towards favourable microsites. We discuss the wide applicability of passive directed dispersal to plant-animal mutualisms and provide new insights into the vulnerability of those mutualisms to global change., (© 2022 Cambridge Philosophical Society.)

Effects of the elephant gut and elephant dung on seed germination and early seedling establishment/growth were investigated in Banyang-Mbo Wildlife Sanctuary using undestroyed seeds of 14 plant species sorted from fresh elephant dung between 1 June 1994 and 31 May 1995 and similar seeds extracted from fresh ripe fruits fallen on the forest floor within the same period both sown in fresh elephant dung and forest soil. Parameters measured were final germination success, germination time and seedling growth rate. Results indicated that two species, Panda oleosa and Poga oleosa, did not germinate at all after 365 d irrespective of their sources and media of planting. Germination success observed in ingested seeds was significantly different from that observed in seeds from fresh fruits. Germination success observed in elephant dung was not significantly different from that in forest soil. Mean germination time varied widely between species and treatments but was generally shorter in seeds that passed through the elephant gut than those collected from fresh ripe fruits and these differences in mean germination time were significant in 92% of the species that germinated. Growth rates of seedlings from ingested seeds were higher than those from fresh ripe fruits especially in elephant dung. Growth medium was highly significant to growth in 10 of 12 species (83%) and source was important only to two species (16%) while their combined interacting effects were significant to three of the 12 species (25%). It is concluded that ingestion of seeds by the elephant is important in the germination of some rain-forest species and the elephant dung that contains the seeds dispersed is very important in the rapid growth of the seedlings. On the basis of germination success plant species that are absolutely or exclusively dependent on elephants for dispersal/germination are absent in Banyang-Mbo Wildlife Sanctuary, while Omphalocarpum elatum and Strychnos aculeata would be on the basis of fruit morphology. [ABSTRACT FROM PUBLISHER]

Frugivory, that is feeding on fruits, pulp or seeds by animals, is usually considered a mutualism when interactions involve seed dispersal, and an antagonism when it results in the predation and destruction of seeds. Nevertheless, most frugivory interactions involve both benefits and disadvantages for plants, and the net interaction outcomes thus tend to vary along a continuum from mutualism to antagonism. Quantifying outcome variation is challenging and the ecological contribution of frugivorous animals to plant demography thus remains little explored. This is particularly true for interactions in which animals do not ingest entire fruits, that is in seed-eating and pulp-eating. Here, we provide a comprehensive review of Neotropical palm-frugivore interactions, with a focus on how frugivore consumption behaviour (i.e. digestive processing, fruit-handling ability and caching behaviour) and feeding types (fruit-eating, pulp-eating and seed-eating) influence interaction outcomes at different demographic stages of palms. We compiled a total of 1043 species-level palm-frugivore interaction records that explicitly captured information on which parts of palm fruits are eaten by animals. These records showed consumption of fruits of 106 Neotropical palm species by 273 vertebrate species, especially birds (50%) and mammals (45%), but also fish (3%) and reptiles (2%). Fruit-eating involved all four taxonomic vertebrate classes whereas seed-eating and pulp-eating were only recorded among birds and mammals. Most fruit-eating interactions (77%) resulted in positive interaction outcomes for plants (e.g. gut-passed seeds are viable or seeds are successfully dispersed), regardless of the digestive processing type of vertebrate consumers (seed defecation versus regurgitation). The majority of pulp-eating interactions (91%) also resulted in positive interaction outcomes, for instance via pulp removal that promoted seed germination or via dispersal of intact palm seeds by external transport, especially if animals have a good fruit-handling ability (e.g. primates, and some parrots). By contrast, seed-eating interactions mostly resulted in dual outcomes (60%), where interactions had both negative effects on seed survival and positive outcomes through seed caching and external (non-digestive) seed dispersal. A detailed synthesis of available field studies with qualitative and quantitative information provided evidence that 12 families and 27 species of mammals and birds are predominantly on the mutualistic side of the continuum whereas five mammalian families, six mammal and one reptile species are on the antagonistic side. The synthesis also revealed that most species can act as partial mutualists, even if they are typically considered antagonists. Our review demonstrates how different consumption behaviours and feeding types of vertebrate fruit consumers can influence seed dispersal and regeneration of palms, and thus ultimately affect the structure and functioning of tropical ecosystems. Variation in feeding types of animal consumers will influence ecosystem dynamics via effects on plant population dynamics and differences in long-distance seed dispersal, and may subsequently affect ecosystem functions such as carbon storage. The quantification of intra- and inter-specific variation in outcomes of plant-frugivore interactions - and their positive and negative effects on the seed-to-seedling transition of animal-dispersed plants - should be a key research focus to understand better the mutualism-antagonism continuum and its importance for ecosystem dynamics., (© 2021 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

Seed dispersal by animals is a complex phenomenon, characterized by multiple mechanisms and variable outcomes. Most researchers approach this complexity by analysing context-dependency in seed dispersal and investigating extrinsic factors that might influence interactions between plants and seed dispersers. Intrinsic traits of seed dispersers provide an alternative way of making sense of the enormous variation in seed fates. I review causes of intraspecific variability in frugivorous and granivorous animals, discuss their effects on seed dispersal, and outline likely consequences for plant populations and communities. Sources of individual variation in seed-dispersing animals include sexual dimorphism, changes associated with growth and ageing, individual specialization, and animal personalities. Sexual dimorphism of seed-dispersing animals influences seed fate through diverse mechanisms that range from effects caused by sex-specific differences in body size, to influences of male versus female cognitive functions. These differences affect the type of seed treatment (e.g. dispersal versus predation), the number of dispersed seeds, distance of seed dispersal, and likelihood that seeds are left in favourable sites for seeds or seedlings. The best-documented consequences of individual differences associated with growth and ageing involve quantity of dispersed seeds and the quality of seed treatment in the mouth and gut. Individual specialization on different resources affects the number of dispersed plant species, and therefore the connectivity and architecture of seed-dispersal networks. Animal personalities might play an important role in shaping interactions between plants and dispersers of their seeds, yet their potential in this regard remains overlooked. In general, intraspecific variation in seed-dispersing animals often influences plants through effects of these individual differences on the movement ecology of the dispersers. Two conditions are necessary for individual variation to exert a strong influence on seed dispersal. First, the individual differences in traits should translate into differences in crucial characteristics of seed dispersal. Second, individual variation is more likely to be important when the proportions of particular types of individuals fluctuate strongly in a population or vary across space; when proportions are static, it is less likely that intraspecific differences will be responsible for changes in the dynamics and outcomes of plant-animal interactions. In conclusion, focusing on variation among foraging animals rather than on species averages might bring new, mechanistic insights to the phenomenon of seed dispersal. While this shift in perspective is unlikely to replace the traditional approach (based on the assumption that all important variation occurs among species), it provides a complementary alternative to decipher the enormous variation observed in animal-mediated seed dispersal., (© 2017 Cambridge Philosophical Society.)