Long-distance Dispersal Of Seeds Research Articles

Foliage shedding in deciduous forests lifts up long-distance seed dispersal by wind

Seed terminal velocity and release height are recognized as key biotic determinants of long-distance dispersal (LDD) of seeds by wind. Yet, potential determinants at the ecosystem level, such as seasonal dynamics in foliage density characterizing many deciduous forests, have received much less attention. We integrated detailed field observations and experiments with a mechanistic wind dispersal model to assess how seasonal variation in foliage density, estimated by leaf-area index (LAI), affects LDD in deciduous forests. We found that the model, previously shown to accurately predict seed dispersal by wind, also reliably describes the effects of LAI variation on wind statistics for a wide range of canopy types. Sparser canopies are characterized by more organized vertical eddy motion that promotes LDD by uplifting seeds to higher elevations where winds are stronger. Yet, sparser canopies are also characterized by reduced mean windspeed aloft. We showed that former effect more than compensates for the latter, i.e., conditions of low LAI are favorable for LDD. This may account for the tendency of many temperate tree species to restrict seed release to either early spring or late fall, when LAI is relatively low. Sensitivity analysis reveals that the typical seasonal variation in LAI can be more important to LDD of seeds by wind than the natural variation in seed terminal velocity. Because our model accurately describes the effects of LAI variation for distinctly different sites, species, and life forms, we suggest that its results reflect a general association between LDD and foliage density dynamics.

Effects of premigratory fasting on the potential for long distance dispersal of seeds by waterfool : an experiment with Marbled Teal

Effets du jeûne prémigratoire sur la potentialité des oiseaux d’eau à disséminer des graines à longue distance : une expérience avec la Sarcelle marbrée. — L’effet possible du jeûne prémigratoire sur la potentialité des oiseaux migrateurs à disséminer au loin des graines a été testé en captivité sur neuf Sarcelles marbrées Marmaronetta angustirostris. En début d’expérience les oiseaux ont été gavés avec un mélange de graines de deux espèces de Scirpus (dont une avec de grosses graines) et de marqueurs en plastique de deux tailles différentes (Ø 1,0 et 0,5 mm). Cinq individus ont été privés de nourriture durant 8 heures (phase de jeûne) puis privés à la fois d’eau et de nourriture durant 8 autres heures (phase de simulation de vol). Quatre individus de contrôle ont subi la phase de vol mais sans jeûne préalable. Plus de 16 heures après le gavage, un nombre significatif de graines et de marqueurs de petite taille fut recueilli dans les fèces alors que les graines et les marqueurs de grande taille en étaient pratiquement absents. Quand la nourriture fut de nouveau mise à disposition après la phase de simulation de vol, les oiseaux qui avaient été auparavant soumis à une phase de jeûne déféquèrent plus de graines de la petite espèce et de petits marqueurs que les individus de contrôle. Ces résultats suggèrent que le jeûne prémigratoire peut favoriser la dispersion à longue distance de graines par les oiseaux via la rétention de propagules dans le tube digestif.

An Experimental Evaluation of the Arctic Fox (Alopex lagopus) as a Seed Disperser

Arctic foxes are evaluated as seed dispersal vectors for Greenlandic plant species through a feeding experiment with subsequent scat analysis and germination test. Seeds of 22 common species with different morphology were tested. Passage time ranged between 4 and 48 h. No significant differences were detected in passage time for seeds with different morphology. Cerastium alpinum and Stellaria longipes had higher germination after passage through the fox’s digestive tract when compared to controls. Sibbaldia procumbens, Oxyria digyna, and Silene acaulis were favored by passage when shorter than 10 h. Salix glauca ssp. callicarpaea, Veronica alpina, Gnaphalium norvegicum, Papaver radicatum, Ranunculus hyperboreus, Chamaenerion latifolium, Luzula parviflora, and bulbils of Polygonum viviparum and Saxifraga cernua were inhibited by passage, whereas the remaining species had germination percentage too low to allow for evaluation. Species with adaptations to wind dispersal seemed particularly vulnerable to gut passage. Arctic foxes are able to provide long-distance dispersal of seeds lacking morphological adaptations to dispersal, but for most species seeds need to be defecated within 12 h to remain viable.

Effects of gut treatment on recovery and germinability of bovine and ovine ingested seeds of four woody species from the Sudanian savanna in West Africa

Passage rate through the digestive tracts of zebu cattle and sheep, and subsequent germination of egested seeds of four woody species from the Sudanian savanna, Acacia dudgeoni , Acacia seyal , Burkea africana and Prosopis africana , were studied. The result indicates large differences in passage rate among woody species, as well as between animals. The values ranged from 46% to 87% for seeds ingested by cattle while the lowest passage rate was 2.3% and the highest being 74% for seeds ingested by sheep. Among plant species, seeds of Prosopis africana had the highest passage rate through the digestive tract of both cattle and sheep. Seed passage through the gut showed a significant positive correlation with seed mass and thickness for cattle and sheep, respectively. The gut treatment and the retention time in the gut did not improve germination capacity and the speed of germination of dormant seeds. For non-dormant seeds of Acacia dudgeoni , the germination capacity was higher for seeds ingested by cattle than sheep. The speed of germination was also significantly higher for egested seeds than the control. It can be concluded that large herbivores could play an essential role in long distance dispersal of seeds. Gut treatment alone was not effective in breaking seed coat-imposed dormancy, although it enhanced the rate of germination of non-dormant seeds. To get a complete picture of the effect of frugivore on the release of seed dormancy, the combined effect of initial mastication and subsequent gut treatment needs to be investigated.

Dandelion Seed Dispersal: The Horizontal Wind Speed Does Not Matter for Long‐Distance Dispersal ‐ it is Updraft!

Abstract: Long‐distance dispersal of seeds (LDD) surely affects most ecological and evolutionary processes related to plant species. Hence, numerous attempts to quantify LDD have been made and, especially for wind dispersal, several simulation models have been developed. However, the mechanisms promoting LDD by wind still remain ambiguous and the effects of different weather conditions on LDD, although recognized as important, have only rarely been investigated. Here we examine the influence of wind speed and updrafts on dispersal of dandelion (Taraxacum officinale agg.), a typical wind‐dispersed herb of open habitats. We used PAPPUS, a weather‐sensitive mechanistic simulation model of wind dispersal, which considers frequency distribution of weather conditions during the period the simulation refers to. A simulation for the 4‐month shedding period of dandelion shows that high wind speed does not promote LDD. In contrast, vertical turbulence, especially convective updrafts, are of overwhelming importance. Mainly caused by updrafts, in the simulations more than 0.05 % of dandelion seeds were dispersed beyond 100 m, a distance commonly used to define LDD. We conclude that long‐distance dispersal of seeds of herbaceous species with falling velocities < 0.5 ‐ 1.0 ms‐1 is mainly caused by convective updrafts.

Genetic structure and reproduction dynamics of Salix reinii during primary succession on Mount Fuji, as revealed by nuclear and chloroplast microsatellite analysis

The early stage of volcanic desert succession is underway on the southeastern slope of Mount Fuji. We used markers of nuclear microsatellites (simple sequence repeats; SSR) and chloroplast microsatellites (cpSSR) to investigate the population genetic structure and reproduction dynamics of Salix reinii, one of the dominant pioneer shrubs in this area. The number of S. reinii genets in a patch and the area of the largest genet within the patch increased with patch area, suggesting that both clonal growth and seedling recruitment are involved in the reproduction dynamics of S. reinii. Five polymorphic cpSSR markers were developed for S. reinii by sequencing the noncoding regions between universal sequences in the chloroplast genome. Nineteen different cpSSR haplotypes were identified, indicating that S. reinii pioneer genets were created by the long-distance dispersal of seeds originating from different mother genets around the study site, where all vegetation was destroyed during the last eruption. Furthermore, the clustered distributions of different haplotypes within each patch or plot suggested that newly colonized genets tended to be generated from seeds dispersed near the initially established mother genets. These results revealed that the establishment of the S. reinii population on the southeastern slope of Mount Fuji involved two sequential modes of seed dispersal: long-distance dispersal followed by short-distance dispersal.

Mechanisms of long-distance dispersal of seeds by wind.

Long-distance dispersal (LDD) is central to species expansion following climate change, re-colonization of disturbed areas and control of pests. The current paradigm is that the frequency and spatial extent of LDD events are extremely difficult to predict. Here we show that mechanistic models coupling seed release and aerodynamics with turbulent transport processes provide accurate probabilistic descriptions of LDD of seeds by wind. The proposed model reliably predicts the vertical distribution of dispersed seeds of five tree species observed along a 45-m high tower in an eastern US deciduous forest. Simulations show that uplifting above the forest canopy is necessary and sufficient for LDD, hence, they provide the means to define LDD quantitatively rather than arbitrarily. Seed uplifting probability thus sets an upper bound on the probability of long-distance colonization. Uplifted yellow poplar seeds are on average lighter than seeds at the forest floor, but also include the heaviest seeds. Because uplifting probabilities are appreciable (as much as 1 5%), and tree seed crops are commonly massive, some LDD events will establish individuals that can critically affect plant dynamics on large scales.

Does seed dispersal limit initiation of primary succession in desert playas?

To investigate the initiation of primary succession in a cold-desert playa-dune complex, we studied the large-scale (2000 m) seed (diaspore) dispersal patterns at Mono Lake, California. Seeds of seven of the ten species reaching the barren playa had wind-dispersal adaptations. Rates of dispersal (numbers of seeds per square metre per day) were as much as three orders of magnitude lower on the playa than in the diverse dune vegetation. However, seed input appeared sufficient to reach potential safe sites on the playa, with a peak input of 66 ± 8 total seeds·m·d. The smooth playa surface, the virtual absence of aboveground barriers, and the high windspeed environment promote the long-distance dispersal of seeds (at least 1300 m for Chrysothamnus spp. and at least 700 m for Sarcobatus vermiculatus). The large spatial scale of sampling revealed a relatively high seed input onto the playa by the dominant pioneer species S. vermiculatus, despite the low abundance of parent vegetation in this region. All of these results implicate low rates of seed entrapment as an obstacle to establishment on this desert playa, rather than a lack of seed input.

Colonization with long-distance seed dispersal and genetic structure of maternally inherited genes in forest trees: a simulation study

Since the last glacial period forest trees have expanded to their present range very rapidly, with rates up to 500 m yr−1 for oaks in Europe, which can be explained only by the dispersion of acorns over long distances. We used a stratified dispersal model, including both diffusive and long-distance dispersal of seeds, to simulate the colonization of a 100 km×300 km grid by populations of oak trees. An appropriate rate of spread is obtained with rare dispersal at distances of the order of tens of kilometres. We simulated the effect of stratified versus diffusive dispersal of seeds on the spatial genetic structure at a maternally inherited locus. Founding events associated with stratified dispersal generate a high amount of genetic differentiation among populations, which is likely to persist for a long time after colonization. Using autocorrelation methods, we show that diffusive and stratified dispersals create quite different spatial patterns of variation for the maternally inherited locus. Stratified dispersal creates patchy patterns that are concordant with a previous experimental investigation of chloroplast DNA variation at a regional scale in the oaks Quercus petraea and Quercus robur. For plant populations that have passed through recent episodes of range expansion, long-distance dispersal events are probably the most important factors of spatial genetic structuring of maternally inherited genes at small or medium geographic scales.

Long-distance wind dispersal of tree seeds

Long-distance seed dispersal figures prominently in most plant conservation biology arguments, yet we possess little more than anecdotes concerning the relationship among deposition (seeds/m2), source strength (seeds/m2), and distance. In this paper we derive two simple models for long-distance deposition. The models are tested at the scale of 100–1600 m from the source and found to be within 5-fold of the observed deposition. There is no discernable decline in deposition for the range 300–1600 m. While we hesitate to extend model predictions to greater distances, both the models and the empirical results allow us to assert that rare wind-dispersed species in woodlots (dispersal distance around 1 km) are effectively isolated from one another at the temporal scale of 1000 years. Key words: plant conservation biology, wind dispersal of seeds, metapopulations.

Systematics of AustralianLepidium species (Brassicaceae) and implications for their origin: Evidence from IEF analysis of Rubisco

Variation in subunit polypeptide composition of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from native AustralianLepidium taxa was analyzed by isoelectric focusing (IEF). Species of grexMonoplocoidea on the one hand, and species of gregesPseudoruderalia andPapillosa on the other, were well separated by Rubisco IEF patterns. The protein data suggest grexMonoplocoidea to be placed in sect.Monoploca whereas gregesPseudoruderalia andPapillosa should be integrated into sect.Dileptium. We suggest that the Rubisco type of American and/or AsianLepidium species was contained in those plants migrating to Australia and evolving into the recent native Australian species. Fossil pollen records and vegetation history indicate that the origin ofLepidium in Australia was restricted to the late Tertiary of Quaternary. Data presented in this study fit best with an immigration by long-distance dispersal of seeds by birds from Asia and/or from South America.

Seed Morphology in Relation to Dispersal, Evolution, and Propagation of Cycas L.

A comparative morphological study of mature seeds of Cycas revoluta, C. media, C normanbyana, C. taiwaniana, and C. wadei revealed a three-layered seed coat consisting of sarcotesta, sclerotesta, and a thin membranous jacket Seeds of C circinalis, C rumphii, and C. thouarsii have an additional layer of spongy tissue, which causes flotation in water. It is speculated that long-distance dispersal of buoyant seeds occurs by the Indian Ocean currents, while nutritionally valuable starch in sarcotesta provides incentive for mammals to affect local dispersal across land Floating seed taxa differ only in minor morphological characters, despite their wide distribution, suggesting a single polymorphic species. Two groups of Cycas may be recognized: the C. revoluta group with relatively small viable seeds that sink in water and float only when inviable, and the C circinalis-rumphii group with large seeds that float regardless of viability.

New Zealand late Cretaceous and cenozoic plant biogeography: A contribution

Palynological data from Australia and New Zealand show marked vegetational changes throughout the Late Cretaceous and Cenozoic in response to climatic changes, fluctuations of the Antarctic ice cap, drifting of the continents and to a lesser extent tectonic activity. New Zealand and New Caledonia separated from Australia and Antarctica about 80 million years ago at which time the New Zealand vegetation had predominantly Austral affinities. Podocarps and southern beeches existed in an environment characterised by long winter nights and low temperatures. As New Zealand moved northeast a gene flow was maintained with Australia by long-distance dispersal of pollen, spores and seeds by wind, water and birds. A similar vegetational history of Nothofagus in Australia, New Zealand and South America can only be explained if the gene pool was similar in each area; this implies continual contact. During the Cenozoic, New Zealand received new taxa, some of which had previously appeared in Australia and some which survived in New Zealand after extinction in Australia. The best examples of this are Acacia which appeared in New Zealand in the Early Pliocene after its Early Miocene appearance in Australia, and Beauprea which became extinct in Australia in the Miocene but still occurred in New Zealand in the Early Pleistocene. Australian and Malayo-Pacific elements in the New Zealand flora became more prominent, as did the endemic element. The New Zealand vegetation was primarily warm-temperate, reaching subtropical in the Early to Middle Miocene and cool-temperate in the Late Miocene and Pliocene. No New Zealand palynofloras can be regarded as tropical since, although Palmae pollen dominates many Late Oligocene and Miocene assemblages, tropical genera such as Mauritia (or Nipa), Anacolosa (Indomalayan), Bombax, Cupania and some genera within the Proteaceae occur only spasmodically, and the abundance of Casuarina and Nothofagus “brassi” beech at this time suggests high humidity, but not necessarily high temperatures. The New Zealand vegetation was greatly modified by Pliocene and Pleistocene glaciations, resulting in the modern unstable disjunct distribution pattern.

Long-distance dispersal of seeds by retention in digestive tract of birds.

Viable seeds of Celtis, Convolvulus, Malva, and Rhus were regurgitated from the digestive tract of kill-deer (Charadrius vociferus) after 160, 144, 152, and 340 hours, respectively; seeds were recovered in the same way, after long-time retention, from least sandpipers (Erolia minutilla). Most other birds do not retain seeds as long. There is evidence that seeds of many species can remain viable in the intestinal tract of some shorebirds long enough to be transported several thousand miles.

Long Distance Dispersal of Seeds by Pant Cuffs

Long Distance Dispersal of Seeds by Pant Cuffs