Gut Retention Research Articles

Closing the gaps for animal seed dispersal: Separating the effects of habitat loss on dispersal distances and seed aggregation.

Habitat loss can alter animal movements and disrupt animal seed dispersal mutualisms; however, its effects on spatial patterns of seed dispersal are not well understood. To explore the effects of habitat loss on seed dispersal distances and seed dispersion (aggregation), we created a spatially explicit, individual‐based model of an animal dispersing seeds (SEADS—Spatially Explicit Animal Dispersal of Seeds) in a theoretical landscape of 0%–90% habitat loss based on three animal traits: movement distance, gut retention time, and time between movements. Our model design had three objectives: to determine the effects of (1) animal traits and (2) habitat loss on seed dispersal distances and dispersion and (3) determine how animal traits could mitigate the negative effects of habitat loss on these variables. SEADS results revealed a complex interaction involving all animal traits and habitat loss on dispersal distances and dispersion, driven by a novel underlying mechanism of fragment entrapment. Unexpectedly, intermediate habitat loss could increase dispersal distances and dispersion relative to low and high habitat loss for some combinations of animal traits. At intermediate habitat loss, movement between patches was common, and increased dispersal distances and dispersion compared to continuous habitats because animals did not stop in spaces between fragments. However, movement between patches was reduced at higher habitat loss as animals became trapped in fragments, often near the parent plant, and dispersed seeds in aggregated patterns. As movement distance increased, low time between movements and high gut retention time combinations permitted more movement to adjacent patches than other combinations of animal traits. Because habitat loss affects movement in a nonlinear fashion under some conditions, future empirical tests would benefit from comparisons across landscapes with more than two levels of fragmentation.

Seed dispersal distributions resulting from landscape‐dependent daily movement behaviour of a key vector species,Anas platyrhynchos

SummaryDispersal via animals (zoochory) is a primary mechanism for seed exchange between habitat patches. Recent studies have established that many plant species can survive waterbird gut passage. To quantify the patterns and consequences of waterbird‐mediated dispersal, information on ingestion and gut passage must be combined with bird movement data. Such analysis has recently revealed seed dispersal kernels by migrating waterbirds. However, since many waterbird populations are largely resident, and migrating populations spend only a minor part of the main dispersal season (autumn–winter) on active migration, daily regional‐scale movements probably cause more frequent dispersal.We synthesized high‐resolution empirical data on landscape‐scale movements and seed gut passage times in a key disperser species, the mallard (Anas platyrhynchos), using a spatially explicit, mechanistic model to quantify dispersal distributions resulting from daily autumn–winter movements. We evaluated how landscape composition and seed traits affect these dispersal patterns.The model indicates that mallards generate highly clumped seed deposition patterns, dispersing seeds primarily between core areas used for foraging and resting. Approximately 34% of all dispersed seeds are transported to communal roost areas, which may function as reservoirs for mallard‐dispersed species, and 7% are transported between foraging areas. Landscape‐dependent movement patterns strongly affect the dispersal distributions, resulting in multi‐modal dispersal kernels, with dispersal distances increasing with fragmentation of freshwater foraging habitat. Seed size‐related gut retention times determine the proportion of seeds being dispersed away from the ingestion area, with larger seeds (20 mm3) having a 8–10% higher potential for long‐distance dispersal than smaller seeds (0·2 mm3), if surviving gut passage. However, twice as many small seeds will finally accomplish long‐distance dispersal due to their higher gut passage survival.Synthesis. Firstly, this study reveals how seed dispersal patterns resulting from daily waterfowl movements are shaped by landscape‐dependent differences in movement patterns. Secondly, seed survival appears more important than retention time in determining the scale of long‐distance dispersal by non‐migrating mallards. We conclude that the frequent flights of staging waterbirds result in directed dispersal over distances inversely related to wetland availability, indicating that they maintain landscape connectivity across a range from wet to increasingly dry landscapes.

Effects of Dietary Fiber on Gut Retention Time in Captive Macaca cyclopis, Macaca fascicularis, Hylobates lar, and Pongo pygmaeus and the Germination of Ingested Seeds

Gut retention time (GRT), defined as the time needed for seeds to pass the digestive tracts of consumers, can affect the germination rates of ingested seeds. GRT can vary with the amount of dietary fiber consumed by primates. We investigated how dietary fiber affects GRT in captive individuals of four hindgut-fermenting primate species: macaques (Macaca cyclopis and Macaca fascicularis), gibbons (Hylobates lar), and orangutans (Pongo pygmaeus). We used Hylocereus undatus seeds as markers to measure GRT in each species when fed high- (18–22%) and low- (14–16%) fiber diets. We also examined the effect of GRT on seed germination in Ficus septica and Trema orientalis (germination time: mean ± SE = 10.4 ± 0.3, 86.9 ± 2.5 days, respectively) by comparing these seeds with the pulp removed, as a control. We found that GRT was longer when gibbons and orangutans fed on a high-fiber diet than on a low-fiber diet, but this was not the case for macaques. The percentage germination of ingested F. septica seeds was lower and germination time was longer than the control. T. orientalis seeds were less likely to germinate than control seeds were but did so more quickly if they did germinate after passing through M. cyclopis and P. pygmaeus. GRT decreased the germination rate of seeds of F. septica, but not seeds of T. orientalis. Together our results suggest that the effect of dietary fiber on GRT differs among primate species, and that the effect of such differences in GRT varies with the seed species they swallow.

Determination of the gut retention of plastic microbeads and microfibers in goldfish (Carassius auratus)

Microplastics are ubiquitous pollutants in aquatic habitats and commonly found in the gut contents of fish yet relatively little is known about the retention of these particles by fish. In this study, goldfish were fed a commercial fish food pellet amended with 50 particles of one of two microplastics types, microbeads and microfibers. Microbeads were obtained from a commercial facial cleanser while microfibers were obtained from washed synthetic textile. Following consumption of the amended pellet, fish were allowed to feed to satiation on non-amended food followed by fasting for periods ranging from 1.5 h to 6 days. Fish sacrificed at different time points were dissected to remove gut contents and the digesta contents retention and microplastic retention was determined. Although a small number of microplastic particles were retained in fish GI-tracts after 6 days (0–3 particles/50), the retention of microplastics was generally similar to the retention of bulk digesta contents. According to a breakpoint regression model fitted to digesta contents and microplastic particles, the 50% and 90% evacuation times were 10 h and 33.4 h, respectively. The results of this study indicate that neither microbeads nor microfibers are likely to accumulate within the gut contents of fish over successive meals.

Comparing methods of acquiring mammalian endozoochorous seed dispersal distance distributions

AbstractResearch on endozoochorous seed dispersal is needed to further understand plant ecology and evolution. There are several methods for calculating the distribution of seed dispersal distances, although many studies use the “combination of gut retention time and movement data” (CGM) method to determine the potential seed dispersal distance distribution (PSD). However, there have been no evaluations of between PSD values acquired by CGM and seed dispersal distance distributions calculated using other methods. The main purpose of this study was to compare methods of determining seed dispersal distance distributions using raccoon dogs (Nyctereutes procyonoides). We calculated estimated seed dispersal distance distribution (ESD) using the bait‐marker method and PSD using the CGM method. There were no differences between the ESD and PSD results with regard to basic dispersal distance distributions. The results indicate that if the region from which animal movement data was acquired and the region from which markers for the bait‐marker method have been collected are the same, the distance distributions using the two methods may match. Additionally, though there were differences in seed mimic gut retention times (GRTs) between the two baits used (median GRT, fruits: 8 h 50 min, animal materials: 12 h 55 min), there were no differences in PSD between the two baits. This indicates that disperser movement has a stronger effect on dispersal distance distribution than GRT when using the CGM method.

Seed Dispersal of Threatened Tree Species by a Critically Endangered Primate in a Brazilian Hotspot

In the northern Atlantic Forest, hunting and habitat loss have eliminated most large mammals that disperse zoochoric fruits. Due to the decrease in populations of large seed dispersers, yellow-breasted capuchins (Sapajusxanthosternos) are currently one of the largest arboreal fruit-eating mammals in the region. During 26 months, we followed 14-25 capuchins aiming to (1) present data on their dietary ecology, (2) verify the conservation status of plants in the diet, and (3) determine distance and habitat of seed deposition based on gut retention time. Capuchins showed a preference for feeding in old secondary forests in spite of the greater availability of primary forests. They fed on 109 species of fruits (42.7% of feeding frequency) and swallowed 85 species of seeds (mean width: 0.73 ± 0.57 cm; mean length: 1.17 ± 0.83 cm). Capuchins consumed mostly oil palm and manilkara fruits. We observed long distances of seed deposition (median 300-360 m); 36.8-41.7% of these events occurred in a distinct habitat, and seeds of 12 late-stage trees swallowed in the primary forest were deposited in old secondary forests. S. xanthosternos has an important role in the first phase of seed dispersal (seed removal from the parent tree and seed deposition), particularly for 23 endemic and 3 endangered plants.

Long-distance seed dispersal by straw-coloured fruit bats varies by season and landscape

On-going fragmentation of tropical forest ecosystems and associated depletion of seed dispersers threatens the long-term survival of animal-dispersed plants. These threats do not only affect biodiversity and species abundance, but ultimately ecosystem functions and services. Thus, seed dispersers such as the straw-coloured fruit bat, E. helvum, which traverse long distances across fragmented landscapes, are particularly important for maintaining genetic connectivity and colonizing new sites for plant species. Using high-resolution GPS-tracking of movements, field observations and gut retention experiments, we quantify dispersal distances for small- and large-seeded fruits foraged by E. helvum during periods of colony population low (wet season) and high (dry season) in an urban and a rural landscape in the forest zone of Ghana. Gut passage time averaged 116 min (range 4–1143 min), comparable to other fruit bats. Movements were generally longer in the urban than in the rural landscape and also longer in the dry than in the wet season. As the majority of seeds are dispersed only to feeding roosts, median dispersal distances were similar for both large (42–67 m) and small (42–65 m) seeds. However, small seeds were potentially dispersed up to 75.4 km, four times further than the previous maximum distance estimated for a similar-sized frugivore. Maximum seed dispersal distances for small seeds were almost twice as long in the rural (49.7 km) compare to the urban (31.2 km) landscape. Within the urban landscape, estimated maximum dispersal distances for small seeds were three times longer during the dry season (75.4 km) compared to the wet season (22.8 km); in contrast, distances in the rural landscape were three times longer in the wet season (67 km) compared to the dry season (24.4). Dispersal distances for large seeds during the dry season (551 m) in the rural landscape were almost twice that in the wet season (319 m). We found no influence of food phenology on dispersal distances. The maximum likelihood for seed dispersal beyond feeding roosts (mean distance from food tree 263 m) was 4.7%. Small seeds were dispersed over even longer distances, >500 and >1000 m, with a likelihood of 3.0 % and 2.3 % respectively. Our data show that E. helvum retains ingested seeds for very long periods and may traverse large distances, probably making it an important long distance seed disperser in tropical Africa. We suggest E. helvumis important for ecosystem functioning and urge its conservation.

Fruit Odor as A Ripeness Signal for Seed-Dispersing Primates? A Case Study on Four Neotropical Plant Species.

Fleshy fruits contain a myriad of secondary metabolites that may fulfill various non-mutually exclusive ecological functions. Among them are defense against pathogens and herbivores, manipulation of frugivores’ gut retention time, or controlling the germination process. In addition, it has been suggested that aroma compounds may be used as fruit-selection cues by frugivores, and that plants may be under selection to provide a reliable signal for ripeness to seed-dispersal vectors through ripe fruit aroma. A previous project demonstrated that fruit odor of two Neotropical primate-dispersed plant species can be used by primates to identify ripe fruits. Here, we provide data supporting the hypothesis that olfactory conspicuousness of ripeness in these two species may be an evolved signal rather than a cue exploited by primates. We analyzed the odors of ripe and unripe fruits of the two species along with odors of two sympatric species whose main dispersal vector is passerine birds. We show that only primate-dispersed species significantly change their odor profiles upon ripening. Thus, odor of bird-dispersed species is not informative regarding their ripeness level and is likely to fulfill other functions. We discuss these data in light of the multiple hypotheses for the presence of fruit secondary metabolites, and we offer a roadmap for future studies to establish the hypothesis that fruit odor is an evolved signal for ripeness.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-016-0687-x) contains supplementary material, which is available to authorized users.

Utilizing an Ingestible Biosensor to Assess Real-Time Medication Adherence.

Medication adherence monitoring has relied largely on indirect measures of pill ingestion including patient self-report, pharmacy refills, electronically triggered pill bottles, and pill counts. Our objective is to describe an ingestible biosensor system comprising a radio-frequency identification (RFID)-tagged gelatin capsule. Once the capsule dissolves in the stomach, the RFID tag activates to transmit a unique signal to a relay device which transmits a time-stamped message to a cloud-based server that functions as a direct measure of medication adherence. We describe a constellation of mobile technologies that provide real-time direct measures of medication adherence. Optimizing connectivity, relay design, and interactivity with users are important in obtaining maximal acceptability. Potential concerns including gut retention of metallic components of the ingestible biosensor and drug dissolution within a gelatin capsule should be considered. An ingestible biosensor incorporated into a medication management system has the potential to improve medication compliance with real-time monitoring of ingestion and prompt early behavioral intervention. Integration of ingestible biosensors for multiple disease states may provide toxicologists with salient data early in the care of poisoned patients in the future. Further research on device design and interventions to improve adherence is needed and will shape the evolving world of medication adherence.

Western lowland gorilla seed dispersal: Are seeds adapted to long gut retention times?

The degree of seed scarification in the frugivore gut, partly dependent on gut retention time, is a key component in determining the extent to which gut passage alters germination performances. Another potential benefit of gut passage arises as a result of the removal of fruit pulp which otherwise may act as a germination inhibitor. Using experiments designed to disentangle the respective effects of pulp removal (germination deinhibition) and seed scarification, and gut retention time as an explanatory variable, we investigated the effect of gut passage on germination performances (percentage and latency) of five tropical tree species dispersed by the western lowland gorilla (Gorilla g. gorilla). The percentage of seeds germinating after gut passage increased for three species, respectively, through the effects of scarification only, deinhibition only, and scarification and deinhibition combined. A negative scarification effect was observed for one species, and no effect of gut passage for another. Passage through the gut led to a decrease in germination latency of three species, as a result of the depulping of seeds. However, seed scarification resulted in germination delays for another species. The gut retention time of the five species averaged 39–56 h and had no effect on intra-specific germination performances except for one species whose germination probability increased as gut retention time increased. As gut retention time often correlates with dispersal distance, the fact that gut retention time per se does not reduce seed viability of these tropical tree species may have positive implications for their population dynamics and maintenance of genetic diversity. If no detrimental effect of gut retention time on germination performance is a general trait among tropical species, the extirpation of large frugivores with long gut retention time, such as the western lowland gorilla, would likely have negative long-term implications for tropical forests.

Seed dispersal of an invasive shrub, Amur honeysuckle (Lonicera maackii), by white-tailed deer in a fragmented agricultural-forest matrix

Ungulates are potentially important seed dispersers for many invasive plant species. While our understanding of which invasive plant species are dispersed by ungulates has improved over the last decade, the factors influencing this process remain poorly understood. To address this, we explored white-tailed deer (Odocoileus virginianus) seed consumption and dispersal of an invasive shrub (Lonicera maackii) in fragmented agricultural-forest matrices in western Ohio. In a pairwise browse preference experiment, deer browsed at similar levels on branches of L. maackii with fruits removed and fruits intact (mean ± 95 % CI 57 ± 14 and 62 ± 14 %, respectively). We found no evidence that white-tailed deer disperse L. maackii seeds along an invasion front, but 31 % of deer pellet groups collected in an invaded area contained germinable L. maackii seeds (maximum number of germinable seeds = 30). By combining hourly movement data specific to fragmented landscapes and gut retention time data, we projected that female deer disperse 91 % of ingested seeds further than 100 m from seed sources (i.e., long-distance seed dispersal), and rarely disperse seeds up to 7.9 km. We conclude that white-tailed deer can be important long-distance seed dispersal vectors of L. maackii, and that invader abundance and/or patch connectivity likely influence patterns of seed dispersal by white-tailed deer.

The potential for birds to disperse the seeds of Acacia cyclops, an invasive alien plant in South Africa

Rooikrans Acacia cyclops is an aggressive invasive tree that threatens natural resources in South Africa. The seeds of A. cyclops have a prominent aril which attracts birds that ingest the seeds and disperse them endozoochorously. Two biological control agents, a Seed Weevil Melanterius servulus and a Flower‐galling Midge Dasineura dielsi, were released on A. cyclops in 1991 and 2002, respectively. Together these agents have substantially reduced seed production and generally far lower numbers of seeds are now available to birds. A consequence of this transition from historically bounteous quantities of seeds to scanty seed availability is that birds may no longer associate with the trees and seed dispersal may be disproportionately reduced. To assess whether this has happened, seed attrition was measured by comparing the amount of seeds that disappeared from two groups of branches, one available to birds and the other enclosed in bird netting. Other types of granivores (mainly field mice) were excluded from both groups of branches with a plastic funnel placed around the stems. Mature seeds were also harvested and fed to caged bird species to determine gut retention times and germination rates of ingested seeds. Attrition rates of seeds showed that birds continue to remove seeds but that only a proportion of the crop is taken. Only two frugivorous species (Knysna Turaco Tauraco corythaix and Red‐winged Starling Onychognathus morio) and two granivorous species (Red‐eyed Dove Streptopelia semitorquata and Laughing Dove Streptopelia sengalensis) ingested A. cyclops seeds during feeding trials. Ingestion by birds enhanced seed germination except for those ingested by Laughing Doves. There were no apparent effects of length of gut passage time and avian body size on seed germination rates. Despite the diminished seed resource due to biological control agents, birds continue to disperse A. cyclops seeds.

Scheduling Exercise-Eating to Optimize Gut Probiotics: A Global Invention

This article describes how optimizing exercise timing can improve gut physiology and health. The goal is to avoid prolonged gut retention of digesta especially overnight. Suboptimal fermentation and eating-exercise timing are among shortcuts to unhealthy gut. It is suggested that early morning and evening physical work supplemented by small and minor evening and night food meals minimizes risks of unnecessary overdigestion and hindgut ill-fermentation, thus improving gut integrity and metabolism. Large evening meals must be avoided in any scenario. Day-time meals should be frequent but small. This helps ensure continuous and modest ingesta digestion and splanchnic metabolism and well-managed waste.

Sortase-deficient lactobacilli: effect on immunomodulation and gut retention.

Surface proteins of probiotic microbes, including Lactobacillus acidophilus and Lactobacillus gasseri, are believed to promote retention in the gut and mediate host-bacterial communications. Sortase, an enzyme that covalently couples a subset of extracellular proteins containing an LPXTG motif to the cell surface, is of particular interest in characterizing bacterial adherence and communication with the mucosal immune system. A sortase gene, srtA, was identified in L. acidophilus NCFM (LBA1244) and L. gasseri ATCC 33323 (LGAS_0825). Additionally, eight and six intact sortase-dependent proteins were predicted in L. acidophilus and L. gasseri, respectively. Due to the role of sortase in coupling these proteins to the cell wall, ΔsrtA deletion mutants of L. acidophilus and L. gasseri were created using the upp-based counterselective gene replacement system. Inactivation of sortase did not cause significant alteration in growth or survival in simulated gastrointestinal juices. Meanwhile, both ΔsrtA mutants showed decreased adhesion to porcine mucin in vitro. Murine dendritic cells exposed to the ΔsrtA mutant of L. acidophilus or L. gasseri induced lower levels of pro-inflammatory cytokines TNF-α and IL-12, respectively, compared with the parent strains. In vivo co-colonization of the L. acidophilus ΔsrtA mutant and its parent strain in germ-free 129S6/SvEv mice resulted in a significant one-log reduction of the ΔsrtA mutant population. Additionally, a similar reduction of the ΔsrtA mutant was observed in the caecum. This study shows for the first time that sortase-dependent proteins contribute to gut retention of probiotic microbes in the gastrointestinal tract.

Small mammals feeding on hypogeous fungi

Fungi serve as a food source for a wide variety of animals. Among mammals, most species feed on fungi occasionally or accidentally while foraging for other type of food, but some species are frequent mycophags and fungi can be a dominant component of their diet. Examples of mycophags can be found among marsupials: wallabies and bettongs; and rodents: squirrels, chipmunks, voles and mice. Hypogeous fungi produce closed, underground sporocarps without opening mechanisms, and thus are unable to release their spores into the air. In case of those fungi, animals feeding on sporocarps and spreading spores in their faeces are considered to be the main vector of spore dispersal. Animals that frequently feed on fungi and other heavy digestible food have developed morphological adaptations such as longer gut retention and a spiral construction of the proximal colon, to digest more fungal material which is rich in nitrogen. The spores stay viable after passing through the animal gut, and in some cases their ability to germinate and form mycorrhiza is enhanced after leaving the intestine. Hypogeous fungi are mycorrhizal partners for plants and it is therefore possible that the interactions between mycorrhizal fungi and animals spreading their spores also play an important role in ecosystem functioning.

Insights into glycogen metabolism in Lactobacillus acidophilus: impact on carbohydrate metabolism, stress tolerance and gut retention.

In prokaryotic species equipped with glycogen metabolism machinery, the co-regulation of glycogen biosynthesis and degradation has been associated with the synthesis of energy storage compounds and various crucial physiological functions, including global cellular processes such as carbon and nitrogen metabolism, energy sensing and production, stress response and cell-cell communication. In addition, the glycogen metabolic pathway was proposed to serve as a carbon capacitor that regulates downstream carbon fluxes, and in some microorganisms the ability to synthesize intracellular glycogen has been implicated in host persistence. Among lactobacilli, complete glycogen metabolic pathway genes are present only in select species predominantly associated with mammalian hosts or natural environments. This observation highlights the potential involvement of glycogen biosynthesis in probiotic activities and persistence of intestinal lactobacilli in the human gastrointestinal tract. In this review, we summarize recent findings on (i) the presence and potential ecological distribution of glycogen metabolic pathways among lactobacilli, (ii) influence of carbon substrates and growth phases on glycogen metabolic gene expression and glycogen accumulation in L. acidophilus, and (iii) the involvement of glycogen metabolism on growth, sugar utilization and bile tolerance. Our present in vivo studies established the significance of glycogen biosynthesis on the competitive retention of L. acidophilus in the mouse intestinal tract, demonstrating for the first time that the ability to synthesize intracellular glycogen contributes to gut fitness and retention among probiotic microorganisms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-014-0094-3) contains supplementary material, which is available to authorized users.

Analysis of the diet of the long-snouted seahorseHippocampus guttulatusby 18SrDNA amplification of prey in faeces

Breeding in captivity for research or exhibition (e.g. in aquaria) can replace the capture of wild specimens of endangered species and allow controlled reinforcement of wild populations. With this aim, diet analysis and establishing the adequate prey are determinant factors for breeding success. However, non-invasive approaches such as faecal DNA analysis are advisable for analysing the diet of these species. Therefore, the aim of the present study was to demonstrate the usefulness of faecal DNA analysis by specific PCR amplification of prey DNA for assessing the diet of the seahorse Hippocampus guttulatus. In a comparison of the suitability of different genes (COI, 18SrRNA and 28SrRNA), 18SrRNA was found to be the most suitable for designing specific primers for the prey types fed to seahorses (Artemia, Palaemonetes and Mysidae). The technique was assessed in feeding experiments in which prey ingestion was recorded daily, and faeces were collected for DNA extraction and presence/absence PCR analysis. Amplification of the prey DNA in faeces was consistent with the sequence of prey supplied (prey eaten the day before was always detected). Differences in the time between feeding and detection in faeces suggested prey-specific gut passage times, which were shorter for Palaemonetes than for Mysidae. This fact highlights the importance of feeding trials to avoid overestimating the consumption of prey with long gut retention when PCR-based methods are used. This molecular technique is thus applicable for studying the feeding behaviour of captive seahorses and could be adapted for use in other marine species.

Quantifying diet-borne metal uptake in Gammarus pulex using stable isotope tracers

Gammarids are aquatic amphipods widely used for water quality monitoring. To investigate the copper and cadmium diet-borne metal uptake in Gammarus pulex, we adapted the pulse-chase stable isotopes-based approach to determine the food ingestion rate (IR), the gut retention time (GRT) and the metal assimilation efficiencies (AE). G. pulex were fed with 65Cu-, 106Cd-, and 53Cr-labeled alder leaves for 7.5h and then with unlabeled leaves for 5d. The metal stable isotope contents in the gammarids, leaves, filtered water and periodically collected feces were determined. Chromium was poorly assimilated by the gammarids; thus, Cr was used as an unassimilated tracer. The first tracer defecation occurred before the first feces harvest, indicating a gut passage time of less than 9h. A 24-h GRT and a 0.69gg−1d−1 IR were estimated. The Cd AE value was estimated as 5–47%, depending on the assimilation determination method applied. The Cu AE value could not be evaluated regardless of the determination method used, most likely because of the rapid Cu regulation in gammarids in addition to analytical uncertainties when determining the Cu content in leaves. Application of the Cd AE value in the framework of the biodynamic bioaccumulation model shows that the diet-borne uptake of Cd significantly contributes (66–95%) to the metal bioaccumulation in G. pulex fed with alder leaves.

Estimation of Seed Shadows Generated by Andean Woolly Monkeys (Lagothrix lagothricha lugens)

Seed dispersal is known to play an important role in the ecology and evolution of plant communities, and there is ample evidence that seed dispersal by primates influences plant population dynamics in tropical forests directly. We used nonparametric statistical methods to estimate the dispersal kernels, i.e., the probability that a seed is moved a particular distance, generated by woolly monkeys (Lagothrix lagothricha lugens) at a sub-Andean forest in Colombia and test the hypothesis that the time of feeding influences dispersal distances. We collected data on monkey ranging patterns with the aid of global positioning system (GPS) units and obtained information on gut retention times from behavioral follows to build a model based on the kernel density estimator. Woolly monkeys drop most seeds hundreds of meters from parent trees and only a small proportion of seeds within close proximity. The time of seed ingestion had a significant effect on dispersal kernels, with seeds from fruits consumed early in the day having a greater chance of landing farther away from the tree than seeds swallowed in the late afternoon. The results of this study build on previous findings suggesting that woolly monkeys have a positive effect on the fitness of plants, which may be exacerbated in mountain forests where the diversity of large frugivores is low.

脊椎动物传播植物肉质果中的次生物质及其生态作用

PDF HTML阅读 XML下载 导出引用 引用提醒 脊椎动物传播植物肉质果中的次生物质及其生态作用 DOI: 10.5846/stxb201212151805 作者: 作者单位: 南京林业大学森林资源与环境学院,南京林业大学森林资源与环境学院,南京林业大学 森林资源与环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（30970470）；江苏高校优势学科建设工程项目 Secondary substances and their ecological effects on seed dispersal in vertebrate-dispersed fleshy fruit plants Author: Affiliation: College of Forest resources and Environment,Nanjing Forestry University,College of Forest resources and Environment,Nanjing Forestry University,College of Forest resources and Environment,Nanjing Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在种子植物-动物的互惠关系中，植物果实成熟后需要吸引种子传播者取食果实，传播其种子至适宜萌发的生境，同时又要防御种子捕食者过度消耗种子。果实内的次生物质（如：配糖生物碱、大黄素、辣椒素）在此过程中起到重要的调控作用。依赖脊椎动物传播的肉质果中往往含有与植物茎、叶内相同的次生物质，其种类繁多，主要分为含氮化合物、酚类化合物和萜类化合物。未成熟果实内富含次生物质（如：单宁、大黄素），主要保护未成熟种子不被潜在的捕食者和食果动物取食，这些次生物质的含量通常随果实成熟而降低；其它次生物质（如：脱辅基类胡萝卜素）的含量随果实成熟而增多，可能起到吸引食果动物的作用。在对脊椎动物捕食的抵御中，果实内不同类型的次生物质促使成熟果实对所有脊椎动物都有毒性（专毒性）或者仅对种子捕食者有毒性（泛毒性）。肉质果内的次生物质对植物-食果动物相互关系的调控作用，还可以通过调节动物取食频次和数量、抑制和促进种子萌发、改变种子在肠道的滞留时间、吸引传播者等生态作用而实现。某种次生物质往往集多种生态作用于一身。目前对肉质果内次生物质与脊椎动物相互关系的探讨还不够深入。未来研究需要综合考虑植物次生物质与果实生理生化、形态学等特征对食果者的综合调控机理；次生物质在种子传播后的调控作用对植物种群或群落结构和分布格局的影响；从动植物协同进化角度探讨植物次生物质的产生、防御和吸引策略与脊椎动物对果实的选择和消费之间的关系等。开展脊椎动物传播肉质果实中次生物质的研究，对完善种子传播机制、植物繁殖和更新格局，丰富动植物相互作用、协同进化理论具有重要的意义。 Abstract:Plant species which depend on vertebrates for dispersing their seeds in flesh fruits to safe sites for establishment often face the trade-off between attracting seed dispersers and preventing their seeds from over consumption by seed predators. Secondary substances such as glycoalkaloids, emodin, and capsaicinoids in fleshy fruits play an important role for regulating this process. There are diverse secondary substances in vertebrate-dispersed fleshy fruits, but they are often the same as those found in the stems and leaves, and mostly belong to the three major categories: nitrogen-containing compounds (e.g. glycoalkaloids and capsaicinoids), phenolic compounds (e.g. emodins and tannins), and terpenoids (e.g. saponins). The content of some secondary substances such as tannins and emodins is abundant in immature fruits, which deters the potential predators or pre-mature disposal by frugivores; the content decreases with the fruit maturity. Other secondary substances (e.g. apocarotenoids) increase with the maturation, which may promote the consumption by dispersers. Secondary substances in vertebrate-dispersed fleshy fruits may modify the relationship between animals and plants by altering the fruit consumability: depending on the type of the secondary substances, the fleshy fruits could be toxic to all vertebrates (non-specific or general toxic) or only to some species (specific or directed toxic). Secondary compounds might be able to regulate animal feeding frequency and the amount of consumption by causing frugivores to leave the fruit plant sooner in a foraging bout; early departure from the plant might reduce the number of fruits consumed by a particular animal, but may increase the overall the likelihood of seed dispersal away from parent plant by other dispersers. Secondary substances in ripe fruit pulp can inhibit pre-dispersal seed germination or enhance post-dispersal seed germination. Gut retention time of seeds in vertebrates could be altered by some secondary substances, permitting either more rapid passage via laxative effects or slower passage rates by constipating effects. The colors, odors, and flavors of the fleshy fruits can be modified by secondary substances, which can attract dispersers by providing foraging and rewarding cues recognized by frugivores. A single secondary substance can have multiple ecological functions. Our knowledge of secondary substances in flesh fruits and their interactions with vertebrate animals are still limited. Future research need to consider diverse aspects of plant secondary substances such as the comprehensive regulatory mechanisms of fruit physiological biochemistry and morphology characteristics to the frugivores; the regulatory mechanisms of secondary substances for plant population and community structure and distribution patterns post dispersal; and the coevolution between the production of secondary substances and their defense and attraction strategies of plants and the selection and consumption of fleshy fruits by vertebrate animals. The research of secondary substances in vertebrate-dispersed fleshy fruits will enhance our knowledge of seed dispersal mechanisms, plant generation and recruitment patterns, and animal-plant interaction and their coevolution. 参考文献 相似文献 引证文献