Seeds tend to disperse further in the tropics

Despite the importance of seed dispersal in a plant's life cycle, global patterns in seed dispersal distance have seldom been studied. This paper presents the first geographically and taxonomically broad quantification of the latitudinal gradient in seed dispersal distance. Although there is substantial variation in the seed dispersal distances of different species at a given latitude, seeds disperse on average more than an order of magnitude further at the equator than towards the poles. This pattern is partially explained by plant life‐history traits that simultaneously associate with seed dispersal distance and latitude, including dispersal mode and plant height. The extended seed shadow of tropical plants could increase the distance between conspecific individuals. This could facilitate species coexistence and contribute to the maintenance of high plant diversity in tropical communities. The latitudinal gradient in dispersal distance also has implications for species’ persistence in the face of habitat fragmentation and climate change.     

种子重量的生态学研究进展

作为植物生活史中的一个关键性特征,种子重量与其它许多植物性状和生态因子有关,种子重量的分异与其它一些植物性状及环境的变化关系在进化生物学上已经成为一个非常有意义的研究内容,且具有一定的实践意义。种子重量被发现与下列的一些植物学和群落学性状有关:植物的生活型、种子的散布能力、种子的散布方式、植物的高度、植物的冠幅、植物的比叶面积、植物的寿命、动物的捕食、植被中植物的数量或多度、土壤中种子的数量或多度、种子的休眠、种子在土壤中的持久性和植物的净初级生产力等,另外生态因子如降雨、温度、坡向、海拔、经度、纬度、光强和干扰等都影响种子的重量。种子的重量被认为是在大量小种子和少量大种子之间的进化折衷,在一定的能量限度内,较大重量的种子一般具有较少的数量,而较小重量的种子一般数量较多,这是种子重量和数量方面具有的一种反向关系。与其它性状相比,很多研究都表明种子重量和植物的生活型的关系密切。没有散布结构或风散布的种子比以动物和水作为散布媒介的种子重量要小。种子重量与捕食的关系现发现有3种格局。种子重量和形状与种子在土壤中的持久性的关系有4种格局。在干旱和阴暗的环境条件下,种子有变大的趋势。大重量种子比小种子赋予幼苗较优势的竞争地位,其原理尚有争论,尚不清楚是否是幼苗阶段的竞争决定了世界上大部分植被类型的物种组成。未来的研究方向主要有以下几个方面:1) 种子重量与植物系统学相结合,探索种子重量的变化规律;2)调查群落三向(纬度、经度和海拔)性的种子重量谱变化规律;3) 群落演替与群落种子重量谱的变化;4) 种子重量与群落中植物个体和种子的数量的关系及机理研究;5) 微生境、微地形如坡向、坡位和林间隙等对种子重量的影响;6) 全球气候变化和种子重量变化的关系。     

Is there a latitudinal gradient in seed production?

We compiled data from seed rain studies at 33 sites from around the world to determine whether the greater mean seed mass of tropical plants is associated with production of fewer seeds per square meter of ground. We found no significant linear relationship between latitude and annual seed rain density, but found some evidence for a mid‐latitude peak in seed rain density (quadratic relationship, p=0.018; R²=0.23). Combining seed rain data with seed mass data suggests that vegetation at the equator produces between 19 and 128 times more total mass of seed per year than does vegetation at 60°. This gradient in seed production would far outweigh the doubling in net primary productivity (NPP) over the same range of latitudes. Thus, our (admittedly small) dataset suggests that tropical vegetation allocates a much greater proportion of NPP to reproduction. This raises two important questions for the future: 1) why might tropical vegetation commit more energy to seed production than vegetation further from the equator? 2) What aspect of plant growth might receive proportionally less energy in tropical ecosystems?     

Can the tropical conservatism hypothesis explain temperate species richness patterns? An inverse latitudinal biodiversity gradient in the New World snake tribe Lampropeltini

Aim  A latitudinal gradient in species richness, defined as a decrease in biodiversity away from the equator, is one of the oldest known patterns in ecology and evolutionary biology. However, there are also many known cases of increasing poleward diversity, forming inverse latitudinal biodiversity gradients. As only three processes (speciation, extinction and dispersal) can directly affect species richness in areas, similar factors may be responsible for both classical (high tropical diversity) and inverse (high temperate diversity) gradients. Thus, a modified explanation for differential species richness which accounts for both patterns would be preferable to one which only explains high tropical biodiversity.
Location  The New World.
Methods  We test several proposed ecological, temporal, evolutionary and spatial explanations for latitudinal diversity gradients in the New World snake tribe Lampropeltini, which exhibits its highest biodiversity in temperate regions.
Results  We find that an extratropical peak in species richness is not explained by latitudinal variation in diversification rate, the mid-domain effect, or Rapoport's rule. Rather, earlier colonization and longer duration in the temperate zones allowing more time for speciation to increase biodiversity, phylogenetic niche conservatism limiting tropical dispersal and the expansion of the temperate zones in the Tertiary better explain inverse diversity gradients in this group.
Main conclusions  Our conclusions are the inverse of the predictions made by the tropical conservatism hypothesis to explain higher biodiversity near the equator. Therefore, we suggest that the processes invoked are not intrinsic to the tropics but are dependent on historical biogeography to determine the distribution of species richness, which we refer to as the 'biogeographical conservatism hypothesis'.     

动物与植物种子更新的关系Ⅱ．动物对种子的捕食、扩散、贮藏及与幼苗建成的关系

植物的繁殖体总是面临来自各类生物（如昆虫、脊椎动物、真菌）的捕食风险。因动物捕食引起的种子死亡率影响植物的适合度、种群动态、群落结构和物种多样性的保持。种子被捕食的时间和强度成为植物生活史中发芽速度、地下种子库等特征的主要选择压力,而种子大小、生境类型等因素也影响动物对植物种子的捕食。捕食者饱和现象被认为是植物和种子捕食者之间的高度协同进化作用的结果,是限制动物破坏种子、提高被扩散种子存活率的一种选择压力。大部分群落中的大多数植物种子被动物扩散。种子扩散影响种子密度、种子被捕食率、病原体攻击率、种子与母树的距离、种子到达的生境类型以及建成的植株将与何种植物竞争,从而影响种子和幼苗的存活,最终影响母树及后代植物的适合度。种子被动物扩散后的分布一般遵循负指数分布曲线,大多数种子并没有扩散到离母树很远的地方。捕食风险、生境类型、植被盖度均影响动物对种子的扩散。植物结实的季节和果实损耗的过程也体现了其对扩散机会的适应。许多动物有贮藏植物种子的行为。动物贮藏植物繁殖体的行为,一方面调节食物的时空分布,提高了贮食动物在食物缺乏期的生存概率;另一方面也为种子萌发提供了适宜条件,促进了植物的扩散。于是,植物与贮食动物形成了一种协同进化关系,这种关系可能是自然界互惠关系（mutualism)的一种。影响幼苗存活和建成的因子包括种子贮蒇点的微生境、湿度、坡向、坡度、林冠盖度等。许多果食性动物吃掉果肉后,再将完好的种子反刍或排泄出来。种子经动物消化道处理后,发芽率常有所提高。     

A latitudinal gradient in seed nutrients of the forest herb Anemone nemorosa

The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post-anthesis and investigated the relative effects of growing degree-hours >5 °C, soil characteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen:phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree-hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitrogen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen availability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success.     

Hidden biodiversity in the Arctic – a study of soil seed banks at Disko Island,Qeqertarsuaq, West Greenland

Seed dispersal is a key process in plant community dynamics, and soil seed banks represent seed dispersal in time rather than in space. Despite their potential importance, seed bank dynamics in the Arctic are poorly understood. We investigated soil seed banks and corresponding plant community composition in three contrasting vegetation types in West Greenland, viz. dwarf shrub heaths, herb slopes and fell‐fields. Through germination testing, 31 species were documented in soil seed banks. All of these were herbaceous, while no dwarf‐shrub species, which represents the dominating growth form in the above‐ground vegetation, were emerging from the seed bank. Consequently, across vegetation types, the lowest similarity between seed bank and above‐ground vegetation was found in dwarf shrub heath. Nine plant species were exclusively found in seed bank, all of which were non‐clonal forbs. Seed bank size (total number of seeds) and species richness seemed to increase with the level of natural disturbance. Additionally, we examined the effect of different experimental light and temperature conditions on the quantity and diversity of germinating seeds. The difference in diversity in vegetation and seed bank at the species level will impact population dynamics, regeneration of vegetation after disturbances and its potential to respond to climate change.     

Latitude, seed predation and seed mass

Aim We set out to test the hypothesis that rates of pre‐ and post‐dispersal seed predation would be higher towards the tropics, across a broad range of species from around the world. We also aimed to quantify the slope and predictive power of the relationship between seed mass and latitude both within and across species. Methods Seed mass, pre‐dispersal seed predation and post‐dispersal seed removal data were compiled from the literature. Wherever possible, these data were combined with information regarding the latitude at which the data were collected. Analyses were performed using both cross‐species and phylogenetic regressions. Results Contrary to expectations, we found no significant relationship between seed predation and latitude (log₁₀ proportion of seeds surviving predispersal seed predation vs. latitude, P = 0.63; R² = 0.02; n = 122 species: log₁₀ proportion of seeds remaining after postdispersal seed removal vs. latitude, P = 0.54; R² = 0.02; n = 205 species). These relationships remained non‐significant after variation because of seed mass was accounted for. We also found a very substantial (R² = 0.21) relationship between seed mass and latitude across 2706 species, with seed mass being significantly higher towards the tropics. Within‐species seed mass decline with latitude was significant, but only about two‐sevenths, as rapid as the cross‐species decline with latitude. Results of phylogenetic analyses were very similar to cross‐species analyses. We also demonstrated a positive relationship between seed mass and development time across ten species from dry sclerophyll woodland in Sydney (P < 0.001; R² = 0.77; Standardized Major Axis slope = 0.14). These data lend support to the hypothesis that growing period might affect the maximum attainable seed mass in a given environment. Main conclusions There was no evidence that seed predation is higher towards the tropics. The strong relationship between seed mass and latitude shown here had been observed in previous studies, but had not previously been quantified at a global scale. There was a tenfold reduction in mean seed mass for every c. 23° moved towards the poles, despite a wide range of seed mass within each latitude.     

Diaspore dispersal season influences root growth and seed traits,but not germination responses,of sympatric Piper species in a seasonal forest

• Seeds may differ in terms of dormancy, longevity, sensitivity to desiccation and dry mass, according to the timing (dry season/rainy season) of diaspore dispersal. In addition, seasonal variations in temperature and water availability can act as signals of the season during seed development, influencing germination responses and root growth. We evaluated the effects of temperature variations and water availability on germination parameters, root growth and seed traits of four coexisting Piper species in seasonal vegetation that differed in diaspore dispersal timing.
• Eight temperature treatments (15, 20, 23, 25, 28, 30, 35 °C, and alternate 30 °C–20 °C) and four induced water potentials (0, −0.3, −0.6 and −1.2 MPa) were used. The parameters germination onset, germination percentage (G%), mean germination time (MGT), root elongation, seed longevity during ex situ storage and dry mass of seeds were evaluated.
• Germination responses observed were independent of the diaspore dispersal timing, such as variations in germination onset, G% and MGT, both in temperature and water availability treatments. In contrast, root elongation, longevity and dry mass of seeds varied according to the time of diaspore dispersal.
• Our results corroborate the hypothesis that the timing of diaspore dispersal is an important factor in controlling the initial development of seedlings in seasonal vegetation, but not in germination responses. The predominance of negative effects of temperature increases and water deficit on root growth shows that the initial stages of plant development can be strongly impacted by these environmental factors.

     

Traits and ecological strategies of Australian tropical and temperate climbing plants

Aim Understanding large scale patterns in trait variation in climbing plants (lianas, vines, scramblers, twiners) is important for the development of a stronger theoretical understanding of climbing plant ecology and for more applied issues such as prediction of community assembly under changing climatic conditions. We compared values of five key functional traits for 388 species of climbing plant from tropical and temperate regions of Australia to quantify variation between these two biogeographic regions. Location Australia. Methods Data on dispersal mode, growth habit, leaf form, leaf size and seed mass were compiled from field measurements and published sources. Comparative analyses were performed in three ways: (1) across species where each species was treated as an independent data point, (2) using evolutionary divergence analyses for each trait, and (3) in multidimensional space using a matrix of similarities between species. Results Tropical climbing plants had 22‐fold greater seed mass and four times greater leaf size than did temperate species. Tropical climbers were more likely to be woody (63%) than were temperate species (40%). Surprisingly we found a similar proportion of animal‐dispersed seeds in the two regions, although we expected animal‐dispersed seeds to be more prevalent in the tropics. We also found similar proportions of simple‐ and compound‐leaved species between the two regions. All of our findings were consistent between cross‐species and phylogenetic analyses indicating that patterns in present‐day species are reflected in the evolutionary history of Australian climbers. Multivariate analyses suggested that there is a spectrum of variation among climbing plants, with tropical species having greater seed mass, leaf size and woody growth compared with temperate climbing plant species. Main conclusions Tropical and temperate climbers of Australia exhibit a mixture of similar and contrasting traits and ecological strategies. Understanding strategy variation along latitudinal gradients will be particularly informative for predicting ecosystem and community structure with climate change.     

Functional traits but not environmental gradients explain seed weight in Mongolian plant species

• Seed weight varies by several orders of magnitude among vascular plant species. However, the importance of potential drivers such as environmental conditions and plant functional traits have rarely been assessed for a larger taxonomic sample.
• We collected seeds of 148 species from 237 sites spread across Mongolia and compared their weight among the major zonal vegetation types, taxonomic groups and a set of functional traits (growth form, dispersal mode, fruit type, storage organs and palatability).
• Seed weight strongly varied among all functional traits and taxonomic groups, but no differences among vegetation zones were detected.
• These results suggest a low impact of environmental conditions on the evolution of seed weight, contrasting the strong phylogenetic signal.

     

Inflow of seeds through the forest edge: evidence from seed bank and vegetation patterns

To determine the influence of the proximity of a forest edge on seed bank composition and diversity, we performed a seed bank sampling at ancient deciduous forests bordering intensive arable fields. Also vegetation patterns were taken into account. We hypothised that forest edges may facilitate the entrance of diaspores of invasive species into the forest and the successive incorporation of these species in the forest seed bank. We noticed a substantial influence of the proximity of an edge on seed bank composition at as well the forested side of the edge as the field side. The forest edge zone was limited to 3 m into the forest and the field edge zone extended 3m into the field. The seed bank samples of field and forest edge are characterised by a higher species diversity and seed density and a higher similarity between seed bank and vegetation, compared to field or forest samples. The forest edges contains fewer pioneer species in comparison with the forest interior and more competitive species and species of edges and clearings compared with field and forest samples. The seed longevity index increases towards the forest interior. We can conclude from our data that the forest and edge seed bank are composed by both seeds from recent dispersal processes and local seed set and by seeds originating from past vegetation on the site. Near the edge, actual seed input seems of primal importance. Further towards the forest interior seed input decreases and long-living seeds of past vegetation become more important. Ancient forest edges thus act as a barrier for seeds of species of the surrounding arable field.     

Evolution of genome size in pines (Pinus) and its life-history correlates: supertree analyses

Genome size has been suggested to be a fundamental biological attribute in determining life-history traits in many groups of organisms. We examined the relationships between pine genome sizes and pine phylogeny, environmental factors (latitude, elevation, annual rainfall), and biological traits (latitudinal and elevational ranges, seed mass, minimum generation time, interval between large seed crops, seed dispersal mode, relative growth rate, measures of potential and actual invasiveness, and level of rarity). Genome sizes were determined for 60 pine taxa and then combined with published values to make a dataset encompassing 85 species, or 70% of species in the genus. Supertrees were constructed using 20 published source phylogenies. Ancestral genome size was estimated as 32 pg. Genome size has apparently remained stable or increased over evolutionary time in subgenus Strobus, while it has decreased in most subsections in subgenus Pinus. We analyzed relationships between genome size and life-history variables using cross-species correlations and phylogenetically independent contrasts derived from supertree constructions. The generally assumed positive relation between genome size and minimum generation time could not be confirmed in phylogenetically controlled analyses. We found that the strongest correlation was between genome size and seed mass. Because the growth quantities specific leaf area and leaf area ratio (and to a lesser extent relative growth rate) are strongly negatively related to seed mass, they were also negatively correlated with genome size. Northern latitudinal limit was negatively correlated with genome size. Invasiveness, particularly of wind-dispersed species, was negatively associated with both genome size and seed mass. Seed mass and its relationships with seed number, dispersal mode, and growth rate contribute greatly to the differences in life-history strategies of pines. Many life-history patterns are therefore indirectly, but consistently, associated with genome size.     

Abundance, distribution and life histories of grassland plants: a comparative study of 81 species

1 This study examines the abundance and distribution of grassland plant species in particular relation to features affecting colonization. Seed production (inversely related to seed size) and recruitment success (positively related) affect colonization ability, suggesting that seed size can be used as a key trait.
2 Data on seed size, dispersal mode, life form, geographical range size and abundance were gathered for 81 grassland plant species in a field study area in Sweden. Seed production and plant size were estimated for 69 of these species. Analyses were performed both across species, with species treated as independent data points, and for 43 'phylogenetically independent contrasts'.
3 The cross-species analyses suggested that local abundance was related to life forms but not dispersal or plant size. Perennials were generally most abundant, as were clonal species. If abundance reflects colonization we predicted that species with intermediately sized seeds (or intermediate seed production) would be most abundant, and this was supported by the phylogenetic contrast but not by cross-species analyses. In the former analysis, a high abundance of species was significantly associated with a small seed size deviation (and seed number deviation) from the median values of these traits in the community.
4 Local abundance, seed production and seed size deviation from the community median value were positively related to geographical range size in the cross-species analysis, but no relationships were seen in the phylogenetic contrast analysis.
5 We conclude that colonization processes do have a significant influence on abundance patterns in grasslands. Seed size is a key trait for colonizing ability, and the effects of the trade-off of seed size vs. seed number must be considered. No single mechanism can be identified that influences both abundance and geographical distribution range.     

Attributes of the seed bank after a century of primary succession on islands in Lake Hjälmaren, Sweden

1 A large number of islands was created when the water table of Lake Hjälmaren, south central Sweden, was lowered between 1882 and 1886. We have complete lists of vascular plant species for 40 of these islands from 1886, 1892, 1903–04, 1927–28 and 1984–85.
2 We have investigated the seed bank on nine of these islands and compared species composition at different soil depths with the species lists from the islands in 1886–1985, and with the present vegetation in the area of seed bank sampling. We have also investigated the distribution in the soil of seeds from species with different ecological attributes, including seed longevity, successional status, seed weight, seed form and species longevity.
3 Seeds in soil samples were allowed to germinate over the course of two summers with an intermediate cold storage. We found 1944 seeds representing 65 taxa. The mean seed density was 84 seeds dm ^–2 .
4 The similarity between the surface soil (0–3 cm) seed bank and the vegetation at the different vegetation analyses increased from 1886 to 1993. The similarity between the present vegetation and the seed bank decreased with increasing soil depth, and the soil at 12–15 cm had no species in common with the present vegetation. Several species now absent from the vegetation were found in the seed bank.
5 Deeply buried seeds came from early successional, annual species with long-term persistent and low-weight seeds, as expected from seed bank theories, but were slightly elongated, which was in contrast to theories. Spherical seeds were associated with the surface soil, as were short-lived and high-weight seeds from late successional, perennial species.     

Are large frugivorous birds better seed dispersers than medium‐ and small‐sized ones? Effect of body mass on seed dispersal effectiveness

Frugivorous birds vary in seed dispersal effectiveness (SDE) depending on their body mass. It has been suggested that large birds are more effective dispersers than small ones because they consume a large number of fruits, disperse seeds of distinct sizes, and transport seeds over long distances. Yet, few studies have evaluated the impact of body mass on SDE of birds. In this study, we compiled one database for the quantity (i.e., frequency of visits to plants and number of seeds removed per visit) and quality (i.e., germination of seeds after gut passage and gut retention time of seeds) of seed dispersal by frugivorous birds to evaluate the impact of body mass on SDE. In addition, we compiled data on plant characteristics such as life‐form, fruit type, number of seeds per fruit, and size of seed to evaluate their influence on the quantity and quality of seed dispersal. Data were analyzed with linear mixed effects models and quantile regressions to evaluate the relationship between body mass of birds and quantity, quality, and SDE, in addition to the influence of plant characteristics on SDE. The body mass of birds was negatively related to the frequency of visits to plants. Furthermore, it was positively related to the number of seeds removed per visit, although negatively related to seed size. The life‐form of plants was the only factor explaining the germination of seeds after gut passage. Yet, the body mass of birds was positively related to the gut retention time of seeds. Small and medium birds have a relatively higher SDE than large birds. These results differ from the assertion that large birds are more effective dispersers of plants. Small and medium birds are also effective dispersers of plants that should be preserved and protected from the impact of human activities.     

Plant functional trait variation in relation to riparian geomorphology: The importance of disturbance

This study examined the patterns of plant functional trait variation in relation to geomorphology, disturbance and a suite of other environmental factors in the riparian margin of the Upper Hunter River, New South Wales, Australia. Vegetation was surveyed on three geomorphic surfaces (point bar, bench and bank) along a 5.5‐km stretch of the Upper Hunter River. Functional traits relating to plant growth and reproduction were collected for the identified species. anova and principal components analysis were used to compare the trait assemblages of species associated with each geomorphic unit. Pearson's correlation coefficients were used to investigate trait variation with respect to environmental variables. There were clear differences in the plant functional trait assemblages associated with the three geomorphic units. Generally the point bar was associated with species that were herbaceous, with small seed mass, a short stature and a high specific leaf area (SLA). Conversely, the bench was associated with grasses that had unassisted seed dispersal and intermediate seed mass and SLA, while species on the bank had tall stature, large seed mass, a high SLA and a perennial life cycle. Variation along the primary gradient of plant functional trait composition was most strongly related to disturbance frequency and to a lesser extent soil nutrients and the proportion of clay and silt, while variation along the secondary gradient was associated with variation in substrate texture as well as soil nutrients.     

Reproductive output of invasive versus native plants

Aim Propagule size and output are critical for the ability of a plant species to colonize new environments. If invasive species have a greater reproductive output than native species (via more and/or larger seeds), then they will have a greater dispersal and establishment ability. Previous comparisons within plant genera, families or environments have conflicted over the differences in reproductive traits between native and invasive species. We went beyond a genus‐, family‐ or habitat‐specific approach and analysed data for plant reproductive traits from the global literature, to investigate whether: (1) seed mass and production differ between the original and introduced ranges of invasive species; (2) seed mass and production differ between invasives and natives; and (3) invasives produce more seeds per unit seed mass than natives. Location Global. Methods We combined an existing data set of native plant reproductive data with a new data compilation for invasive species. We used t‐tests to compare original and introduced range populations, two‐way ANOVAs to compare natives and invasives, and an ANCOVA to examine the relationship between seed mass and production for natives and invasives. The ANCOVA was performed again incorporating phylogenetically independent contrasts to overcome any phylogenetic bias in the data sets. Results Neither seed mass nor seed production of invasive species differed between their introduced and original ranges. We found no significant difference in seed mass between invasives and natives after growth form had been accounted for. Seed production was greater for invasive species overall and within herb and woody growth forms. For a given seed mass, invasive species produced 6.7‐fold (all species), 6.9‐fold (herbs only) and 26.1‐fold (woody species only) more seeds per individual per year than native species. The phylogenetic ANCOVA verified that this trend did not appear to be influenced by phylogenetic bias within either data set. Main conclusions This study provides the first global examination of both seed mass and production traits in native and invasive species. Invasive species express a strategy of greater seed production both overall and per unit seed mass compared with natives. The consequent increased likelihood of establishment from long‐distance seed dispersal may significantly contribute to the invasiveness of many exotic species.     

Experimental assessment of plant seed retention times in fur of cattle and horse

Epizoochorous dispersal of plant seeds is an important long-distance dispersal mechanism. Yet little is known about retention times of seeds in animal furs and hence about potential dispersal distances of the seeds. Here, we used marked seeds of 12 plant species to determine seed depletion curves on Galloway cattle and Haflinger horse in three vegetation types (forest, tall herbage vegetation and meadow), in both dry and rainy weather conditions. In the long fur of Galloway cattle, seeds were retained significantly longer than in the short fur of Haflinger horse. In general, seed retention times were not considerably affected by the structure of the surrounding vegetation. The impact of the weather was negligible, only affecting the retention of some plant species. Negative exponential functions were fitted to the seed depletion curves. Using the parameters of curve estimations in the different conditions of animal species and vegetation structure, half-life seed retention times of up to 13 h for Galloway cattle and up to more than 4 h for Haflinger horse could be calculated, with corresponding potential half-life dispersal distances in the order of magnitude of tens of metres to a few kilometres. Different seed traits correlated with seed retention times in the long cattle fur and in the short horse fur, respectively.