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393 results for “seed dispersal”
Forest cover and connectivity have pervasive effects on the maintenance of evolutionary distinct interactions in seed dispersal networks
<p>Seed dispersal by animals is one of the most important ecological processes in tropical forests, entailing millions of years of evolutionary adaptations of plants and frugivorous animals forming networks of interactions that, ultimately, contribute to the resilience of such forests. We analyze 29 seed dispersal networks in the threatened Atlantic Forest biodiversity hotspot, with data on the frequency of feeding visits by birds to fruiting plants to answer: (1) which are the effects of forest cover and landscape connectivity on the maintenance of phylogenetic diversity (PD) of interacting birds and plants and the evolutionary distinctiveness of the interactions (EDi) between them; and (2) how EDi and plant/bird PD affects the robustness of the interaction networks? We found that forest cover positively influences both plant and bird PD and EDi. Landscape connectivity is an important predictor of bird PD, but not plant PD, suggesting that the spatial arrangement of forest remnants is essential for guaranteeing bird movement among forest fragments. Furthermore, interaction networks of areas with higher PD and EDi had great robustness to the simulated extinction of species, which underscore the importance of larger forest blocks for conserving evolutionary information and, consequently, the health and natural resistance of seed dispersal networks against environmental change.</p>
Seasonal variation in impact of non-native species on tropical seed dispersal networks
<p>Invasive non-native species can alter animal-mediated seed dispersal interactions and ultimately affect the stability of recipient communities. The degree of such disturbances, however, is highly variable and depends on several factors, two of which have received little attention: the relative timing of native and non-native fruiting phenologies, and the associated variation in relative resource availability across the fruiting period. Both are likely to alter plant-seed disperser interactions threatened by biological invasions. Here we investigated the impact of plant invasions on the seasonal dynamics of frugivory and seed dispersal networks across a large-scale experimental setup and a plant invasion gradient on a tropical island. We recorded fruit and frugivore abundances, and plant-frugivore interactions across 8 inselbergs (i.e. rocky outcrops) with different levels of plant invasion during 10 months on the island of Mahé, Seychelles. By combining four sampling methods of plant-frugivore interactions we constructed quantitative seed dispersal networks at all sites across two 5-month seasons: the on-peak and off-peak fruiting season. Our findings showed that, by fruiting mostly synchronously with natives, non-native plants compete with natives for dispersal services, predominantly carried out by native frugivores. Variation in native seed dispersal was driven by plant invasion and seasonality. Specifically, native seed dispersal declined with the degree of invasion; dispersal frequency increased with fruit abundance more strongly during the off-peak fruiting season; and networks became increasingly specialised during off-peak. These results indicated that during the main fruiting peak seed dispersal services were saturated, which likely intensified the competition between native and non-native fruits. When resources were scarce during off-peak fruiting season, native and non-native frugivores were more selective in their fruit choice at sites dominated by non-native plants. We showed that native plant and frugivore populations and native seed dispersal interactions were more vulnerable in invaded plant communities, where non-native plants compete with natives for dispersal services potentially reducing native recruitment. As invasive non-native plants dominate many ecosystems worldwide, particularly on islands, our findings showed that controlling plant invasions in vulnerable native communities can be critical to maintain native ecosystem functions and biodiversity.</p>
Increasing efficiency and reducing bias in the detection of seed-dispersal interactions based on mist-netted birds
<p>Efficient and unbiased sampling of ecological interactions is essential to our understanding of the functions they mediate. Seed dispersal by frugivorous birds is a key mutualism for plant regeneration and community dynamics. Mist-netting is one of the most widely used methods to sample avian seed dispersal through the identification of seeds in droppings of captured birds kept inside cloth bags. However, birds may drop seeds on the ground before being extracted from the net, leading to a fraction of missing information due to ineffective sampling. Worryingly, this fraction could be unevenly distributed across bird and plant species, leading to sampling biases. Here, we assess the effectiveness of using a 1- m wide mesh below mist nets to sample seeds dropped by entangled birds. We used data from birds mist-netted during one-year-round. We sampled nearly 50% of interaction events and 75% of dispersed seeds on the mesh band below the mist nets (i.e. lost information without this optimization). The proportion of seeds sampled on the mesh bands was not evenly distributed among bird species but strongly related to bird size, ranging from 57-63% in warblers to 84-94% in thrushes. Moreover, the proportion of seeds sampled on the mesh was negatively related to seed size, although this relationship was weaker. We also evaluated accumulation curves of species and pairwise interactions with increasing sampling effort, both with and without using the mesh bands. The number of seed species sampled increased by 21% when using the mesh bands and the number of pairwise interactions by 36%. Our findings provide strong evidence on how inefficient and biased traditional mist-netting can be for sampling community-wide seed-dispersal interactions. We thus urge the use of mesh bands in future studies to increase sampling effectiveness and avoid biases, which will ultimately improve our understanding of the seed dispersal function.</p>
Pericarpial nectary-visiting ants do not provide fruit protection against pre-dispersal seed predators regardless of ant species composition and resource availability
<p> This dataset describes the number of flowers, fruits and seed set of <em>Tocoyena formosa</em> in branches exposed (control) and isolated (ant exclusion) from ants, as well as the visiting ants and seed predators reared from fruits collected from both treatments.</p>
Evaluation of seed-dispersal services by ants at a temperate pasture: Results of direct observations in an ant suppression experiment
<p><em>Ant dispersal</em></p> <p>Ants disperse seeds of many plant species adapted to myrmecochory. While advantages of this ant–plant mutualism for myrmecochorous plants (myrmecochores) have been previously studied in temperate region mostly in forests, our study system was a pasture. Moreover, we used a unique combination of observing the effect of ant‐activity suppression on ant dispersal and comparison of the contribution of ant and unassisted dispersal to the distance from mother plant. We established plots without and with ant‐activity suppression (enclosures). We offered diaspores of a myrmecochorous (<em>Knautia arvensis</em>), and a non‐myrmecochorous (<em>Plantago lanceolata</em>) species in a choice test and followed ants carrying diaspores during days and nights (focus of previous studies was on diurnal dispersal). We measured frequency and distances of ant dispersal and compared them with unassisted dispersal recorded using sticky trap method. The dispersal frequency was lower in enclosures (3.16 times). Ants strongly preferred diaspores of the myrmecochore to non‐myrmecochore with 586 and 42 dispersal events, respectively (out of 6400 diaspores of each species offered). Ant dispersal resulted in more even and on average longer distances (maximum almost tenfold longer, 994 cm) in comparison to unassisted dispersal. Ant dispersal altered the distribution of distances of the myrmecochore from roughly symmetric for unassisted dispersal to positively skewed. Ants dispersed heavier diaspores farther. Ants dropped the majority of diaspores during the dispersal (which reduces clustering of seeds), while several (11%) were carried into anthills. Anthills are disturbed microsites presumably favorable for germination in competitive habitats. Ants provided non‐negligible dispersal services to myrmecochorous <em>K. arvensis</em> but also, to a lesser extent, of non‐myrmecochorous <em>P. lanceolata</em>.</p> <p><em>Unassisted dispersal</em></p> <p>A sticky trap of the same size as the experimental plots of the cafeteria experiment (3 m × 3 m) was used to record unassisted dispersal (i.e., without any biotic dispersal agent, mostly by gravity and additionally wind). We used linoleum covered with insect glue to trap the falling diaspores. Five full‐sized individuals (with majority of infructescences with mature seeds) of <em>K. arvensis</em> were fixed in a water container in the center of the plot for approximately 10 days. The procedure was repeated five times during July and August. The distances of trapped diaspores were measured in the same manner as in the case of ant dispersal, thus the dispersal by ants and unassisted dispersal can be compared.</p>
Partitioning Seed Dispersal Rate Amongst Vertebrates Vs Invertebrates Along a Land-Use Gradient
<b>Description: </b><p>Seed perdation and dispersal experiments</p><p><b>Project: </b>This dataset was collected as part of the following SAFE research project: <a href="https://www.safeproject.net/projects/project_view/72"><b>Partitioning Seed Dispersal Rate Amongst Vertebrates Vs Invertebrates Along a Land-Use Gradient</b></a></p><p><b>XML metadata: </b>GEMINI compliant metadata for this dataset is available <a href="https://www.safeproject.net/datasets/xml_metadata?id=77">here</a></p><p><b>Data worksheets: </b>There are 1 data worksheets in this dataset:</p><ol><li><p><b>Seed removal experiments</b> (Worksheet Data)</p><p>Dimensions: 904 rows by 13 columns</p><p>Description: Experimental seed removal trials. Each trial consisted of 20 pumpkin seeds being placed on a plate, with seed fates ascertained the following day.</p><p>Fields: </p><ul><li><b>Location</b>: SAFE project sample site (Field type: Location)</li><li><b>Point </b>: SAFE project sample site (Field type: ID)</li><li><b>Date</b>: Date seeds were placed in field (Field type: Date)</li><li><b>Treatment</b>: Experimental treatment (Field type: Categorical)</li><li><b>NPlacement</b>: Unknown variable (Field type: ID)</li><li><b>RemainUneat</b>: How many seeds remained on the plate and had no evidence of having been eaten? (Field type: Numeric)</li><li><b>RemovUneat</b>: How many seeds were removed from the plate and had no evidence of having been eaten? (Field type: Numeric)</li><li><b>RemainEat</b>: How many seeds remained on the plate but had evidence of having been eaten? (Field type: Numeric)</li><li><b>RemovEat</b>: How many seeds were removed from the plate and also had evidence of being eaten? (Field type: Numeric)</li><li><b>RemovUnknown</b>: How many seeds were removed from the plate and had an unknown fate? (Field type: Numeric)</li><li><b>Rain</b>: How heavily did it rain last night? 0 being no rain and 5 being torrential rain (Field type: Numeric)</li><li><b>TreatmentSuccessFail</b>: Was the treatment successful? (Field type: Categorical)</li></ul><br></li></ol><p><b>Date range: </b>2013-05-07 to 2013-07-27</p><p><b>Latitudinal extent: </b>4.6350 to 4.7523</p><p><b>Longitudinal extent: </b>116.9632 to 117.5934</p>
Legacy effects of seed dispersal mechanisms shape the spatial interaction network of plant species in Mediterranean forests
<p>1. Seed dispersal by frugivores plays a key role in structuring and maintaining tree diversity in forests. However, little is known about how the spatial legacy of seed dispersal and early recruitment shapes spatial patterns and the spatial interaction network of plant species in mature forest communities.</p> <p>2. We analysed two fully mapped mixed Pine-Oak forest communities using spatial point pattern analysis to determine (i) the detailed structure of the intraspecific spatial patterns of saplings and adults, (ii) the intra- and interspecific spatial interaction of saplings, adults, and saplings relative to adults, (iii) the spatial patterns of species richness at the community level, and (iv) whether seed dispersal mechanisms affect the plant-plant interaction networks and the ratio of adult to sapling neighbourhood densities used as surrogate for spatial self-thinning.</p> <p>3. The intraspecific spatial patterns of saplings and adults showed in general complex nested cluster structures that were similar for sapling and adult stages, despite of substantial self-thinning in some dry-fruited species. The spatial network of saplings was characterized by positive spatial interactions. Adults of several tree species facilitated saplings in their proximity; however, adults of dry-fruited species, but not those of fleshy-fruited ones, lost almost all positive interactions that occurred at the sapling stage. Besides, interaction strength between adults was positive and often significantly stronger if both species were fleshy-fruited. At the community level, the forests were structured into multispecies clumps across all life stages.</p> <p>4. Synthesis. Our analyses highlight the importance of the spatial legacy of seed dispersal and early recruitment in the assembly of plant communities. Particularly, animal seed dispersal can lead to multispecies clusters and positive spatial associations across life stages in Mediterranean forests, with surprisingly little signatures of negative interactions. Our analysis suggests that changes of the spatial structure across plant life stages are driven by seed dispersal mechanisms and subsequent spatial self-thinning, generating a spatial footprint at the sapling stage that conditions the long-term interactions between adult plants. Combining spatial point pattern analysis with network analysis and species traits is a promising way to disentangle the processes underlying observed patterns of local diversity. </p>
Data from: Within-species trait variation can lead to size limitations in seed dispersal of small-fruited plants
<p>The inability of small-gaped animals to consume very large fruits may limit seed dispersal of the respective plants. This has often been shown for large-fruited plant species that remain poorly dispersed when large-gaped animal species are lost due to anthropogenic pressure. Little is known about whether gape-size limitations similarly influence seed dispersal of small-fruited plant species that can show a large variation in fruit size within species.</p> <p>In this study, fruit sizes of 15 plant species were compared with the gape sizes of their 41 animal dispersers in the temperate, old-growth Białowieża Forest, Poland. The effect of gape-size limitations on fruit consumption was assessed at the plant species level, and for a subset of nine plant species, also at the individual level, and subindividual level (i.e., fruits of the same plant individual). In addition, for the species subset, fruit-seed trait relationships were investigated to determine whether a restricted access of small-gaped animals to large fruits results in the dispersal of fewer or smaller seeds per fruit.</p> <p>Fruit sizes widely varied among plant species (74.2%), considerably at the subindividual level (17.1%), and to the smallest extent among plant individuals (8.7%). Key disperser species should be able to consume fruits of all plant species and all individuals (except those of the largest-fruited plant species), even if they are able to consume only 28-55% of available fruits. Fruit and seed traits were positively correlated in eight out of nine plant species, indicating that gape size limitations will result in 49% fewer (in one plant species) or 16-21% smaller seeds (in three plant species) dispersed per fruit by small-gaped than by large-gaped main dispersers, respectively.</p> <p>Our results show that a large subindividual variation in fruit size is characteristic for small-fruited plant species, and increases their connectedness with frugivores at the level of plants species and individuals. Simultaneously, however, the large variation in fruit size leads to gape-size limitations that may induce selective pressures on fruit size if large-gaped dispersers become extinct. This study emphasizes the mechanisms by which gape-size limitation at the species, individual and subindividual level shape plant-frugivore interactions and the co-evolution of small-fruited plants.</p>
Dispersal syndromes are poorly associated with climatic niche differences in the Azorean seed plants
<p><b>Aim: </b>Environmental niche tracking is linked to the species ability to disperse. While well investigated on large spatial scales, dispersal constraints also influence small-scale processes and may explain the difference between the potential and the realized niche of species at small-scales. Here we test whether niche size and niche fill differ systematically according to dispersal syndrome within isolated oceanic islands. We expect species with higher dispersal abilities (anemochorous or endozoochorous) will have a higher niche fill, despite of their environmental niche size.</p> <p><b>Location:</b> Azores archipelago</p> <p><b>Taxon:</b> Native seed plants</p> <p><b>Methods:</b> We combined a georeferenced database of the species distribution within the archipelago (Azorean Biodiversity Portal/GBIF) with an expert-based dispersal syndrome categorization and a high-resolution climatic grid (CIELO model). Using four climatic variables (Annual Mean Temperature, Mean Diurnal Range, Annual Precipitation, Precipitation Seasonality), we calculated a 4-dimensional hypervolume to estimate the niche size of each species. Niche fill was quantified as the suitable climatic space of the island that was occupied by the focal species.</p> <p><b>Results:</b> Endozoochorous species display higher niche fill compared to epizoochorous and hydrochorous species, and larger niches than anemochorous and epizoochorous. Differences among the remaining groups are not significant neither for niche fill nor for niche size.</p> <p><b>Main Conclusions:</b> Although endozoochorous species track their niche more efficiently at small-scales than other dispersal syndromes, the differences between dispersal syndromes are not consistent. The ability of a species to track its niche at small-scales is not tightly related to its dispersal syndrome. Although intuitively appealing, dispersal syndrome classifications might not be the most appropriate tools for understanding dispersal processes at small-scales.</p>
Limited seed dispersal shapes fine-scale spatial genetic structure in a Neotropical dioecious large-seeded palm
<p><span>Seed and pollen dispersal contribute to gene flow and shape the genetic patterns of plants over fine spatial scales. We inferred fine-scale spatial genetic structure (FSGS) and estimated realized dispersal distances in Phytelephas aequatorialis, a Neotropical dioecious large-seeded palm. We aimed to explore how seed and pollen dispersal shape this genetic pattern in a focal population. For this purpose, we genotyped 138 seedlings and 99 adults with 20 newly developed microsatellite markers. We tested if rodent-mediated seed dispersal has a stronger influence than insect-mediated pollen dispersal in shaping FSGS. We also tested if pollen dispersal was influenced by the density of male palms around mother palms in order to further explore this ecological process in large-seeded plants. Rodent-mediated dispersal of these large seeds occurred mostly over short distances (mean 34.76 ± 34.06 m) while pollen dispersal distances were two times higher (mean 67.91 ± 38.29 m). The spatial extent of FSGS up to 35 m and the fact that seed dispersal did not increase the distance at which male alleles disperse suggest that spatially limited seed dispersal is the main factor shaping FSGS and contributes only marginally to gene flow within the population. Pollen dispersal distances depended on the density of male palms, decreasing when individuals show a clumped distribution and increasing when they are scattered. Our results show that limited seed dispersal mediated by rodents shapes FSGS in P. aequatorialis, while more extensive pollen dispersal accounts for a larger contribution to gene flow and may maintain high genetic diversity.</span></p>
Seed dispersal by waterbirds: a mechanistic understanding by simulating avian digestion
<p>Waterbirds disperse plant species via ingestion and egestion of seeds (endozoochory). However, our understanding about the regulating effects of seed traits, underlying mechanisms and possible (co)evolutionary processes is limited by our traditional reliance on data from feeding experiments with living waterbirds. Here, we overcome these limitations by developing and applying a new bioassay that realistically simulates digestive processes for Anseriformes waterbirds. We test three hypotheses: (1) seed survival and germination are most affected by mechanical digestion in the waterbird gizzard; (2) seed size, hardness, imbibition and shape regulate seed survival; and (3) plants growing in aquatic habitats benefit most from endozoochory by waterbirds. Experiments with 28,200 seeds of 48 plant species demonstrated species-specific seed survival that was entirely determined by digestion in the avian gizzard. Intestinal digestion did not affect seed survival but affected seed establishment (germinability and germination time) for 21% of the species. Large, hard seeds survived the simulations the best, in contrast to generally higher seed survival for smaller seeds during in vivo experiments. This mechanistically explains that small seeds escape digestive processes rather than being inherently more resistant (the 'escape mechanism'), while large seeds are retained until fully digested or regurgitated (the 'resistance and regurgitation mechanism'). Plants growing in wetter habitats had similar seed survival, but digestive processes stimulated their germinability and accelerated their germination more than for terrestrial plants. This indicates a relative advantage of endozoochory for plant species growing in wet habitats, possibly reflecting a co-evolutionary response related to dormancy breaking by gut passage. Simulating seed gut passage using a bioassay allowed establishing mechanisms and identifying relevant seed traits involved in seed dispersal by waterbirds. This information enhances our understanding of how animal species shape plant species distributions, which is extremely relevant now that current anthropogenic pressures already severely impact plant dispersal capacities.</p>
Seed size, seed dispersal traits, and plant dispersion patterns for native and introduced grassland plants
<p>Most terrestrial plants disperse by seeds, yet the relationship between seed mass, seed dispersal traits, and plant dispersion is poorly understood. We quantified seed traits for 48 species of native and introduced plants from grasslands of western Montana, USA, to investigate the relationships between seed traits and plant dispersion patterns. Additionally, because the linkage between dispersal traits and dispersion patterns might be stronger for actively dispersing species, we compared these patterns between native and introduced plants. Finally, we evaluated the efficacy of a global trait database, the TRY plant traits database, versus locally collected data for examining these questions.</p> <p>This archive contains species-level data used in analyses, including species metadata (origin, growth form), mean values of measured seed traits (size metrics and type of dispersal structures), two metrics of dispersion (local and broad scales, respectively) derived from grassland surveys in the study region, and information on the seed mass accessed from the TRY traits database. Note that the latter seed mass data could not be included in the archive, but can be acquired directly from the TRY plant traits database (<a href="https://www.try-db.org/TryWeb/Home.php">https://www.try-db.org/TryWeb/Home.php</a>).</p>
Data for: Exploitation competition between seed predators and dispersers introduced to Hawaiian forests
<p>Exploitation competition occurs when one group of organisms reduces the availability of a resource for another group of organisms. For instance, plants produce a certain number of fruits for seed dispersal by fruit-eating animals (hereafter frugivores), and fruit consumption by one group of frugivores can reduce the number of fruits available for other frugivores. However, it is uncertain whether exploitation competition is common among frugivores, particularly in novel ecosystems, where food resources are generally thought to be abundant and invasive species are dietary generalists. In a novel ecosystem in Hawai'i, we used gut passage experiments with captive birds to identify roles of introduced frugivores and found they were either distinctly seed dispersers or predators. We then experimentally tested how frugivory by seed predators influenced frugivory by seed dispersers. Specifically, we used exclosures around fruiting plants that blocked seed predator access, while permitting seed disperser access, and we had two control treatments that allowed for access by all frugivores (n=139 plants). When seed predators were excluded from plants, there was more frugivory by dispersers compared to controls, and results varied by year and plant species. Overall, we show that introduced frugivores occupied distinct ecological roles (seed predator or seed disperser), exploitation competition occurred between these introduced frugivore groups, and seed predators had both direct (via seed destruction) and indirect (via reduction in frugivory by dispersers) effects on seed dispersal. Thus, in this novel ecosystem, multiple frugivory is subtractive, and competition for fruit between introduced seed predators and seed dispersers scales up to affect invasions and the conservation of native flora. </p>
Data from: Seed removal, seed dispersers, and the allocation of tissues in Myrtaceae seeds
<p><span>To avoid seed predation, plants may invest in protective seed tissues. Often related to seed size, allocation in seeds' physical defenses can also be influenced by dispersers. We explore the relationships between seed traits (seed mass and hardness) and seed removal in 22 Myrtaceae species of the Brazilian Atlantic Forest, a dominant and diverse fleshy-fruited taxon dispersed by birds, rodents, and other mammals. Our goal is to understand how seed traits influence seed removal rates, and whether dispersers can affect tissue allocation in the seed coat. Seeds were exposed to field removal experiments. In the lab, total seed mass and seed coat mass were obtained. To evaluate the influence of seed traits on removal, we performed Kruskal-Wallis and Simple Linear Regression tests. We assessed seed coat and seed mass covariation through standardized major-axis allometric regressions. Harder seeds were larger than softer ones. Seed traits affect removal rates, as tougher and heavier seeds had lower removal. Seed mass significantly predicts seed coat proportion in seven of the 14 species tested. Bird-dispersed species tend to exhibit lower proportions of seed coat as seed mass increases, whereas rodent-dispersed species apparently present the opposite trend, with seed coat proportion increasing with seed mass. Such difference may be caused by the contrasting seed predation pressure represented by birds and rodents. Energy allocation for defense, expressed in seed coat proportion, is greater in large seeds, as these are mostly dispersed by rodents whose propensity to cache and disperse seeds is greater for large and well-protected seeds.</span></p>
Density dependence of seed dispersal and fecundity profoundly alters the spread dynamics of plant populations
<ol> <li>Plant population spread has fundamental ecological and evolutionary importance. Both determinants of plant population spread, fecundity and dispersal, can be density-dependent, which should cause feedback between population densities and spread dynamics. Yet it is poorly understood how density-dependence affects key characteristics of spread: spread rate at which the location of the furthest forward individual moves, edge depth (the geographical area over which individuals contribute to spread) and population continuity (occupancy of the spreading population).</li> <li>We present a general modelling framework for analysing the effects of density-dependent fecundity and dispersal on population spread and parameterize this framework with experimental data from a common-garden experiment using five wind-dispersed plant species grown at different densities. </li> <li>Our model shows that density-dependent fecundity and dispersal strongly affect all three population spread characteristics for both exponential and lognormal dispersal kernels. Spread rate and edge depth are strongly correlated but show weaker correlations with population continuity. Positive density-dependence of fecundity increases all three spread characteristics. Increasingly positive density-dependence of dispersal increases spread rate and edge depth but generally decreases population continuity. Density-dependent fecundity and dispersal are largely additive in their effect on spread characteristics. For population continuity, the joint effects of density-dependent fecundity and dispersal are somewhat contingent on the dispersal kernel.</li> <li>The common-garden experiment and the experimentally parameterized mechanistic dispersal model revealed density-dependent fecundity and dispersal across study species. All study species exhibited negative density-dependent fecundity, but they differed qualitatively in the density-dependence of dispersal distance and probability of long-distance dispersal. The negative density-dependence of fecundity and dispersal found for three species reinforced each other in reducing spread rate and edge depth. The positively density-dependent dispersal found for two species markedly increased spread rate and edge depth. Population continuity was hardly affected by population density in all study species except Crepis sancta in which it was strongly reduced by negatively density-dependent fecundity.</li> <li> <em>Synthesis</em>. Density-dependent fecundity and seed dispersal profoundly alter population spread. In particular, positively density-dependent dispersal should promote the spread and genetic diversity of plant populations migrating under climate change but also complicate the control of invasive species.</li> </ol>
From seed dispersal service to reproductive collapse: density-dependent outcome of a palm-mammal interaction
<p>Interspecific ecological interactions are inherently context-dependent. They may vary in both magnitude and sign depending on the biotic and abiotic conditions, depicting a mutualism-antagonism continuum. However, how population abundances and the activity of interacting species modulate these interactions remains underexplored. Here, we chose the interaction between the Mediterranean palm <em>Chamaerops</em> <em>humilis</em> and the feral goat <em>Capra</em> <em>hircus</em> in Mallorca (Balearic Islands, Spain). We selected three study plots with low, intermediate and high intensities of goat activity where we characterized palm distribution, seed rain, seed predation, and early palm recruitment during two consecutive years. Since goats can cause both costs (e.g. florivory) and benefits (e.g. seed dispersal) to <em>C. humilis</em> performance, we investigated the following three questions: (1) Does the spatial distribution of adult palms vary depending on the intensity of goat activity? (2) Does the intensity of goat activity influence seed rain and its potential spatial association with adult palms? (3) To what extent does the intensity of goat activity determine post-dispersal events such as seed predation and seedling emergence? We found that adult palms showed a more clumped and complex distribution (double-cluster process) in plots with low and intermediate goat activity compared to that with high goat activity (simple-cluster process). In the low goat activity plot, dispersed seeds were spatially aggregated around adult palms, showing twice insect-seed predation and nearly three times lower seed germination success than those in the intermediate goat activity plot. Palm seed dispersal and recruitment were almost nil in the high goat activity plot due to heavy consumption of palm inflorescences and developing fruits by goats. Our findings demonstrate how the net outcome of plant-animal interactions can change from mutualism to antagonism, from reproductive service to reproductive collapse, depending on the abundance and the activity of the interacting species.</p>
Haemanthus deformis seed dispersal data
<p>Most plants with fleshy fruits have seeds that are ingested by animals, but a less well-understood mode of seed dispersal involves fleshy fruits containing seeds that are discarded by frugivorous animals because they are too large or toxic to be ingested. We studied the seed dispersal biology of <em>Haemanthus</em> <em>deformis</em>, an amaryllid lily species found in a mosaic of bush clumps in a grassland matrix in South Africa. We asked whether seed dispersal is directed in and among bush clumps and whether germination and survival are greater for seeds dispersed to bush clumps than to those dispersed into grassland. Using camera trapping, we found that fruits are consumed mainly by birds and rodents. The pulp was removed from the seeds which were then discarded without ingestion. Whilst many seeds were dispersed close to the parent plant, most (c. 78.5%) were dispersed further than one meter away from the parent plant. Longer distance dispersal resulted mainly from birds flying off with seeds in their bill or from rodents engaging in scatter-hoarding behaviour. Seedling survival was most successful within bush clumps as compared to grasslands and shade was identified as a primary requirement for seedling survival. Seeds from which the fruit pulp had been removed germinated faster than those in intact fruits. <em>Haemanthus</em> <em>deformis</em> deploys a system of directed seed dispersal, whereby both birds and rodents contribute to dispersal of seeds within patchy bush clumps that are favourable for seedling survival.</p>
Data from: Non-native mammals are weak candidates to substitute ecological function of native avian seed-dispersers in an island ecosystem
<p>Although prominent examples exist of non-native species causing substantial ecological harm, many have neutral or positive effects, including filling surrogate roles once performed by extinct native organisms. We tested the ecological roles of two non-native mammals as seed dispersers or seed predators in Guåhan, which, due to invasive brown treesnakes (<em>Boiga</em> <em>irregularis</em>), is devoid of native seed dispersers – birds and bats. We conducted feeding trials with captive rats (<em>Rattus</em> spp.), which are present but uncommon due to predation by snakes, and pigs (<em>Sus</em> <em>scrofa</em>), which are abundant. We examined if and how they interacted with common forest fruits. We then compared how any gut-passed or handled seeds germinated compared to seeds left in whole fruit or depulped seeds.</p> <p>Rats and pigs interacted with most of the fruits and seeds (>80%) that they were fed. Of those, most seeds were destroyed – 78% for rats and 90% for pigs, across both native and non-native plant species. Compared to seeds germinating within whole fruits, rats improved germination of the seeds that they handled without ingesting, while pigs diminished the germination of seeds that they handled. The small percentage of seeds (approximately 1.5% for rats and 5% for pigs) that survived gut passage germinated in higher proportions than those in whole fruits. Percentages of seed survival to germination are lower than those found in similar studies with native avian frugivores. Our results indicate that pigs and rats have mixed effects on seeds, but are not suitable surrogates for native seed dispersers.</p>
Gulls contribute to olive seed dispersal within and among islands in a Mediterranean coastal area
<p><strong>Aim: </strong>To analyse the role of non-frugivorous birds on seed dispersal, seed dispersal by gulls is expected to be especially instrumental in island ecosystems, as these have a smaller subset of frugivores when compared to the mainland, and because long-distance dispersal is required for plant colonization. Here we investigated the seed dispersal of olives by gulls among ten islands of the same archipelago to reveal if gulls contribute to long-distance seed dispersal including different islands, and how gulls' adaptation to domestic olives and individual differences in foraging activities affect their seed dispersal pattern.</p> <p><strong>Location: </strong>Balearic Islands in the Western Mediterranean Sea, Spain</p> <p><strong>Taxon:</strong> Yellow-legged gulls ( <em>Larus michahellis</em>), Domestic and wild Olives ( <em>Olea europaea</em> and <em>O. europaea var.</em> <em>sylvestris</em>)</p> <p><strong>Methods</strong>: We developed seed dispersal models of the two ecotypes of olives dispersed by gulls across an archipelago, based on GPS tracking data, gut passage time, and seed viability.</p> <p><strong>Results</strong>: Mean dispersal distances were 7.67 (±12.48) km in wild and 12.57 (±13.08) km in domestic olives. Seven-point one percent of wild and 8.5% of domestic olives were dispersed among islands. Among these, 8.2% of domestic seeds were transported from large to small islands where gull colonies are located, whereas wild olives were dispersed in more variable directions. Such dispersal pattern of two olive ecotypes were consistent despite the differences in dispersal distances among individuals.</p> <p><strong>Main conclusions:</strong> Gulls contributed to long-distance olive seed dispersal including different islands. The seed dispersal of domestic olives to longer distances with specific directions may facilitate colonization and expansion of that variant if the conditions of seed deposition sites are suitable. Our findings indicate that gulls are relevant vectors for long-distance dispersal of large fleshy fruits in island ecosystems where specialist large frugivores are absent.</p>
Dataset: Limited seed dispersal, allelopathy and unfavorable microclimatic conditions prevent the recovery of oak forests within Eucalyptus plantations
<p>This repository contains the files associated with the following article:</p> <p>Ernesto I. Badano, Pablo Siller-Clavel. Limited seed dispersal, allelopathy and unfavorable microclimatic conditions prevent the recovery of oak forests within <em>Eucalyptus</em> plantations. Published in <em>European Journal of Forest Research</em>.</p> <p>The repository provides an interactive map, optimized for Google Earth, that shows the administrative area of the Park Lázaro Cárdenas del Rio located in the state of Puebla, Mexico (yellow polygon) and the areas covered by plantations of <em>Eucalyptus camaldulensis</em> (red polygons) by the years in which the study was conducted (2009-2011). The areas that are not highlighted within the park correspond to oak forest remnants and some deforested areas. The interactive map also provides the geographic coordinates of the 100 square plots of 1x1 m used to sample the oak seed banks within forest remnants and plantations in 2009 and 2010, as well as the geographic coordinates of the 200 experimental plots located in each of these habitat types. To display this information, click on the corresponding the boxes located in the lateral bar of Google Earth.</p> <p>The data that support the result of the study are provided in Microsoft Excel files. The first of these files (Dataset 01 - Acorn density.xlsx) has a single sheet indicating the number of acorns recorded on 100 square plots of 1x1 m randomly distributed in the understories of forest remnants and plantations. The second file (Dataset 02 - Acorn germination trials.xlsx) has two sheets with the data used to estimate acorn germination rates of <em>Quercus castanea</em> and <em>Quercus laeta</em> in the <em>in vitro</em> and greenhouse germination trials. The third file (Dataset 03 - Field experiment.xlsx) has two sheets, where the first one contains the data used to estimate acorn germination rates and seedling survival of <em>Quercus castanea</em> and <em>Quercus laeta</em> on soil of <em>Eucalyptus</em> plantations and oak forests in these two habitats, and the second one contains the microclimatic data (photosynthetic photon flux density, air temperature, rainfall and volumetric soil water content) measured in plantations and forests.</p>
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