Diaspore Dispersal Research Articles

Comparative study on mechanical properties and biomineralization of hooks in the diaspores of three epizoochorous plant species

Most of the plants using epizoochory show adaptations to this diaspore dispersal strategy by having the diaspores covered by barbs, hooks, spines or viscid outgrowths, which allow diaspores to easily attach to an animal surface. Many previous studies have been mainly focused on the dispersal distances and efficiency, or effectiveness of diverse attachment structures depending on their size, anatomy, and morphology. However, the knowledge about the mechanical properties of these structures remains rather poor. In this study, we use a combination of scanning electron microscopy, energy dispersive X-ray element analysis and nanoindentation, to examine the microstructure, biomineralization and mechanical properties of single hooks in Arctium minus, Cynoglossum officinale and Galium aparine. Both the biomineralization and mechanical properties of the hooks strongly differ in examined plant species; mechanical properties depend on the biomineralization pattern, such as the accumulation of silicon and calcium. Elastic modulus and hardness decrease in the series C. officinaleG. aparineA. minus. Anisotropic mechanical properties are found between the radial and longitudinal directions in each single hook. By characterizing the mechanical properties and biomineralization of plant hooks, this paper contributes to the understanding of attachment biomechanics related to seed dispersal. Statement of significanceThe dispersal of seeds is essential for plant survival. Many of the plants that use the outside surface of animals to transport the seeds show adaptations to this dispersal strategy by having the seeds covered with hooks. Although these hooks have various sizes, morphologies and anatomical structures, all of them provide mechanical interlocking to animal surfaces. To reduce the risk of interlocking failure, the hooks are usually reinforced by mineralization. However, the relationship between mineralization, mechanical properties and specialized function of plant hooks has been largely overlooked. Here we perform a characterization study on the hooks of three plant species. Our results deepen the current understanding of the mineralization-material-function relationship in specialized hooks of plant seeds.

Effect of Vegetation Structure on Lift-Off and Dispersal Velocities of Diaspores with Different Morphological Characteristics in Secondary Wind Dispersal

Diaspore dispersal is crucial in shaping plant population dynamics, biodiversity, and ecosystem functions. The effect of the vegetation structure on the secondary wind dispersal of diaspores with different appendage types is not well understood. Using a wind tunnel and a high-definition video camera, we accurately measured the lift-off and dispersal velocities of diaspores from sixteen plant species across six wind velocities (2, 4, 6, 8, 10, and 12 m s−1) under six simulated vegetation structures. Vegetation structure and appendage type were pivotal factors, explaining 41.1% and 42.3% of the variance in lift-off velocity and accounting for 12.0% and 25.3% of the variability in diaspore dispersal velocity, respectively. Vegetation coverage was the main factor influencing near-surface wind velocity, and the lift-off and dispersal velocities of diaspores changed significantly when vegetation coverage exceeded 40%. Diaspores with one wing, having high lift-off velocities and low dispersal velocities, adopt the anti-long-distance wind dispersal strategy, whereas diaspores with pappus, having low lift-off velocities and high dispersal velocities, adopt the long-distance wind dispersal strategy. In contrast, diaspores with thorn, discoid, balloon, and four wings adopt the non-long-distance wind dispersal strategy, suitable for environments such as low-coverage deserts and desert steppes but not high-coverage typical steppes. This study could help comprehend the effect of the vegetation structure on the dispersal process of diaspores, which facilitate habitat restoration and biodiversity conservation of grassland and forest ecosystems.

A classification system for seed (diaspore) monomorphism and heteromorphism in angiosperms

Abstract‘Seed heteromorphism’ is a broadly- and loosely-defined term used to describe differences in size/mass, morphology, position on mother plants and ecological function (e.g. dispersal, dormancy/germination) of two or more seeds or other diaspores produced by an individual plant. The primary aim of this review paper was to characterize via an in-depth classification scheme the physical structural design (‘architecture’) of diaspore monomorphism and diaspore heteromorphism in angiosperms. The diaspore classification schemes of Mandák and Barker were expanded/modified, and in doing so some of the terminology that Zohary, Ellner and Shmida, and van der Pijl used for describing diaspore dispersal were incorporated into our system. Based on their (relative) size, morphology and position on the mother plant, diaspores of angiosperms were divided into two divisions and each of these into several successively lower hierarchical layers. Thus, our classification scheme, an earlier version of which was published in the second edition of ‘Seeds’ by Baskin and Baskin, includes not only heteromorphic but also monomorphic diaspores, the Division to which the diaspores of the vast majority of angiosperms belong. The scheme will be useful in describing the ecology, biogeography and evolution of seed heteromorphism in flowering plants.

The ecological footprint of outdoor activities: Factors affecting human-vectored seed dispersal on clothing

In the Anthropocene, humans are among the most abundant long-distance seed dispersal vectors globally, due to our increasing mobility and the growing global population. However, there are several knowledge gaps related to the process of human-vectored dispersal (HVD) on clothing. In a multi-site field experiment covering various habitat types in three countries of Central-Europe, we involved 88 volunteer participants and collected 251 HVD samples and 2008 subsamples from their socks and shoes. We analysed the number of diaspores and species in the samples. Specifically, we studied the effects of site characteristics (variables related to habitat types and season), vector characteristics (activity type, gender, clothing type, shoe type) and plant characteristics (species pool of the visited habitats and plant traits) on the number of diaspores and array of species dispersed. We assessed the habits of people that could be relevant for HVD with a questionnaire survey. A total of 35,935 diaspores of 229 plant taxa were identified from the samples, which indicates a huge potential of HVD in dispersing diaspores across habitats and regions. Most diaspores were recorded in grassland habitats, and more diaspores were dispersed during fieldwork than excursions. Clothing type also played a decisive role: there were more diaspores and species when wearing short-top shoes and short trousers than long ones. Even though our study was carried out mainly in natural or semi-natural habitats, a large number of dispersed species were disturbance-tolerants and weeds and only a few were specialists, suggesting the controversial role of HVD in conservation. At the individual level, people can reduce the number of diaspores through their clothing choices and diaspore removal habits, while providing adequate equipment for staff, operating cleaning stations, and increasing awareness of employees are main ways in which unintended diaspore dispersal can be tackled at the institutional level.

Strategies of diaspore dispersal investment in Compositae: the case of the Andean highlands.

Understanding diaspore morphology and how much a species invests on dispersal appendages is key for improving our knowledge of dispersal in fragmented habitats. We investigate diaspore morphological traits in high-Andean Compositae and their main abiotic and biotic drivers and test whether they play a role in species distribution patterns across the naturally fragmented high-Andean grasslands. We collected diaspore trait data for 125 Compositae species across 47 tropical high-Andean summits, focusing on achene length and pappus-to-achene length ratio, with the latter as a proxy of dispersal investment. We analysed the role of abiotic (temperature, elevation and latitude) and biotic factors (phylogenetic signal and differences between tribes) on diaspore traits and whether they are related to distribution patterns across the Andes, using phylogenomics, distribution modelling and community ecology analyses. Seventy-five percent of the studied species show small achenes (length <3.3 mm) and 67% have high dispersal investment (pappus length at least two times the achene length). Dispersal investment increases with elevation, possibly to compensate for lower air density, and achene length increases towards the equator, where non-seasonal climate prevails. Diaspore traits show significant phylogenetic signal, and higher dispersal investment is observed in Gnaphalieae, Astereae and Senecioneae, which together represent 72% of our species. High-Andean-restricted species found across the tropical Andes have, on average, the pappus four times longer than the achene, a significantly higher dispersal investment than species present only in the northern Andes or only in the central Andes. Small achenes and high diaspore dispersal investment dominate among high-Andean Compositae, traits typical of mostly three tribes of African origin; but traits are also correlated with the environmental gradients within the high-Andean grasslands. Our results also suggest that diaspore dispersal investment is likely to shape species distribution patterns in naturally fragmented habitats.

Trade-offs between diaspore dispersal and dormancy within a spike of the invasive annual grass Aegilops tauschii.

Differences in dispersal and dormancy of heteromorphic diaspores of Aegilos tauschii may increase its flexibility to invade/occupy weedy unpredictable habitats by spreading risk in space and time. In plant species that produce dimorphic seeds, there often is a negative relationship between dispersal and dormancy, with high dispersal-low dormancy in one morph and low dispersal-high dormancy in the other, which may function as a bet-hedging strategy that spreads the risk of survival and ensures reproductive success. However, the relationship between dispersal and dormancy and its ecological consequences in invasive annual grasses that produce heteromorphic diaspores is not well studied. We compared dispersal and dormancy responses of diaspores from the basal (proximal) to the distal position on compound spikes of Aegilops tauschii, an invasive grass with heteromorphic diaspores. Dispersal ability increased and degree of dormancy decreased as diaspore position on a spike increased from basal to distal. There was a significant positive correlation between length of awns and dispersal ability, and awn removal significantly promoted seed germination. Germination was positively correlated with GA concentration and negatively correlated with ABA concentration, and the ABA: GA ratio was high in seeds with low germination/high dormancy. Thus, there was a continuous inverse-linear relationship between diaspore dispersal ability and degree of dormancy. This negative relationship between diaspore dispersal and degree of dormancy at different positions on a spike of Aegilops tauschii may facilitate seedling survival in space and time.

Inflated Ovary May Increase the Dispersal Ability of Three Species in the Cold Deserts of Central Asia.

Among the diaspores of angiosperms an inflated ovary (IO) is a novel morphological trait, but no studies have evaluated its effects on dispersal. The primary aim of this study was to determine the effect of the IO on diaspore dispersal in three cold desert species (Carex physodes, Calligonum junceum, and Sphaerophysa salsula). Various morphological features and the mass of fruits and seeds of each species were measured. The role of an IO in diaspore dispersal by wind and water was determined by comparing responses of intact (inflated) IOs and flattened fruits and seeds. Mature diaspores of three species were dispersed by wind, and the IO significantly increased dispersal distance in the field and at different wind speeds in the laboratory. The floating time on water was greater for inflated fruits than flattened fruits and seeds. Since the seed remains inside the IO until after dispersal is completed, the IO of the three species enhances diaspore dispersal. This is the first detailed study on how an IO increases diaspore/seed dispersal. Furthermore, after primary dispersal by wind, secondary dispersal can occur via wind or surface runoff of water, and each method is enhanced by the presence of an IO.

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.

Soil disturbance impacts on ant‐diaspore multilayer networks in a tropical savanna

Abstract1. Current anthropogenic disturbances have changed natural environments, broadly impacting ecosystem services and functions. Here, the authors focused on the secondary dispersal of diaspores by ants, which serve an important ecological function in the natural regeneration of degraded habitats.2. The authors experimentally studied the effects of vegetation suppression and soil disturbance on (i) diaspore removal, (ii) the quality of secondary removal, and (iii) the structure of interaction networks between ants and diaspores. The authors tested whether the disturbance affected the species richness of seed removers, diaspore removal rate, removal distance and time, and removal effectiveness. Additionally, the authors tested whether the structure of ant‐diaspore networks, that is, specialisation, modularity and robustness, is altered by soil disturbance. To do that, the authors studied three degraded and three preserved areas in the Brazilian Cerrado.3. The authors observed 25 ant species interacting with the diaspores. Disturbance did not affect ant species richness, removal distance or removal rate, but ants took twice as long to remove the diaspores in the preserved habitat. The frequency of interaction networks was higher in the preserved habitat, and the effectiveness of species in removing the diaspores differed between habitats. Surprisingly, the authors observed that ants considered effective dispersers mostly occurred in degraded habitats, highlighting the potential of myrmecochory in the regeneration of impacted environments.4. The findings point to the potential of ants in acting as secondary seed dispersal, improving the restoration of areas highly impacted by soil disturbance. Moreover, this study contributes to understanding the effects of anthropogenic disturbances on ecological interactions and ecosystem functions.

Temperature dependence of O2 respiration in mangrove leaves and roots: implications for seedling dispersal phenology.

Seasonal differences in diaspore dispersal of three mangrove species, Kandelia obovata, Bruguiera gymnorrhiza and Rhizophora stylosa, suggest that respiratory energy production and demand may differ as a result of interspecific differences in temperature dependence of growth and maintenance processes during seedling establishment. We analyzed growth, temperature dependencies of respiratory O2 consumption and amounts of respiratory chain enzymes in seedlings of these species grown at various temperatures. Respiration rates measured at the low reference temperature, RREF , were highest in leaves of 15°C-grown K. obovata, whose dispersal occurs in the cold season, while root RREF of 15°C-grown R. stylosa was 60% those of the other species, possibly because of warm conditions during its establishment phase. In leaves and roots of K. obovata and leaves of R. stylosa, the overall activation energy, Eo , changed with growth temperature associated with changes in the ratios of the amount of protein in the two respiratory pathways. However, Eo of seedlings of B. gymnorrhiza, which has a long dispersal phase, were constant and independent of growth temperature. The different temperature responses of seedling respiration and growth among these three species may reflect the seasonal temperature range of seedling dispersal and establishment in each species.

The systematic significance of pod morphological and anatomical variations in Indian Crotalaria L. (Leguminosae)

Pod morphological and anatomical variations of Indian Crotalaria were evaluated to understand the systematic significance and dispersal mechanisms. Pods show variation between species with respect to size, colour, persistence of calyx, presence of trichomes and number of seeds per pod. Pods with length less than 1.5 cm have thicker endocarp when compared to the combined thickness of exocarp+mesocarp (exception being C. berteroana). These pods are likely indehiscent and are dispersed as a unit (enclosing the seeds). On the other hand, pods 1.5 cm or longer have thicker exocarp+mesocarp with respect to the endocarp. These pods dehisce and disperse seeds by explosive mechanism. Seed dispersal is assisted by the sclerenchymatous zone. The angular arrangement of sclereids in opposite directions in the two halves of the narrow fruit enables spiralization soon after explosion of the pods. The orientation of the fibres in the endocarp relative to the longitudinal axis of the fruit is the major factor determining dehiscence. Pericarp anatomy has been categorised into two major types, Type I: with the non-sclerenchymatous zone (exocarp+mesocarp) thicker than the sclerenchymatous zone (endocarp); and Type II: with the sclerenchymatous zone (endocarp) thicker than the non-sclerenchymatous zone (exocarp+mesocarp). The seemingly identical dispersal mechanism in the form of diaspore shows convergent evolution which occurs shows convergent evolution which occurs multiple times in different clades independently (viz., Calycinae and Crotalaria). C. pusilla and C. medicaginea pods possess air cavities, which may be an additional adaptation for diaspore dispersal.

Genetic melting pot and importance of long-distance dispersal indicated in the Gladiolus imbricatus L. populations in the Polish Carpathians

The genetic diversity in 11 populations of Gladiolus imbricatus in five mountain ranges, including the Tatra, Pieniny, Gorce, Beskid Niski (Western Carpathians) and Bieszczady Mts (Eastern Carpathians), was studied with inter-simple sequence repeat (ISSR) markers. The species is a perennial plant occurring in open and semi-open sites of anthropogenic origin (meadows and forest margins). We checked a hypothesis on the microrefugial character of the plant populations in the Pieniny Mts, a small calcareous Carpathian range of complicated relief that has never been glaciated. Plant populations in the Tatra and Pieniny Mts had the highest genetic diversity indices, pointing to their long-term persistence. The refugial vs. the non-refugial mountain ranges accounted for a relatively high value of total genetic variation [analysis of molecular variance (AMOVA), 14.12%, p = 0.003]. One of the Pieniny populations was of hybridogenous origin and shared genetic stock with the Tatra population, indicating there is a local genetic melting pot. A weak genetic structuring of populations among particular regions was found (AMOVA, 4.5%, p > 0.05). This could be an effect of the frequent short-distance and sporadic long-distance gene flow. The dispersal of diaspores between the remote populations in the Western Carpathians and Eastern Carpathians could be affected by the historical transportation of flocks of sheep from the Tatra to Bieszczady Mts.

Evidence of endozoochory in upland geese Chloephaga picta and white-bellied seedsnipes Attagis malouinus in sub-Antarctic Chile.

Birds are known to act as potential vectors for the exogenous dispersal of bryophyte diaspores. Given the totipotency of vegetative tissue of many bryophytes, birds could also contribute to endozoochorous bryophyte dispersal. Research has shown that fecal samples of the upland goose (Chloephaga picta) and white‐bellied seedsnipe (Attagis malouinus) contain bryophyte fragments. Although few fragments from bird feces have been known to regenerate, the evidence for the viability of diaspores following passage through the bird intestinal tract remains ambiguous. We evaluated the role of endozoochory in these same herbivorous and sympatric bird species in sub‐Antarctic Chile. We hypothesized that fragments of bryophyte gametophytes retrieved from their feces are viable and capable of regenerating new plant tissue. Eleven feces disk samples containing undetermined moss fragments from C. picta (N = 6) and A. malouinus (N = 5) and six moss fragment samples from wild‐collected mosses (Conostomum tetragonum, Syntrichia robusta, and Polytrichum strictum) were grown ex situ in peat soil and in vitro using a agar Gamborg medium. After 91 days, 20% of fragments from A. malouinus feces, 50% of fragments from C. picta feces, and 67% of propagules from wild mosses produced new growth. The fact that moss diaspores remained viable and can regenerate under experimental conditions following the passage through the intestinal tracts of these robust fliers and altitudinal and latitudinal migrants suggests that sub‐Antarctic birds might play a role in bryophyte dispersal. This relationship may have important implications in the way bryophytes disperse and colonize habitats facing climate change.

Functional packaging of seeds.

SummaryThe encapsulation of seeds in hard coats and fruit walls (pericarp layers) fulfils protective and dispersal functions in many plant families. In angiosperms, packaging structures possess a remarkable range of different morphologies and functionalities, as illustrated by thermo and hygro‐responsive seed pods and appendages, as well as mechanically strong and water‐impermeable shells. Key to these different functionalities are characteristic structural arrangements and chemical modifications of the underlying sclerenchymatous tissues. Although many ecological aspects of hard seed encapsulation have been well documented, a detailed understanding of the relationship between tissue structure and function only recently started to emerge, especially in the context of environmentally driven fruit opening and seed dispersal (responsive encapsulations) and the outstanding durability of some seed coats and indehiscent fruits (static encapsulations). In this review, we focus on the tissue properties of these two systems, with particular consideration of water interactions, mechanical resistance, and force generation. Common principles, as well as unique adaptations, are discussed in different plant species. Understanding how plants integrate a broad range of functions and properties for seed protection during storage and dispersal plays a central role for seed conservation, population dynamics, and plant‐based material developments.

The Effect of Informal Tourist Trails on the Abiotic Conditions and Floristic Composition of Deciduous Forest Undergrowth in an Urban Area

The study aimed to assess the effect of informal tourist trails on the abiotic conditions and floristic composition of deciduous forest undergrowth in an urban area. The study was carried out in the Wolski Forest in Kraków (Poland) in 2020 using a total of 400 plots (1 m × 1m) situated in close (CL) and further (FU) vicinity of informal (&lt;50 cm in width) and formal (≥150 cm in width) tourist trails in the forest interior and forest edge sites.Agreater content of N-NH4, P, and K occurred in the forest interior sites, while greater light intensity, species number, total plant cover, and stem height were found in the forest edge sites. Greater light intensity and a higher percentage of total and damaged plant cover were recorded in CLplots, while a greater height of plants was seen in FUplots. The number of species was higher in plots located along informal trails than in plots along formal trails. The dominance of therophytes and autochorous species along informal trails in the forest interior sites might be a result of successful diaspore dispersal by people walking, while the substantial share of zoochorous species along formal trails suggests their dissemination by dogs accompanying visitors. The dominance of forest and ruderal taxa in the forest interior sites suggests unfavourable conditions for the germination of meadow and grassland species. The higher cover-abundance of alien plants in CL plots along informal trails and FU plots along formal traits suggests that alien plants growing near the formal trails are more exposed to mechanical damage.

The role of mucilage envelope in the endozoochory of selected plant taxa

Myxodiaspory (formation of mucilage envelope around seeds and fruits) is a common adaptation to dry habitats known in many families of Angiosperms. The mucilage envelope of some seeds seems to be also a unique morphological adaptation which protects myxospermatic diaspores while passing through the bird’s digestive system. To evaluate the protective potential of mucilage, we fed the diaspores of seven plant species (representing three different mucilage types and three species of non-mucilaginous plants) to pigeons, Columba livia domestica. Twenty-four hours later, we collected the droppings of pigeons and examined a total of 18,900 non-destroyed diaspores to check for mucilage presence and germination ability. Out of all the examined diaspores, 4.5% were mucilaginous seeds. Among them, the highest number (12.2–13.5%) of viable diaspores belonged to the hemicellulosic type of mucilage (from Plantago species). Only 3.7% of germinating diaspores with pectic mucilage (Linum usitatissimum) were collected, and no seeds representing cellulosic mucilage (e.g., Ocimum basilicum). For non-mucilaginous plants, we collected only a few individual seeds (0.1% out of 8100 seeds used). We noted that the mucilaginous seeds found in the droppings were able to germinate; however, the germination ability was generally smaller in comparison to the control (i.e., not digested) seeds. Our results revealed that the presence of mucilage envelope has an impact on diaspore dispersal and survivability. With our experiments, we demonstrated for the first time that the mucilage envelope, especially of the non-cellulosic type, supports endozoochory. We also showed that non-mucilaginous seeds can be occasionally dispersed via endozoochory and are able to germinate. The results of our studies can explain the ways of plants distribution at a small, local scale as well as in long-distance dispersal, e.g., between islands or even continents.

Awn Morphology Influences Dispersal, Microsite Selection and Burial of Australian Native Grass Diaspores

© Copyright © 2020 Cavanagh, Morgan and Godfree. Seed dispersal is a vital part of a plant’s life cycle that enables progeny to reach new sites suitable for burial and establishment. Awns are characteristic of many grass species and enable diaspores to self-disperse. Little is known, however, about the role of different awn morphologies in dispersal or burial. The objective of this study was to investigate the influence of awn morphology on diaspore surface dispersal and burial among representative Australian Poaceae. Surface dispersal, burial and microsite selectivity of diaspores were compared across 30 grass species and ten awn morphological types using laboratory and natural simulation experiments. The presence of an awn significantly facilitated surface dispersal and burial of diaspores, with awn length and hygroscopic activity being positively related to both surface dispersal and burial depth. Geniculate (once-bent) and bigeniculate (twice-bent) awns were the most efficient at surface dispersal. Burial efficiency, however, was influenced by microsite conditions; a surface obstruction increased burial for almost all awn types, while falcate (curved)-awned species were effective at burying without such objects. This study indicates that awn morphologies likely play different functional roles in the success of Australian grass progeny.

Seed dispersal of wild radishes and its association with within-population spatial distribution

BackgroundThe wild radishes, Raphanus raphanistrum and R. pugioniformis (Brassicaceae) are native to the East Mediterranean region. However, whereas R. raphanistrum is widely distributed worldwide, the endemic R. pugioniformis is limited to specific habitats. In R. raphanistrum the diaspores of the indehiscent fruits comprise glabrous, light, single-seeded segments, whereas the intact fruits of R. pugioniformis are heavy and covered with spiny backward-pointing trichomes. We aimed to investigate whether the structure of the diaspores was directly associated with long- and short-range dispersal in R. raphanistrum and R. pugioniformis, respectively. We further surveyed within-population spatial distributions, to test the hypothesis that short- and long-range dispersal contribute to a patchy vs. uniform distribution patterns of R. pugioniformis and R. raphanistrum, respectively.ResultsThe results indicated that dispersal by wind and run-off water was substantially lower for diaspores of R. pugioniformis than for those of R. raphanistrum diaspores. Supporting the hypothesis that backward-pointing trichomes promote adherence to soil particles, the displacement on soil surface of R. pugioniformis fruits depended on their orientation relative to wind direction. Furthermore, trichome removal from fruits of R. pugioniformis significantly reduced wind velocity needed to remove fruits that were placed on soils typical of the species’ natural habitats. The spatial-distribution survey results indicated a patchy distribution of R. pugioniformis populations as compared with the more uniform arrangement in the studied populations of R. raphanistrum; consistent with the unidirectional vs. homogeneous wind dispersal of the respective diaspores, with respect to wind direction. In addition, R. pugioniformis population sizes changed less between years than those of R. raphanistrum.ConclusionsOverall, our results indicate that fruit structure is strongly linked to dispersal ability and spatial distribution of the two closely related wild radish species. Whereas R. raphanistrum inhabits homogenous sandy soil habitats, the distribution range of R. pugioniformis includes heterogeneous environments in which growth niches are scarcer. We suggest that the different modes of dispersal have evolved as adaptive traits appropriate to the species’ specific habitats.

Environmental variables drive phenological events of anemocoric plants and enhance diaspore dispersal potential: A new wind-based approach

Phenological studies of Brazilian savanna vegetation have described a generalized phenological pattern for all species, mainly based on rainfall and temperature. Few studies have considered wind as an explanatory factor; abiotic factors may impact differently on phenophases, and one phenophase may influence the performance of another. Thus, we aim to describe the phenological patterns of five anemocoric plant species (Aspidosperma tomentosum, Dalbergia miscolobium, Kielmeyera coriacea, Peixotoa tomentosa and Qualea multiflora) in the face of different climatic conditions, mainly evaluating the effects of wind on the ripe diaspore. We addressed three main questions: (1) What is the phenological behavior of each of these five anemocoric species in a seasonal environment? (2) Which climatic variables best explain each phenophase? (3) Does the dispersal of ripe diaspores peak shortly after deciduousness? We found that (i) our focal species showed similar phenological patterns, except for the floral bud and flower phenophases of two species (A. tomentosum and P. tomentosa), and the young fruit phase; (ii) each abiotic variable has a specific level of influence for each phenophase, but the most important variables were rainfall and wind speed; and (iii) the dispersal peak of ripe diaspores occurred shortly after deciduousness, and when plants had fewer leaves. We conclude that the phenological patterns of these five anemocoric plants are similar, but that the patterns observed are not necessarily those described for Cerrado species. Additionally, we found that wind is an important factor in the expression of specific phenophases, and that the performance of some phenological events can be influenced by others, especially diaspore dispersal.

Ants as diaspore removers of non‐myrmecochorous plants: a meta‐analysis

Diaspore (e.g. seeds, fruits) dispersal is pivotal for plant communities and often involves several steps and different dispersing agents. Most studies focusing on diaspore dispersal by animals have highlighted the role of vertebrates, neglecting the role of ants in the diaspore dispersal of non‐myrmecochorous plants. Diaspore dispersal by ants is especially relevant in the current scenario of declining of vertebrate populations and, consequently, collapse of the dispersal system of large‐seeded plants. Although ants can never compensate for the dispersal service provided by vertebrates, they can mitigate the impact of vertebrate decline via removal of diaspores deposited on the ground. We have used a meta‐analytical approach to investigate the contribution of ants in the removal of non‐myrmecochorous diaspores (through vertebrate exclusion experiments). We considered the number of diaspore removal as effect size and factors such as plant growth forms, diaspore and ant size, habitat type as moderators. In addition, we investigated the role of such factors on the diaspore removal distance by ants. Ants played complementary role to non‐myrmecochorous diaspore removal services provided by vertebrates (mean Hedges’ g of −0.30). The ant diaspore removal was 69% higher for diaspores from shrubs than that of tree diaspores and removal of small‐sized diaspores were 69% and 70% higher in comparison to medium‐ and large‐sized diaspores, respectively. Regarding the diaspore removal distance by ants, those of tree species were removed 32% farther than those of shrub species, and diaspores were removed three‐ times farther in the savanna than in rainforest ecosystems. Our results highlight the shrubs and small‐sized diaspores. Regarding the diaspore removal distance, the ants can be crucial for the dispersal of tree diaspores and in the savanna ecosystems. Finally, considering the biodiversity crisis, the ants may play an even more important role than appreciated in diaspores dispersal.