The Effects of Habitat on Dispersal Patterns of an Invasive Thistle, Cynara Cardunculus

Dispersal of offspring is a critical step in the spread of invasive species, yet dispersal patterns are seldom well studied, inhibiting effective management and ecological understanding of invasions. Dispersal patterns can be affected by characteristics of the parent plant and by climatic or site characteristics, including community vegetation structure, but these factors have not been studied in the context of plant invasion processes. Cynara cardunculus (L.) is a polycarpic perennial thistle invasive in coastal grasslands in California that produces large numbers of wind-dispersed seeds. This study quantified and compared C. cardunculus dispersal patterns in an exotic grassland (vegetated site) and an agricultural field (non-vegetated site). Seed size variation in C. cardunculus was also quantified within inflorescences, between inflorescences, and between years of production, and compared across dispersal distances. Results indicate that dispersal distance increased dramatically from less than 20 m in the vegetated site to more than 40 m in the non-vegetated site. Plants producing fewer seeds produced heavier seeds and dispersal distance decreased over time, but seed size was not related to dispersal distance, which may serve to spread the risk to seeds or seedlings across the environment. C. cardunculus has great potential for dispersal in open areas such as agricultural fields or disturbed sites, but may be limited in highly structured natural communities. Management of C. cardunculus and other wind-dispersed plant invasions may be improved by prioritizing populations with open or disturbed areas downwind and minimizing the removal of vegetation during dispersal.     

Impact of Grazing on Individual Male Movement in Roesel's Bush-Cricket Metrioptera roeseli: One Possible Clue to Species Range Expansion

One aid to understanding species distribution patterns is to gather detailed information on individual movement behavior. To gather information on dispersal capabilities in Roesel's bush-cricket Metrioptera roeseli an individual-based study was carried out. In four areas with two different cattle grazing regimes 35 individuals were released and their movements recorded for a mean of 80 h. Bush-crickets in grazed areas moved significantly further between the censuses and more individuals in grazed areas moved >5 m from the release point. The further away an individual was from the release point, the more likely he was to continue moving away. There was also a positive correlation between distance from the release point and the step length of the individual. The movement pattern found may make it easier for the species to find and reach new favorable habitats and withstand the negative effects of fragmentation.     

Estimating human-mediated dispersal of seeds within an Australian protected area

Dispersal is critical step in plant invasions but there is limited information about human-mediated long distance seed dispersal, including in protected areas. Seed dispersal by hikers was quantified for five invasive species (the native Acaena novae-zelandiae, and the non-native weeds Rumex acetosella Anthoxanthum odoratum, Dactylis glomerata and Festuca rubra) in part of Australia’s Kosciuszko National Park. The proportion of seeds remaining attached to trousers and socks was quantified for replicated short (150 m) and long (5,000 m) distance walks. Functions were fitted for each dataset, and parameters compared among species and between trousers and socks. Dispersal data were combined with attachment rates and the number of people undertaking walks to estimate the total number of weed seeds that might be dispersed. The power exponential function gave the best fit for the majority of datasets, indicating that detachment probability decreased with distance. Seeds of all five species were more tightly attached to socks than trousers, with some seeds still present on socks at 5,000 m. Anthoxanthum and Acaena seeds were more tightly attached to clothing than the other species. Theoretically 1.9 million seeds could be dispersed on socks or 2.4 million seeds on trousers through a season but the actual numbers are likely to be much lower because of limited weed seed at the start of the walks. Because of differences in attachment and detachment rates, seeds from Acaena were more likely to be dispersed longer distances. Long distance human-mediated seed dispersal is potentially a major cause of spread of invasive weeds into protected areas that favours some invasive species over others.     

千岛湖岛屿社鼠的扩散特征

2009年7月—11月,2010年3月—11月对千岛湖两个岛屿上的社鼠(Niviventer confucianus)种群进行标志重捕,通过分析扩散个体的性别、年龄及扩散距离等,探讨陆桥岛屿环境下社鼠的扩散特征。研究结果显示:岛屿环境下社鼠的扩散率为37.96%,不同季节社鼠的扩散率存在差异,社鼠倾向于在春季发生扩散,尤其是3月份,社鼠扩散个体数最多;对于整个捕获史而言,雌雄扩散个体数存在极显著的差异(x~2=12.542,df=1,P0.001),雄性个体更倾向于发生扩散;而在繁殖高峰期,当怀孕鼠存在时,雄性扩散数亦大于雌性,两者存在显著差异(x~2=4.504,df=1,P=0.034)。扩散个体体重的季节差异不显著;扩散与社鼠的年龄密切相关,社鼠更加倾向于在亚成年阶段发生扩散;另外,家群大小对社鼠扩散个体数量也有显著影响,家群越大,扩散个体越多;对扩散距离进行分析发现存在显著的性别差异(t=-9.229,df=50,P0.001),雌性个体的平均扩散距离为(282.97±16.14)m,显著大于雄性的(146.70±6.80)m,而扩散距离与年龄、体重、最大活动距离均无显著相关性。     

Seed dispersal by lizards on a continental‐shelf island: predicting interspecific variation in seed rain based on plant distribution and lizard movement patterns

Aim We estimated the patterns of seed deposition provided by the eyed lizard, Timon lepidus, and evaluated whether these patterns can be generalized across plant species with different traits (fruit and seed size) and spatial distributions. Location Monteagudo Island, Atlantic Islands National Park (north‐western Spain). Methods We radio‐tracked seven lizards for 14 days and estimated their home ranges using fixed kernels. We also geo‐referenced all fruit‐bearing individuals of four plant species dispersed by eyed lizards in the study area (Corema album, Osyris alba, Rubus ulmifolius and Tamus communis), measured the passage time of their seeds through the lizard gut, and estimated seed predation in four habitats (bare sand, grassland, shrub and gorse). Seed dispersal kernels were estimated using a combination of these data and were combined with seed predation probability maps to incorporate post‐dispersal seed fate (‘seed survival kernels’). Results Median seed gut‐passage times were around 52–98 h, with maximum values up to 250 h. Lizards achieved maximum displacement in their home ranges within 24–48 h. Seed predation was high (80–100% of seeds in 2 months), particularly under Corema shrub and gorse. Seed dispersal kernels showed a common pattern, with two areas of preferential seed deposition, but the importance of these varied among plant species. Interspecific differences among dispersal kernels were strongly reduced by post‐dispersal seed predation; hence, seed survival kernels of the different plant species showed high auto‐ and pairwise‐correlations at small distances (< 50 m). As a result, survival to post‐dispersal seed predation increased with dispersal distance for O. alba and T. communis, but not for C. album. Main conclusions Seed dispersal by lizards was determined primarily by the interaction between the dispersers’ home ranges and the position of the fruit‐bearing plants. As a result, seed rain shared a common template, but showed considerable variation among species, determined by their specific spatial context. Seed predation increased the spatial coherence of the seed rain of the different species, but also resulted in contrasting relationships between seed survival and dispersal distance, which may be of importance for the demographic and evolutionary processes of the plants.     

Movement of Weed Seeds in Reclamation Areas

The presence or absence of obstructions can affect seed dispersal. Reclamation activities often cause changes in the type and amount of such obstructions. The consequences of removing obstructions on the dispersal of undesirable species are unknown. In western North America, reclamation may often proceed in areas surrounded by the invasive Bromus tectorum L. (cheatgrass). The importance of preventing cheatgrass seed dispersal from surrounding landscapes is an unknown factor in reducing cheatgrass competition in these areas. I quantified cheatgrass seed dispersal in the early stages of reclamation, when soils were bare. Four groups of 100 sterilized, fluorescently marked cheatgrass seeds were released in each of three areas in NW Colorado, USA. Seeds were located at night using blacklights four times over 14 days, and the distance between each seed and the point of release was measured. Across sites, dispersal distance averaged 2.4 m, 5% of seeds traveled further than 7.6 m, and maximum recorded distance was 20.8 m. Maximum distances reported in this study are 50‐fold higher than previously reported for intact sagebrush ecosystems. I suggest that the difference is due to a lack of impediments to secondary dispersal on bare soil. When reclamation areas are surrounded by weeds such as cheatgrass, seeds dispersing from the perimeter may influence restoration outcome.     

Small local population sizes and high habitat patch fidelity in a specialised solitary bee

Andrena hattorfiana is a rare solitary bee which has declined during the last decades throughout western Europe. It is specialised to forage pollen from plants of the family Dipsacaceae. Knowledge of distribution, dispersal propensity, and local population sizes is essential for successful conservation of A. hattorfiana. The investigated local bee populations (n = 78) were dominated by small local populations and 60% were smaller than 10 female individuals and 80% were smaller than 50 female individuals. The area of the median occupied habitat patch was 1.25 hectare and harboured 7 female bees. Mark-release-recapture studies of female A. hattorfiana revealed a sedentary behaviour. Among pollen-foraging female bees the average registered distance moved was 46 m. The patch emigration rate was about 2%, with an observed maximum colonization distance of 900 m. Only 10% of the individuals crossed areas without the pollen plant within grassland patches, such as unpaved roads, stone walls and small tree-stands, even if these areas were less than 10 m wide. This study shows that solitary bees can occur in local populations of extremely small size and they have a sedentary behaviour. These are features that usually increase the risk of local population extinction.     

Study design and mark-recapture estimates of dispersal: a case study with the endangered damselfly Coenagrion mercuriale

Accurate data on dispersal ability are vital to the understanding of how species are affected by fragmented landscapes. However, three factors may limit the ability of field studies to detect a representative sample of dispersal events: (1) the number of individuals monitored, (2) the area over which the study is conducted and (3) the time over which the study is conducted. Using sub-sampling of mark-release-recapture data from a study on the endangered damselfly Coenagrion mercuriale (Charpentier), we show that maximum dispersal distance is strongly related to the number of recaptured individuals in the mark-release-recapture study and the length of time over which the study is conducted. Median dispersal distance is only related significantly to the length of the study. Spatial extent is not associated with either dispersal measure in our analysis. Previously consideration has been given to the spatial scale of dispersal experiments but we demonstrated conclusively that temporal scale and the number of marked individuals also have the potential to affect the measurement of dispersal. Based on quadratic relationships between the maximum dispersal distance, recapture number and length of study, we conclude that a previous study was of sufficient scale to characterise the dispersal kernel of C. mercuriale. Our method of analysis could be used to ensure that the results of mark-release-recapture studies are independent of levels of spatial and temporal investment. Improved confidence in dispersal estimates will enable better management decisions to be made for endangered species.     

DISPERSAL AND POPULATION-GENETIC STRUCTURE OF THE COOPERATIVE SPIDER,AGELENA CONSOCIATA,IN WEST AFRICAN RAINFOREST

Dispersal experiments and gel electrophoresis of allozyme polymorphisms were used to investigate the selective mode underlying cooperative behavior in the rainforest spider, Agelena consociata. Previous work has indicated that individual selection alone does not explain the cooperative and even altruistic behavior noted for this African species, which exists in groups of up to hundreds of adults. We found no evidence for active dispersal by reproductives or any age class of this spider. Nest fragmentation by falling tree limbs and storms is indicated as the cause of new nest formation within local areas, while passive dispersal by vertebrate carriers that either have some association with the nests (bats) or move through them is indicated as the probable mode of longer-distance dispersal. The population-genetic structure observed for A. consociata supports the data obtained on dispersal. Wright's F_ST statistic and G tests for genetic heterogeneity indicate that the populations are subdivided into genetically heterogeneous colonies. Comparisons utilizing Nei's genetic distance show colonies separated by as few as 30 m to be as genetically distinct as are colonies separated by many kilometers. There is also a marked scarcity of heterozygotes, and individuals within nests and associated colonies are genetically related about as much as are full siblings. The results of these analyses indicate that kin selection or some type of family-group selection may have been important in the evolution of cooperative behavior in the species.     

Radio-Tracking Suggests High Dispersal Ability of the Great Capricorn Beetle (<Emphasis Type="Italic">Cerambyx cerdo</Emphasis>)

Dispersal ability is among the key factors affecting the survival of species in today’s fragmented landscapes. One of the most straightforward methods to provide direct measures of animal dispersal is telemetry. Despite its merits, this method has rarely been used for saproxylic beetles. In this study, we examined dispersal ability of the Great Capricorn beetle Cerambyx cerdo (Coleoptera: Cerambycidae), an endangered veteran oak specialist. Using a radio-tracking approach, we tracked 26 individuals (15 males and 11 females) equipped with transmitters for 4 to 17 days (median 14). We observed no disturbance of movements or flight problems due to the transmitter. The daily probability of movement by an individual was 64% and the longest displacement in one day was 1498 m for males and 1080 m for females. For 15% of all individuals, the tracking distance covered was >2200 m. Our results indicate that C. cerdo individuals often move among trees over an area of several kilometres. Such findings contrast with previous results based on a mark-recapture study. The relatively high mobility of the species should be reflected in strategies aiming at its conservation.     

Disjunct distribution of Hypericum nummularium L. (Hypericaceae): molecular data suggest bidirectional colonization from a single refugium rather than survival in distinct refugia

Hypericum nummularium has a strongly disjunct, bi‐areal distribution in Europe: it is abundant in the Pyrenees and grows in a very restricted part of the Alps, more than 1000 km away. My aim was to estimate the genetic divergence between these areas and to identify the factors responsible for the disjunction: glacial relicts, bidirectional colonization from a common refugium, long‐distance dispersal and/or human introduction? Internal transcribed spacers (ITS) sequencing (680 bp) and amplified fragment length polymorphism (AFLP) fingerprinting (104 polymorphic markers) showed very low differentiation between populations in the Alps and the Pyrenees, indicating that H. nummularium probably survived in a single refugium. Moreover, levels of genetic diversity were similar in the two areas, making human introduction and long‐distance dispersal unlikely. Thus, the species probably survived in one refugium, subsequently colonizing both areas more or less simultaneously. The comparison of genetic and geographical distances suggested a step by step migration in the Alps (isolation by distance), whereas random dispersal events were more likely in the Pyrenees. Finally, I discuss possible causes for the restricted distribution area of H. nummularium in the Alps (e.g. unsuitable habitat, low dispersal capacities) and conclude that strong human disturbance is probably the major limit to the expansion of the species in this region. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87 , 437–447.     

Long-term movements of self-marked caddisfly larvae (Trichoptera: Sericostomatidae) in a California coastal mountain stream

1. Over 140 000 larvae of the case-building caddisfly Gumaga nigricula were self-marked as they incorporated glitter into small portions of their cases while reared in streamside troughs. These marked individuals were released into stream pools and their movements monitored in the dry season, when base flow was low and no spates occurred, and in the wet season when base flow was high and several spates occurred. 2. Of the 9,000–10 000 larvae released in each of two stream pools in the dry season, 4–20% (i.e. 377–1817 marked individuals) were observed on three sampling dates (4, 11 and 24 d after release). Most larvae (87–93%) remained within 4 m up- or downstream of the release line after 24 d. No larvae were found outside of the release pools, even after 37 d. 3. Of the > 120 000 larvae released in one stream pool near the beginning of the wet season, 408 larvae were recaptured 130–167 d later, a period that included 30 days of high flow associated with six spates. Estimated survivorship over this period was 0.7–6.2%; there was no relationship between survival and larval size at release. Most (75%) recaptured larvae were found in the pool where they were originally released. The remaining larvae were found downstream of the release pool. Larvae had generally dispersed only a short distance downstream of the release pool (median = 18 m, maximum = 222 m). In addition, four marked pupae were later found 436 m downstream of the release pool. 4. These results illustrate the sedentary nature of larval G. nigricula as well as the important role that high flow events play in larval mortality and dispersal. These case-building larvae move very little during low flow periods, even when food resources appear limiting. In contrast, the frequency and distance of larval dispersal are much greater during periods with high flow. 5. Our observations for G. nigricula support previously published inferences that larval dispersal within a stream can be limited for some aquatic insects. However, our observations also suggest that, even for a relatively sedentary species like G. nigricula, larval dispersal during periods with high flow may contribute significantly to gene flow within a stream reach.     

Mobility and metapopulation structure of Geocrinia alba and Geocrinia vitellina,two endangered frog species from southwestern Australia

Abstract Dispersal rates can have an important impact on many population processes. Dispersal can lead to population regulation and regional stability in the face of local instability through the formation of a metapopulation. This may be particularly true for frogs because they often have patchy distributions. In this paper I investigate dispersal by male Geocrinia alba and Geocrinia vitellina, using a mark-recapture study. Pit traps were used to determine whether frogs move out of their breeding habitat. I found that both species were very philopatric. Between the 1993 and 1994 breeding seasons, 76–86% of individuals were displaced less than 10m and 90–97% were displaced less than 20m. Dispersal was even lower within each breeding season, with 92–95% of individuals being displaced less than 5 m. Pit trapping indicated that some individuals of both species move out of the swamps in late autumn and return at the beginning of the breeding season, in late winter and early spring. Therefore, although displacement may be very restricted, the frogs are likely to move greater distances. The extreme breeding-site philopatry exhibited by G. alba and G. vitellina suggests that movement between disjunct populations is unlikely and that populations in continuous habitat may be relatively isolated from one another by distance alone. This is consistent with previous predictions based on genetic studies, which suggested there was very little migration between populations. These data support the contention that neither species is likely to exist as a metapopulation because recolonization of vacant habitat is improbable.     

The relation between dispersal and survival of Lobesia botrana larvae and their density in vine inflorescences

Dispersal and survival of Lobesia botrana Den. & Schiff. (Lepidoptera: Tortricidae) larvae in a simulated first generation and the relationship with their density on vine inflorescences were studied under field conditions. Artificial infestations with neonate larvae were conducted at densities of 5, 10, 15, 20 and 25 individuals per vine inflorescence. Larvae had a considerable dispersal capacity on the vine espalier and were able to reach several inflorescences around those artificially infested. Dispersal downwards (63.1%) was significantly more frequent than upwards (36.9%), probably because larvae move down the vine plant using silk threads. However, the fact that there was upwards dispersal provides evidence that larvae are capable of active locomotion upwards on the vine plant structure. Mean distances covered by larvae ranged between 10 and 30 cm, with a maximum as far as 45 cm. The longest displacements were not associated with the downward dispersal. The maximum distance covered by larvae was positively correlated with larval density. Mean distance and larval density were not correlated, but mean distances covered at high larval densities were significantly higher than at low densities. At higher larval densities, the proportion of larvae which established in the artificially infested inflorescences decreased whereas the proportion of dispersing individuals increased. However, as a result of the balance between establishment and dispersal, larval survival did not differ significantly among larval densities (26–44%). The results obtained suggest that larval dispersal must be taken into account when preimaginal stages are sampled to determine whether damage thresholds are reached in an integrated pest management program.     

Study of Aedes albopictus dispersal in Rome,Italy, using sticky traps in mark–release–recapture experiments

We report the results of three mark–release–recapture experiments carried out in an urban area in Rome, Italy, to study the active dispersal of Aedes albopictus (Diptera: Culicidae). The 4.3% recapture rate obtained supports the use of sticky traps in MRR experiments to study the dispersal of Ae. albopictus females. Most fluorescent dust‐marked females were recaptured at the gravid stage at 50–200 m from the release sites during the first 9 days after release. The average of daily‐MDTs (Mean Distance Traveled) was 119 m and the maximum observed distance travelled ranged from 199 m to 290 m in the three replicates. These data provide the first information about the dispersal of Ae. albopictus in a temperate European area and appear to be consistent with the few data available on this subject from other urban areas, where dispersal was constrained by physical barriers. Although caution should be taken in generalizing these results, they should be considered when planning control activities in urban areas in Italy, as well as in other European countries. This is particularly relevant if control is intended to interrupt pathogen transmission in cases of possible arbovirus epidemics, such as the Chikungunya outbreak that occurred in Ravenna, Italy in 2007.     

Satellite tracking of Bulwer's Petrels Bulweria bulwerii in the Canary Islands

Capsule?The breeding foraging and post-breeding dispersal movements of five satellite-tagged Bulwer's Petrels from the Canary Islands were recorded. Foraging trips lasted 5.6 days in average (n?=?3), while the mean distance covered was 1261 km, and foraging areas were located over the continental slope and the adjacent pelagic waters, around 1200–2000 m depth and up to 350 km from the colony. After the chick-rearing period, birds dispersed southwestwards to the tropical waters of the central Atlantic.     

Sexual dimorphism in between and within patch movements of a monophagous insect: Tetraopes (Coleoptera: Cerambycidae)

Summary Movements of milkweed beetles (Tetraopes tetraophthalmus and Tetraopes femoratus) were monitored using mark-release-recapture techniques to compare the within- and between-patch movement patterns of individuals in a naturally occurring population. Within-patch and between-patch movement patterns differ in both frequency and distance traveled for males and females of both study species. Males move farther than females and are more likely to move between patches. Individuals recognize and alter movement upon encountering patch edges. Results suggest that laboratory estimates of Tetraopes vagility give a misleading indication of actual dispersal.     

Estimation of dispersal distances of the obligately plant‐associated ant Crematogaster decamera

1. In obligate symbioses with horizontal transmission, the population dynamics of the partner organisms are highly interdependent. Host population size limits symbiont number, and distribution of partners is restricted by the presence and thus dispersal abilities of their respective partner. The Crematogaster decamera–Macaranga hypoleuca ant–plant symbiosis is obligate for both partners. Host survival depends on colonisation by its ant partner while foundress queens require hosts for colony establishment. 2. An experimental approach and population genetic analyses were combined to estimate dispersal distances of foundresses in their natural habitat in a Bornean primary rainforest. 3. Colonisation frequency was significantly negatively correlated with distance to potential reproductive colonies. Results were similar for seedlings at natural densities as well as for seedlings brought out in the area experimentally. Population genetic analysis revealed significant population differentiation with an F_ST of 0.041 among foundresses (n = 157) located at maximum 2280 m apart. In genetic spatial autocorrelation, genotypes of foundresses were significantly more similar than expected at random below 550 m and less similar above 620 m. Direct estimation of dispersal distances by pedigree analysis yielded an average dispersal distance of 468 m (maximum 1103 m). 4. For ants that disperse on the wing, genetic differentiation at such small spatial scales is unusual. The specific nesting requirements of the queens and the necessity for queens to find a host quickly could lead to colonisation of the first suitable seedling encountered, promoting short dispersal distances. Nonetheless, dispersal distances of C. decamera queens may vary with habitat or host spatial distribution.     

The Reaction of the Medium in Relation to Root Formation in Coleus

Background: As seed dispersal can vary among years and individuals, studies that focus on a single year or on a few individuals may lead to erroneous conclusions.

Aims: To study temporal and spatial intraspecific variation of seed dispersal in Scrophularia canina, a widespread species with capsule-type fruit.

Methods: Primary seed dispersal was quantified by placing traps in each cardinal direction around 10 individuals during two consecutive years. We correlated several seed shadow parameters (modal dispersal distance, kurtosis, skewness, percentiles, slope, and seed percentage beneath the plant canopy) with three plant features (maximum height, lateral spread and seed production).

Results: Scrophularia canina dispersed their seeds by boleochory, giving rise to a typical leptokurtic curve, but behaving as a barochorous species, because about 90% of seeds landed beneath the plant canopy. Temporal dispersal in S. canina included several seed waves associated with maximum wind speeds. Plant lateral spread was significantly positively correlated with seed percentiles and percentage of seeds beneath the plant canopy regardless of year. A seed production effect was only evident when both years were considered together.

Conclusions: Although time-consuming, investigation of the dispersal process for more than 1 year provides more realistic information on seed dispersal. Lateral spread is the main plant feature determining seed shadow.     

Seed Dispersal by Salvin's Curassow,Mitu salvini (Cracidae), in a Tropical Forest of Colombia: Direct Measurements of Dispersal Distance1

Seed dispersal by Salvin's curassows (Mitu salvini) was studied in a lowland tropical forest at La Macarena on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of a well-habituated pair of birds from 0600 to 1800 h for 19 days. Ibtal observation time was 222 h. The daily distance traveled by the birds ranged from 630 to 3750 m, with a mean of 1959 m (± 776 m). The total home range was ca 34.4 ha. Although curassows were observed consuming fruits of 13 species belonging to the families Rubiaceae, Meliaceae, Moraceae, Burseraceae, Leguminosae, and Lecythidaceae, only seeds of Geophila re fens (Rubiaceae) and Picas spbenophylla (Moraceae) were found in their feces. For G. repens, the mean and maximum retention times were 1 h 52 min (± 1 h 20 min) and 6 h 08 min, and the mean and maximum direct dispersal distances were 245 m (± 164 m) and 633 m. More than half the seeds were dispersed in canopy gaps. For F. sphenophylla, the mean and maximum retention times were 3 h 1 5 mm (± .37 min) and 7 h 08 min, and the mean and maximum direct dispersal distances were 329 m (± 46 m) and 451 m. Nearly 60 percent of the estimated seed intake of G. repens and 92-94 percent of F. sphenophylla were digested or damaged. The retention times and the dispersal distances for Streptogyna americana, which has adhesive burrs, were also measured. The mean and maximum retention times were 1 h 55 min (± 1 h 56 min) and 9 h 11 min, and the mean and maximum direct dispersal distances were 128 m (± 68 m) and 280 m. This is the first study in which direct measurements were made for retention times and dispersal distances of the epizoochory and endozoochory for birds in the field.