Seed Dispersal Research Articles

Interactions between ants and non-myrmecochorous diaspores in a West African montane landscape

AbstractMyrmecochory, the dispersal of seeds with lipid-rich appendages by ants, is a significant ant–plant interaction. Less well understood is the potential for ant dispersal of non-myrmecochorous seeds. Here we investigate ant–diaspore interactions in a West African montane habitat. We combine observation with depot experiments to determine ant species that move diaspores and distance moved across a forest-edge-grassland gradient. We recorded seed cleaning by ants using a bird/mammal dispersed Paullinia pinnata to determine whether seed cleaning improved plant fitness. We found that two out of a total of 17 ant species (Pheidole sp. 1 and Myrmicaria opaciventris) interacted with 10 species of non-myrmecochorous diaspores across nine plant families. Diaspores were from large canopy trees, understorey trees and vines. Both ant species interacted with small (≤0.24 g) and large (≥0.24 g) diaspores. Ants individually moved small diaspores up to 1.2 m and worked together to clean larger ones. Our experiments with P. pinnata showed that ants removed the pulp of 70% of fruit over 5 days. Cleaned seeds germinated significantly faster and produced seedlings with significantly longer shoot length and higher fresh weight than seedlings from intact seeds. Together our results suggest that ant dispersal may be less significant than seed cleaning in Afromontane forests. However, given the decline in vertebrate frugivores across Africa, a small dispersal advantage may become increasingly important to plant fitness.

New evidence of seed dispersal identified in Australian mammals

Context Mammal–seed interactions are important for structuring vegetation communities across a diverse range of ecosystems worldwide. In Australia, mammals are typically considered to be seed predators and to play insignificant roles in seed dispersal. However, very few studies have investigated endozoochorous seed dispersal in Australian species. The translocation of Australian mammals for the purposes of ecosystem restoration is increasing. Digging mammals (i.e. species that dig to obtain food or create shelter) are commonly the focus of these translocations because they are considered to be ecosystem engineers, but an understanding of their role in seed dispersal is lacking. Aims The aim of the present study was to expand the understanding of endozoochory in Australian digging mammals by determining whether seeds consumed by select species remain viable and able to germinate. Methods Scat samples were collected from five digging mammal species, known to consume seeds or fruit, across nine sites in Western and South Australia. The samples were searched for seeds, with the recovered seeds identified and tested for viability and germination capacity. Key results The abundance of intact seeds in scats was generally low, but 70% of the retrieved seeds appeared viable. Five species of seed germinated under laboratory conditions. These seeds were retrieved from bilby (Macrotis lagotis), boodie (Bettongia lesueur), golden bandicoot (Isoodon auratus) and quenda (I. fusciventer) scats. Conclusions Seeds consumed by Australian digging mammals can remain viable and germinate, indicating that digging mammals play a more important role in seed dispersal than previously considered. Implications Digging mammals have the potential to contribute to ecosystem restoration efforts through the dispersal of viable seeds, but there is also a risk that non-native species could be dispersed. These costs and benefits should be considered by practitioners when planning reintroductions of digging mammals.

Numerical Analysis to Predict Temperature Distribution of Passion Fruit Seeds During Drying

HighlightsA temperature distribution occurred due to temperature differences between the surface and inside passion fruit seeds.The temperature distribution occurred simultaneously in all directions.The temperature distribution decreased at greater depths inside the seeds.The same temperature distribution pattern occurred in the vertical and horizontal directions.Abstract. Optimization of the drying process can be determined based on temperature distribution patterns using numerical analysis with the finite element method (FEM). This study compiled a numerical analysis using FEM to predict the temperature distribution in passion fruit seeds during drying. The study was conducted using a circulating-air tray dryer. Temperature distribution data on passion fruit seeds were measured using a data logger. The results showed that numerical analysis using FEM quickly and accurately simulated the temperature distribution in passion fruit seeds during drying. The model was validated by comparing the temperature distribution data measured in the drying chamber with the simulation results, with a relative error of 0.45% to 1.27%. Numerical analysis using FEM provides an useful reference for controlling temperature distribution during drying because this method is easy to implement and results in low errors. Keywords: Drying, Finite element methods, Numerical analysis, Passion fruit seeds, Temperature distribution.

Role of Tartaric Acid in the Ecology of a Zoochoric Fruit Species, Tamarindus indica. L

ABSTRACT Zoochoric plants usually produce fruits with a mechanical barrier in the exocarp, or chemical inhibitors in the fruit pulp (mesocarp) or seed coat (endocarp) to achieve required dormancy. Tamarindus indica L. is one such zoochoric tree species, but the role of possible bioactive chemicals in the ecology of its fruit and seed dispersal has not been explored before. We investigated the germination inhibitory effects of T. indica fruit pulp by comparing germination of intact T. indica fruits with depulped T. indica seeds. This experiment revealed that attached pulp (including exocarp) delayed or decreased germination via an unverified mechanism. We then analyzed the pulp (including exocarp) to find out if there was a dominant bioactive chemical, by creating extracts using both alcohol and aqueous fractionation, and then analyzed them using GLC-MS analysis. We discovered that tartaric acid was the main bioactive chemical present in the methanol fraction (but not aqueous), so decided to test its effect on T. indica seed germination. We exposed viable depulped T. indica seeds to varying concentrations of pure tartaric acid in distilled water and found germination inhibition was observed at a concentration of 0.4 mg/ml. Therefore, since tartaric acid is the major chemical component in T. indica fruit pulp, it is possible that it could play a crucial role in the zoochoric dispersal of seeds by inhibiting germination while they are still attached to the tree or have just fallen close to the parent tree so that they have an opportunity to reach distant sites favorable for germination.

Crystallographic orientation and strain distribution in AlN seeds grown on 6H–SiC substrates by the PVT method

AlN crystal is prepared on 6H–SiC substrate by PVT method, the growth pattern is [0001]AlN‖[0001]6H–SiC and [101̄0]AlN‖[101̄0]6H–SiC and the stress in AlN layer decreases with the increase of thickness.

Orchidaceae in a fragment of restinga on the north coast of Bahia, Brazil

Abstract Área de Proteção Ambiental das Lagoas e Dunas do Abaeté (APA Abaeté) is an urban fragment of restinga in an environmentally protected area in the municipality of Salvador, Bahia, Brazil. The area is impacted by irregular disposal of solid waste, clandestine removal of sand from dunes, suppression and fragmentation of original vegetation cover and urban growth of neighborhoods. A recent floristic study revealed new records of orchid species for this conservation unit but highlighted strong threats to the orchid flora. In this context, a taxonomic study of Orchidaceae in APA Abaeté was undertaken with the aim of facilitating the recognition of species in the field and supporting the establishment of more effective local conservation actions for orchids, which should include the manual dispersion of seeds and the relocation of individuals. Orchidaceae is the sixth most represented family in APA Abaeté, with 15 genera and 19 species, including Encyclia dichroma and Koellensteinia florida, endemic species of the Atlantic Forest. The most relevant morphological characteristics for the identification of species in the area are: growth type; climbing habit; caulome thickness; shape and consistency of leaf blades; inflorescence type and position; and color and resupination of flowers.

Victoria L. Sork—Recipient of the 2020 Molecular Ecology Prize

Victoria L. Sork—Recipient of the 2020 Molecular Ecology Prize

Urban ecological network

Protected Areas (PAs) have been implemented to preserve the remnants of native vegetation, playing a fundamental role in biodiversity conservation. For PAs to be potentially efficient, they must connect to other PAs and/or other remnants in the anthropic landscape, with the matrix permeability being an imperative factor in the dispersion of species, seeds, and pollens. The study's objective was to delineate an ecological network of protected areas inserted in an urban landscape. Geoprocessing and Graph Theory techniques were used to assess functional connectivity between PAs. The focus species used were forest birds, which are endemic to the Atlantic Forest. The information about dispersion capabilities came from the consultation of experts and resulted in a resistance surface. The dispersion model simulation in the landscape resulted in the least-cost path (LCP) and designed the urban ecological network. The LPC was characterized considering the buffer equal to 100m width. The resistance values for each land-use/land-cover, representing endemic bird species of the Atlantic Forest, were equal to one for the native forest located within the PAs. The LCPs were designed by 136 connectors, mostly by native forest (61.3%) and anthropic grasslands (21%). The riparian forests are an essential part of the LCP. The promotion of connectivity between PAs in an anthropic landscape needs the effectiveness of ecological restoration and/or conservation actions and matrix permeability analysis. The connection between PAs by ecological networks must be implemented as a conservation strategy in cities concerning the current era of urban expansion.

Velocity of the falling dispersal units in Zelkova abelicea: remarkable evolutionary conservation within the relict tree genus.

Seed dispersal is extremely important for the recovery and restoration of forest communities. Relict tree genus Zelkova possesses a unique dispersal mechanism: mature fruits fall with the entire twig, and the dried leaves that are still attached function as a drag-enhancing appendage, carrying the fruits away from the parent tree. This singular adaptation has never been investigated in Z. abelicea. Drop tests with dispersal units and individual fruits of Z. abelicea were performed in controlled conditions to measure their dispersal velocity and to define their flight mode. Zelkova abelicea uses both slowly falling dispersal units with chaotic motion, as well as fast falling individual fruits using a straight path. The falling velocity of Z. abelicea dispersal units is 1.53 m s-1 , which is virtually identical to that of the East Asiatic Z. serrata (1.51 m s-1 ). In contrast, the falling velocity of individual fruits was m s-1 (Z. serrata: 5.36 m s-1 ). Members of the genus Zelkova, growing today in distant regions, show remarkable evolutionary conservation of the velocity and flight mechanics of their dispersal units. This is surprising because the Mediterranean and East Asiatic Zelkova species have been separated at least 15-20 mya. Zelkova abelicea, although growing in the Mediterranean with completely different forest structure and composition, still uses the same dispersal mechanism. The dispersal capacity of the genus Zelkova is less efficient than that of other wind dispersed trees, and it presumably evolved for short-distance ecological spread and not for long-distance biogeographical dispersal.

Hypothesis of tumbleweed-like dispersal of Drosera seeds

Erect-growing tuberous sundews of Drosera subgenus Ergaleium section Ergaleium produce seeds of diverse size and shape. Seeds produced by such species as D. andersoniana, D. macrantha, and D. pallida are large and winged, and fit the classic model of those dispersed by the wind. However, many species in this section produce small, round seeds (e.g. D. gigantea, D. salina, and D. yilgarnensis) that appear better suited to dispersal by gravity or water than by the wind. I propose here, that long-distance dispersal of these species may also be facilitated by the transport of detached plant parts, with seed, by the wind.

A simple standardized protocol to evaluate the reliability of seed rain estimates

AbstractSeed dispersal has key implications for community dynamics and restoration ecology. However, estimating seed rain (the number and diversity of seeds arriving in a given area) is challenging, and the lack of standardization in measurement prevents cross-site comparisons. Seed trap effectiveness and accuracy of seed sorting methods are key components of seed rain estimates in need of standardization. We propose and describe a standardized protocol for evaluating the effectiveness of two seed trap types (sticky and funnel traps) and the accuracy of a seed sorting method. We used widely available seeds (arugula, quinoa, sesame and sunflower) to produce a gradient of seed size, weight and colour. Proof-of-concept was tested in a tropical grassland, where traps were set for 30 days. Our results suggest that we underestimate dispersal of seeds with less than 2 mm width that can be easily mistaken for debris and soil particles or that fail to adhere to sticky traps. Seeds on sticky traps may be more vulnerable to removal by wind and rain, whereas seeds in funnel traps are more susceptible to decay. We found no evidence of observer bias on seed sorting for funnel trap samples. However, accuracy on seed sorting for funnel trap samples tended to decline for seeds with less than 2 mm width, suggesting a size-dependence in seed retrieval success. Our standardized protocol addressing trap effectiveness and seed sorting methods will increase the reliability of data obtained in seed rain studies and allow more reliable comparisons between datasets.

Adaptive associations among life history, reproductive traits, environment, and origin in the Wisconsin angiosperm flora.

We tested 25 classic and novel hypotheses regarding trait-origin, trait-trait, and trait-environment relationships to account for flora-wide variation in life history, habit, and especially reproductive traits using a plastid DNA phylogeny of most native (96.6%, or 1494/1547 species) and introduced (87.5%, or 690/789 species) angiosperms in Wisconsin, USA. We assembled data on life history, habit, flowering, dispersal, mating system, and occurrence across open/closed/mixed habitats across species in the state phylogeny. We used phylogenetically structured analyses to assess the strength and statistical significance of associations predicted by our models. Introduced species are more likely to be annual herbs, occupy open habitats, have large, visually conspicuous, hermaphroditic flowers, and bear passively dispersed seeds. Among native species, hermaphroditism is associated with larger, more conspicuous flowers; monoecy is associated with small, inconspicuous flowers and passive seed dispersal; and dioecy is associated with small, inconspicuous flowers and fleshy fruits. Larger flowers with more conspicuous colors are more common in open habitats, and in understory species flowering under open (spring) canopies; fleshy fruits are more common in closed habitats. Wind pollination may help favor dioecy in open habitats. These findings support predictions regarding how breeding systems depend on flower size, flower color, and fruit type, and how those traits depend on habitat. This study is the first to combine flora-wide phylogenies with complete trait databases and phylogenetically structured analyses to provide powerful tests of evolutionary hypotheses about reproductive traits and their variation with geographic source, each other, and environmental conditions.

Reproductive system and interaction with fauna in a Mediterranean Pyrophite shrub

ABSTRACT The ULEX model, in its present state, involves the study of the biomass and the population of the shrub Ulex parviflorus Pourret, but while being a dynamic model, it is static in the sense that it does not imply the appearance of new specimens of this plant. As a complement to the ULEX model in its two dynamic and spatial aspects, and with the idea of extending the model, the authors have introduced from a biological and statistical point of view four characteristics of this species, flowering, pollination, fructification, taking special interest in the role played by the pollinators (bees) and dispersion of seeds.

VOLATILE ORGANIC COMPOUNDS

Diverse amount of volatile organic compounds is synthesized by plants, proven to be of utmost importance to the plants in various stages of their perpetuation cycle. Their functions are attraction of insects for pollination, dispersal of seeds, helping plants to withstand competition from neighboring plants, contributing towards maintaining plant biodiversity, helping in growth of agriculturally important plants and aiding plants in combating both abiotic stress and biotic stress. Calcium ions and ROS (reactive oxygen species) plays a crucial role as signaling molecules in plants in pathways dealing with induction of synthesis of VOCs in response to various biotic and abiotic stresses and the mechanisms elucidating the survival of plants in such conditions. Apart from this, the concern arising from the expected effects of global climatic changes on rate of synthesis and emission of VOCs in plants has also been expressed. The later part of the paper highlights the beginning of a novel field of metabolic engineering which deals with engineering of biochemical pathways of biosynthesis of VOCs in a manner so as to maximize the yield of beneficial VOCs and at the same time minimizing the yield of harmful VOCs to obtain desired results. The achievements that have been attained, the unintended effects that creep in and the challenges that need to be overcome to make advancements in the field of metabolic engineering have also been included.

Dispersal and germination of winged seeds of Brandisia hancei, a shrub in karst regions of China

Brandisia hancei (Paulowniaceae) is a widely distributed shrub in karst regions in southwestern China. Its seeds have a membranous wing, and they mature just before the rainy season begins. To assess the effect of the wing on seed dispersal and germination of B. hancei, we measured the dispersal distance at varying wind speeds and release heights, falling duration from different release heights, floating duration on still water, rates of imbibition of water, and drying and soil adherence to seeds. Germination experiments were conducted on intact and de-winged seeds immediately after harvest. The wing increased the falling duration in still air and the floating ability on water. Dispersal distance of winged and de-winged seeds did not differ at a wind speed of 2.8 m s−1, but at 3.6 and 4.0 m s−1 dispersal distances were greater for de-winged than for winged seeds. Seed wing had little effect of absorption and retention of water, but significantly increased soil adherence to the seeds. Mature seeds were non-dormant and germinated to over 90% with a mean germination time of about 10 days. By combining the environmental conditions in karst habitat with the seed traits of B. hancei, we conclude that dispersal and germination of winged seeds are adapted to the precipitation seasonality in heterogeneous habitats absence of soil.

Ant preference for seeds without awns increases removal of exotic relative to native grass seeds

1. The removal of seeds by granivorous ants can affect plant recruitment through either seed loss from predation or the dispersal and recruitment of seeds that are removed but not consumed. Consequently, variation in ant selection preferences can influence patterns of seed removal and affect plant community composition, including the spread of exotic plant species.2. We conducted a seed removal experiment to determine whether: 1) rates of removal by ants differed between three native and three exotic grass species in an Australian temperate grassland; and 2) differences in removal rates were associated with the presence or absence of awns.3. We found that seeds of the three exotic species, none of which had awns, were removed by ants at a higher rate than those of the three native species, all of which had awns. Removal rates of native species increased when awns were manually removed, suggesting the awns of native species acted as a removal barrier.4. While we do not know the fate of seeds removed from our experiment, differences among species in removal rates mirrored differences in their spatial spread in a separate seed addition experiment. Exotic species removed by ants at a higher rate in the removal experiment had more widely dispersed seedlings than native species in the seed addition experiment, potentially indicating a role for granivorous ants in dispersing exotic seeds. Identifying ant selection preferences and directly linking removal to seed fate could help explain how exotic grass species move around the landscape.

Seed Shadows of Northern Pigtailed Macaques within a Degraded Forest Fragment, Thailand

Research Highlights: Frugivores able to disperse large seeds over large distances are indispensable for seedling recruitment, colonization and regeneration of tropical forests. Understanding their effectiveness as seed dispersal agents in degraded habitat is becoming a pressing issue because of escalating anthropogenic disturbance. Although of paramount importance in the matter, animal behaviour’s influence on seed shadows (i.e., seed deposition pattern of a plant population) is difficult to evaluate by direct observations. Background and Objectives: We illustrated a modeling approach of seed shadows incorporating field-collected data on a troop of northern pigtailed macaques (Macaca leonina) inhabiting a degraded forest fragment in Thailand, by implementing a mechanistic model of seed deposition with random components. Materials and Methods: We parameterized the mechanistic model of seed deposition with macaque feeding behavior (i.e., consumed fruit species, seed treatments), gut and cheek pouch retention time, location of feeding and sleeping sites, monthly photoperiod and movement patterns based on monthly native fruit availability using Hidden Markov models (HMM). Results: We found that northern pigtailed macaques dispersed at least 5.5% of the seeds into plantation forests, with a majority of medium- to large-seeded species across large distances (mean > 500 m, maximum range of 2300 m), promoting genetic mixing and colonization of plantation forests. Additionally, the macaques produced complementary seed shadows, with a sparse distribution of seeds spat out locally (mean >50 m, maximum range of 870 m) that probably ensures seedling recruitment of the immediate plant populations. Conclusions: Macaques’ large dispersal distance reliability is often underestimated and overlooked; however, their behavioral flexibility places them among the last remaining dispersers of large seeds in disturbed habitats. Our study shows that this taxon is likely to maintain significant seed dispersal services and promote forest regeneration in degraded forest fragments.

The Ectopic Expression of Btr2 in Aegilops tauschii Switches the Disarticulation Layer From Above to Below the Rachis Node.

Seed dispersal among wild species belonging to the tribe Triticeae is typically achieved by the formation of a brittle rachis. The trait relies on the development of a disarticulation layer, most frequently above the rachis node (resulting in wedge type dispersal units), but in some species below the rachis node (resulting in barrel type dispersal units). The genes responsible for the former type are the complementary pair Btr1 and Btr2, while the genetic basis of the latter type has yet to be determined. Aegilops tauschii forms barrel type dispersal units and previous study showed this species lacked an intact copy of Btr1. Here it has been demonstrated that Ae. tauschii carries two of Btr2; and that Btr2 transcript is present in a region below the rachis node where the abscission zone forms. The implication is that in this species, the Btr2 product is involved in the formation of barrel type dispersal units.

Identifying the optimal spatial distribution of tracers for optical sensing of stream surface flow

Abstract. River monitoring is of particular interest as a society that faces increasingly complex water management issues. Emerging technologies have contributed to opening new avenues for improving our monitoring capabilities but have also generated new challenges for the harmonised use of devices and algorithms. In this context, optical-sensing techniques for stream surface flow velocities are strongly influenced by tracer characteristics such as seeding density and their spatial distribution. Therefore, a principal research goal is the identification of how these properties affect the accuracy of such methods. To this aim, numerical simulations were performed to consider different levels of tracer clustering, particle colour (in terms of greyscale intensity), seeding density, and background noise. Two widely used image-velocimetry algorithms were adopted: (i) particle-tracking velocimetry (PTV) and (ii) particle image velocimetry (PIV). A descriptor of the seeding characteristics (based on seeding density and tracer clustering) was introduced based on a newly developed metric called the Seeding Distribution Index (SDI). This index can be approximated and used in practice as SDI=ν0.1/ρρcν1, where ν, ρ, and ρcν1 are the spatial-clustering level, the seeding density, and the reference seeding density at ν=1, respectively. A reduction in image-velocimetry errors was systematically observed for lower values of the SDI; therefore, the optimal frame window (i.e. a subset of the video image sequence) was defined as the one that minimises the SDI. In addition to numerical analyses, a field case study on the Basento river (located in southern Italy) was considered as a proof of concept of the proposed framework. Field results corroborated numerical findings, and error reductions of about 15.9 % and 16.1 % were calculated – using PTV and PIV, respectively – by employing the optimal frame window.

The importance of individual movement and feeding behaviour for long-distance seed dispersal by red deer: a data-driven model

BackgroundLong-distance seed dispersal (LDD) has strong impacts on the spatiotemporal dynamics of plants. Large animals are important LDD vectors because they regularly transport seeds of many plant species over long distances. While there is now ample evidence that behaviour varies considerably between individual animals, it is not clear to what extent inter-individual variation in behaviour alters seed dispersal by animals.MethodsWe study how inter-individual variation in the movement and feeding behaviour of one of Europe’s largest herbivores (the red deer, Cervus elaphus) affects internal seed dispersal (endozoochory) of multiple plant species. We combine movement data of 21 individual deer with measurements of seed loads in the dung of the same individuals and with data on gut passage time. These data serve to parameterize a model of passive dispersal that predicts LDD in three orientations (horizontal as well as upward and downward in elevation).With this model we investigate to what extent per-seed probabilities of LDD and seed load vary between individuals and throughout the vegetation period (May–December). Subsequently, we test whether per-seed LDD probability and seed load are positively (or negatively) correlated so that more mobile animals disperse more (or less) seeds. Finally, we examine whether non-random associations between per-seed LDD probability and seed load affect the LDD of individual plant species.ResultsThe studied deer dispersed viable seeds of at least 62 plant species. Deer individuals varied significantly in per-seed LDD probability and seed loads. However, more mobile animals did not disperse more or less seeds than less mobile ones. Plant species also did not differ significantly in the relationship between per-seed LDD probability and seed load. Yet plant species differed in how their seed load was distributed across deer individuals and in time, and this caused their LDD potential to differ more than twofold. For several plant species, we detected non-random associations between per-seed LDD probability and seed load that generally increased LDD potential.ConclusionsInter-individual variation in movement and feeding behaviour means that certain deer are substantially more effective LDD vectors than others. This inter-individual variation reduces the reliability of LDD and increases the sensitivity of LDD to the decline of deer populations. Variation in the dispersal services of individual animals should thus be taken into account in models in order to improve LDD projections.