Beyond simply fruit or seed size, actual dimensions or shape can influence foraging decisions of endozoochorous and synzoochorous dispersers. For example, fruit diameter independent of length or overall mass is thought to be the most important metric of fruit size for frugivorous birds based on how fruits are swallowed . Acorn shape also influences preference by the European jay ; when diameter was held constant, jays preferred longer acorns; when length was constant, they chose wider acorns; and when mass was constant, they chose longer and slimmer acorns over shorter and wider acorns . How widespread such patterns are is unknown. As noted previously, patterns of anemochorous dispersal are not driven solely by seed mass, but are influenced by the relationship between seed mass and the dispersal structure, which varies intraspecifically. It is generally thought that wing loading, frequently measured as fruit mass per unit surface area of the dispersal structure, is the major determinant of dispersal ability in wind-dispersed species. Thus, in trees , shrubs and forbs , increasing wing loading results in shorter dispersal distances or greater falling velocities, implying shorter dispersal distances. Other traits of propagules also lead to intraspecific variation in wind dispersal. Sheldon and Burrows argued that the fine details of pappus architecture influence dispersal moreSome fleshy-fruited species exhibit fruit colour polymorphism, round pot producing two or more colour morphs, sometimes on different plants and sometimes on the same plant .

Selection of particular colour morphs ranges from relatively strong to weak to non-existent . Selection can be consistent across large geographic areas or vary across years and populations or even among individuals of a disperser species . In the only study we know addressing selection among individual plants, the deer M. muntjak preferred C. axillaris trees with yellow fruits over those producing yellowish-green fruits . The basis of colour morph selection is unclear, but there is no evidence we are aware of that in colour polymorphic systems morphs differ in size, pulp:seed ratio or major nutrients . Inter individual variation in fruiting phenology is widespread in herbaceous forbs , shrubs and trees , but this variation may or may not affect seed dispersal. In C. corymbosa, later fruiting trees were visited by more species, but this had no real effect on dispersal because the additional frugivore species ate very few fruits . Olea europaea var. sylvestris individuals that ripened fruit earlier were favoured in 1 of 2 years , while O. tenera trees ripening fruits earlier had greater and more rapid fruit removal than late-ripening trees . In Q. serrata, acorns produced later in the season were larger with lower tannin concentrations, making them more valuable food items . Phenological variation potentially affects dispersal quality as well. Although not linked to individual plant fruiting phenology, González-Varo et al. demonstrated that dispersal quantity and quality changed through the fruiting season of the bird-dispersed Pistacia lentiscus.

The presence, species identity, density and relative desirability of co-occurring fruiting neighbours can influence inter individual variation in seed dispersal. Some argue that trees compete with neighbours for dispersal and that intraspecific competition should be more intense than interspecific competition, especially in the tropics where it was thought there was little overlap in dispersal assemblages across species . However, facilitation of dispersal by neighbours is also a possibility if the collective lure of multiple fruiting trees disproportionately attracts dispersers . In fact, this scenario has been proposed as another driver of hub and non-hub dispersal networks since frugivores are assumed to choose high-quality patches to forage in without considering the number of trees contributing to that patch . As expected, intraspecific competition has been found to reduce the quantity of dispersal of many tropical and temperate trees and shrubs . However, many studies also have found intraspecific facilitation of the quantity of seed dispersal across taxa and ecosystems . Thus, both intraspecific competition and facilitation have been found to affect the quantity of dispersal in both tropical and temperate systems, but given the relative scarcity of empirical work and its bias to tropical systems, general patterns are not clear. In a multispecies comparison, species fruiting in high densities were more likely to have dispersal reduced by neighbours , whereas species fruiting in low density were more likely to have dispersal increased by neighbours , a logical expectation . Further, whether competition or facilitation of dispersal by conspecific fruiting neighbourhoods occurs can be affected by the heterospecific fruiting neighbourhood .

Heterospecific fruiting neighbourhoods might also influence inter individual variation in dispersal quantity and quality, although we have even less empirical evidence for heterospecific than conspecific interactions, and outcomes appear to be complex. Dispersal of the tropical tree Eugenia uniflora was unaffected by heterospecific fruiting neighbourhoods . Similarly, Solanum americanum in monospecific patches and in mixed patches with Cestrum diurnum did not differ in the quantity of seeds dispersed; however, in the presence of C. diurnum, S. americanum seeds were dispersed in smaller seed loads among more defecations, resulting in reduced potential competition and increased number of sites occupied . In the south-eastern USA, the native shrub Morella cerifera marginally facilitated the dispersal of the invasive shrub Triadica sebifera and improved its germination, but inhibited seedling growth . In California oak woodlands, the high-quality disperser California scrub-jay responded numerically and functionally to Quercus lobata with large acorn crops when the dominant Q. douglasii had low acorn production, but not when Q. douglasii produced abundant acorns . By contrast, the seed predator acorn woodpecker had a constant response to Q. lobata trees independent of background acorn production. Consequently, Q. lobata trees received high quality dispersal when Q. douglasii acorns were sparse, but little dispersal and extensive seed predation when Q. douglasii acorns were abundant. Synzoochorous foragers collect seeds both for current consumption and future use, but preferences often differ between consumed and cached items , opening the potential for complex, indirect seed–seed interactions. For example, one seed species could provide a preferred short-time food supply and therefore subsidize caching of another species more suitable for long-term storage. Such ‘apparent predation’ was documented between Quercus robur and Q. rubra in Poland . Finally, fruiting neighbourhoods can affect dispersal quality as well as quantity. With both endozoochorous and synzoochorous dispersal, higher density fruiting neighbourhoods have been shown to result in shorter dispersal distances .Beyond fruiting neighbourhoods, effects of other aspects of habitat structure on seed dispersal have been addressed from local within-patch variation in structure to landscape-scale variation. Here we give a brief overview from the perspective of inter individual variation in seed dispersal, emphasizing smaller scale population-level variation, with scale defined by the dispersal agent. Note that the drivers and consequences of habitat effects on inter individual variation in seed dispersal operate at much larger spatial scales for plants that are dispersed by mobile animals than for those dispersed abiotically. At the scale of meters to tens of meters, the distances of P. mahaleb individuals from nests and rock outcrops affected the composition of the avian disperser assemblages foraging on those plants . Similarly, round plastic planter but at a larger spatial scale, three nearby stands with vegetation differing in vertical structure and species composition differed substantially in seed disperser assemblages foraging on P. mahaleb . In both cases, differences in assemblages resulted in differences in the quantity of dispersal, the handling of fruits and seeds, and the microhabitat destination of dispersed seeds. In a highly heterogeneous forest, C. monogyna individuals growing with dense tree cover dispersed more seeds and over longer distances than did individuals growing with more sparse cover .

Similarly, with greater amount and continuity of forest cover, the carnivore Martes foina dispersed seeds longer distances . Lastly, Corema album seeds were dispersed by the same three species in three adjacent habitat patches varying in vegetation structure, but all three species exhibited among-habitat variation in both the quantity and quality of dispersal . More discrete habitat patchiness can also drive inter individual variation in dispersal quantity and quality. In O. europaea var. sylvestris, genetic information on avian dispersers and seed parents revealed major differences in dispersal for trees in remnant forest stands versus isolated trees in adjacent agricultural fields , with forest and isolated trees differing substantially in the assemblage of birds dispersing their seeds and in the destinations of dispersed seeds. In continuous forest, G. glandarius dispersed more Q. ilex acorns, dispersed them further, and cached them in better microhabitats than when foraging in adjacent open dehesas with only scattered oaks, while within dehesas, trees close to forest or in spatial clumps were more likely to be dispersed . Numerous studies have addressed habitat fragmentation effects on seed dispersal. In the Amazonian tree Duckeodendron cestroides, dispersed by arboreal and terrestrial mammals, both the quantity and the mean and maximum distance of dispersal were greater in continuous forest than in fragments . Similarly, for the bird-dispersed African tree Leptonychia usambarensis, compared to continuous forest, fragments had fewer species and individuals of seed dispersers, had fewer seeds removed and had seedlings located closer to parents . Fragmentation combined with hunting led to the loss of larger-gaped dispersers and a reduction in seed dispersal of larger fruits, resulting in rapid evolution of reduced fruit and seed size in Euterpe edulis . Fragmentation can also impact synzoochorous dispersal. In Astrocaryum aculeatum, decreasing forest patch area was associated with a higher quantity of dispersal , but lower quality of dispersal , likely due to changes in rodent community composition . However,fragmentation does not always negatively affect seed dispersal; forest fragmentation in Poland reduced the number of larger frugivores without decreasing fruit removal . A meta-analysis of primarily tropical fleshy-fruited species suggested that fragmentation does not affect visitation or seed removal rates, and only marginally reduces dispersal distances. By contrast, a meta-analysis of a worldwide data set suggested that fragmentation reduced interaction rates , but not disperser diversity ; at a major biome level, fragmentation reduced disperser diversity only in temperate zones but reduced interaction rates in both temperate and tropical zones. Additionally, inter- or intraspecific variation in disperser traits such as movement distance, movement frequency and gut retention time of seeds represent one mechanism explaining how fragmentation can positively or negatively affect dispersal distances . Beyond fragmentation, habitat disturbance, degradation and simplification can impact dispersal quantity and quality. In oaks , timber harvest resulted in 67 % reduction in SDE by rodents, probably due to increased vegetation cover facilitating recovery of cached acorns . In a Mediterranean system, habitat degradation reduced the abundance, species richness and movement of avian dispersers, resulting in reduced fruit removal, seed dispersal distances, seed survival and seedling success . Other studies have shown that increasing forest disturbance can result in decreased likelihood of plants being visited by dispersers , as well as decreased species richness of dispersers and reduced dispersal distances and of rates of seed dispersal . These results are compatible with meta-analyses showing degradation to have a greater negative impact than fragmentation on seed dispersal , and habitat degradation generally reducing abundance and diversity of dispersers . Habitat structure also can impact seed dispersal by wind, by altering the wind speed that initiates seed release, and by damping wind speeds. In Taeniatherum caput-medusae and Tragopogon dubius, taller surrounding vegetation reduced dispersal distances . Modelling suggests this should be common in herbaceous communities . Modelling further suggests that forest canopy height heterogeneity influences the likelihood of LDD; seeds released over shorter parts of the canopy encounter greater turbulence and are more likely to be ejected and experience LDD . Lastly, accelerated seed dispersal by wind along linear disturbances in the Canadian oil sands region has been reported .Movements of frugivorous birds are influenced by subtle variation in topographic relief, which can affect which individual fruiting trees are encountered during foraging and where seeds are deposited ; this is likely true for other animal vectors as well. However, little empirical work directly addresses the role of topography in inter individual variation in seed dispersal. In Ecuador, contrasting results were found for two fleshy-fruited shrub species ; Miconia fosteri on ridges had a greater number and proportion of fruits removed than did those at the bottom of slopes, while M. serrulata had a greater number but not proportion of fruits removed on slopes than on either ridges or at the bottom of slopes.