Seed Retention Time Research Articles

Biotic dispersal in eelgrass Zostera marina

Dispersal is a critical process in the life history of nearly all plant species and can be facili - tated by both abiotic and biotic mechanisms. Despite an abundance of vertebrate fauna utilizing seagrass meadows as a feeding area and thus capable of consuming and excreting seeds, little work has been conducted on biotic seed dispersal mechanisms. The objectives of this study were to (1) determine whether seeds of the seagrass Zostera marina could pass through the digestive systems of resident and tran - sient vertebrates of a seagrass bed and remain viable and (2) determine seed retention times in the guts of each species to estimate dispersal distances of Z. ma- rina seeds by vertebrate dispersers. Excretion and germination rates of consumed seeds for 3 fish species (Fundulus heteroclitus,Sphoeroides maculatus,Lagodon rhomboides), 1 turtle species (Malaclemys terrapin) and 1 waterfowl species (Aythya affinis) showed Z. marina seeds could survive passage through spe- cies' digestive systems and successfully germinate. Excretion rates were generally highest for F. hetero- clitus, S. maculatus, and M. terrapin, lowest for A. affi- nis, and moderate for L. rhomboides. Analyses sug - gest seeds were significantly affected by species' digestive tracts. Maximum dispersal distances are es- timated to be 200, 60, 1500, and 19 500 m for F. hetero- clitus, L. rhomboides, M. terrapin, and A. affinis, re- spectively. Data here provide strong evidence that biotic dispersal can occur in Z. marina, and biotically transported seeds can be dispersed to isolated areas unlikely to receive seeds via abiotic mechanisms. Bio - tic dispersal may rival or exceed abiotic mechanisms. Future seagrass dispersal models should incorporate biotic dispersal as a seed transport mechanism.

Do larger frugivores move seeds further? Body size, seed dispersal distance, and a case study of a large, sedentary pigeon

AbstractAimWorld‐wide declines in large‐bodied frugivores may change seed deposition patterns dramatically if body mass influences seed dispersal‐related traits, such as dispersal distance. We quantified movement patterns and seed dispersal distances by Hemiphaga novaeseelandiae (kereru), the fifth‐largest surviving pigeon world‐wide. We then reviewed how body mass affects seed dispersal distance among fruit‐eating birds globally.LocationTaranaki and Canterbury, New Zealand.MethodsWe radio‐tracked 24 kereru, following each bird continuously for up to 8.5 h, for a total of 43 tracking‐days during the peak fruiting season (February–April). We estimated seed dispersal distances for three fleshy‐fruited species using a mechanistic model based on kereru movements and seed retention times. We analysed global data for volant avian frugivores to determine the effect of body mass on time spent in fruiting trees, seed retention time, and dispersal distance.ResultsKereru were highly sedentary, with an average of 32 ± 39 (mean ± SD) minutes and maximum of 315 minutes between flights. Kereru flew a mean of 77 ± 159 m and maximum of 1457 m in a single flight. They dispersed 66–87% of ingested seeds away from the parent plant. Mean seed dispersal distances for Beilschmiedia tawa, Vitex lucens and Pseudopanax arboreus were 95, 98 and 61 m, respectively, with all species dispersed up to 1469 m. For all three species, 79–88% of seeds were dispersed < 100 m and < 1% were dispersed > 1 km from the parent plant. Globally, both the mean time spent in fruiting trees and seed retention time increased with increasing frugivore body mass. However, retention time increased faster, and therefore the dispersal distance and percentage of seeds moved away from the parent increased with body mass.Main conclusionsDespite sedentary behaviour, kereru disperse many seeds away from the parent plant due to their even longer gut passage time, a function of their large size. Large‐bodied frugivores are disproportionately important as dispersers not only because they can swallow larger fruits, but also because they are more likely to deposit seeds away from the parent plant and at greater distances.

Linking frugivore behavior to plant population dynamics

Despite the acknowledged importance of frugivores as seed dispersal agents we still lack a general understanding of the mechanisms by which these animals could shape plant populations and communities. We used a spatially explicit stochastic simulation to explore how frugivore movement decisions interact with landscape properties, thus affecting plant population dynamics through dispersal. The model simulated bird movement, foraging, seed deposition and plant recruitment. We assumed that plants lived only for one season and that recruitment was a function of local seed density. We also considered the effect of perches as non‐food landscape features. Our simulation experiments consisted in varying the parameters governing bird foraging decisions in relation to 1) how fruit abundance biased their movement, and 2) how the willingness to visit a plant or perch decreased with distance to current location. Simulated plant population dynamics was strongly influenced by bird behavior. The scale of foraging decisions had a much stronger effect on plant dynamics than biases due to fruit abundance. Birds tended to concentrate their activities in the center of the landscape where plants became more abundant, increasing local competition. The presence of perches reduced this tendency resulting in larger population sizes. The importance of perches highlights the fact that behaviors other than foraging can have a strong impact on the patterns of seed deposition and hence on plant population dynamics. Several recent studies have combined animal movement data with seed retention time in order to predict seed dispersal kernels. These studies usually emphasize the ecological implications of the scale and shape of such kernels. However, our simulation results reveal that movement directionality and the fact that birds moved mostly among plants and perches can have a major impact on plant population dynamics.

Frugivory by Taiwan Barbets (Megalaima nuchalis) and the effects of deinhibition and scarification on seed germination

We investigated the frugivory of Taiwan Barbets ( Megalaima nuchalis Gould, 1863) on passage time and germination of 19 species of commonly consumed fruits, distinguished the deinhibition and scarification effects, and tested if complete bird-gut passage increases seed germination. We measured fruit and seed size and seed retention times (SRTs) and examined the germination of intact fruits and pulp-removed and defecated seeds. Germination latency in intact fruits of most species was prolonged, whereas in more non-figs (7/12), the seed germinability increased after ingestion, and nearly all figs germinated by higher proportions after defecation or depulping. Yet, figs revealed major differences from non-figs. SRTs of both non-figs and figs were negatively dependent on fruit size, which was positively correlated to seed size in non-figs only. The germinability was negatively correlated and the germination onset time was positively correlated with SRTs of the last seeds in non-figs, but neither was correlated with SRTs in figs. Most (14/17) species with germination success were enhanced either by deinhibition and scarification, or the fruits hardly germinated but were aided by pulp removal. Deinhibition revealed greater effects than scarification in increasing the germinability and shortening latency, thus aiding, in particular, non-fig seeds with shorter SRTs or that are often culled during feeding.

Effects of Frugivore Preferences and Habitat Heterogeneity on Seed Rain: A Multi-Scale Analysis

Seed rain mediated by frugivores is influenced by (1) the seed-deposition distances following fruit ingestion, (2) the disperser activity, as determined by its behaviour and habitat preferences, and (3) the structure of the habitat within the landscape. Here, we evaluated such components using the fleshy-fruited shrub Ephedra fragilis and the frugivorous Balearic lizard Podarcis lilfordi. We estimated seed-deposition patterns based on the displacements and habitat preferences of lizards, derived from visual surveys and telemetry data. The influence of variables potentially determining lizard habitat preference (i.e., height, slope, four measures of habitat abundance and four measures of habitat fragmentation) was evaluated at three spatial scales: ‘home-range’ (c. 2.5–10*103 m2; telemetry data), ‘within home-range’ (c. 100 m2; telemetry data) and ‘microhabitat’ (<100 m2; visual survey). Cumulative lizard displacement (from each telemetric location to the initial capture point) saturated before the peak of seed defecation (seed-retention time), indicating that lizard home-range size and habitat preferences were the main determinants of the spread and shape of seed shadows. Shrub cover was positively correlated with habitat preference at the three scales of analysis, whereas slope was negatively correlated at the home-range scale. Model scenarios indicated that spatially-aggregated seed rain emerged when we incorporated the joint effect of habitat preference at the two largest (home-range and within home-range) scales. We conclude that, in order to predict seed rain in animal dispersed plants, it is important to consider the multi-scale effects of habitat preference by frugivores.

Comparison of germination rates and fruit traits of indigenous Solanum giganteum and invasive Solanum mauritianum in South Africa

There is a global threat of invasive alien plants to biodiversity and ecosystem services. Of these, fleshy-fruited species are credited as some of the worst invaders and this is largely due to their mutualisms with local dispersers. Comparative studies between invasive and indigenous species can shed new insights into the traits which promote invasive plants success over their indigenous counterparts. This study compared the germination success of indigenous Solanum giganteum and invasive Solanum mauritianum, following ingestion by Red-winged Starlings (Onychognathus morio, Sturnidae) and Speckled Mousebirds (Colius striatus, Coliidae) and compared these with de-pulped seed and whole fruit controls. Nutritive and morphological fruit traits were also considered. Seed retention times were only obtained for Red-winged Starlings on both diets, and these did not differ. For both plant species, ingested and de-pulped seeds had similar germination success and mean daily germination, irrespective of frugivore type. However, pulp removal was important for S. giganteum. The type of avian frugivore affected the onset of germination, with the comparatively larger Red-winged Starlings promoting earlier germination of both S. mauritianum and S. giganteum seeds when compared to their controls, except for de-pulped S. mauritianum. These germinated at the same time as ingested S. mauritianum, but significantly earlier than de-pulped S. giganteum. Speckled Mousebirds consumed more S. mauritianum than S. giganteum, while Red-winged Starlings showed the opposite. While S. mauritianum had larger yellow fruits, their seeds were smaller, lighter and more numerous than those in the red fruits of S. giganteum. Furthermore, S. mauritianum fruits contained considerably more sugar content than S. giganteum fruits. In summary, offering greater nutritional rewards and generating greater reproductive outputs than indigenous species, can explain why fleshy-fruited exotics become highly invasive.

Retention time variability as a mechanism for animal mediated long-distance dispersal.

Long-distance dispersal (LDD) events, although rare for most plant species, can strongly influence population and community dynamics. Animals function as a key biotic vector of seeds and thus, a mechanistic and quantitative understanding of how individual animal behaviors scale to dispersal patterns at different spatial scales is a question of critical importance from both basic and applied perspectives. Using a diffusion-theory based analytical approach for a wide range of animal movement and seed transportation patterns, we show that the scale (a measure of local dispersal) of the seed dispersal kernel increases with the organisms' rate of movement and mean seed retention time. We reveal that variations in seed retention time is a key determinant of various measures of LDD such as kurtosis (or shape) of the kernel, thinkness of tails and the absolute number of seeds falling beyond a threshold distance. Using empirical data sets of frugivores, we illustrate the importance of variability in retention times for predicting the key disperser species that influence LDD. Our study makes testable predictions linking animal movement behaviors and gut retention times to dispersal patterns and, more generally, highlights the potential importance of animal behavioral variability for the LDD of seeds.

The role of avian frugivores in germination of seeds of fleshy-fruited invasive alien plants

Many highly invasive plant species have fleshy fruits which are eaten by native frugivorous animals. These frugivores play an important role in long-distance seed dispersal, and may also affect germination success. The aim of this study was to determine whether generalist frugivores enhance or decrease seed germination of invasive alien species through pulp removal or seed coat abrasion, besides serving as dispersal agents. Fruits of four fleshy-fruited invasive alien plant species, namely Solanum mauritianum, Cinnamomum camphora, Lantana camara and Psidium guajava, were fed to three generalist avian frugivorous species, which have been observed feeding on these fruits in the wild. Seed retention time was recorded as this affects dispersal distance and the duration that seeds are exposed to the effects of the gut. Seeds removed from excreta, seeds from manually de-pulped fruit, and whole fruit were planted in soil trays housed in a greenhouse. Daily germination counts were done. Seed retention times differed significantly between bird species for all fruits, except those of C. camphora. However, all frugivores had a similar effect on the germination success of seeds of S. mauritianum, L. camara and P. guajava, showing that gut retention time was not important. Germination of seeds from manually de-pulped fruits did not differ from that of ingested seeds of all plant species, suggesting that seed coat abrasion was also not important. Pulp removal resulted in significantly higher germination rates, both in the two species with larger, multi-seeded fruit (S. mauritianum and P. guajava), and in the two species having single-seeded fruit with waxy exocarps (C. camphora and L. camara). Pulp removal also resulted in significantly earlier germination of L. camara and P. guajava seeds. Therefore, frugivores not only accelerate dispersal, but also greatly enhance seed germination of all fleshy-fruited invasive alien species in this study.

Knysna Turacos ( Tauraco corythaix) do not improve seed germination of ingested fruit of some indigenous South African tree species

Seed dispersal plays an important role in the persistence, regeneration and maintenance of plant communities. It is therefore not surprising that much attention has been paid to the germination potential of seeds ingested by frugivorous animals. Consequently the aim of this study was to determine what effect ingestion of seeds by Knysna Turacos ( Tauraco corythaix) has on the germination rate and germination percentage of indigenous South African tree species. Fruits from twelve tree species were fed to the Turacos in separate trials and seed retention times were determined as it has been suggested that a longer seed retention time may increase germination rates. At the end of each trial, seeds were extracted from excreta of individual birds and planted in trays containing potting soil. Germination was recorded daily until 14 days of no germination. Knysna Turacos seed retention times were in the range of those obtained by other studies, with Ficus sur seeds having the fastest retention times (12.4 ± 0.8 min) and Celtis africana the slowest (34.6 ± 5.6 min). Seed ingestion by Knysna Turacos did not influence the rate at which seeds germinated in 83% of the tree species, but ingested Ficus lutea and Ficus natalensis seeds germinated significantly sooner than whole fruit seeds. Future studies relating the composition of indigenous forest fruits to food preferences of Knysna Turacos may give insight into their role as potential seed dispersers of indigenous fruiting tree species.

Disentangling the drivers of reduced long-distance seed dispersal by birds in an experimentally fragmented landscape

Seed dispersal is a crucial component of plant population dynamics. Human landscape modifications, such as habitat destruction and fragmentation, can alter the abundance of fruiting plants and animal dispersers, foraging rates, vector movement, and the composition of the disperser community, all of which can singly or in concert affect seed dispersal. Here, we quantify and tease apart the effects of landscape configuration, namely, fragmentation of primary forest and the composition of the surrounding forest matrix, on individual components of seed dispersal of Heliconia acuminata, an Amazonian understory herb. First we identified the effects of landscape configuration on the abundance of fruiting plants and six bird disperser species. Although highly variable in space and time, densities of fruiting plants were similar in continuous forest and fragments. However, the two largest-bodied avian dispersers were less common or absent in small fragments. Second, we determined whether fragmentation affected foraging rates. Fruit removal rates were similar and very high across the landscape, suggesting that Heliconia fruits are a key resource for small frugivores in this landscape. Third, we used radiotelemetry and statistical models to quantify how landscape configuration influences vector movement patterns. Bird dispersers flew farther and faster, and perched longer in primary relative to secondary forests. One species also altered its movement direction in response to habitat boundaries between primary and secondary forests. Finally, we parameterized a simulation model linking data on fruit density and disperser abundance and behavior with empirical estimates of seed retention times to generate seed dispersal patterns in two hypothetical landscapes. Despite clear changes in bird movement in response to landscape configuration, our simulations demonstrate that these differences had negligible effects on dispersal distances. However, small fragments had reduced densities of Turdus albicollis, the largest-bodied disperser and the only one to both regurgitate and defecate seeds. This change in Turdus abundance acted together with lower numbers of fruiting plants in small fragments to decrease the probability of long-distance dispersal events from small patches. These findings emphasize the importance of foraging style for seed dispersal and highlight the primacy of habitat size relative to spatial configuration in preserving biotic interactions.

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.

Frugivory and seed dispersal by hornbills (Bucerotidae) in tropical forests

I summarize the current knowledge of frugivory and seed dispersal by hornbills in tropical forests. Many studies report on frugivory by hornbills but few specifically identify hornbills as effective dispersers. Hornbills are able to disperse a diverse array of fruits in tropical forests (748 plant species from 252 genera and 79 families) and move many of the seeds far from the parent trees. They digest only the fleshy parts of fruits that they swallow and then regurgitate/defecate the seeds intact. The relatively long seed retention times (>1 h) and propensity for depositing seeds away from the parent trees while foraging suggest high-quality dispersal. Some seeds might be aggregated at nest and roost sites, but hornbills are capable of dispersing seeds over several kilometers, resulting in a relatively even spread of seeds throughout the forest. Based on the results summarized here, hornbills provide excellent seed dispersal services to tropical plants in their respective habitats.

Internal dispersal of seeds by waterfowl: effect of seed size on gut passage time and germination patterns

Long distance dispersal may have important consequences for gene flow and community structure. The dispersal of many plants depends on transport by vertebrate seed dispersers. The shapes of seed shadows produced by vertebrates depend both on movement patterns of the dispersers and on the dynamics and effects of passage through the disperser's gut (i.e. the retention time, survival and germination of ingested seeds). A combination of experiments with captive waterbirds and aquatic plant seeds was used to analyse the following: (a) the effects of inter- and intra-specific variation in seed size and duck species on seed retention time in the gut and (b) the relationship between retention time and the percent germination and germination rates of seeds. Among the three Scirpus species used, those with smaller seeds showed higher survival after ingestion by birds and longer retention times inside their guts than those with larger seeds. For Potamogeton pectinatus, only seeds from the smaller size class (<8 mg) survived ingestion. Retention time affected the percent germination and germination rate of Scirpus seeds but in a manner that varied for the different plant and bird species studied. We recorded both linear and non-linear effects of retention time on percent germination. In addition, germination rate was positively correlated with retention time in Scirpus litoralis but negatively correlated in Scirpus lacustris. Small seed size can favour dispersal over larger distances. However, the effects of retention time on percent germination can modify the seed shadows produced by birds due to higher percent germination of seeds retained for short or intermediate periods. The changes in dispersal quality associated with dispersal distance (which is expected to be positively related to retention time) will affect the probability of seedling establishment over longer distances and, thus, the spatial characteristics of the effective seed shadow.

Endozoochory of Mediterranean aquatic plant seeds by teal after a period of desiccation: Determinants of seed survival and influence of retention time on germinability and viability

The capacity of eight wetland seeds to be internally dispersed by common teal ( Anas crecca L.) after a dry period typical of natural Mediterranean wetlands was experimentally quantified. These plant taxa ( Chara spp., Echinochloa crus-galli (L.) P. Beauv., Eleocharis palustris (L.) Roem. & Schult, Polygonum lapathifolium L., Potamogeton nodosus Poir., Potamogeton pusillus L., Schoenoplectus mucronatus (L.) Palla, Scirpus maritimus L.) were frequently ingested by teal in the field. Captive teal were fed with known quantities of dry seeds and faecal samples were collected at intervals of 1–2 h for 48 h. The proportion of seeds retrieved after gut passage that germinated varied between taxa from 3% to 83%. From 2% to 63% of the seeds ingested were recovered intact, and 18-95% of these were still viable. Therefore, an overall 32% of the seeds ingested were evacuated in a viable condition, ranging from 0.2% for Chara spp. to 54% for S. mucronatus. Mean seed retention time was 3–5 h. Overall, 94% of seeds were evacuated within 12 h, but 2% were recovered after more than 24 h. Seed viability was reduced at longer retention times, although viable seeds of all taxa except Chara spp. were recovered 44–48 h after the experiment began. Germinability was increased by gut passage, although for some species this effect was only significant after stratification, indicating that they exhibit both mechanical and physical dormancy. Seed germination was accelerated by gut passage, especially at longer retention times. Gut passage increased the proportion of viable seeds, suggesting selective digestion of non-viable ones. Endozoochorous transport by teal appears to be a widespread dispersal mechanism among wetland plants.

Importance of common palm civets (Paradoxurus hermaphroditus) as a long-distance disperser for large-seeded plants in degraded forests

Information on the dispersal distance achieved by disturbance-tolerant frugivores is critical for predicting the possibility of plant population persistence and the speed of vegetation recovery in degraded forests. We estimated the dispersal kernel of one large-seeded plant with ‘primate fruits’ rambutans (Nephelium lappaceum), generated by common palm civets (Paradoxurus hermaphroditus) in the degraded forest in the Tabin Wildlife Reserve, Sabah, Malaysia. We predicted that for the dispersal distance, civets are superior to macaques, which are another potential disperser for large-seeded ‘primates fruit’ in degraded forests. Observations on feeding trials showed that the civets often swallowed seeds, but both the macaques never did. Thus the mean seed retention times of the civets, 2.6 h, were much longer than those of macaques: 75 seconds for the long-tailed macaques and 156 seconds for the pig-tailed macaques. Radio tracking the activity of the common palm civets (4 males and 3 females) demonstrated that they traveled several hundreds of meters during gut passage time. The estimated mean dispersal distance was 216 m. Male dispersed the seeds in significantly longer distance (270 m) than female (156 m), reflecting the difference in home range size between sexes. These results indicated that common palm civets play an important role in the dispersal of large-seeded plants as long-distance dispersers, probably surpassing macaques.

BEHAVIOR RATHER THAN DIET MEDIATES SEASONAL DIFFERENCES IN SEED DISPERSAL BY ASIAN ELEPHANTS

Digestive physiology and movement patterns of animal dispersers determine deposition patterns for endozoochorously dispersed seeds. We combined data from feeding trials, germination tests, and GPS telemetry of Asian elephants (Elephas maximus) to (1) describe the spatial scale at which Asian elephants disperse seeds; (2) assess whether seasonal differences in diet composition and ranging behavior translate into differences in seed shadows; and (3) evaluate whether scale and seasonal patterns vary between two ecologically distinct areas: Sri Lanka's dry monsoon forests and Myanmar's (Burma) mixed-deciduous forests. The combination of seed retention times (mean 39.5 h, maximum 114 h) and elephant displacement rates (average 1988 m in 116 hours) resulted in 50% of seeds dispersed over 1.2 km (mean 1222-2105 m, maximum 5772 m). Shifts in diet composition did not affect gut retention time and germination of ingested seeds. Elephant displacements were slightly longer, with stronger seasonal variation in Myanmar. As a consequence, seed dispersal curves varied seasonally with longer distances during the dry season in Myanmar but not in Sri Lanka. Seasonal and geographic variation in seed dispersal curves was the result of variation in elephant movement patterns, rather than the effect of diet changes on the fate of ingested seeds.

Seed Dispersal by Geochelone carbonaria and Geochelone denticulata in Northwestern Brazil1

ABSTRACTThe role of red‐footed tortoises (Geochelone carbonaria) and yellow‐footed tortoises (G. denticulata) as seed dispersal agents was investigated in northwestern Brazil from 5 to 26 January 2002 by analyzing fecal samples for frequency and viability of seed species and estimating daily displacement of tortoises from recaptured and thread‐trailed individuals. Fourteen of 19 fecal samples contained a total of 646 seeds represented by 11 plant species. The most abundant species was Ficus sp. (N= 400) with 100 percent of seeds viable, followed by Aechmea sp. (N = 88) with 93 percent of seeds viable, and Genipa americana (N= 59) with 91 percent of seeds viable. Mean minimum retention time of seeds was 1.6 d and mean daily displacement of tortoises based on recaptured (N= 7) and thread‐trailed tortoises (N= 2) was 57 m. Thus, the diversity and proportion of viable seeds consumed by tortoises, combined with the seed retention times and daily movements, suggest they may be effective dispersal agents. These preliminary findings warrant further investigation into the ecological role of these tortoises in Neotropical ecosystems and their contribution to the maintenance of species diversity and forest structure.

Experimental assessment of plant seed retention times in fur of cattle and horse

Epizoochorous dispersal of plant seeds is an important long-distance dispersal mechanism. Yet little is known about retention times of seeds in animal furs and hence about potential dispersal distances of the seeds. Here, we used marked seeds of 12 plant species to determine seed depletion curves on Galloway cattle and Haflinger horse in three vegetation types (forest, tall herbage vegetation and meadow), in both dry and rainy weather conditions. In the long fur of Galloway cattle, seeds were retained significantly longer than in the short fur of Haflinger horse. In general, seed retention times were not considerably affected by the structure of the surrounding vegetation. The impact of the weather was negligible, only affecting the retention of some plant species. Negative exponential functions were fitted to the seed depletion curves. Using the parameters of curve estimations in the different conditions of animal species and vegetation structure, half-life seed retention times of up to 13 h for Galloway cattle and up to more than 4 h for Haflinger horse could be calculated, with corresponding potential half-life dispersal distances in the order of magnitude of tens of metres to a few kilometres. Different seed traits correlated with seed retention times in the long cattle fur and in the short horse fur, respectively.

Differences in endozoochorous dispersal between aquatic plant species, with reference to plant population persistence in rivers

Summary 1. In river ecosystems, populations are continuously subjected to unidirectional downstream currents resulting in a downstream movement of populations. To ensure long‐term population persistence in rivers, organisms must have a mechanism for upstream dispersal, which allows them to re‐colonise upstream areas.2. In this study we assessed differences in the potential for endozoochorous seed dispersal of Sparganium emersum and Sagittaria sagittifolia, two aquatic plant species with different seed morphologies, by mallard (Anas platyrhynchos) and teal (Anas crecca), two duck species with different body weights.3. We found no significant differences in seed retrieval (the proportion of ingested seeds retrieved after gut passage) and seed retention time (time between seed ingestion and retrieval), between mallard and teal, despite the difference in body weights. We did find a significantly higher germination (%) over retention time of S. emersum seeds retrieved from teal compared with mallard, most likely related to a more efficient removal of the seed coat during passage through the gut of teal.4. There were large differences between S. emersum versus S. sagittifolia in: (i) seed retrieval (22.65 ± 20.8% versus 1.60 ± 2.4%, respectively); (ii) seed retention time in duck gut, with a maximum of 60 h versus 12 h; (iii) the effect of gut passage on seed germination, with an increase of approximately 35% versus a decrease of 25%; and (iv) the effect of gut passage on seed germination rate, with an acceleration of 10 days versus a delay of 3 days on average. The results show that S. emersum has a higher potential for endozoochorous dispersal by ducks and postdispersal establishment than S. sagittifolia.5. We propose that, in rivers, bird‐mediated seed dispersal may promote re‐colonisation of upstream areas, enabling long‐term plant population persistence.

Frugivoria e dispersão de sementes pelo lagarto teiú Tupinambis merianae (Reptilia: Teiidae)

Os lagartos teiús possuem uma dieta generalista, podendo agir como importantes dispersores de sementes em florestas semidecíduas do sudeste do Brasil. Foram estudadas a frugivoria e a dispersão de sementes de lagartos teiús usando animais em cativeiro, através da oferta de frutos de uma floresta semidecídua. Frutos de trinta espécies vegetais foram oferecidos aos lagartos em cativeiro, com diâmetro variando de 0,81 a 10,0 cm. Não foram encontradas diferenças estatísticas na germinação entre as sementes que passaram pelo trato digestivo do lagarto e as controle de Eugenia uniflora (chi²= 0.69, P&gt;0.50), Genipa americana (chi²= 6.4, P&gt;0.975), Cereus peruvianus (chi²= 0.018, P&gt;0.10), e Solanum viarum (chi²= 6.23, P&gt;0.975). O tempo de retenção da semente no tubo digestivo do teiú variou de 22 a 23 h para Solanum lycocarpum e 43 a 44 h para Syagrus romanzoffiana. Nossos resultados indicam que o lagarto teiú tem potencial para agir como um importante dispersor de sementes nos trópicos.