Long-distance Dispersal Of Seeds Research Articles

Effects of tidal creeks on Spartina Alterniflora expansion: A perspective from multi-scale remote sensing

Rapid expansion of Spartina Alterniflora (S. alterniflora) has led to severe ecological consequences in coastal wetlands in China. Better understanding of the mechanism of S. alterniflora expansion is of great importance for its control and management. Although previous research has reported that the expansion of S. alterniflora is closely related to tidal creeks via field investigations, few studies have quantitatively investigated their relationships using remote sensing at different scales. In this study, we utilized time series satellite remote sensing imagery with different spatial resolutions to investigate the effects of tidal creeks on S. alterniflora expansion at both landscape scale and patch scale. We took the Yellow River Delta (YRD), China as our study area, where S. alterniflora has spread across the intertidal wetlands during the past decade. At landscape scale, we first derived the yearly maps of S. alterniflora and tidal creeks during 2009–2020 based on Landsat-series satellite imagery, then analyzed the spatio-temporal relationship between S. alterniflora and tidal creeks. By using grid analysis method, we evaluated the change of S. alterniflora area and tidal creek length and compared their change time. The results showed that 30.46 % of the grids experienced no change in tidal creeks while expansion of S. alterniflora, and 54.02 % of the grids experienced S. alterniflora area increase after the lengthening of tidal creeks. The results indicated that relationship between tidal creeks and S. alterniflora in YRD was dominated by “tidal creeks promoting S. alterniflora expansion”. We then simulated the S. alterniflora expansion at patch scale using an improved spatially explicit individual-based model based on S. alterniflora maps derived from Landsat imagery (30 m) and GF-1 high spatial resolution imagery (2 m), respectively. The results showed that consideration of long-distance dispersal of seeds along the direction of tidal creeks considerably enhanced the simulation accuracy, regardless of the spatial resolution of the S. alterniflora maps. High-resolution S. alterniflora maps yielded higher simulation accuracies. Our study suggests that the long-distance dispersal of seeds led by tidal creeks is an important manner for S. alterniflora expansion. Satellite remote sensing imagery have great potential to discover the mechanism of S. alterniflora expansion, facilitating control of S. alterniflora at the early invasion stage.

Owl-mediated diploendozoochorous seed dispersal increases dispersal distance and supports seedling establishment

Seed dispersal is an essential process contributing to the maintenance of plant populations. Zoochory is a widespread way of plant dispersal in every terrestrial ecosystem that can ensure the long-distance dispersal of seeds. Secondary seed dispersal (SSD) by far-ranging raptors is a special type of zoochory, which might have a role in colonizing new habitats. We used the barn owl (Tyto alba) as model species to test the effectivity and seasonality of SSD in open semi-natural landscapes. We collected 582 pellets from six sites in East-Hungary throughout one year. We identified prey items in the pellets and determined the viable seed content of the pellets by germination experiments. We found that herbivorous Microtus arvalis L. was the most abundant prey item through which most of the seeds spread. Owls dispersed the seeds of generalist and disturbance-tolerant plants, indicating the habitat type where small mammals occur abundantly. In another experiment we tested the effect of the pellet material on the seedling survival and found that prey remains enhanced establishment of seedlings. Our study suggests that SSD by barn owl is occasional but important event in long-distance seed dispersal. Since the studied owl species uses several habitat types and has larger mobility than the rodents, the revealed dispersal mechanism can considerably increase seed dispersal distance and seed exchange between habitat types.

Spatiotemporal process of long-distance seed dispersal in a pantropically distributed sea hibiscus group.

Long-distance dispersal (LDD) of seeds plays an essential role in the migration of plants to a new habitat and maintaining gene flow among geographically isolated populations. Pantropical plants with sea-drifted seeds, which have one of the largest distributions in all flowering plants, have achieved their global distribution by LDD. However, the spatiotemporal processes to achieve the wide distribution and the role of LDD in it have not yet been elucidated. In this study, we conducted phylogenomic analyses on the plastome, genome-wide nuclear SNP, and low-copy gene data of Hibiscus tiliaceus and its relatives. The dated phylogeny suggested that global expansion started approximately 4 million years ago (Ma), and species diversification occurred 1Ma. Plastome phylogeny confirmed the nonmonophyly of the haplotypes in the two widely distributed coastal species, H. tiliaceus and H. pernambucensis. In contrast, genome-wide nuclear SNP phylogenies demonstrated clear genetic segregation among species and/or geographical regions. Ancestral polymorphisms in chloroplast genomes shared among widely distributed species have remained below the range of rapid expansion and speciation of marginal populations. This study demonstrated that the LDD of sea-drifted seeds contributed to the rapid expansion and pantropical distribution of sea hibiscus in the last few million years, and adaptation to local environment or isolation by regional effect after LDD promoted speciation, suppressing gene flow.

Genetic patterns reveal differences between the invasion processes of common ragweed in urban and non-urban ecosystems

Invasive alien plant species (IAPS) in urban ecosystems can significantly impact ecosystems and human wellbeing. However, our knowledge on the IAPS in urban ecosystems are limited due to the small number of studies. In this study, we examined features of the invasion process of common ragweed ( Ambrosia artemisiifolia L.) by using a comparative study approach and genetic population methods. We conducted field surveys in 19 prefecture-level cities in East China and collected samples of 37 urban and 18 non-urban populations in 16 cities. Using information from six microsatellite loci and two chloroplast spacers extracted from the samples, we tested hypotheses on the source, genetic diversity, and genetic patterns of urban populations of common ragweed. We found that urban populations of common ragweed had more modern and diverse invasion sources than that of non-urban populations. Also, urban populations had more complex genetic patterns than non-urban populations as we identified seven genetic clusters in urban populations and four genetic clusters in non-urban populations. Nevertheless, no significant difference was found between the genetic diversity of urban and non-urban populations. In addition, we observed a significant isolation by distance (IBD) pattern in non-urban populations (Mantel test, R 2 =0.160, p -value=0.001) but not in urban populations (R 2 =0.003, p -value=0.253). The patterns may be shaped by the long-distance dispersal of seeds of common ragweed in urban environments through human activities such as transportation. Our results contribute to a better understanding of the invasion process of IAPS in urban ecosystems.

Responses to nutrient addition, shading and clipping in a range expanding invasive plant, Mikania micrantha

AbstractInvasive plants often spread in their new range. During range expansion, the population density at the invasion front may be low compared to that at the invasion centre, and this may select for an acquisitive growth strategy, such as rapid growth, stronger responses to nutrient addition, less tolerance to shading and more tolerance to biomass removal. In this study, we tested this idea using 27 populations of an invasive plant, Mikania micrantha, which is spreading on Hainan island of China in the past 20 years. Nutrient addition increased biomass of M. micrantha, and shading and clipping reduced it. Population density, frequency of occurrence and their interaction with nutrient addition, shading or clipping did not influence plant biomass and root to shoot ratio (RSR). For the western populations, both population density and frequency of occurrence were negatively correlated with RSR in the shading treatment. Overall, populations of M. micrantha differed little in growth. The reasons for these results may be that the spread distance and residence time of M. micrantha on Hainan island are too short to drive any evolutionary change, strong interspecific invaders may prevent M. micrantha from acquiring abundant resources when population density and frequency are low, and long distance dispersal of seeds and pollen may potentially mix genes, preventing adaptive evolution. These results indicate that M. micrantha may not evolve to be more invasive during range expansion. Future studies can examine if populations of M. micrantha differ in other aspects, such as seed dispersal ability and competitive ability.

Spatial Analysis as a Tool for Plant Population Conservation: A Case Study of Tamarix chinensis in the Yellow River Delta, China

Saltcedar (Tamarix chinensis) is undergoing population declination and fragmentation due to climate change and human disturbance. The existing restoration strategies usually focus on improving the environmental conditions based on the environment–saltcedar relationship, while they ignore the role of spatial autocorrelation resulting from biological interaction and ecological processes. This oversight limits the efficiency and sustainability of the restoration. Here, we explored the spatial pattern of the saltcedar population in the Yellow River Delta, China, and its relationship with environmental factors, incorporating spatial autocorrelation. The plant and soil parameters were extracted by an airborne LiDAR system integrated with fixed soil environment measurements. The environment–saltcedar relationship incorporating spatial autocorrelation was evaluated with different regression models. Results showed that saltcedars aggregated at small scales (2–6 m), resulting from intraspecific facilitation and wind dispersal of seeds, while intraspecific competition was responsible for the random distribution at large scales (>10 m). The long-distance dispersal of seeds through water explained the significant positive spatial autocorrelation of saltcedars at distances up to 125 m. Consequently, resulting from intraspecific facilitation and seed dispersal, aggregation distribution and positive spatial autocorrelation within the saltcedar population improved the adaptability of saltcedar to environmental stress and thereby reduced the impact of environmental factors on the abundance of saltcedar.

Frugivore zoogeochemistry in tropical forest ecosystems

Frugivore zoogeochemistry in tropical forest ecosystems

The morpho-genetic and ecological niche analyses reveal the existence of climatically restricted Cycas zeylanica complex in Sri Lanka

Taxonomy and phylogenesis of Sri Lankan cycad species of the subsection Rumphiae has not been fully resolved and therefore, we conducted an island-wide survey of cycads of the subsection to assess their morphological or genetic variations while exploring the phylogenetic relationship between Sri Lankan Rumphiae and other world cycad species. Further, we assessed the possible distribution of the species in the region through climatic profiling, using maximum entropy modeling approach. We analyzed 21 variable morphological features in collected specimens and used the polymorphism of trnH-psbA locus to understand the phylogeny. The distance tree drawn from the principal component analysis revealed a significant variation in female reproductive structures. The maximum likelihood tree separated Sri Lankan Cycas zeylanica to a well-supported unigeneric clade (bootstrap = 96, posterior probability = 100) with shallow divergence. Ecological niche modeling supported the existence of Cycas zeylanica in South East Asia and in southern Western Ghats in India in addition to the Wet Zone of Sri Lanka. We rename the taxa as Cycas zeylanica complex based on the observed high morphological diversity of female reproductive structures which might have ascended due to multiple introductions of South East Asian cycads by long distance dispersal of seeds through sea currents.

Variable seed behavior increases recruitment success of a hardwood tree, Zelkova serrata, in spatially heterogeneous forest environments

Abstract Variable seed behavior (e.g., seed heteromorphism) plays an important role in enhancing plant fitness by spreading risk in spatially and temporally changing environments. This adaptation is common in herbs but rare in trees. Zelkova serrata, one of the most important commercial tree species in Japan, has two types of seeds: shoot seeds that disperse via a seed-bearing shoot and single seeds that disseminate after separating from shoots. To evaluate whether the seeds of Z. serrata show heteromorphism, we compared several inherent ecological properties (e.g., seed mass, degree of seed dormancy, and dispersal ability) between the two seed types and assessed the effects of variable seed behavior on recruitment success in forest environments. The degree of seed dormancy did not differ between the two seed types. Seed mass increased with a delayed seed dispersal time but did not differ between the two types at any time. Seed dispersal ability was greater in shoot seeds than in single seeds. These inherent seed behaviors suggest that the two types of seeds do not reflect seed heteromorphism. The results, however, indicate that shoot seeds dispersed larger seeds over much greater distances than did single seeds, particularly at later seed dispersal times, whereas a greater number of single seeds were disseminated near adults. To evaluate the effects of variable seed dispersal ability on seedling establishment in forest environments, we measured seedling performance at different distances (≤27.5 m) from adults isolated from one another in the forest understory. Seedling density, survival, and growth did not vary with distance from adults (i.e., there was little negative distance-dependent seedling mortality), which suggests that single seeds can contribute to persistent seedling banks near conspecific adults. To evaluate the advantages of long-distance dispersal of shoot seeds for recruitment on disturbed sites (i.e., gaps), we compared the occurrence and relative abundance of Z. serrata among 1100 plots with different slopes; steep slopes are closely associated with gap creation (e.g., landslides). The occurrence and relative abundance of Z. serrata increased with slope inclination, which suggests that shoot seeds may enhance recruitment success in disturbed sites along steep slopes, thereby generating Z. serrata-dominated forests. This suggests that the variability in seed behavior of Z. serrata may enhance recruitment success in spatially heterogeneous forest environments. Knowledge of the unique reproductive behaviors and the wide range of habitats suitable for this species is important for forest managers when making sustainable timber production plans for Z. serrata.

Gene flow of common ash (Fraxinus excelsior L.) in a fragmented landscape.

Gene flow dynamics of common ash (Fraxinus excelsior L.) is affected by several human activities in Central Europe, including habitat fragmentation, agroforestry expansion, controlled and uncontrolled transfer of reproductive material, and a recently introduced emerging infectious disease, ash dieback, caused by Hymenoscyphus fraxineus. Habitat fragmentation may alter genetic connectivity and effective population size, leading to loss of genetic diversity and increased inbreeding in ash populations. Gene flow from cultivated trees in landscapes close to their native counterparts may also influence the adaptability of future generations. The devastating effects of ash dieback have already been observed in both natural and managed populations in continental Europe. However, potential long-term effects of genetic bottlenecks depend on gene flow across fragmented landscapes. For this reason, we studied the genetic connectivity of ash trees in an isolated forest patch of a fragmented landscape in Rösenbeck, Germany. We applied two approaches to parentage analysis to estimate gene flow patterns at the study site. We specifically investigated the presence of background pollination at the landscape level and the degree of genetic isolation between native and cultivated trees. Local meteorological data was utilized to understand the effect of wind on the pollen and seed dispersal patterns. Gender information of the adult trees was considered for calculating the dispersal distances. We found that the majority of the studied seeds (55–64%) and seedlings (75–98%) in the forest patch were fathered and mothered by the trees within the same patch. However, we determined a considerable amount of pollen flow (26–45%) from outside of the study site, representing background pollination at the landscape level. Limited pollen flow was observed from neighbouring cultivated trees (2%). Both pollen and seeds were dispersed in all directions in accordance with the local wind directions. Whereas there was no positive correlation between pollen dispersal distance and wind speed, the correlation between seed dispersal distance and wind speed was significant (0.71, p < 0.001), indicating that strong wind favours long-distance dispersal of ash seeds. Finally, we discussed the implications of establishing gene conservation stands and the use of enrichment planting in the face of ash dieback.

Genetic variation in the invasive weed Mikania micrantha (Asteraceae) suggests highways as corridors for its dispersal in southern China.

Roads as corridors of seed or fruit spatial dispersal have major impacts on the establishment and spread of invasive species, but their precise role in population genetic variation remains poorly understood. The South American weed Mikania micrantha has spread rapidly across southern China since its introduction to the Shenzhen area in 1984. This study investigated how its genetic diversity is distributed along highways, and whether highways have acted as corridors for the rapid expansion of M. micrantha METHODS: Twenty-seven roadside populations were sampled along four highways in southern China, and 787 samples were examined using 12 microsatellite markers. Variation in genetic diversity among populations was quantified and patterns of genetic differentiation were analysed. A high level of genetic diversity was found at both the species and the population levels in this self-incompatible plant (expected heterozygosity = 0·497 and 0·477, respectively; allelic richness = 2·580 and 2·521, respectively). The Wright F-statistic value among populations (0·044, P < 0·01) and the analysis of molecular variance (91% of genetic variation residing within populations, 9% among populations within highways and 0% among the four highways) showed a relatively low level of genetic differentiation among populations, while the principal coordinate and cluster analyses also indicated a lack of clear geographical genetic structure among populations. The calculated Nm value of 5·5 signifies strong gene flow. The pattern of genetic variation is consistent with facilitated dispersal along highways. The genetic admixtures among the roadside populations imply the occurrence of multiple population introductions during colonization. The long-distance dispersal of seeds associated with vehicular transportation on highways may have played important roles in shaping the genetic variation. This finding highlights the importance of highways as corridors for the spread of M. micrantha in southern China.

Ecological systems as computer networks: Long distance sea dispersal as a communication medium between island plant populations

Ecological systems are known to exchange genetic material through animal species migration and seed dispersal for plants. Isolated plant populations have developed long distance dispersal as a means of propagation which rely on meteorological such as anemochory and hydrochory for coast, island and river bank dwelling species. Long distance dispersal by water, in particular, in the case of water current bound islands, calls for the analogy with computer networks, where each island and nearby mainland site plays the role of a network node, the water currents play the role of a transmission channel, and water borne seeds as data packets.In this paper we explore this analogy to model long distance dispersal of seeds among island and mainland populations, when traversed with water currents, in order to model and predict their future genetic diversity. The case of Pancratium maritimum L. populations in Tunisia is used as a proof of concept, where their genetic diversity is extrapolated.

Monodominance in tropical forests: modelling reveals emerging clusters and phase transitions.

Tropical forests are highly diverse ecosystems, but within such forests there can be large patches dominated by a single tree species. The myriad presumed mechanisms that lead to the emergence of such monodominant areas is currently the subject of intensive research. We used the most generic of these mechanisms, large seed mass and low dispersal ability of the monodominant species, in a spatially explicit model. The model represents seven identical species with long-distance dispersal of small seeds, competing with one potentially monodominant species with short-distance dispersal of large seeds. Monodominant patches emerged and persisted only for a narrow range of species traits; these results have the characteristic features of phase transitions. Additional mechanisms may explain monodominance in different ecological contexts, but our results suggest that percolation-like phenomena and phase transitions might be pervasive in this type of system.

Sea, wind, or bird: Origin of &lt;i&gt;Fagus multinervis&lt;/i&gt; (Fagaceae) inferred from chloroplast DNA sequences

울릉도의 낙엽활엽수림에 ìš°ì í•˜ê³ ìžˆëŠ” 너도밤나무를 대상으로 엽록체 반수체형(haplotype)의 다양성과 ê³µê°„ì  분포를 íŒŒì• í•˜ê¸° 위해 울릉도 ì „ì—­ì—ì„œ 채집한 총 144개체로부터 psbA-trnH 구간의 염기서열을 ê²°ì •í•˜ì˜€ë‹¤. 너도밤나무의 ê·¼ì—°ì¢ ì„ 포함하여 계통분석을 수행한 ê²°ê³¼, 너도밤나무의 엽록체 반수체형은 일본산 F. japonica와 중국산 F. engleriana 분계조와 자매관계를 이루는 것으로 나타났다. 또한, 분석한 ëª¨ë“ ë„ˆë„ë°¤ë‚˜ë¬´ì˜ 개체들은 동일한 염기서열을 ê°–ê³ ìžˆëŠ” 것으로 나타나, 엽록체 반수체형의 다양성은 매우 낮은 것으로 íŒëª ë˜ì—ˆë‹¤. 이러한 결과는 동위효소 분석에 근거한 ìœ ì „ìž 다양성이 매우 높다는 기존 연구 결과와 대비되는 것으로서, 너도밤나무는 핵 ìœ ì „ìžì˜ 다양성은 높으나 엽록체 ìœ ì „ìžì˜ 다양성은 낮은 것으로 판단되며, 이것은 두 가지 가설로 ì„¤ëª í• ìˆ˜ 있다. 하나는 너도밤나무의 조상이 울릉도로 이주하여 ì •ì°©í• ì´ˆê¸° 단계에서 엽록체 반수체형이 ì§€ì—­ì ì¸ 구조를 갖는 조상 모집단으로부터 ì¢ ìžê°€ ì§€ì†ì ìœ¼ë¡œ ìœ ìž ëœ 결과로 í•´ì„í• ìˆ˜ 있다. 다른 하나는 육지의 조상 모집단으로부터 새 또는 태풍에 의해 소수의 ì¢ ìžê°€ ìœ ìž ë˜ì–´ ì •ì°©í•œ 후, 바람에 의해 조상 모집단의 화분이 ì§€ì†ì ìœ¼ë¡œ ìœ ìž ëœ 결과인 것으로 ì¶”ë¡ í• ìˆ˜ 있다. 울릉도 내의 다양한 ê³ ìœ ìžìƒì‹ë¬¼ì˜ 기원을 ê·œëª í•˜ëŠ” 데 있어서 ëª¨ê³„ìœ ì „ì„ 함으로 인해 ì¢ ìžì˜ 이동을 ì¶”ì í• ìˆ˜ 있는 엽록체 DNA에 근거한 ë¹„êµê³„í†µì§€ë¦¬í•™ì  연구가 필요한 것으로 사료된다. 주요어: 너도밤나무, 엽록체 DNA, 반수체형, 울릉도

In the elephant's seed shadow: the prospects of domestic bovids as replacement dispersers of three tropical Asian trees.

As populations of the world's largest animal species decline, it is unclear how ecosystems will react to their local extirpation. Due to the unique ecological characteristics of megaherbivores such as elephants, seed dispersal is one ecosystem process that may be affected as populations of large animals are decimated. In typically disturbed South Asian ecosystems, domestic bovids (cattle, Bosprimigenius, and buffalo, Bubalus bubalis) may often be the species most available to replace Asian elephants (Elephas maximus) as endozoochorous dispersers of large-fruited mammal-dispersed species. We use feeding trials, germination trials, and movement data from the tropical moist forests of Buxa Tiger Reserve (India) to examine whether domestic bovids are viable replacements for elephants in the dispersal of three large- fruited species: Dillenia indica, Artocarpus chaplasha, and Careya arborea. We find that (1) once consumed, seeds are between 2.5 (C. arborea) and 26.5 (D. indica) times more likely to pass undigested into elephant dung than domestic bovid dung; and (2) seeds from elephant dung germinated as well as or better than seeds taken from bovid dung for all plant species, with D. indica seeds from elephant dung 1.5 times more likely to germinate. Furthermore, since wild elephants have less constrained movements than even free-roaming domestic bovids, we calculate that maximum dispersal by elephants is between 9.5 and 11.2 times farther than that of domestic bovids, with about 20% of elephant-dispersed seeds being moved farther than the maximum distance seeds are moved by bovids. Our findings suggest that, while bovids are able to disperse substantial numbers of seeds over moderate distances for two of the three study species, domestic bovids will be unable to routinely emulate the reliable, long-distance dispersal of seeds executed by elephants in this tropical moist forest. Thus while domestic bovids can attenuate the effects of losing elephants as dispersers, they may not be able to prevent the decline of various mammal-dispersed fruiting species in the face of overhunting, habitat fragmentation, and climate change.

Regurgitation by waterfowl: An overlooked mechanism for long-distance dispersal of wetland plant seeds

Birds commonly regurgitate indigested particles after foraging. Many frugivorous birds regurgitate seeds ingested with the flesh of fruits, which importantly contributes to plant dispersal in terrestrial ecosystems. In freshwater ecosystems, waterbirds are known to defecate viable seeds in their faeces, but little is known about regurgitation as a potential additional seed dispersal mechanism. We experimentally fed eight mallards (Anas platyrhynchos) with a high and low volume of seeds of ten wetland plant species, and monitored regurgitation and defecation of intact seeds over 24h. Regurgitation occurred at least once in all individual mallards and was induced by two different mechanisms: (i) feeding of high food volumes was significantly associated with regurgitation of all seed species from the crop after retention times of 1–3h, and (ii) large indigestible seeds were expelled from the gizzard 11 or more hours after feeding. Seed regurgitation was much less plant species-specific than survival of seeds passing digestion, which suggests it is a particularly suitable dispersal mechanism for plant species unable to disperse by endozoochory (such as plant species with large, soft-bodied seeds). Observations of regurgitation by wild waterbirds are needed to improve our knowledge on this additional role of waterbirds in ecosystem functioning.

Time-spatial distribution of Pinus in the Korean Peninsula

Despite the ecological and landscape importance and the public popularity of conifers, especially in the case of Pinus of Pinaceae in the Korean Peninsula, not much scientific information related to vegetation is known. A wide range of fossil data has been collated and analyzed to understand the past vegetation history and current distribution and ecology, and to predict the future ranges of Pinus species in Korea in connection with climate change.Though the existing earliest Pinus (diploxylon) dates to the Cretaceous, Pinus became more common since the Miocene, and shows widespread distribution in lowland and montane areas during the Quaternary. Separation of geographical distribution of haploxylon and diploxylon Pinus since the Pleistocene may be the result of the climatic fluctuations and availability of diverse habitat. Dominance of Pinus during the Holocene may be related to both natural climatic warming as well as anthropogenic disturbance, such as, selective deforestation, agricultural activities and fire.The present occurrence of cold-tolerant Pinus pumila at northern and central alpine and subalpine belts of the Korean Peninsula indicates that the cool and hostile climate at high elevation guaranteed the survival of glacial relics in post glacial climate. The presence of Pinus koraiensis at mid elevations on mountains of northern and central Korea might be due to the cool climate in the Pleistocene.Thanks to a mild climate and seeds with wings, combined with an abundance of poor soil provided by human disturbance, Pinus densiflora became a dominant tree species at lowland and montane areas. The presence of Pinus thunbergii mainly along southern coastal regions may also be related to the local climatic condition. Disjunctive distributions of Pinus parviflora on remote islands, such as Ulleung Island and some Japanese Isles, demands further study regarding the long distance dispersal of seeds by birds, and relation to an oceanic climate. More information is needed to discuss the distributions of Pinus tabulaeformis var. mukdensis at sites in northern Korea. Special concern and protection are required for vulnerable conifer species with limited or narrow distributional ranges on high mountains and in rapidly changing environments, due climate change and environmental degradation.

Estimation of the Probability of Long-Distance Dispersal: Stratified Diffusion of &amp;lt;i&amp;gt;Spartina alterniflora&amp;lt;/i&amp;gt; in the Yangtze River Estuary

The relative contribution of long-distance dispersal and local diffusion in the spread of invasive species has been a subject of much debate. Invasion of the intertidal mudflats by Spartina alterniflora is an ideal example of stratified diffusion, involving both long-distance dispersal of seeds and local diffusion due to clonal growth. In conjunction with experimental data on range radius-versus-time curve, a traveling wave equation-based model is used to investigate the sensitivity of the spread rate of exotic S. alterniflora to parameters of long distance dispersal (c, maximum colonial establishment rate) and local colony diffusion (r, intrinsic growth rate) at two tidal marshes, the Eastern Chongming and the Jiuduansha Islands, at the Yangtze River estuary. Both Eastern Chong ming and Jiuduansha Islands are now national natural reserves in China, which were established in 2005. However, the mudflats and salt marshes in the two reserves are now heavily infested with introduced S. alterniflora, which may threaten the estuarine ecosystems and their biodiversity. S. alterniflora was first found in 1995 on Chongming. For rapid sediment accretion in mudflats in the estuary, S. alterniflora was also intentionally introduced to Jiuduansha in 1997 and Chongming in 2001, which has led to a rapid range expansion in the estuary. Our results show that range expansion of species with stratified diffusion is affected by both long-distance dispersal and local colony diffusion, and that there is a critical c*, below which the spread rate is more influenced by long-distance dispersal than by local diffusion. After applying this model to the invasion of S. alterniflora in the Yangtze River estuary, we derive that c = 1.7 × 10-3, c* = 0.126 and c = 4.8 × 10-3 km-2·yr-1, c* = 0.140 km-2·yr-1 at Chongming and Jiuduansha (Shanghai), respectively. Our results suggest that the range spread of S. alterniflora in the Yangtze River estuary is more influenced by long-distance dispersal than local colony diffusion, and that S. alterniflora generates about 1.7 × 10-3 to 4.8 × 10-3 colonies per square kilometers per year. This study provides important information about dispersal dynamics of S. alterniflora that may be useful for finding optimal control strategies. ·

Dietary characteristics of Emus (Dromaius novaehollandiae) in semi-arid New South Wales, Australia, and dispersal and germination of ingested seeds

The Emu (Dromaius novaehollandiae) eats a wide range of seeds and other plant material but little is known of the seeds eaten and dispersed in arid Australia. This study aimed to determine the species of seed and fruits eaten by Emus through the year and investigate the effect of the passage of seeds through the Emu gut on seed germination. Emu scats were opportunistically collected in all seasons of 2005 at Nanya Research Station, western New South Wales. Seeds of 29 plant species were retrieved, identified and counted from 221 scats. Seeds of perennial species, such as Belah (Casuarina pauper), Ruby Saltbush (Enchylaena tomentosa), Common Emu-bush (Eremophila glabra) and Nitre-bush (Nitraria billardierei), predominated. Seed composition of scats was more diverse in summer than in winter, autumn and spring. Seeds of Common Emu-bush, Berrigan (Eremophila longifolia) and Sweet Quandong (Santalum acuminatum) showed no germination after passage through the gut. Ruby Saltbush and Nitre-bush showed very low germination rates. The Emu is a generalist feeder, capable of ingesting and dispersing large numbers of plant species. Through high seed consumption and long gut-retention time, Emus could potentially play a significant role in long-distance dispersal of seeds and, through such dispersal, in the vegetation dynamics of arid Australia.

Influence of Long-Distance Seed Dispersal on the Genetic Diversity of Seed Rain in Fragmented Pinus densiflora Populations Relative to Pollen-Mediated Gene Flow

Long-distance dispersal (LDD) of seeds has a critical impact on species survival in patchy landscapes. However, relative to pollen dispersal, empirical data on how seed LDD affects genetic diversity in fragmented populations have been poorly reported. Thus, we attempted to indirectly evaluate the influence of seed LDD by estimating maternal and paternal inbreeding in the seed rain of fragmented 8 Pinus densiflora populations. In total, the sample size was 458 seeds and 306 adult trees. Inbreeding was estimated by common parentage analysis to evaluate gene flow within populations and by sibship reconstruction analysis to estimate gene flow within and among populations. In the parentage analysis, the observed probability that sampled seeds had the same parents within populations was significantly larger than the expected probability in many populations. This result suggested that gene dispersal was limited to within populations. In the sibship reconstruction, many donors both within and among populations appeared to contribute to sampled seeds. Significant differences in sibling ratios were not detected between paternity and maternity. These results suggested that seed-mediated gene flow and pollen-mediated gene flow from outside population contributed some extent to high genetic diversity of the seed rain (H E > 0.854). We emphasize that pine seeds may have excellent potential for gene exchange within and among populations.