Potential differences in seed dispersals of low‐height vegetation between single element and windbreak‐like clumps

Wind speed is one of the most important factors for seed wind dispersal. A wind speed reduction region, which could be influenced by vegetation arrangement, will form in the lee of vegetation and therefore affects the seed dispersal. Here, by taking shrub as an example, quantitative differences in seed dispersals of low vegetation between single element and windbreak‐like clumps are numerically investigated. The local variation of stream‐wise wind speed is focused. Empirically parameterized functions of leeward wind distributions are employed. It reveals that the accumulative probability of dispersed seeds from a point source with considering leeward wind reduction could be well fitted by a logistic function. For a fixed release height or vegetation porosity, accumulative probabilities for single element and those for windbreak‐like clumps would intersect at a leeward location. This intersection location decreases linearly with release height but exponentially with porosity. The fitting parameter r₀ (the center of logistic function) for single element increases as the same manner for windbreak‐like clumps, with regard to the increase of release height, porosity, and height. But, the increasing rates for single element are higher than those for windbreak‐like clumps. The fitting parameter p (the power index of logistic function) for single element is generally larger than that for windbreak‐like clumps. With the increase of release height, p decreases at first but increases then for single element, while it shows opposite trend for windbreak‐like clumps. p decreases with porosity for both single element and windbreak‐like clumps. But, the decreasing rate for single element is lower than that for windbreak‐like clumps. p increases exponentially with height for windbreak‐like clumps, while it almost keeps constant for single element. These results suggest the potential importance of vegetation arrangement on seed dispersal and therefore possibly provide additional reason for the disagreement among observed dispersal kernels.     

The relationship between the Gabor elementary function and a stochastic model of the inter-spike interval distribution in the responses of visual cortex neurons

In a previously reported study (Berger et al. 1990) we analyzed distributions of interspike intervals recorded extracellularly from cat visual cortex under four stimulus conditions. Stimuli were gratings differing in orientation and spatial frequency. The probability density function of first passage time for a random walk with drift process, which is defined by its barrier height and drift coefficient, was used to characterize the generating process of axonal discharge under resting and stimulus conditions. Drift coefficient and barrier height were derived from the sample mean and standard deviation of the measured inter-spike intervals. For cells with simple receptive fields, variations in spatial frequency produced changes only in drift coefficient. Variations in barrier height were produced only by changes in orientation of the stimulus. Currently, the method used to analyze these data was implemented in a simulation which displayed the relationship between the interval distribution of impulses, the random walk which represents the time series characteristic of the spike train model and the Gabor filter function which represents the geometry of the receptive field process.     

Aggregated spatial distributions of species in a subtropical karst forest,southwestern China

Aims Spatial distribution patterns of species reflect not only the ecological processes but also the habitat features that are related to species distribution. In karst topography, species distribution patterns provide more specific information about their environments. The objectives of this study are as follows: (i) to analyse and explain the spatial distribution patterns of conspecific trees in an old-growth subtropical karst forest; (ii) to investigate pattern changes at different spatial scales; (iii) to test the spatial pattern similarity (or dissimilarity) between trees at different abundances, diameter at breast height classes, canopy layers and different functional groups (shade tolerance and seed dispersal mode); (iv) to examine whether habitat heterogeneity has an important effect on the species spatial distribution.Methods The spatial distributions of woody species with ≥20 individuals in a 1-ha subtropical karst forest plot at Maolan in southwestern China were quantified using the relative neighbourhood density Ω based on the average density of conspecific species in a circular neighbourhood around each species.Important findings Aggregated distribution is the dominant pattern in the karst forest, but the ratio of aggregated species in total species number decreases with an increase in spatial scale. Less abundant species are more aggregated than most abundant species. Aggregation is weaker in larger diameter classes, which is consistent with the prediction of self-thinning. Seed dispersal mode influences spatial patterns, with species dispersed by animals being less aggregated than those dispersed by wind and gravity. Other species functional traits (e.g. shade tolerance) also influence the species spatial distributions. Moreover, differences among species habitat associations, e.g. with rocky outcrops, play a significant role in species spatial distributions. These results indicate that habitat heterogeneity, seed dispersal limitation and self-thinning primarily contribute to the species spatial distributions in this subtropical karst forest.     

Modelling fungal growth on surfaces

Fungal growth in time and space at the substrate surface was modelled for a simple system mimicking solid-state fermentation, using a polycarbonate Nucleopore membrane laid over a glucose solution. Biomass production depends on both tip density and the diffusion of glucose within the fungal hyphae. The model predicts early increases in both height and concentration, followed by a period in which the biomass profile moves with a constant wavefront. The rate of increase in height increases as tip diffusivity increases or as the Monod saturation constant for glucose decreases. © Rapid Science Ltd. 1998     

Nest distribution shaping within-stream variation in Atlantic salmon juvenile abundance and competition over small spatial scales

1. Spatial heterogeneity in population density is predicted to have important effects on population characteristics, such as competition intensity and carrying capacity. Patchy breeding distributions will tend to increase spatial heterogeneity in population density, whereas dispersal from breeding patches will tend to decrease it. The potential for dispersal to homogenize densities is likely to differ both among organisms (e.g. plants vs. mobile animals) and throughout ontogeny (e.g. larvae vs. adults). However, for mobile organisms, experimental studies of the importance of breeding distributions from the wild are largely lacking. 2. In the present study, experimental manipulations replicated over eight natural streams and 2 years enabled us to test for effects of the distribution of Atlantic salmon eggs over spatial scales which are relevant to local interactions among individuals. Artificial nests were placed along 250 m study reaches at one of two levels of nest dispersion - patchy (two nests per stream) and dispersed (10 nests per stream) - while holding total egg density (eggs m(-2) stream area) constant. 3. Nest dispersion had significant effects on the spatial distribution of the resulting juveniles in their first summer. Patchy nest distributions resulted in a highly right-skewed frequency distribution of local under-yearling densities (among 25 m sampling sections), as sample sections adjacent to the nest sites had relatively high densities. In contrast, dispersed nest distributions yielded approximately normal density distributions. Sections with high relative densities in the patchy nest distribution treatments also had relatively small juvenile body sizes, and patchy egg distribution appeared to produce a higher redistribution of individuals from the first to the second juvenile growth season than the dispersed distribution. 4. Because patchy breeding distribution combined with limited early dispersal can create spatial variation in density over scales directly relevant for individual interactions, this will be one important component in determining mean levels of early juvenile competition and its spatial variation within populations. Assuming random or ideal-free distribution of individuals may therefore underestimate the mean level of density experienced by juveniles over surprisingly small spatial scales (orders of magnitude smaller than total spatial extent of populations), even for mobile organisms.     

Salt effects on membranes of the hypodermis and mesophyll cells of Avicennia germinans (Avicenniaceae): a freeze-fracture study

Freeze-fracture electron microscopy was used to investigate intramembranous particle (IMP) densities and particle distributions in the plasma membrane and tonoplast of the cells of secreting and nonsecreting leaves of Avicennia germinans (L.) Steam. Intramembranous particle densities of the protoplasmic (P) and exoplasmic (E) face of the plasma membrane and tonoplast were significantly higher in hypodermal cells of secreting leaves than of nonsecreting leaves. In contrast, no significant differences in the frequency of intramembranous particles were found in any membrane faces of secreting or nonsecreting mesophyll cells. However, particle densities were higher in the plasma membrane and tonoplast of the mesophyll cells, compared to the hypodermal cells, with the exception of the P-face of hypodermal plasma membranes of secreting tissue, which had the highest particle density measured. Particle distributions were dispersed and no discernible patterns such as paracrystalline arrays or other multi-IMP structures were observed. Results support the hypothesis that secretion is coupled to changes in membrane ultrastructure, and the possibility that salt secretion is an active process driven by integral membrane proteins such as the H⁺/ATPase. Additionally, the hypodermal cells of the leaf may function as storage reservoirs for salt as well as water, suggesting a regulatory role in salt secretion.     

Components of the plasma membrane of growing axons. I. Size and distribution of intramembrane particles

The plasmalemma of mature and growing olfactory axons of the bullfrog has been studied by freeze-fracture. Intramembrane particles (IMPs) of mature olfactory axons are found to be uniformly distributed along the shaft. However, during growth, a decreasing gradient of IMP density is evident along the somatofugal axis. The size histograms of axolemmal IMPs from different segments of growing nerve reveal regional differences in the particle composition. The distribution of each individual size class of particles along the growing nerve forms a decreasing gradient in the somatofugal direction; the slope of these gradients varies directly with particle diameter. These size-dependent density gradients are consistent with a process of lateral diffusion of membrane components that are inserted proximally into the plasma membrane. The membrane composition of the growth cone, however, appears to be independent of these diffusion gradients; it displays a mosaic pattern of discrete domains of high and low particle densities. The relative IMP profiles of these growth cone regions are similar to one another but contain higher densities of large IMPs than the neighboring axonal shaft. The shifting distributions of intramembrane particles that characterize the sprouting neuron give new insights into cellular processes that may underlie the establishment of the functional polarity of the neuron and into the dynamics of axolemmal maturation.     

Low crop plant population densities promote pollen-mediated gene flow in spring wheat (Triticum aestivum L.)

Transgenic wheat is currently being field tested with the intent of eventual commercialization. The development of wheat genotypes with novel traits has raised concerns regarding the presence of volunteer wheat populations and the role they may play in facilitating transgene movement. Here, we report the results of a field experiment that investigated the potential of spring wheat plant population density and crop height to minimize gene flow from a herbicide-resistant (HR) volunteer population to a non-HR crop. Pollen-mediated gene flow (PMGF) between the HR volunteer wheat population and four conventional spring wheat genotypes varying in height was assessed over a range of plant population densities. Natural hybridization events between the two cultivars were detected by phenotypically scoring plants in F₁ populations followed by verification with Mendelian segregation ratios in the F_1:2 families. PMGF was strongly associated with crop yield components, but showed no association with flowering synchrony. Maximum observed PMGF was always less than 0.6%, regardless of crop height and density. The frequency of PMGF in spring wheat decreased exponentially with increasing plant population density, but showed no dependence on either crop genotype or height. However, increasing plant densities beyond the recommended planting rate of 300 cropped wheat plants m⁻² provided no obvious benefit to reducing PMGF. Nevertheless, our results demonstrate a critical plant density of 175–200 cropped wheat plants m⁻² below which PMGF frequencies rise exponentially with decreasing plant density. These results will be useful in the development of mechanistic models and best management practices that collectively facilitate the coexistence of transgenic and nontransgenic wheat crops.     

Transport of nucleosome core particles in semidilute DNA solutions

We studied the diffusion of native and trypsinized nucleosome core particles (NCPs), in aqueous solution and in concentrated DNA solutions (0.25-100 mg/ml) using fluorescence correlation spectroscopy (FCS). The highest DNA concentrations studied mimic the DNA density inside the cell nucleus. The diffusion coefficient of freely diffusing NCPs depends on the presence or absence of histone tails and is affected by the salt concentration due to the relaxation effect of counterions. NCPs placed in a network of long DNA molecules (30-50 kbp) reveal anomalous diffusion. We demonstrate that NCPs diffusion is in agreement with known particle transport in entangled macromolecular solutions as long as the histone tails are folded onto the particles. In contrast, when these tails are unfolded, the reversible adsorption of NCPs onto the DNA network has to be taken into account. This is confirmed by the fact that removal of the tails leads to reduction of the interaction between NCPs and the DNA network. The findings suggest that histone tail bridging plays an important role in chromatin dynamics.     

Dispersal of the winged fruits of Nuytsia floribunda (Loranthaceae)

Fruits of the tree Nuytsia floribunda are dispersed by wind during autumn to mid-winter when conditions are suitable for germination. While the greatest density of fallen fruits occurs beneath the canopy, most are dispersed well beyond the tree in the direction of the prevailing west-southwesterly winds, with a minor peak corresponding to the easterlies. A multiple regression equation, which accounted for 77.5% of variance, was derived to account for the greatest dispersal distance per tree. This comprises, in decreasing order of importance, tree height, log (fruit load), and leeward and windward plant cover in the vertical plane. Extrapolation indicated a maximum distance of about 50 m can be expected, which is insufficient to account for the location of at least 6.5% of adult trees at the study site. This supports other evidence that suckering may play a major role in the spread of this species. Additional experiments confirmed the importance of wind velocity in the distance reached by fruits and the absence of biotic dispersal agents.     

Lasting effects of maternal behaviour on the distribution of a dispersive stream insect

1. Predicting population dynamics at large spatial scales requires integrating information about spatial distribution patterns, inter-patch movement rates and within-patch processes. Advective dispersal of aquatic species by water movement is considered paramount to understanding their population dynamics. Rivers are model advective systems, and the larvae of baetid mayflies are considered quintessential dispersers. Egg laying of baetids along channels is patchy and reflects the distribution of oviposition sites, but larvae are assumed to drift frequently and far, thereby erasing patterns created during oviposition. Dispersal kernels are often overestimated, however, and empirical tests of such assumptions are warranted because of the pivotal role distribution patterns can have on populations. 2. We tested empirically whether the egg distribution patterns arising from oviposition behaviours persisted and were reflected in the distribution patterns of larval Baetis rhodani. In field surveys, we tested for associations between egg mass and larval densities over 1 km lengths of four streams. A control species, the mayfly Ephemerella ignita, was employed to test for covarying environmental factors. We estimated drift rates directly to test whether larvae dispersed between riffles (patches of high egg mass density) and whether drift rates were density-dependent or density-related - expected outcomes if drift erases patterns established by maternal behaviours. 3. Positive associations between egg masses and larval benthic densities were found for neonate and mid-stage larvae of Baetis, but not the control species, suggesting persistence of the patchy distribution patterns established at oviposition. Drift rates were high, and riffles were net exporters of neonate and mid-stage larvae, but drift rates were unrelated to benthic densities and few drifters reached the next riffle. Riffles were sinks for large larvae, suggesting ontogenetic shifts in habitat use, but little long-distance dispersal. 4. Overall, the results suggest that most neonate and mid-stage larvae of B. rhodani remain close to the natal riffle, and late-stage larvae disperse shorter distances than routinely assumed. The persistence of maternal effects on distribution patterns well into juvenile life of an allegedly iconic disperser suggests that traditional models of how dispersal influences the population dynamics of many lotic invertebrates may be incorrect.     

Turtle groups or turtle soup: dispersal patterns of hawksbill turtles in the Caribbean

Despite intense interest in conservation of marine turtles, spatial ecology during the oceanic juvenile phase remains relatively unknown. Here, we used mixed stock analysis and examination of oceanic drift to elucidate movements of hawksbill turtles (Eretmochelys imbricata) and address management implications within the Caribbean. Among samples collected from 92 neritic juvenile hawksbills in the Cayman Islands we detected 11 mtDNA control region haplotypes. To estimate contributions to the aggregation, we performed ‘many‐to‐many’ mixed stock analysis, incorporating published hawksbill genetic and population data. The Cayman Islands aggregation represents a diverse mixed stock: potentially contributing source rookeries spanned the Caribbean basin, delineating a scale of recruitment of 200–2500 km. As hawksbills undergo an extended phase of oceanic dispersal, ocean currents may drive patterns of genetic diversity observed on foraging aggregations. Therefore, using high‐resolution Aviso ocean current data, we modelled movement of particles representing passively drifting oceanic juvenile hawksbills. Putative distribution patterns varied markedly by origin: particles from many rookeries were broadly distributed across the region, while others would appear to become entrained in local gyres. Overall, we detected a significant correlation between genetic profiles of foraging aggregations and patterns of particle distribution produced by a hatchling drift model (Mantel test, r = 0.77, P < 0.001; linear regression, r = 0.83, P < 0.001). Our results indicate that although there is a high degree of mixing across the Caribbean (a ‘turtle soup’), current patterns play a substantial role in determining genetic structure of foraging aggregations (forming turtle groups). Thus, for marine turtles and other widely distributed marine species, integration of genetic and oceanographic data may enhance understanding of population connectivity and management requirements.     

Hierarchical Bayesian model reveals the distributional shifts of Arctic marine mammals

Aim

Our aim involved developing a method to analyse spatiotemporal distributions of Arctic marine mammals (AMMs) using heterogeneous open source data, such as scientific papers and open repositories. Another aim was to quantitatively estimate the effects of environmental covariates on AMMs’ distributions and to analyse whether their distributions have shifted along with environmental changes.

Location

Arctic shelf area. The Kara Sea.

Methods

Our literature search focused on survey data regarding polar bears (Ursus maritimus), Atlantic walruses (Odobenus rosmarus rosmarus) and ringed seals (Phoca hispida). We mapped the data on a grid and built a hierarchical Poisson point process model to analyse species’ densities. The heterogeneous data lacked information on survey intensity and we could model only the relative density of each species. We explained relative densities with environmental covariates and random effects reflecting excess spatiotemporal variation and the unknown, varying sampling effort. The relative density of polar bears was explained also by the relative density of seals.

Results

The most important covariates explaining AMMs’ relative densities were ice concentration and distance to the coast, and regarding polar bears, also the relative density of seals. The results suggest that due to the decrease in the average ice concentration, the relative densities of polar bears and walruses slightly decreased or stayed constant during the 17‐year‐long study period, whereas seals shifted their distribution from the Eastern to the Western Kara Sea.

Main conclusions

Point process modelling is a robust methodology to estimate distributions from heterogeneous observations, providing spatially explicit information about ecosystems and thus serves advances for conservation efforts in the Arctic. In a simple trophic system, a distribution model of a top predator benefits from utilizing prey species’ distributions compared to a solely environmental model. The decreasing ice cover seems to have led to changes in AMMs’ distributions in the marginal Arctic region.     

Energy deposition by protons and alpha particles in spherical sites of nanometer to micrometer diameter

Summary Monte Carlo simulated proton- and alpha-particle tracks in water vapor were used to develop an analytical function for calculating number distributions of ionizations induced in spherical sites. For charged particles crossing the site, Fermi-like functions were used to approximate the ionization distributions. Ionization event distributions due to particles passing outside the site were approximated with an exponentially decreasing function. The function parameters were calculated for protons and alpha particles in the energy range 0.3–5.0 MeV/ amu and for site diameters of 1 to 1000 nm. The quality of fit obtained is very good for the particles, energy range and site diameters considered.On leave from the Institute of Nuclear Physics, ul. Radzikowskiego 152, PL-31342 Kraków, Poland     

Holocene re‐colonisation,central–marginal distribution and habitat specialisation shape population genetic patterns within an Atlantic European grass species

Corynephorus canescens (L.) P.Beauv. is an outbreeding, short‐lived and wind‐dispersed grass species, highly specialised on scattered and disturbance‐dependent habitats of open sandy sites. Its distribution ranges from the Iberian Peninsula over Atlantic regions of Western and Central Europe, but excludes the two other classical European glacial refuge regions on the Apennine and Balkan Peninsulas. To investigate genetic patterns of this uncommon combination of ecological and biogeographic species characteristics, we analysed AFLP variation among 49 populations throughout the European distribution range, expecting (i) patterns of SW European glacial refugia and post‐glacial expansion to the NE; (ii) decreasing genetic diversity from central to marginal populations; and (iii) interacting effects of high gene flow and disturbance‐driven genetic drift. Decreasing genetic diversity from SW to NE and distinct gene pool clustering imply refugia on the Iberian Peninsula and in western France, from where range expansion originated towards the NE. High genetic diversity within and moderate genetic differentiation among populations, and a significant pattern of isolation‐by‐distance indicate a gene flow drift equilibrium within C. canescens, probably due to its restriction to scattered and dynamic habitats and limited dispersal distances. These features, as well as the re‐colonisation history, were found to affect genetic diversity gradients from central to marginal populations. Our study emphasises the need for including the specific ecology into analyses of species (re–)colonisation histories and range centre–margin analyses. To account for discontinuous distributions, new indices of marginality were tested for their suitability in studies of centre–periphery gradients.     

A non-local model for a swarm

 This paper describes continuum models for swarming behavior based on non-local interactions. The interactions are assumed to influence the velocity of the organisms. The model consists of integro-differential advection-diffusion equations, with convolution terms that describe long range attraction and repulsion. We find that if density dependence in the repulsion term is of a higher order than in the attraction term, then the swarm profile is realistic: i.e. the swarm has a constant interior density, with sharp edges, as observed in biological examples. This is our main result. Linear stability analysis, singular perturbation theory, and numerical experiments reveal that weak, density-independent diffusion leads to disintegration of the swarm, but only on an exponentially large time scale. When density dependence is put into the diffusion term, we find that true, locally stable traveling band solutions occur. We further explore the effects of local and non-local density dependent drift and unequal ranges of attraction and repulsion. We compare our results with results of some local models, and find that such models cannot account for cohesive, finite swarms with realistic density profiles. Received: 17 September 1997 / Revised version: 17 March 1998     

Short class I major histocompatibility complex cytoplasmic tails differing in charge detect arbiters of lateral diffusion in the plasma membrane

Directed and Brownian movement of class I major histocompatibility complex (MHC) molecules on cell membranes is implicated in antigen presentation. Previous studies indicated that the class I MHC cytoplasmic tail imposes constraints on the molecule's diffusion. Here we used single particle tracking to study the mobility of the wild-type mouse H-2L(d) class I MHC molecule and of seven cytoplasmic tail variants. Six of the variants have cytoplasmic tails of four or seven residues (differing in net charge), and one is tailless, yet all are susceptible to confinement in membrane domains. However, truncation of the cytoplasmic tail to 0-4 residues decreases the proportion of particles exhibiting confined diffusion and increases the proportion exhibiting simple diffusion. Particularly for the truncated mutants (tail length of 0-7 residues), many of the particles have complex trajectories and do not move at a constant speed or in the same mode of diffusion throughout the observation period. Several particles of the tailless H-2L(d) mutant display a type of directed diffusion that is rarely observed for other H-2L(d) mutants. Taken together, these data show that even short cytoplasmic tails can influence markedly class I MHC mobility and that cytoplasmic tail length and sequence affect the molecule's diffusion in the membrane.     

Noise underlies switching behavior of the bacterial flagellum

We report the switching behavior of the full bacterial flagellum system that includes the filament and the motor in wild-type Escherichia coli cells. In sorting the motor behavior by the clockwise bias, we find that the distributions of the clockwise (CW) and counterclockwise (CCW) intervals are either exponential or nonexponential with long tails. At low bias, CW intervals are exponentially distributed and CCW intervals exhibit long tails. At intermediate CW bias (0.5) both CW and CCW intervals are mainly exponentially distributed. A simple model suggests that these two distinct switching behaviors are governed by the presence of signaling noise within the chemotaxis network. Low noise yields exponentially distributed intervals, whereas large noise yields nonexponential behavior with long tails. These drastically different motor statistics may play a role in optimizing bacterial behavior for a wide range of environmental conditions.     

Exploring the interaction of avian frugivory and plant spatial heterogeneity and its effect on seed dispersal kernels using a simulation model

Seed dispersal by avian frugivores is one of the key processes influencing plant spatial patterns, but may fail if there is disruption of plant–frugivore mutualisms, such as decline in abundance of dispersers, fragmentation of habitat, or isolation of individual trees. We used simulation model experiments to examine the interaction between frugivore density and behaviour and the spatial arrangement of fruiting plants and its effect on seed dispersal kernels. We focussed on two New Zealand canopy tree species that produce large fruits and are dispersed predominantly by one avian frugivore (Hemiphaga novaeseelandiae). Although the mean seed dispersal distance decreased when trees became more aggregated, there were more frugivore flights between tree clusters, consequently stretching the tails of the dispersal kernels. Conversely, when trees were less aggregated in the landscape, mean dispersal distances increased because seeds were deposited over larger areas, but the kernels had shorter tails. While there were no statistically meaningful changes in kernel parameters when frugivore density changed, decreases in density did cause a proportional reduction in the total number of dispersed seeds. However, birds were forced to move further when fruit availability and fruit ripening were low. Sensitivity analysis showed that dispersal kernels were primarily influenced by the model parameters relating to disperser behaviour, especially those determining attractiveness based on distance to candidate fruiting trees. Our results suggest that the spatial arrangement of plants plays an important role in seed dispersal processes – although tree aggregation curbed the mean seed dispersal distance, it was accompanied by occasional long distance events, and tree dispersion caused an increase in mean dispersal distance, both potentially increasing the probability of seeds finding suitable habitats for germination and growth. Even though low frugivore densities did not cause dispersal failure, there were negative effects on the quantity of seed dispersal because fewer seeds were dispersed.     

Intraspecific variation in seed dispersal of a Neotropical tree and its relationship to fruit and tree traits

The distribution of wind‐dispersed seeds around a parent tree depends on diaspore and tree traits, as well as wind conditions and surrounding vegetation. This study of a neotropical canopy tree, Platypodium elegans, explored the extent to which parental variation in diaspore and tree traits explained (1) rate of diaspore descent in still air, (2) distributions of diaspores dispersed from a 40‐m tower in the forest, and (3) natural diaspore distributions around the parent tree. The geometric mean rate of descent in still air among 20 parents was highly correlated with geometric mean wing loading^1/2 (r = 0.84). However, diaspore traits and rate of descent predicted less variation in dispersal distance from the tower, although descent rate⁻¹ consistently correlated with dispersal distance. Measured seed shadows, particularly their distribution edges, differed significantly among six parents (DBH range 62–181 cm) and were best fit by six separate anisotropic dispersal kernels and surveyed fecundities. Measured rate of descent and tree traits, combined in a mechanistic seed dispersal model, did not significantly explain variation among parents in natural seed dispersal distances, perhaps due to the limited power to detect effects with only six trees. Seedling and sapling distributions were at a greater mean distance from the parents than seed distributions; saplings were heavily concentrated at far distances. Variation among parents in the distribution tails so critical for recruitment could not be explained by measured diaspore or tree traits with this sample size, and may be determined more by wind patterns and the timing of abscission in relation to wind conditions. Studies of wind dispersal need to devote greater field efforts at recording the “rare” dispersal events that contribute to far dispersal distances, following their consequences, and in understanding the mechanisms that generate them.