Seed traits and bird species influence the dispersal parameters of wetland plants

相似文献   

Multi-species territoriality and dynamic of neotropical forest understorey bird flocks

1. Eleven contiguous mixed-species bird flocks, with colour-banded individuals, were monitored continuously during 3 years in a 132-ha study area of primary rainforest in French Guiana.
2. Flock members were divided into six categories according to their flocking propensity and occurrence: 10 core or permanent species and 56 regular, occasional or incidental species. Each core species was represented by a single breeding pair with their fledglings and extra 'floaters' (unmated subadults and adults).
3. Flock home ranges overlapped slightly, but were communally defended by all core species in areas of overlap. Their size varied from 3·2 to 14·3 ha and was inversely correlated with vegetation density, but not flock size or species composition.
4. Flock number, size and composition, as well as boundaries were highly stable between seasons and years. Each flock had a single permanent gathering site and bathing site in late afternoon, the latter sometimes shared by 2–3 flocks.
5. Core species produced 0·18–0·73 fledglings per pair per year, which stayed in their natal flock for 200 to over 421 days. Then, these individuals usually moved between two and six different flocks, sometimes for up to 3 years, before finding a mate and a flock where they could settle and breed. Once breeding, they probably remained for life in the same flock. The mean annual survival rate was at least 0·75.
6. This highly evolved and stable organization, associated with a low breeding success and high survival rate was a critical factor maintaining low species density, delayed reproduction and a proportion of floating individuals buffering population fluctuations.
7. These social groups with their multi-species territoriality and co-evolved roles of flock members were similar to those described elsewhere in South America. They seem to be a general phenomenon in neotropical lowland rainforests.     

A waterfowl seed-dispersal network from the Neotropical region is nested and modular

Seed dispersal by vertebrates is fundamental for the persistence of plant species, forming networks of interactions that are often nested and modular. Networks involving angiosperms and frugivorous birds are relatively well-studied in the Neotropical region, but there are no previous studies of networks involving waterbirds. Here, we describe the structure of a Neotropical waterfowl seed-dispersal network and identify the species that have an important role for the network structure. We used information on 40 plant taxa found in fecal samples of five common waterfowl species to calculate the nestedness (NODF), weighted nestedness (WNODF), modularity, and weighted modularity of the network. We found that the network was nested, with yellow-billed teal showing the highest contribution both to nestedness and weighted nestedness. Twenty-four plant species contributed positively to weighted nestedness, with Salzmann's mille graines presenting the highest influence both to nestedness and weighted nestedness. The network was modular, but the weighted modularity was not significant. These results need to be considered with caution due to incomplete interaction sampling for two species. Ringed teal, Brazilian teal, and yellow-billed teal were considered hub modular species. Among plants, beak sedges and water snowflake were considered modular hub species, while Salzmann's mille graines and spikerush were network connectors. The structure of this Neotropical waterbird seed-dispersal network differed from the only previous waterfowl network study, from Europe, which found similar level of nestedness but no significant modularity. We include several possible explanations for this discrepancy and identified priorities for future research into waterbird–plant interaction networks. Abstract in Portuguese is available with online material.     

Seed dispersal by waterbirds in southern Africa: comparing the roles of ectozoochory and endozoochory

相似文献   

Seed dispersal potential by wild mallard duck as estimated from digestive tract analysis

相似文献   

Influence of life history and seasonal hydrology on lipid storage in three neotropical fish species

The seasonal dynamics of energy (lipid) storage in three neotropical fish species with differing life histories were evaluated. Lipid content was substantially greater in the liver than in dorsal musculature of all three species. Two piscivores ( Cichla temensis and Serrasalmus manueli ) showed large, statistically significant seasonal fluctuations in liver lipid content. Liver lipid content increased during high water, through the falling water, and into the early dry season for both piscivores. Seasonal variation in dorsal muscle lipid content was large and statistically significant for C. temensis , but was small and non‐significant for S. manueli . Cichla temensis appeared to 'finance' costs associated with reproduction by accumulating lipids during the falling‐water period when migratory prey allowed the species to subsidize their energetic dynamics. Semaprochilodus kneri , a migratory algivore and detritivore, showed no significant seasonal variation in dorsal muscle lipid content and minimally significant seasonal variation in liver lipid content. Statistically significant effects of lipid content on δ¹³C was observed when tissue lipid content varied by >12%, while biological interpretation of food web statistics based on δ¹³C values appears robust to minor variations in lipid content. Nonetheless, when lipid content varied by larger amounts ( e.g . >35% for C. temensis and S. manueli liver tissue) lipids appeared to have a large potential effect on δ¹³C and food web statistics calculated from such measurements may have been biased. Surprisingly, even large variation in tissue lipid content did not affect δ¹⁵N.     

Fine-scale genetic structure and gene dispersal inferences in 10 neotropical tree species

The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies.     

Genetic and environmental influences on natal dispersal distance in a resident bird species

We analyzed more than 1,600 dispersal events from two populations of a North American cooperatively breeding woodpecker species to determine what factors influence natal dispersal distance and whether distance traveled affects reproduction later in life. We found significant heritability of natal dispersal distance, in both males and females, indicating substantial additive genetic variance for this behavioral trait. Natal dispersal distance additionally was affected by social and ecological factors: individuals dispersing in their first year of life moved longer distances than those staying on their natal site as helpers for a prolonged time prior to dispersal, and increasing territory isolation led to longer dispersal distances. Successful dispersers incurred fitness costs, with lifetime fledgling production (in both sexes) and lifetime production of recruits to the breeding population (in females only) decreasing with increasing natal dispersal distance. We conclude that natal dispersal distance has a genetic basis but is modulated by environmental and social factors and that natal dispersal distance in this species is (currently) under selection.     

Roles of species-preferential seed dispersal by ants and endozoochory in Melampyrum (Orobanchaceae)

Aims Melampyrum pratense and M. subalpinum are two myrmecochorous species, which possess similar habitat requirements and frequently occur together. Despite this, their population sizes differ markedly. Melampyrum pratense populations are usually very large, whereas M. subalpinum has rather small and isolated populations. We suggest that such an imbalance might be partially influenced by the difference in ant-mediated seed-removal rates. Genus Melampyrum is considered to be exclusively myrmecochorous, though to achieve the recent distribution of some Melampyrum species during the Holocene myrmecochory would be highly insufficient. We suggest that endozoochory takes place in the long-distance migration, whereas myrmecochory is important for the removal of seeds on a local scale.Methods For seed-preference analysis, M. pratense and M. subalpinum mixed seed samples were placed around Formica polyctena anthills. After a period of time, the remaining seeds of both species were counted for each sample. The results were analysed by analysis of variance and generalized linear mixed-effect model. To test myrmecochorous removal distances, M. pratense seeds were covered with fluorescent dactyloscopic powder and placed in the vicinity of a large ant trail. The area around the starting plot was searched in the dark using UV LED torchlight 7h after the beginning. The distance from the starting plot was measured for each seed found. Birds, rodents, leporine and a ruminant were fed with M. pratense seeds and fresh plants to test the possibility of endozoochorous dispersal of the species. Animal droppings were searched for intact seeds.Important findings Our field studies show that from mixed seed samples, containing both species, ants significantly preferred the seeds of M. pratense. This may be one of factors that has positive influence on M. pratense success in seed dispersal on mixed stands and consequently in the colonization of favourable sites. Experiments focusing on ant-mediated dispersal distance revealed that F. polyctena ants are able to move seeds over a distance of 36 m in only 7h. This distance is among the furthest known myrmecochorous removals of forest plant seeds. A new Melampyrum seed disperser Oligolophus tridens (Opiliones) was observed repeatedly. Our pilot study documented that Melampyrum seeds are able to pass through the digestive tract of a cow intact. This suggests that large ruminants such as deer, bison or forest-grazing livestock may function as important long-distance dispersers of Melampyrum species.     

Crayfish invasion facilitates dispersal of plants and invertebrates by gulls

相似文献   

Social constraints limit dispersal and settlement decisions in a group-living bird species

Dispersal is a fundamental process affecting the genetic structureof populations, speciation, and extinction. Nevertheless, ourunderstanding of the evolution of dispersal is limited by ourpaucity of knowledge on dispersal decisions at the individuallevel. We investigated the effect of interactions between residentsand juvenile dispersers on individual dispersal and settlementdecisions in Siberian jays (Perisoreus infaustus). In this group-livingbird species, some offspring remain on the parental territoryfor up to 3 years (retained juveniles) whereas other offspringdisperse within 2 months of fledging (dispersers). We foundthat retained juveniles constrained settlement decisions ofdispersers by aggressively chasing dispersers off their territory,resulting in dispersers continuing to disperse and settlingin groups without retained juveniles. Experimental removal ofmale breeders during the dispersal period also demonstratedthat dispersers were unable to settle in high-quality breedingopenings, which were instead filled by older nonbreeding residents.Rather, dispersers immigrated into groups without retained offspringwhere they became subordinate group members, queuing for a breedingopening. Also, they preferably settled in groups with shortqueues where no same-sex juveniles were present. Dispersal didnot inflict a cost to dispersers through increased mortality.However, the presence of immigrants was costly for breedersbecause it increased the rate of conflicts during the breedingseason which negatively affected nestling condition. These resultsdemonstrate that resident individuals constrain both dispersaland settlement decisions of dispersers. Social interactionsbetween residents and dispersers can thus be a key factor tounderstand the evolution of dispersal.     

The effect of seed morphology on the potential dispersal of aquatic macrophytes by the common carp (Cyprinus carpio)

1. The potential for seed dispersal by fish (ichthyochory) will vary among aquatic plants because of differences in seed size and morphology. 2. To examine how seed morphology influences the probability of dispersal by the common carp (Cyprinus carpio), we studied seed ingestion, retention time and subsequent egestion and germination of seeds of Sparganium emersum and Sagittaria sagittifolia, two aquatic plant species with similar sized but morphologically different seeds. 3. We compared dispersal probabilities between the two plant species, in which the probability of dispersal is assumed to be a function of the probabilities of seed ingestion, egestion and germination, and the dispersal distance is assumed to be a function of seed egestion rate over time. 4. We found that, although the soft seeds of S. sagittifolia had an approximately 1.5 times higher probability of being ingested by the carp than the hard seeds of S. emersum (83.15% ± 1.8% versus 56.16% ± 2.7%, respectively), the latter had an almost twofold higher probability of surviving the passage through the digestive tract (38.58% ± 2.7% versus 20.97% ± 1.5%, respectively). Patterns of seed egestion over time did not differ between the two plant species, despite the difference in seed morphology. Gut passage had a different effect on seed germination between plant species. Compared with non‐ingested controls, seeds of S. emersum showed a 12.6% increase in germination and a 2.1 day acceleration in germination rate, whereas seeds of S. sagittifolia displayed a 47.3% decrease and 5.1 day delay, respectively. 5. Our results suggest that seed morphology affects the dispersal probability and postdispersal establishment, but not the dispersal distance, of aquatic plants that are dispersed by fish.     

Epizoochorous dispersal by ungulates depends on fur,grooming and social interactions

The transport phase of the animal‐mediated plant dispersal process is critical to dispersal effectiveness as it determines the spatial distribution of the diaspores released and their chance for further recruitment. Assessing this specific phase of the dispersal process generally requires combining diaspore retention times with the associated distances covered. Here, we specifically tested the effect of grooming behavior, interindividual contacts and ungulate fur on diaspore retention times and associated dispersal distances for the hooked diaspores of Xanthium strumarium L. experimentally attached to tamed individuals of three ungulate species. We used a comparative approach based on differing fur quality on different body zones of these three ungulates. During 6‐hr sessions, we monitored for grooming and social interactions that may induce intended or inadvertent diaspore detachment. Additionally, we proposed innovative approaches to directly assessing diaspore dispersal distances by red deer in situ. Fat‐tailed functions fitted diaspore retention time, highlighting the potential for long‐distance dispersal events. The longer the hair, the higher the retention capacity of diaspores in the animal's fur. As predicted, donkey retained diaspores longer than red deer and dwarf goat; and we also confirmed that diaspores attached to the short hair of the head fell off more quickly than did those on the other body zones. Dwarf goat groomed more often than both red deer and donkey, but also when it carried diaspores. Up to 14% of the diaspores detached from animal fur after specific grooming behavior. We observed, in controlled conditions, for the first time and for each ungulate species, interindividual transfers of diaspores, representing 5% of the diaspores attached to animals’ fur. Our results militate for incorporating animal behavior into plant dispersal modeling approaches.     

Seed dispersal effectiveness by a large‐bodied invasive species in defaunated landscapes

Animal‐dispersed plants are increasingly reliant on effective seed dispersal provided by small‐bodied frugivores in defaunated habitats. In the Neotropical region, the non‐native wild pig (Sus scrofa) is expanding its distribution and we hypothesized that they can be a surrogate for seed dispersal services lost by defaunation. We performed a thorough analysis of their interaction patterns, interaction frequencies, seed viability, and characteristics of the seed shadows they produce. We found 15,087 intact seeds in 56% of the stomachs and 5,186 intact seeds in 90% of the scats analyzed, 95% of which were smaller than 10 mm in diameter. Wild pigs were the third most effective disperser among 21 extant frugivore species in a feeding trail experiment in terms of quantity of seeds removed. Gut retention time was 70 ± 23 hr, indicating wild pigs can promote long‐distance seed dispersal. Seed survival after seed handling and gut passage by wild pigs was positively related with seed size, but large seeds were spat out and only smaller seeds were defecated intact, for which we observed a positive or neutral effect on germination relative to manually de‐pulped seeds. Finally, deposition of seeds was four times more frequent in unsuitable than suitable sites for seedling recruitment and establishment. Seed dispersal effectiveness by wild pigs is high in terms of the quantity of seeds dispersed but variable in terms of the quality of the service provided. Our study highlights that negative and positive effects delivered by non‐native species should be examined in a case by case scenario. Abstract in Portuguese is available with online material.