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1.
Several North American trees are hypothesized to have lost their co‐evolved seed disperser during the late‐Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon (Diospyros virginiana) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and coyote (Canis latrans), and two Pleistocene analogs; the Asian elephant (Elephas maximus) and alpaca (Vicugna pacos). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white‐tailed deer (Odocoileus virginianus)—a species not capable of dispersing persimmon seeds—comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human‐induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.  相似文献   

2.
  • To determine seed removal influence on seed populations, we need to quantify pre‐ and post‐dispersal seed removal. Several studies have quantified seed removal in temperate American deserts, but few studies have been performed in tropical deserts. These studies have only quantified pre‐ or post‐dispersal seed removal, thus underestimating the influence of seed removal. We evaluated pre‐ and post‐dispersal seed removal in the columnar cactus Stenocereus stellatus in a Mexican tropical desert.
  • We performed selective exclosure experiments to estimate percentage of seeds removed by ants, birds and rodents during the pre‐ and post‐dispersal phases. We also conducted field samplings to estimate abundance of the most common seed removers.
  • Birds (10–28%) removed a higher percentage of seeds than ants (2%) and rodents (1–4%) during pre‐dispersal seed removal. Melanerpes hypopolius was probably the main bird removing seeds from fruits. Ants (62–64%) removed a higher percentage of seeds than birds (34–38%) and rodents (16–30%) during post‐dispersal seed removal. Pogonomyrmex barbatus was probably the main ant removing seeds from soil.
  • Birds and ants are the main pre‐ and post‐dispersal seed removers in S. stellatus, respectively. Further studies in other S. stellatus populations and plants with different life forms and fruit types will contribute to evaluate seed removal in tropical American deserts.
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3.
Aim We estimated the patterns of seed deposition provided by the eyed lizard, Timon lepidus, and evaluated whether these patterns can be generalized across plant species with different traits (fruit and seed size) and spatial distributions. Location Monteagudo Island, Atlantic Islands National Park (north‐western Spain). Methods We radio‐tracked seven lizards for 14 days and estimated their home ranges using fixed kernels. We also geo‐referenced all fruit‐bearing individuals of four plant species dispersed by eyed lizards in the study area (Corema album, Osyris alba, Rubus ulmifolius and Tamus communis), measured the passage time of their seeds through the lizard gut, and estimated seed predation in four habitats (bare sand, grassland, shrub and gorse). Seed dispersal kernels were estimated using a combination of these data and were combined with seed predation probability maps to incorporate post‐dispersal seed fate (‘seed survival kernels’). Results Median seed gut‐passage times were around 52–98 h, with maximum values up to 250 h. Lizards achieved maximum displacement in their home ranges within 24–48 h. Seed predation was high (80–100% of seeds in 2 months), particularly under Corema shrub and gorse. Seed dispersal kernels showed a common pattern, with two areas of preferential seed deposition, but the importance of these varied among plant species. Interspecific differences among dispersal kernels were strongly reduced by post‐dispersal seed predation; hence, seed survival kernels of the different plant species showed high auto‐ and pairwise‐correlations at small distances (< 50 m). As a result, survival to post‐dispersal seed predation increased with dispersal distance for O. alba and T. communis, but not for C. album. Main conclusions Seed dispersal by lizards was determined primarily by the interaction between the dispersers’ home ranges and the position of the fruit‐bearing plants. As a result, seed rain shared a common template, but showed considerable variation among species, determined by their specific spatial context. Seed predation increased the spatial coherence of the seed rain of the different species, but also resulted in contrasting relationships between seed survival and dispersal distance, which may be of importance for the demographic and evolutionary processes of the plants.  相似文献   

4.
Establishing whether herb seed endozoochory is accidental or has evolved independently or in combination with other dispersal mechanisms may be valuable in the study of plant–animal interactions, but it remains unexplored for birds. We tested whether an Australian cockatoo, the galah (Eolophus roseicapilla), swallows entire seeds when feeding on other tissues without subsequent seed digestion, thus enhancing seed dispersal (the ‘foliage is the fruit’ hypothesis). Our preliminary sampling provides strong evidence supporting that this seed predator also acts as a legitimate endozoochorous disperser. A large proportion of droppings contained numerous seeds of six herb species of three plant families, surviving gut passage to be dispersed as viable propagules. The wide range in the number of seeds found in combinations with up to five species in particular droppings suggests both simultaneous and sequential passive ingestion without seed digestion and/or focused seed predation and digestion. As expected for inadvertent ingestion and inefficient digestion, our findings suggest that seed number and richness of dispersed plants are associated traits in this particular mutualistic interaction. This relationship can have important implications in community‐wide processes, favouring herbs whose seeds are disseminated in a viable state over those predated or negatively affected by gut transit.  相似文献   

5.
The forests of southeastern Amazonia are highly threatened by disturbances such as fragmentation, understory fires, and extreme climatic events. Large‐bodied frugivores such as the lowland tapir (Tapirus terrestris) have the potential to offset this process, supporting natural forest regeneration by dispersing a variety of seeds over long distances to disturbed forests. However, we know little about their effectiveness as seed dispersers in degraded forest landscapes. Here, we investigate the seed dispersal function of lowland tapirs in Amazonian forests subject to a range of human (fire and fragmentation) and natural (extreme droughts and windstorms) disturbances, using a combination of field observations, camera traps, and light detection and ranging (LiDAR) data. Tapirs travel and defecate more often in degraded forests, dispersing much more seeds in these areas [9,822 seeds per ha/year (CI95% = 9,106; 11,838)] than in undisturbed forests [2,950 seeds per ha/year (CI95% = 2,961; 3,771)]. By effectively dispersing seeds across disturbed forests, tapirs may contribute to natural forest regeneration—the cheapest and usually the most feasible way to achieve large‐scale restoration of tropical forests. Through the dispersal of large‐seeded species that eventually become large trees, such frugivores also contribute indirectly to maintaining forest carbon stocks. These functions may be critical in helping tropical countries to achieve their goals to maintain and restore biodiversity and its ecosystem services. Ultimately, preserving these animals along with their habitats may help in the process of natural recovery of degraded forests throughout the tropics. Abstract in Portuguese is available with online material.  相似文献   

6.
Large frugivores play an important role as seed dispersers and their extinction may affect plant regeneration. The consequences of such extinctions depend on the likelihood of other species being functionally redundant and on how post‐dispersal events are affected. We assess the functional redundancy of two seed dispersers of the Atlantic Forest, the muriqui (Brachyteles arachnoides) and the tapir (Tapirus terrestris) through the comparison of their seed dispersal quality, taking into account post‐dispersal events. We compare tapirs and muriquis for: (1) the dung beetle community associated with their feces; (2) the seed burial probability and burial depth by dung beetles; and (3) the seed mortality due to predators or other causes according to burial depth. We determine how seed burial affects seed dispersal effectiveness (SDE) and compare the dispersal quality of four plant species dispersed by these frugivores. Muriqui feces attract 16‐fold more dung beetles per gram of fecal matter and seeds experience 10.5‐fold more burial than seeds in tapir feces. In both feces types, seed mortality due to predation decreases with burial depth but seed mortality due to other causes increases. Total seed mortality differ within plant species according to the primary disperser. Therefore, the effect of seed burial on SDE varies according to the plant species, burial depth, and primary disperser. As tapirs and muriquis differently affect the seed fate, they are not functionally redundant. Since the effect of the primary disperser persists into the post‐dispersal events, we should consider the cascading effects of these processes when assessing functional redundancy.  相似文献   

7.
Owing to the late Pleistocene extinctions, the megafauna of Europe, Australia and the Americas disappeared, and with them the dispersal service they offered megafaunal fruit. The African savanna elephant, the largest remaining megaherbivore, offers valuable insights into the seed dispersal services provided by extinct megafauna in prehistoric times. Elephant seed dispersal studies have for the most part concentrated on African and Asian forest elephants. African savanna elephants are morphologically distinct from their forest counterparts. Like the forest elephants they consume large quantities of fruit from a large number of tree species. Despite this little is known of the savanna trees that rely on elephants for their dispersal or the spatial scale at which these seeds are dispersed. We combined information from feeding trials conducted on four park elephants with field telemetry data from 38 collared elephants collected over an 8‐year period in APNR/Kruger National Park to assess the seed dispersal service provided by savanna elephants. This study provides the first detailed account of the spatial scale at which African savanna elephants disperse seeds. Our mechanistic model predicts that 50 percent of seeds are carried over 2.5 km, and distances up to 65 km are achievable in maximum gut passage time. These findings suggest the savanna elephant as the longest distance terrestrial vertebrate disperser yet investigated. Maintaining their ecological role as a seed disperser may prove a significant factor in the conservation of large‐fruited tree diversity within the savannas. These results suggest that extinct megafauna offered a functionally unique dispersal service to megafaunal fruit.  相似文献   

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11.
The historical and contemporary loss of large‐bodied frugivores has disrupted many plant‐disperser mutualisms, with potentially profound consequences for plants. Although several aspects of seed dispersal by megafrugivores have already been examined, the role of these species in promoting seed‐mediated gene flow has remained unexplored. We evaluated the role of the Amazonian tapir (Tapirus terrestris), the largest Neotropical frugivore, in shaping plant genetic structure through seed‐mediated gene flow. We used microsatellites to analyze the genetic patterns of Syagrus romanzoffiana seedlings recruited in tapir latrines and around conspecific adult palms, the two sites where seeds and seedlings are most frequently found in this species. While the genetic diversity of seedlings was rather similar in both sites, the kinship structure was substantially weaker in latrines. Most seedlings recruited around adult palms were half‐ or full‐sibs originating from those adults. In contrast, seedlings recruited in latrines came from several (>5, on average) contributing mothers other than the nearest adult (95%) and were mostly non‐sibs (72%). Kinship patterns indicated that tapir‐mediated dispersal promotes the admixture of genotypes across space. Also, our results suggested that genetic diversity and the number of contributing mothers in latrines increase with the number of fruiting adults visited by tapirs before defecating and with the accumulation of feces over time. We provide evidence of the relevance of tapirs in mobilizing maternal progenies (and genotypes) across the landscape and recruiting clusters of unrelated seedlings. This study suggests a key role for plant–megafrugivore interactions in seed‐mediated gene flow and emphasizes the importance of preserving such mutualisms.  相似文献   

12.
Large‐seeded plants may suffer seed dispersal limitation in human‐modified landscapes if seed dispersers are absent or unable to disperse their seeds. We investigated dispersal limitation for the large‐seeded tree Virola surinamensis in a human‐modified landscape in southern Costa Rica. During two fruiting seasons, we monitored crop size, seed removal rates, the number of fruiting conspecifics within 100 m, and feeding visitation rates by frugivores at trees located in high and low forest disturbance conditions. Seed removal rates and the total number of seeds removed were high regardless of the disturbance level, but these parameters increased with tree crop size and decreased with the number of fruiting V. surinamensis trees within a 100 m radius. Trees at low disturbance levels were more likely to be visited by seed dispersers. Black mandibled toucans (Ramphastos ambiguus) and spider monkeys (Ateles geoffroyi) were the most important seed dispersers, based on visitation patterns and seed removal rates. Spider monkey feeding visits were more frequent at high disturbance levels, but the monkeys preferentially visited isolated trees with large yields and surrounded by a low number of fruiting Virola trees within 100 m. Toucan visitation patterns were not constrained by any of the predictors and they visited trees equally across the landscape. We suggest that isolated and highly fecund Virola trees are an important food resource for spider monkeys in human‐modified landscapes and that toucans can provide resilience against seed dispersal limitations for large‐seeded plants in human‐modified landscapes in the absence of hunting.  相似文献   

13.
Seed dispersal selection pressures may cause morphological differences in cone structure and seed traits of large‐seeded pine trees. We investigated the cone, seed, and scale traits of four species of animal‐dispersed pine trees to explore the adaptations of morphological structures to different dispersers. The four focal pines analyzed in this study were Chinese white pine (Pinus armandi), Korean pine (P. koraiensis), Siberian dwarf pine (P. pumila), and Dabieshan white pine (P. dabeshanensis). There are significant differences in the traits of the cones and seeds of these four animal‐dispersed pines. The scales of Korean pine and Siberian dwarf pine are somewhat opened after cone maturity, the seeds are closely combined with scales, and the seed coat and scales are thick. The cones of Chinese white pine and Dabieshan white pine are open after ripening, the seeds fall easily from the cones, and the seed coat and seed scales are relatively thin. The results showed that the cone structure of Chinese white pine is similar to that of Dabieshan white pine, whereas Korean pine and Siberian dwarf pine are significantly different from the other two pines and vary significantly from each other. This suggests that species with similar seed dispersal strategies exhibit similar morphological adaptions. Accordingly, we predicted three possible seed dispersal paradigms for animal‐dispersed pines: the first, as represented by Chinese white pine and Dabieshan white pine, relies upon small forest rodents for seed dispersal; the second, represented by Korean pine, relies primarily on birds and squirrels to disperse the seeds; and the third, represented by Siberian dwarf pine, relies primarily on birds for seed dispersal. Our study highlights the significance of animal seed dispersal in shaping cone morphology, and our predictions provide a theoretical framework for research investigating the coevolution of large‐seeded pines and their seed dispersers.  相似文献   

14.
The potential for seed‐eating birds to spread viable seeds was investigated using captive‐feeding trials to determine seed preference, passage time through the gut, and viability of passed seeds for bronzewing pigeons (Phaps chalcoptera), peaceful doves (Geopelia striata), crested pigeons (Ocyphaps lophotes), Senegal doves (Streptopelia senegalensis), zebra finches (Taeniopygia guttata), black ducks (Anas superciliosa) and wood ducks (Chenonetta jubata). Test seeds were bladder clover (Trifolium spumosum), crimson clover (Trifolium incarnatum), gorse (Ulex europaeus), canola (Brassica napus) and red panicum (Setaria italica). Their consumption was compared with that of commercial seed mixes. Although all test seeds were recognizable foods, their consumption usually decreased in the presence of other foods, except for canola, where consumption rates were maintained. Hard‐seeded bladder clover was the only species where viable seeds were passed by obligate seedeaters. In contrast, viable seeds of canola and gorse were passed by seed‐eating omnivorous/herbivorous ducks, although the germination of passed seeds (42%) was reduced significantly compared with that of untreated control seed (67%). Field validation with wild, urban bronzewings and Australian magpies (Gymnorhina tibicen) offered canola and commercial seed yielded similar outcomes, with a range of viable seeds recovered from magpie soft pellets. Mean seed passage time in captive birds ranged from 0.5 to 4.3 h for all test seeds and commercial seed mixes, suggesting that these bird species may potentially disperse seed over moderate distances. Despite the low probability of individual birds spreading viable seed, the high number of birds feeding in the wild suggests that the potential for granivorous and seed‐eating omnivorous birds to disperse viable seeds cannot be discounted, particularly if exozoochorous dispersal is also considered.  相似文献   

15.
Elephants, the largest terrestrial mega-herbivores, play an important ecological role in maintaining forest ecosystem diversity. While several plant species strongly rely on African elephants (Loxodonta africana; L. cyclotis) as seed dispersers, little is known about the dispersal potential of Asian elephants (Elephas maximus). We examined the effects of elephant fruit consumption on potential seed dispersal using the example of a tree species with mega-faunal characteristics, Dillenia indica L., in Thailand. We conducted feeding trials with Asian elephants to quantify seed survival and gut passage times (GPT). In total, 1200 ingested and non-ingested control seeds were planted in soil and in elephant dung to quantify differences in germination rates in terms of GPT and dung treatment. We used survival analysis as a novel approach to account for the right-censored nature of the data obtained from germination experiments. The average seed survival rate was 79% and the mean GPT was 35 h. The minimum and maximum GPT were 20 h and 72 h, respectively. Ingested seeds were significantly more likely to germinate and to do so earlier than non-ingested control seeds (P = 0.0002). Seeds with the longest GPT displayed the highest germination success over time. Unexpectedly, seeds planted with dung had longer germination times than those planted without. We conclude that D. indica does not solely depend on but benefits from dispersal by elephants. The declining numbers of these mega-faunal seed dispersers might, therefore, have long-term negative consequences for the recruitment and dispersal dynamics of populations of certain tree species.  相似文献   

16.
《Biotropica》2017,49(2):170-176
In seed predation studies, removal of a seed is only the first step of a dynamic process that may result in dispersal rather than seed death. This process, termed seed fate, has received little attention in African forests, particularly in Central Africa. We experimentally assessed the initial steps of seed fate for two tree species—the large‐seeded Pentaclethra macrophylla and the relatively small‐seeded Gambeya lacourtiana—in northeastern Gabon. Specifically, we evaluated whether seed size and seed consumer identity are important determinants of seed fate. We established experimental stations under conspecific fruiting trees, each comprising three seeds fitted with telemetric thread tags to facilitate their recovery, and a motion‐sensitive camera to identify visiting mammals. In total, animals removed 76 tagged seeds from experimental stations. Small Murid rats and mice primarily removed small Gambeya seeds, whereas large‐bodied rodents and mandrills primarily removed large Pentaclethra seeds. Gambeya seeds were carried shorter distances than Pentaclethra seeds and were less likely to be cached. The two large‐bodied rodents handled seeds differently: Cricetomys emini larderhoarded nearly all (= 15 of 16) encountered Pentaclethra seeds deep in burrows, while Atherurus africanus cached all (= 5 of 5) encountered Pentaclethra seeds singly under 1–3 cm of leaf litter and soil, at an average distance of 24.2 m and a maximum distance of 46.3 m from experimental stations. This study supports the hypothesis that seed fate varies based on seed size and seed consumer identity, and represents the first telemetric experimental evidence of larderhoarding and scatterhoarding in the region.  相似文献   

17.
Endozoochory and fire are crucial ecological factors determining germination success and recruitment in many plant species. Fire is a well‐known germination trigger while endozoochory may allow seed dispersal along with an increase in germination. Their interaction has rarely been addressed, however, even though both factors are pervasive in human‐transformed ecosystems like most Neotropical Dry Forests (NDF). For three common Mesoamerican tree species (Acacia pennatula, Enterolobium cyclocarpum, and Guazuma ulmifolia), we used feeding trials to assess the preference of cattle, which are their main seed dispersal agent. We also experimentally tested the interaction between gut passage and fire as triggers of germination. The fruits of the three species were eaten by cattle, but the small seeds of G. ulmifolia were ingested 10‐fold more than those of the other species. While gut passage did not have any effect on germination, heat‐shocks above 90 °C increased the number of germinating seeds by 15 percent. These results suggest that cattle may be a key dispersal vector in NDF, but that fire may be an important germination trigger. Physical dormancy in these species may have been selected for by extinct megaherbivores because it was a key trait ensuring seed survival after gut passage. However, in light of the recent expansion of cattle‐ranching and fire occurrence in NDF, it has become a useful exaptation facilitating the colonization of disturbed areas.  相似文献   

18.
Savannas are highly diverse and dynamic environments that can shift to forest formations due to protection policies. Long‐distance dispersal may shape the genetic structure of these new closed forest formations. We analyzed eight microsatellite loci using a single‐time approach to understand contemporary pollen and effective seed dispersal of the tropical tree, Copaifera langsdorffii Desf. (Fabaceae), occurring in a Brazilian fire‐ and livestock‐protected savanna. We sampled all adult trees found within a 10.24 ha permanent plot, young trees within a subplot of 1.44 ha and open‐pollinated seeds. We detected a very high level of genetic diversity among the three generations in the studied plot. Parentage analysis revealed high pollen immigration rate (0.64) and a mean contemporary pollen dispersal distance of 74 m. In addition, half‐sib production was 1.8 times higher than full‐sibs in significant higher distances, indicating foraging activity preference for different trees at long distances. There was a significant and negative correlation between diameter at breast height (DBH) of the pollen donor with the number of seeds (r = ?0.640, P‐value = 0.032), suggesting that pollen donor trees with a higher DBH produce less seeds. The mean distance of realized seed dispersal (recruitment kernel) was 135 m due to the large home range dispersers (birds and mammals) in the area. The small magnitude of spatial genetic structure found in young trees may be a consequence of overlapping seed shadows and increased tree density. Our results show the positive side of closed canopy expansion, where animal activities regarding pollination and seed dispersal are extremely high.  相似文献   

19.
Hunting pressure, fragmentation and deforestation have caused global declines in animal abundance, and the consequences for plant communities are poorly understood. Many large‐seeded plants, for instance, depend on large and endangered vertebrates for seed dispersal. In some Semi‐deciduous Atlantic Forests, endangered tapirs (Tapirus terrestris) are major dispersers of pindó palms (Syagrus romanzoffiana). Here, we compare recruitment patterns of pindó palms between protected and disturbed (defaunated) Atlantic Forest areas in Argentina and evaluate the potential consequences of the lack of the main disperser for pindó palm regeneration. We analyzed the number and spatial pattern of pindó adults, offspring, and tapir dung piles within ten plots established in an area spanning tapir latrines inside Iguazú National Park and in a fragmented forest area outside the park where tapir is locally extinct. In both areas, we evaluated recruitment levels beneath 24 adult palms in circular plots centered on adult stems. We found lower pindó palm recruitment outside the park where offspring tended to be aggregated around adult palms. In contrast, in Iguazú National Park offspring were spatially associated with tapir dung‐piles, in which most offspring were registered. Recruitment under adults was higher outside the park suggesting a lower rate of seed removal in disturbed areas. Our results show that tapir dispersal promotes higher recruitment levels of pindó offspring and shapes their spatial pattern, breaking the spatial association with adult (presumably maternal) palms. These results are useful for predicting the impact of local tapir extinction on this palm.  相似文献   

20.
The interaction between granivorous scatterhoarding mammals and plants is a conditional mutualism: scatterhoarders consume seeds (acting as predators), but the movement of seed by scatterhoarders may contribute to dispersal (acting as mutualists). Understanding the ecological factors that shape this relationship is highly relevant in anthropogenically disturbed tropical forests where large‐bodied frugivores are extirpated. In such forests, large‐seeded trees that once depended on these frugivores for dispersal may now only have scatterhoarders as prospective dispersers. We studied Carapa oreophila (Meliaceae) in an Afromontane forest, to test the hypotheses that the proportion of seeds immediately consumed or hoarded (dispersed) would vary over a disturbance gradient. Temporal replication also afforded exploration of how habitat effects might vary with food availability. Using a Bayesian framework, we demonstrate that seeds were more likely to be hoarded in less disturbed forest, irrespective of temporal variation in food abundance. In contrast, forest disturbance only appeared to increase seed predation in temporal replicates that coincided with sustained food availability. These results highlight the potential variability in the dynamics between plants and scatterhoarders over fine temporal scales, elucidating possible ecological scenarios where scatterhoarders might act as mutualists (contributing positively to plant recruitment). Our study also fills important knowledge gaps about the importance of scatterhoarders as dispersers in tropical forests depleted of large‐bodied frugivores, particularly in Africa where scatterhoarding mutualisms have not been extensively studied.  相似文献   

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