Post-dispersal Seed Predation Research Articles

Temperature influences postdispersal predation of weed seeds

Temperature is a key factor for the living organisms on earth. It influences weed management practices, either directly or indirectly. Field experiments were conducted to determine the effect of temperature on the postdispersal seed predation of four important weed species (Cuscuta compestris, Stellaria media, Taraxacum officinale and Veronica persica) in two lucerne fields in Mashhad and Chenaran, north‐eastern Iran. These two cities have the same climate: temperate and cold alpine but the temperature varies between them. Wire mesh cages were used to determine the relative importance of birds in predation and pitfall traps were used to detect the species and the activity density of invertebrate predators. The results showed that the predation preference of different weed species was significantly different between and within fields. Seed predation fluctuated widely throughout the sampling periods, matching the periodic forage harvest and regrowth cycle of lucerne. Despite the level of seed predation fluctuating, it declined toward the last sampling periods. Using wire mesh exclusion cages showed no significant effect of birds on weed seed predation in both fields. Ants, crickets and carabid beetles were the invertebrate seed predators that were caught in the pitfall traps. There were significant correlations between the mean temperature and predator activity densities and also between the predated seeds and the mean air temperature in both locations. The results of this study indicate the significant effect of temperature on postdispersal weed seed predation. Therefore, with respect to climate change and increasing global warming, it would be possible to focus on postdispersal seed predation in weed management in the future.

Post-Dispersal Seed Predation Rates in a Puerto Rican Pasture

The dispersal and survival of seeds are two of the main factors limiting forest regeneration in tropical pastures of anthropogenic origin. Here we report on the quantity, diversity, and predation rates of seeds dispersed by birds in a pasture in northern Puerto Rico. From May through August of 2009, we sampled the bird-generated seed rain under isolated trees and shrubs in the pasture using seed traps. The pasture was adjacent to a fragment of secondary forest that served as the source of seeds. The seed traps collected 3,844 seeds (including pieces) belonging to 28 plant species, with five species accounting for 78.6 percent of the sample. Predation of seeds —calculated as the ratio of seed fragments to intact seeds- was detected in eleven plant species, with some species suffering significantly higher predation rates than others. For example, seeds of Cissampelos pereira and Casearia Sylvestris experienced low predation (<0.3), while the majority of seeds from Cordia polycephala and Erythroxylon brevipes where predated (>0.6). Predation rates where in an inverse relationship with the density of seed deposition and with seed size across species. The physical evidence on the seed traps (i.e., seed coat fragments, fecal samples) points to rodents as the main agents of seed predation. We conclude that post-dispersal seed predation by rodents can serve as an important ecological filter that could shape the early community dynamics of forest recovery in abandoned Puerto Rican pastures.

Post-Dispersal Seed Predation, Germination, and Seedling Survival of Five Rare Florida Scrub Species in Intact and Degraded Habitats

Abstract Knowledge of seed ecology is important for the restoration of ecosystems degraded by anthropogenic activities. Current efforts to preserve and reintroduce populations of plant species endemic to Florida are hindered by a lack of information on demographic responses to human alteration. Comparisons of seed removal, germination, and establishment in both intact and degraded habitats will aid in management decisions for species in need of protection. Our objectives were to assess the impact of post-dispersal seed predation on plant populations in degraded and intact habitats, and to investigate the effects of habitat and microsite on seed germination and establishment. For five rare Florida scrub species with different seed sizes (Liatris ohlingerae, Eryngium cuneifolium, Polygonella basiramia, Hypericum cumulicola, Paronychia chartacea subsp. chartacea), we conducted a seed removal experiment with seeds exposed to insects and vertebrates, and to insects only, with a no-access control. We also plant...

Post-dispersal predation of weed seeds in rice fields

Summary: Post-dispersal weed seed predation can cause a substantial reduction in the number of weed seeds entering the seed bank and, as a consequence, reduce the number of weeds growing in subsequent seasons. Investigations on seed predation on four tropical rice fields in the Philippines were conducted to determine (i) the magnitude of post-dispersal seed predation after rice harvest, (ii) whether vertebrates or invertebrates are the main seed predators, (iii) whether seed predation is affected by crop residue, (iv) whether seed predation is affected by proximity to the field edge, and (v) whether predation differs among seeds of the grasses Digitaria ciliaris, Echinochloa colona and Eleusine indica. Seed removal rate over a 14-day period ranged from 78% to 91% among fields, was slightly higher in the interior of the fields (89%) than in the field margins (85%) and slightly higher without residue cover (89%) than with (86%). Selective exclosures indicated that invertebrates, presumed to be mainly fire ants (Solenopsis geminata), were the main seed predators (96%) and vertebrates, presumed to be mainly rodents, secondary predators (38%). Seed removal of D. ciliaris was higher (93%) than of E. indica (88%) and E. colona (75%). Results suggest substantial seed predation could contribute to ecologically-based weed management in rice. Further studies are required to determine season-long seed predation rates and to confirm the identity of the predators involved. Ways to integrate these seed predators into prevailing cropping practices need to be developed. © 2010 International Rice Research Institute. Weed Research

The Fate of Seeds Dispersed by Golden Lion Tamarins (Leontopithecus Rosalia) in an Atlantic Forest Fragment, Brazil

Frugivores, as seed dispersers may influence the spatial patterns of adult and juvenile plants, but a large portion of the potential recruitment of plant populations is lost to seed predators. The majority of seeds dispersed by primates are killed by seed predators or moved by secondary dispersers. Little is known about post-dispersal seed-predation and seedling distribution of exploited plant species. This study iinvestigated the survival and establishment of seedlings from seeds defecated by the golden lion tamarin ( Leontopithecus rosalia), a frugivorous endemic primate of the Atlantic Forest of Brazil. Two groups of golden lion tamarins were studied in the União Biological Reserve from April 2003 to March 2004. Seeds from fruits consumed by tamarins and collected from their feces were evaluated with respect to the following: germination success, seed disappearance or secondary dispersal on the forest floor, seed predation, and seedling establishment and survival for the length of the study period. The tamarin groups consumed 88 fruit species. Of these, 38 were used to run 107 experiments which indicated that more than 50% of the seeds disappeared, about 15% died before germinating and seeds of 22 species reached the seedling stage. At the end of the study, only 15 of these species still had surviving seedlings. Studies on seed fate are important for understanding the role of the golden lion tamarind in the natural process of forest regeneration in the lowland Atlantic Forest of the state of Rio de Janeiro in Brazil.

Consistent pattern of habitat and species selection by post-dispersal seed predators in a Mediterranean mosaic landscape

There is still little information on effects of habitat degradation on post-dispersal seed predation at the landscape scale. The aim of this study was to determine the influence of habitat degradation and seed species on the variability of post-dispersal seed-predation rate. Experimental seed removal was investigated in six Mediterranean woody plant species, four trees (Pinus sylvestris, Quercus ilex, Acer opalus ssp. granatense, and Sorbus aria) and two shrubs (Berberis vulgaris and Crataegus monogyna), in an extensively used mosaic landscape on the Sierra Nevada massif (SE Spain). Seed depots were distributed over 2 years in five differently degraded landscape units, each one with three plots: shrubland; native forest; and dense, cleared and fenced reforestation stands. Predation was the highest in native forest, shrubland, and fenced reforestation, and the lowest in dense and cleared reforestation stands, being partially due to a positive correlation between shrub cover and post-dispersal seed predation. However, the main factors driving post-dispersal seed predation were intrinsic to seeds, as species preference explained most of the variance in our model for predation. The plant-species ranking was Quercus > Pinus > Sorbus > Berberis > Acer > Crataegus, the dominant tree species being the most depredated. These findings are novel because they suggest for the first time that species-selection patterns by post-dispersal seed predators tended to remain constant through both study years in all habitats comprising a mosaic landscape, whether native forest, reforestation stands or successional shrubland.

The Effect of Dung and Dispersal on Postdispersal Seed Predation of Attalea phalerata (Arecaceae) by Bruchid Beetles1

ABSTRACTLow postdispersal mortality of palm seeds in tapir dung is hypothesized to result from the mechanical barrier provided by dung against bruchid infestation and/or from the distance to adult palms at which seeds are dispersed. We tested these hypotheses by distributing endocarps of Attalea phalerata Mart. ex Spreng. in experimental dung piles in Beni, Bolivia. Predation rates were significantly lower for seeds covered by dung than for exposed or partially covered seeds, but did not differ between seeds placed below and 50 m away from palms. Thus, dung, not short‐distance dispersal, protects seeds against bruchid beetles, and may ultimately promote survival of palm seeds.

A Multi-species Assessment of Post-dispersal Seed Predation in the Central Chilean Andes

Post-dispersal seed predation in alpine communities has received little attention despite evidence that seeds removed by granivores can decrease plant recruitment into ecosystems. Moreover, few studies have assessed the effects of removal of seeds of a range of species after dispersal on the seeds remaining in ecosystems. A comparison was made of the magnitude of seed removal by ants and birds of nine different shrubby-, herbaceous- and cushion-plant species in the central Chilean Andes in order to assess the interactions between birds, ants and wind, and the types of seeds. A total of 324 soil-covered plates, each containing 50 seeds of one species, were placed in the field at an altitude of 2700 m and assigned to one of four treatments: control, exclusion of ants, birds, and both. The design also allowed the effects of wind to be assessed. Seed removal from plates was monitored over 20 d. Mean accumulative seed removal by granivores averaged over all nine species combined was 25%. However, large differences between species were evident, with limited seed removal (3-11%) in three herbaceous species (Alstroemeria pallida, Sisyrinchium arenarium, Pozoa coriacea), moderate (18-33%) in five species, including a shrub (Chuquiraga oppositifolia), two herbs (Taraxacum officinale, Rhodophiala rhodolirion), and two cushion-plants (Laretia acaulis, Azorella monantha), and substantial (78%) in the shrub Anarthrophyllum cumingii. The magnitudes of losses caused by birds compared with ants did not differ for the majority of species, although removal by birds was greater than by ants in A. cumingii, and smaller for C. oppositifolia. Post-dispersal seed removal is shown to be an important cause of decreased potential plant species recruitment into alpine ecosystems. The substantial differences in the magnitude of seed losses to ants and birds demonstrate the need for evaluation of seed removal on a wide range of species in any given ecosystem.

Effects of Species, Density, Patch‐type, and Season on Post‐dispersal Seed Predation in a Puerto Rican Pasture1

ABSTRACTAn experimental study of seed removal of four woody species in an abandoned pasture revealed significant main effects of species, density (higher densities survived more than lower densities), and patch‐type (seeds under shrub patches survived more than in grass patches), but no effects of season. Rates of seed loss decreased with seed size across species. Significant interactions between species and density and between species and patch‐type were also observed.

Cropping system effects on giant foxtail (Setaria faberi) demography: I. Green manure and tillage timing

Manipulation of cropping systems to improve weed management requires a better understanding of how crop- and soil-related factors affect weed life cycles. Our objective was to assess the impacts of timing of primary tillage and use of legume green manure on giant foxtail demography and soil properties. We measured giant foxtail seed survival and dormancy, seedling emergence and survival, and fecundity, in addition to soil phytotoxicity, chemical properties affecting soil fertility and soil water, in the transition between the wheat and corn phases of a wheat–corn–soybean crop sequence. Postdispersal predation of giant foxtail seeds was measured in all three phases of the crop sequence. Wheat was grown either as a sole crop (W) or underseeded with red clover (R), and residues from this phase were rototilled either in the fall (FT) or in spring (ST). There were strong interactions between Red clover and Tillage timing in their effects on giant foxtail recruitment and fecundity in corn. Giant foxtail seedling emergence was 30% lower, and time to 50% emergence was more than 1 wk later, in the ST/R treatment than in the ST/W, FT/W, and FT/R treatments, which did not differ. However, fecundity of giant foxtail was 200% greater in the ST/R treatment than in the other three treatments because of suppressed early corn growth. The net effect of the ST/R treatment on giant foxtail demography in corn was to greatly increase inputs to the seedbank compared with the ST/W, FT/W, and FT/R treatments. Giant foxtail demography in the wheat phase was also affected by Red clover. There was a 200% increase in daily rates of postdispersal seed predation in the wheat phase of the R treatment compared with the W treatment. High-seed predation in the wheat phase and low fecundity in the corn phase of the FT/R treatment suggest that population growth rate of giant foxtail will be lower in this treatment than in the other treatments. The degree of soil phytotoxicity from red clover residues, the changes in the amount of interference from the corn crop early in the growing season, and the differential suitability of crop residues in the different rotations as habitat for seed predators all contributed to changes in giant foxtail demography. Understanding the effects of cropping system characteristics on entire weed life cycles will facilitate the design of integrated suites of complementary weed management tactics.

Effects of Species, Density, Patch-type, and Season on Post-dispersal Seed Predation in a Puerto Rican Pasture1

An experimental study of seed removal of four woody species in an abandoned pasture revealed significant main effects of species, density (higher densities survived more than lower densities), and patch-type (seeds under shrub patches survived more than in grass patches), but no effects of season. Rates of seed loss decreased with seed size across species. Significant interactions between species and density and between species and patch-type were also observed.

Fruit removal, pyrene dispersal, post-dispersal predation and seedling establishment of a bird-dispersed tree

The recruitment of a dioecious bird-dispersed tree, the hollyIlex aquifolium (Aquifoliaceae), was studied consideringthe stages of fruit removal by birds, seed rain, post-dispersal seed predation,seed germination and seedling survival. The main objective was to test theeffect of different microhabitats within a beech forest on recruitment stages.Migrant thrushes were the main dispersers of this tree whose fruit crops wereentirely removed during two study years. Seed rain was greatest beneath hollytrees regardless of their sex and lowest in the open sites. Post-dispersal seedpredation was examined by two experiments and did not differ betweenmicrohabitats despite its quantitative importance (about 70%). Seedlingemergence, which probably corresponded to seeds from several cohorts, wasgreater beneath trees than in open sites and the density of second-yr to 5cm seedlings depended on the presence-absence of ungulateherbivores and litter. While the former had a detrimental effect, the latterhada beneficial effect on seedling abundance. Seedling survival showed nosignificant variations between microhabitats but depended on seedling densityinsome microhabitats (holly, beech). Finally, the initial seed arrival seemed todetermine microhabitat suitability for holly seedling establishment. However,under heavy browsing the density of seedlings may be strongly reduced leadingtomicrohabitat homogeneity for holly seedling establishment.

Pre- and post-dispersal seed predation in a mediterranean-type climate montane sclerophyllous forest in central Chile

Most seed-predation studies have evaluated pre- or post-dispersal predation separately, in one or a few species. Assessments of the overall importance of pre- v. post-dispersal seed predation at the community level are generally lacking. Here, we quantify levels of pre and post-dispersal seed predation in &gt;25 plant species in a mediterranean-type climate montane forest in central Chile in two periods of study (1995–1996 and 1997–1998). Almost all species analysed suffered at least some seed losses to pre-dispersal and/or post-dispersal seed predation. However, among species, magnitudes of both pre- and post-dispersal seed predation proved highly variable, ranging between 0 and 100% and exceeding 50% in five and nine species, respectively. High inter-annual variability in both pre- and post-dispersal seed predation, at both the species and overall community levels, was observed, with only a small number of species suffering large losses during both periods of study. At the overall community level, percentage seed losses to pre-dispersal predation were not significantly different from those experienced in the postdispersal phase. Rodents were the most important seed removers in seven species. However, the three groups of granivores analysed (rodents, birds and insects) were similar in their importance as post-dispersal predators in most plant species. Groups of species suffering similar levels of seed losses to pre- or post-dispersal predators did not share any particular seed characteristics, suggesting that differences in the seed traits studied seem to be relatively unimportant in determining variation in seed predation.

Variation in Post‐dispersal Seed Predation in Mature Peruvian Lowland Tropical Forest and Fallow Agricultural Sites1

ABSTRACTVariation in post‐dispersal seed predation between mature forest and fallow swidden agriculture sites (young forest) was examined for 26 tree and liana species in Peruvian lowland tropical forest. Exclosures were also used to determine the relative importance of vertebrate and invertebrate seed predators. Although species differed significantly in levels of predation, predation of seeds exposed to vertebrates was high (&gt;75%) for all species, while seed predation by invertebrates was lower and more variable. Seed and seedling predation by insects was significantly higher in mature forest, while seed predation by rodents was higher in fallow areas. Other sources of mortality (primarily desiccation) were higher for seeds in fallow areas. The percentage of seeds moved was significantly different among species but not between forests.RESUMESLa variación en depredación de semillas, después de dispersadas, se examinó en el bosque maduro y la purma (áreas de agricultura en sucesión) para 26 especies de árboles y lianas en un bosque tropical de bajura en Perú. Se utilizaron tratamientos de exclusión para determinar la importancia relativa de depredadores de semillas vertebrados e inverte‐brados. Aunque las especies difirieron significativamente en niveles de depredación, la depredación de las semillas expuestas a vertebrados fue alta (&gt;75%) para todas las especies, mientras que la depredación de semillas por inver‐tebrados fue más baja y más variable. La depredación de semillas y plántulas por insectos fue significativamente mas alta en el bosque maduro, mientras que la depredación de semillas por roedores fue más alta en purmas. Otras causas de mortalidad (principalmente desecación) fueron más comunes en las purmas. El porcentaje de semillas movidas difirió significativamente entre especies pero no entre los dos tipos de bosque.

Variation in Post-dispersal Seed Predation in Mature Peruvian Lowland Tropical Forest and Fallow Agricultural Sites1

Variation in post-dispersal seed predation between mature forest and fallow swidden agriculture sites (young forest) was examined for 26 tree and liana species in Peruvian lowland tropical forest. Exclosures were also used to determine the relative importance of vertebrate and invertebrate seed predators. Although species differed significantly in levels of predation, predation of seeds exposed to vertebrates was high (>75%) for all species, while seed predation by invertebrates was lower and more variable. Seed and seedling predation by insects was significantly higher in mature forest, while seed predation by rodents was higher in fallow areas. Other sources of mortality (primarily desiccation) were higher for seeds in fallow areas. The percentage of seeds moved was significantly different among species but not between forests.

An Assessment of Post-Dispersal Seed Predation in Temperate Rain Forest Fragments in Chiloe Island, Chile

Seeds of seven tree species, six shrub species, and one epiphyte were tested for their rates of removal by seed predators in two remnant patches (15-20 ha) of old-growth temperate forest in Chilo6 Island, southern Chile (42?30'S). Field assays were aimed at assessing the rates of post-dispersal seed consumption, mainly by rodents and understory birds. Assays were conducted in summer and early fall of 1996 and 1997. We investigated whether seed consumption differed among habitats, between seasons and among species differing in seed mass and abundance in the canopy of remnant patches. Trays containing 20 seeds each, 6-8 replicate trays per species and habitat, were placed in the forest floor in each of three habitats: forest edges adjacent to pastures, forest interior (100 m away from any edge), and inside canopy gaps formed by tree falls. Overall, 7-65% of the seeds in experimental trays were removed by predators from 43 to 93% of all the trays within five days. Removal rates increased from mid-summer to early fall, presumably as a result of increasing density of birds and rodents. When seed removal rates differed among habitats, more seeds were taken from trays placed in forest interior than under canopy gaps. Forest margins had intermediate rates of seed removal. Marked differences in seed removal rates observed among species were unrelated to seed mass or plant species abundance. We conclude that season and habitat are the most important variables determining the intensity of seed predation in forest fragments. Seed predation rates recorded in five-day assays suggest that the regeneration of woody species, particularly in forest interior, may be affected by post-dispersal seed consumption by vertebrates.

Influence of tillage and crop residue on postdispersal predation of weed seeds

Field experiments were conducted from 1995 to 1997 in southern Ontario to determine the influence of tillage and ground cover on the quantity of postdispersal seed predation of common lambsquarters and barnyardgrass. Ground-dwelling invertebrates were the dominant seed predators and were responsible for 80 to 90% of all seeds consumed. Predation was highest in no-till and moldboard-plowed environments (averaging 32% in both) and lowest in chisel-plowed environments (averaging 24%). This indicates that the relationship between the level of disturbance and predation is nonlinear and that other factors, such as the mobility of invertebrates and food availability, may also play important roles in determining the quantity of seed predation. In no-till, the type of crop residue also influenced the quantity of predation, with highest seed predation found in plots with corn residue (averaging 31%) and lowest in those with soybean and wheat residue (24 and 21%, respectively). It is apparent that there is an optimum combination of residue quantity and quality that maximizes the quantity of seed predation. Based on the experimental design used in this study, no feeding preference by seed predators was detected between common lambsquarters and barnyardgrass. Density-dependent feeding, however, was evident for both species. Most biological control efforts have centered around predators with specific feeding habits. We contend that invertebrates with opportunistic feeding strategies that feed on weed seeds may be the most significant broad spectrum and natural form of biological weed control affecting weed population dynamics. Populations of beneficial arthropods should be conserved, and management strategies that augment the size of their natural populations should be encouraged.

Differential Postdispersal Seed Predation in Disturbed and Intact Temperate Forest

Differential Postdispersal Seed Predation in Disturbed and Intact Temperate Forest

Factors Limiting the Recruitment of Eucalyptus salmonophloia in Remnant Woodlands .II. Postdispersal Seed Predation and Soil Seed Reserves

This study examined post-dispersal seed predation and soil seed reserves in four remnant populations of E. salmonophloia in the central wheatbelt of Western Australia to determine the effect of these factors on recruitment. Diurnal observations of post-dispersal seed predation at regular intervals of 2 months were undertaken over a 12 month period using artificial baits. Four species of ants were seen removing seeds from artificial baits regularly. Surveys of soil seed reserves revealed that E. salmonophloia does not form a soil seed bank despite a continual seed rain from canopy seed reserves. These observations suggest that ants probably destroy a large proportion of E. salmonophloia seed following dispersal. Burial of E. salmonophloia seeds in the soil in autumn, winter, spring and summer suggest that any seeds which do escape predation are unlikely to persist in the soil for much longer than 12 months and probably germinate with the onset of winter rains. Both the depredation of seeds by ants and the short term viability of seed in the soil contribute to the inability of E. salmonophloia to form a soil seed reserve.

Post-Dispersal Seed Predation in Grassland: Its Magnitude and Sources of Variation

1 Post-dispersal seed predation by rodents and invertebrates, was studied in two grassland sites in Berkshire, UK. The influence of season, seed density, seed burial, seed species, as well as withinand between-habitat variation on the removal of nineteen species of herbaceous seeds was investigated using exclosure experiments. 2 Analysis examined two components of seed predation: seed encounter (the probability of at least one seed being removed) and seed exploitation (the proportion of seeds removed once encountered). Seed removal was greatest from treatments to which rodents had access, losses attributable to invertebrates were negligible. 3 Burial reduced rodent encounter at both seed densities used and explained almost 21% of the variation, while having only a limited effect on the proportion of seeds exploited. Burial increased the variation in encounter attributable to the other sources examined and altered the direction of habitat, season and species effects. Interpretation of surface seed predation data to details of plant recruitment for seeds which form buried seed banks should be undertaken with caution. 4 Examination of rodent seed removal patterns revealed that on average 14% of the variation in both seed encounter and exploitation was attributable to small-scale spatial differences within habitats related to the distribution of small mammals. 5 No significant between site variation was found for encounter (<2%) while seed density effects accounted for approximately 1 % of the variation. Single seeds were encountered less than half as frequently as seeds in groups of 10. Density-dependence varied with seed size, with predation of large seeds less influenced by a reduction in seed density. 6 No significant species variation was found for seed encounter (species means ranged from 50 to 60%). In contrast, species effects for seed exploitation were significant and species means ranged from 20 to 95%.