Gut Retention Time Research Articles

Effects of bear endozoochory on germination and dispersal of huckleberry in the Canadian Rocky Mountains.

Berries are a staple of bear diets during late summer and fall in the southern Rocky Mountains, enabling bears to build up fat reserves and prepare to enter torpor during winter. In turn, bears can benefit fruiting shrubs through dispersal of their seeds. Bears are highly mobile species and seed passage through their guts (endozoochory) can influence seed germination in three ways: deinhibition (removal of germination inhibiting compounds), scarification (mechanical or chemical alteration) and fertilization (enhancement of germination from increased nutrients). We conducted a germination experiment to assess the ways each mechanism of bear endozoochory affects germination success of huckleberry (Vaccinium membranaceum.) in the southern Canadian Rocky Mountains. The potential for bears to act as long-distance seed dispersers was also investigated, using a combination of available literature on bear gut retention times and movement data of 74 GPS radio-collared grizzly bears. Deinhibition had a positive significant impact (28.5% germination for the Seeds from Berry treatment compared to 0.2% for Whole Berry at 60 days), while scarification and fertilization did not have detectable positive effects on huckleberry germination success. These results suggest that the removing germination-inhibiting compounds in berry pulp is the primary mechanism through which endozoochory can increase germination in huckleberry seed. We estimated that 50% of the seeds defecated by bears in the region are dispersed 1.1 km away from feeding places (and up to 7 km). The surfaces covered by the seed shadow was up to 149.6 km2, demonstrating that bears can act as effective vectors of seeds over long distances. Endozoochory bolsters the germination success of seeds from fruiting shrubs, and enables seeds to spread to new locations using bears as dispersal agents. Development, resource extraction, and climate change may disrupt the beneficial relationship between bears and huckleberries, where huckleberries help bears gain fat, and bears help spread huckleberry seeds-a process that may become increasingly important as climate change alters habitats.

Direct evidence of frugivory in the Mesozoic bird Longipteryx contradicts morphological proxies for diet

Diet is one of the most important aspects of an animal's ecology, as it reflects direct interactions with other organisms and shapes morphology, behavior, and other life history traits. Modern birds (Neornithes) have a highly efficient and phenotypically plastic digestive system, allowing them to utilize diverse trophic resources, and digestive function has been put forth as a factor in the selectivity of the end-Cretaceous mass extinction, in which only neornithine dinosaurs survived.1 Although diet is directly documented in several early-diverging avian lineages,2 only a single specimen preserves evidence of diet in Enantiornithes, the dominant group of terrestrial Cretaceous birds.3 Morphology-based predictions suggest enantiornithines were faunivores,4,5,6 although the absence of evidence contrasts with the high preservation potential and relatively longer gut-retention times of these diets. Longipteryx is an unusual Early Cretaceous enantiornithine with an elongate rostrum; distally restricted dentition7; large, recurved, and crenulated teeth8; and tooth enamel much thicker than other paravians.9 Statistical analysis of rostral length, body size, and tooth morphology predicts Longipteryx was primarily insectivorous.4,5 Contrasting with these results, two new specimens of Longipteryx preserve gymnosperm seeds within the abdominal cavity interpreted as ingesta. Like Jeholornis, their unmacerated preservation and the absence of gastroliths indicate frugivory.10 As in Neornithes,11 complex diets driven by the elevated energetic demands imposed by flight, secondary rostral functions, and phylogenetic influence impede the use of morphological proxies to predict diet in early-diverging avian lineages.

Nylon microfibers develop a distinct plastisphere but have no apparent effects on the gut microbiome or gut tissue status in the blue mussel, Mytilus edulis.

Ingestion of microplastics (MP) by suspension-feeding bivalves has been well-documented. However, it is unclear whether exposure to MP could damage the stomach and digestive gland (gut) of these animals, causing ramifications for organism and ecosystem health. Here, we show no apparent effects of nylon microfiber (MF) ingestion on the gut microbiome or digestive tissues of the blue mussel, Mytilus edulis. We exposed mussels to two low concentrations (50 and 100 particles/L) of either nylon MF or Spartina spp. particles (dried, ground marsh grass), ca. 250-500 μm in length, or a no particle control laboratory treatment for 21 days. Results showed that nylon MF, when aged in coarsely filtered seawater, developed a different microbial community than Spartina spp. particles and seawater, however, even after exposure to this different community, mussel gut microbial communities resisted disturbance from nylon MF. The microbial communities of experimental mussels clustered together in ordination and were similar in taxonomic composition and measures of alpha diversity. Additionally, there was no evidence of damage to gut tissues after ingestion of nylon MF or Spartina spp. Post-ingestive particle processing likely mediated a short gut retention time of these relatively large particles, contributing to the negligible treatment effects.

Traits for transport: Alien wetland plants gain an advantage during endozoochorous seed dispersal by waterfowl

Abstract The expansion of alien plant species is of global concern, yet our understanding of their dispersal mechanisms is limited. Here we address the potential of alien plant seeds to disperse via ingestion, transport and egestion in waterfowl (endozoochory). Based on their general rapid expansions, we expected alien plant species to have several advantages for endozoochory compared to native plant species. We hypothesised that seeds of alien species would have higher passage rate, longer gut retention times, higher germinability after gut passage and shorter time‐to‐germination after egestion by waterfowl. In order to test our hypotheses, we compared the endozoochorous dispersal ability of six pairs of congeneric alien and native wetland plant species in a feeding experiment with mallards (Anas platyrhynchos). We focused on differences in seed survival, gut retention time, germinability and time‐to‐germination. In the analyses we corrected for seed shape and volume as these seed traits are known to have important effects. With gut passage, alien species had higher passage rates and germinated slower, whereas native species had shorter retention times and greater germinability. Controlling for seed traits did not alter these conclusions, but seed traits affected all aspects of the endozoochory process. This suggests that alien species may have particular traits correlated with a higher endozoochory potential. Among control seeds, alien seeds germinated faster and their germinability was higher than natives. Seed traits explained differences in germinability and time‐to‐germination in control seeds. Seeds of alien plant species have traits that correlate with successful endozoochory. This may provide alien species with a competitive advantage over native plant species by ensuring higher endozoochory rates in new environments, potentially enabling their rapid expansions. Our study underlines the important role of seed traits in the endozoochory potential of alien and native plant species, notably through their influence on retention time and germination.

DNA metabarcoding analysis of three material types to reveal Joro spider (Trichonephila clavata) trophic interactions and web capture

Introduced species alter established trophic interactions and molecular analysis can resolve changes in community structure and associated foraging links. Joro spiders (Trichonephila clavata) were recently introduced to the United States and their range is rapidly expanding across the east coast. Here, we used DNA metabarcoding of fecal samples, prey remains from webs, and dissected guts to compare diet composition of female Joro spiders in the southeastern United States. We amplified DNA from three material types using arthropod-targeted COI primers and sequenced with IIlumina MiSeq. Prey remains from webs had the highest diversity, richness, as well as the highest proportion of prey reads relative to Joro spider reads. Recovery of prey reads from fecal samples and dissected gut content was low and both were overwhelmed by Joro spider DNA. Although fecal samples and gut content had high proportions of Joro spider reads, fecal samples had higher prey diversity and richness. Moreover, we detected prey DNA from fecal samples several days after capture from the field, which reveals initial gut retention time estimates for fecal samples collected from web-building spiders. Combined, our results offer a first glimpse at the complexity of trophic associations for an introduced web-building spider and identify a viable material, prey remains from webs, as a source of prey DNA for estimates of biodiversity associated with web-building spiders.

Seed Size, Not Dispersal Syndrome, Determines Potential for Spread of Ricefield Weeds by Gulls.

Recent field data suggest that migratory gulls disperse many rice field weeds by gut passage (endozoochory), most of which are dry fruited and widely assumed to have no long-distance dispersal mechanisms, except via human activity. We investigated this mechanism with a feeding experiment, in which seeds of five common rice field weeds (in order of increasing seed size: Juncus bufonius, Cyperus difformis, Polypogon monspeliensis, Amaranthus retroflexus, and the fleshy-fruited Solanum nigrum) were fed to seven individuals of lesser black-backed gulls Larus fuscus held in captivity. We quantified seed survival after collecting faeces at intervals for 33 h after ingestion, then extracting intact seeds and running germination tests, which were also conducted for control seeds. All five species showed high seed survival after gut passage, of >70%. Gut retention times averaged 2-4 h, but maxima exceeded 23 h for all species. Germinability after gut passage was 16-54%, and gut passage accelerated germination in J. bufonius and S. nigrum, but slowed it down in the other species. All species had lower germinability after gut passage compared to control seeds (likely due to stratification prior to the experiment), but the loss of germinability was higher in smaller seeds. There was no evidence that the different dispersal syndromes assigned to the five species (endozoochory, epizoochory or barochory) had any influence on our results. In contrast, mean gut retention time was strongly and positively related to seed size, likely because small seeds pass more quickly from the gizzard into the intestines. Non-classical endozoochory of dry-fruited seeds by waterbirds is a major but overlooked mechanism for potential long-distance dispersal, and more research into this process is likely essential for effective weed management.

Linking animal migration and ecosystem processes: Data-driven simulation of propagule dispersal by migratory herbivores.

Animal migration is a key process underlying active subsidies and species dispersal over long distances, which affects the connectivity and functioning of ecosystems. Despite much research describing patterns of where animals migrate, we still lack a framework for quantifying and predicting how animal migration affects ecosystem processes. In this study, we aim to integrate animal movement behavior and ecosystem functioning by developing a predictive modeling framework that can inform ecosystem management and conservation.We propose a framework to model individual‐level migration trajectories between populations' seasonal ranges as well as the resulting dispersal and fate of propagules carried by the migratory animals, which can be calibrated using empirical data at every step of the modeling process. As a case study, we applied our framework to model the spread of guava seeds, Psidium guajava, by a population of migratory Galapagos tortoises, Chelonoidis porteri, across Santa Cruz Island. Galapagos tortoises are large herbivores that transport seeds and nutrients across the island, while Guava is one of the most problematic invasive species in the Galapagos archipelago.Our model can predict the pattern of spread of guava seeds alongside tortoises' downslope migration range, and it identified areas most likely to see establishment success. Our results show that Galapagos tortoises' seed dispersal may particularly contribute to guava range expansion on Santa Cruz Island, due to both long gut retention time and tortoise's long‐distance migration across vegetation zones. In particular, we predict that tortoises are dispersing a significant amount of guava seeds into the Galapagos National Park, which has important consequences for the native flora.The flexibility and modularity of our framework allow for the integration of multiple data sources. It also allows for a wide range of applications to investigate how migratory animals affect ecosystem processes, including propagule dispersal but also other processes such as nutrient transport across ecosystems. Our framework is also a valuable tool for predicting how animal‐mediated propagule dispersal can be affected by environmental change. These different applications can have important conservation implications for the management of ecosystems that include migratory animals.

Are seeds of trees with higher fruit production dispersed farther by frugivorous mammals?

ABSTRACT Previous studies have estimated distributions of seed dispersal distance by a variety of methods. But apart from direct observation, these methods cannot clarify the absolute numbers of seeds dispersed by each disperser. Without the ability to calculate absolute spreading volumes, each dispersers’ contribution cannot be quantitatively evaluated. To resolve this problem, we estimated and compared quantities and distances of seed dispersal by mammalian seed dispersers. We focused on the fruits of Cerasus leveilleana and five species of frugivorous mammals that forage on it, central Japan. We tracked wild individuals of each species and gut retention times of seeds in captive individuals. By observing wild C. leveilleana trees for 2 years, we calculated fruit production, visitation frequency, and numbers of fruits removed per visit by each species. The mammal species differed greatly in body size and foraging behavior, and thus in the seed dispersal patterns that they generated: not only in dispersal distance, especially long distance, but also in the number of seeds removed. In particular, total seed removal and long-distance dispersal tended to be greater when fruit production was greater, and they were strongly affected by occasional visitation by bears. Therefore, understanding the relative functional importance of seed dispersers requires direct comparison of their effectiveness at seed dispersal. Large differences in the seed disperser fauna between years due to interannual variation in fruit production suggest that observations of many trees with different amounts of fruit production over multiple years are needed to clarify how fruiting trees and seed dispersers interact.

Frugivory and seed dispersal by the Red-footed Tortoise Chelonoidis carbonaria

Seed dispersal by frugivores is essential in plant life cycles, with birds and mammals the principal and well-studied dispersal agents. However, there is an increasing recognition that terrestrial tortoises could also be considered important seed dispersers in many ecosystems. The red-footed tortoise (Chelonoidis carbonaria) is one of the largest terrestrial tortoises in South America and is thought to disperse large seeds. However, little is known about their role as seed dispersers, and their potential use as restorers of defaunated areas. Here, we assessed the maximum width of seeds this species could ingest, the mean gut retention time (GRT), and the post-consumption germination capacity for tropical fruit species. Forty different fruit species were offered to eight captive individuals, obtaining a maximum seed width swallowed of 23 mm. We used four native plant species to measure the GRT within four tortoises, and we found a mean retention time of 18.92 ± 4.81 days. We also found that sex is an important indicator of GRT, with females presenting longer retention periods. This novel finding may be due to the higher metabolic defecating and dispersing rates of males. Although germination proportions varied between the four plant species used in the experiment, overall defecated seeds germinated faster than control seeds. We conclude that red-footed tortoises are potentially important seed dispersers due to their ability to swallow a large quantity and size of seeds while accelerating seed germination rates. This species should be considered a viable ecological substitute for large frugivores in rewilding projects, as C. carbonaria performs similar functions to large dispersers that have been extirpated due to defaunation processes.

Experimental assessment of endozoochorous dispersal of Prosopis flexuosa seeds by domestic ungulates

AbstractQuestionThe spatial and temporal dynamics of plant communities in various ecosystems are shaped by the movements of seeds expressed as different dispersal modes. In desert rangeland, many plants produce relatively large fruits that are limited in their long‐distance dispersal abilities and, therefore, depend on transport inside animals, a process termed endozoochory. Evaluating the effectiveness of this process from experimental data is crucial for assessing the potential of domestic ungulates as effective long‐distance seed dispersers and, consequently, as management and restoration tools in degraded rangelands.MethodsIn this study we jointly estimated recovery, gut retention time (RT) and germination probability of Prosopis flexuosa seeds (a tree species of Monte desert in Argentina) transported by goats, horses and cattle (n = 4) through a seed‐feeding experiment. Also, in horses and cattle, we used plastic particles to distinguish between seed loss due to mastication and due to degradation in the gut.ResultsResults showed higher seed recovery in horses (26%) than in cattle (3%) and goats (5%), and different values of RT and germination of seeds among species (in decreasing order, RT was: cattle > goats > horses; and germination was: goat > horses > cattle = control seeds).ConclusionsWe concluded that the quality of seed treatment by horses is better than by the other species, because of the high seed recovery and high germination compared to control seeds. To get a complete picture of this mutualistic interaction, future studies could inquire about the physical and chemical properties of faeces as substrate and the environmental conditions of sites where seeds are deposited.

Microplastic uptake and gut retention time in Japanese anchovy (Engraulis japonicus) under laboratory conditions

To explore the impact of microplastic (MP) pollution on planktivorous fish, we examined the uptake and retention of MPs by Japanese anchovy (Engraulis japonicus) under laboratory conditions. MP uptake was size selective in adult anchovy—0.3-mm MPs were taken up in significantly larger amounts than 0.85-mm MPs—but not in juveniles. There were no significant differences in the uptake of MPs of three different colors, suggesting that anchovy do not select for MP coloration. More than 90% of the MPs were excreted within 20 h of ingestion, indicating that MP retention time is similar to the processing time of food items. Our findings suggest that Japanese anchovy tend to take up MPs that are equivalent in size to prey items, but that the impacts of MP ingestion are likely to be limited under the current state of oceanic MP contamination.

Larger Doesn't Mean Longer: Neither Body Size Nor Seed Size Affect the Gut Retention Times of Aldabra Giant Tortoises

Seed dispersal through endozoochory is a critical ecosystem function worldwide. Seed gut retention time (GRT; the duration that seeds are retained in the digestive tract) is an important part of the qualitative component of the seed dispersal effectiveness framework. GRT is a major determinant of when and how far away seeds are dispersed, aiding seeds in escaping predation in space as well as in time. In this study, we examined whether the size of the disperser and/or the size of the ingested seeds affect the GRT in Aldabra Giant Tortoises (Aldabrachelys gigantea) on Aldabra Atoll, Seychelles. We selected tortoises of varying body mass (mean ± 1 SD = 48.6 ± 27.2 kg, range = 0.6–104.0 kg) and fed them different-sized artificial seeds (plastic beads; 2, 4.5, and 10 mm diameter). Tortoises defecated the first beads a mean of 12.0 ± 2.7 d after ingestion, and the last beads 20.4 ± 6.0 d after ingestion. Mean GRT was 14.6 ± 3.7 d. We show that neither tortoise body size nor bead size had an effect on the patterns and time of defecation. We discuss the relevance of our result for seed dispersal and for rewilding projects that use Aldabra Giant Tortoises as substitute species for extinct giant tortoises on other oceanic islands.

Detection of prey DNA in bat feces: Effects of time since feeding, meal size, and prey identity

AbstractMolecular analyses of feces are widely used to study the feeding ecology of bats. However, little is known about how detectability of prey DNA from bat feces is influenced by gut retention time, mass of prey eaten, or prey identity, which hampers the interpretation of field data. Here, we address these knowledge gaps by conducting a feeding experiment in which different insect species and meal sizes were offered to two bat species, Myotis daubentonii and Pipistrellus nathusii. The feeding regime consisted of three main and three side prey species fed in different masses, whereupon feces were collected over 72 h and examined for prey DNA using a species‐specific multiplex PCR system. DNA of all three main prey species was detectable from feces produced within 1 h after consumption of a meal. Prey detectability decreased over the following 10–20 h, and after 40 h only spurious detections occurred. For both prey and bats, species identity affected detectability: for example, mealworms were detected for a longer time post‐feeding compared to wax moths/house flies, and the latter were detected for a shorter time in M. daubentonii than in P. nathusii. While DNA from all three side prey species was detectable, signals were weak and detections limited to the first 20 h after consumption. These findings indicate that detectability of prey DNA from bat feces is foremost affected by the mass of prey consumed and time post‐feeding, whereas it does not strongly differ between prey species. To increase the detection of prey ingested in low mass, we suggest collecting fecal samples soon after bats return from foraging, as detectability is highest right after feeding occurs, and detections largely depict the previous foraging bout (with detection windows usually <24 h).

Frugivory Specialization in Birds and Fruit Chemistry Structure Mutualistic Networks across the Neotropics.

AbstractThe interaction between fruit chemistry and the physiological traits of frugivores is expected to shape the structure of mutualistic seed dispersal networks, but it has been understudied compared with the role of morphological trait matching in structuring interaction patterns. For instance, highly frugivorous birds (i.e., birds that have fruits as the main component of their diets), which characteristically have fast gut passage times, are expected to avoid feeding on lipid-rich fruits because of the long gut retention times associated with lipid digestion. Here, we compiled data from 84 studies conducted in the Neotropics that used focal plant methods to record 35,815 feeding visits made by 317 bird species (155 genera in 28 families) to 165 plant species (82 genera in 48 families). We investigated the relationship between the degree of frugivory of birds (i.e., how much of their diet is composed of fruit) at the genus level and their visits to plant genera that vary in fruit lipid content. We used a hierarchical modeling of species communities approach that accounted for the effects of differences in body size, bird and plant phylogeny, and spatial location of study sites. We found that birds with a low degree of frugivory (e.g., predominantly insectivores) tend to have the highest increase in visitation rates as fruits become more lipid rich, while birds that are more frugivorous tend to increase visits at a lower rate or even decrease visitation rates as lipids increase in fruits. This balance between degree of frugivory and visitation rates to lipid-poor and lipid-rich fruits provides a mechanism to explain specialized dispersal systems and the occurrence of certain physiological nutritional filters, ultimately helping us to understand community-wide interaction patterns between birds and plants.

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

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

Low activities of digestive enzymes in the guts of herbivorous grouse (Aves: Tetraoninae)

Avian herbivores face the exceptional challenge of digesting recalcitrant plant material while under the selective pressure to reduce gut mass as an adaptation for flight. One mechanism by which avian herbivores may overcome this challenge is to maintain high activities of intestinal enzymes that facilitate the digestion and absorption of nutrients. However, previous studies in herbivorous animals provide equivocal evidence as to how activities of digestive enzymes may be adapted to herbivorous diets. For example, “rate-maximizing” herbivores generally exhibit rapid digesta transit times and high activities of digestive enzymes. Conversely, “yield-maximizing” herbivores utilize long gut retention times and express lower activities of digestive enzymes. Here, we investigated the activities of digestive enzymes (maltase, sucrase, aminopeptidase-N) in the guts of herbivorous grouse (Aves: Tetraoninae) and compared them to activities measured in several other avian species. We found that several grouse species exhibit activities of enzymes that are dramatically lower than those measured in other birds. We propose that grouse may use a “yield-maximizing” strategy of digestion, which is characterized by relatively long gut retention times and generally lower enzyme activities. These low activities of intestinal digestive enzyme could have ecological and evolutionary consequences, as grouse regularly consume plants with compounds known to inhibit digestive enzymes. However, more comprehensive studies on passage rates, digestibility, and microbial contributions will be necessary to understand the full process of digestion in herbivorous birds.

The gut retention time of microplastics in barnacle naupliar larvae from different climatic zones and marine habitats.

Microplastic ingestion has been widely documented in marine zooplankton, but the retention time of microplastics in their digestive gut are still poorly studied, especially among species from different climatic zones and marine habitats. This study evaluated the ingestion and gut retention time of four sizes of fluorescent microplastic beads (1.3, 7.3, 10.6, and 19.0μm) in stage II naupliar larvae of nine barnacle species from different habitats (epibiotic on turtles, mangroves, coral reefs, and rocky shores) and climatic zones (subtropical/tropical and temperate). Microbeads were not lethal to all species (climatic zones/habitats) tested from the four sizes of non-fluorescent virgin microbeads (1.7, 6.8, 10.4 and 19.0μm, each at concentrations 1, 10, 100, and 1000 beads mL-1). Gut retention time of microplastic beads in barnacle naupliar larvae significantly increased with decreasing size. Microbeads resided in digestive tracts generally 3-4 times longer in rocky shore and coral reef barnacles than in muddy shore and epibiotic ones. However, species from different climatic zone did not differ in retention time. Our results suggested nauplius larvae from rocky shore and coral reef barnacles appear to be more susceptible to the impacts of longer retained microplastics (e.g., toxic chemicals present on the surface).

Enhancement of the gut-retention time of resveratrol using waxy maize starch nanocrystal-stabilized and chitosan-coated Pickering emulsions

To enhance its gut health-promoting activity and bioaccessibility, resveratrol was loaded in emulsions stabilized by octenyl succinic anhydride-modified waxy maize starch nanocrystals and then coated with chitosan. Resveratrol loaded in > 0.1% chitosan-coated emulsions adhered more robustly onto porcine intestinal mucosa than did resveratrol powder (23-fold) and chitosan-uncoated emulsions (7-fold). Unlike chitosan-uncoated emulsions, chitosan-coated emulsions were stable during gastric digestion and slowly hydrolyzed in a small intestinal environment. After in vitro digestion, > 90% of the soluble fractions of resveratrol loaded in chitosan-coated and chitosan-uncoated emulsions were 14-fold greater than that of resveratrol powder. The findings suggest that the chitosan-coating can enhance both the gut-retention time of resveratrol and its bioavailability, resulting in prolonged bioactivity of non-oxidized resveratrol. Moreover, the colloidal stability of resveratrol-loaded and chitosan-coated emulsions was maintained for 2 months (pH 4; 25 °C). This study provides useful information to guide development of an effective oral delivery system for resveratrol.

Endozoochory by Goats of Two Invasive Weeds with Contrasted Propagule Traits

Invasive plants have very important ecological and socioeconomic impacts. Producing and dispersing many viable seeds are key plant functional traits for invaders. Ungulate grazing plays an important role in the endozoochorous seed dispersal within grasslands and rangelands. Grazing can be applied as a practical and economical control method for plant invasions. We analyzed the effects of seed passage through the goat digestive system on the germination and viability for Sorghum halepense and Malva parviflora, common invasive species with contrasted propagules and seed traits. Both studied species produced seeds able to survive, in a small percentages (c. 0.80–1.70%), after being eaten by goats. Most of the seeds (c. 40–55%) of both species were retrieved between 24–48 h after ingestion. Goat passage provoked a decrease (> 60%) in the germination percentage and seed viability of S. halepense that was higher with longer gut retention times. In M. parviflora, the goat gut passage did not break its primary physical dormancy, since no retrieved seed germinated with similar viability as the uneaten seeds (c. 90%). In view of our results, goat grazing can be applied as a useful method to control S. halepense and M. parviflora invasions. Goats should be kept in corrals for at least 4 days after grazing to prevent transferring viable seeds to uninfected areas.

Are large frugivorous birds better seed dispersers than medium- and small-sized ones? Effect of body mass on seed dispersal effectiveness.

Frugivorous birds vary in seed dispersal effectiveness (SDE) depending on their body mass. It has been suggested that large birds are more effective dispersers than small ones because they consume a large number of fruits, disperse seeds of distinct sizes, and transport seeds over long distances. Yet, few studies have evaluated the impact of body mass on SDE of birds. In this study, we compiled one database for the quantity (i.e., frequency of visits to plants and number of seeds removed per visit) and quality (i.e., germination of seeds after gut passage and gut retention time of seeds) of seed dispersal by frugivorous birds to evaluate the impact of body mass on SDE. In addition, we compiled data on plant characteristics such as life‐form, fruit type, number of seeds per fruit, and size of seed to evaluate their influence on the quantity and quality of seed dispersal. Data were analyzed with linear mixed effects models and quantile regressions to evaluate the relationship between body mass of birds and quantity, quality, and SDE, in addition to the influence of plant characteristics on SDE. The body mass of birds was negatively related to the frequency of visits to plants. Furthermore, it was positively related to the number of seeds removed per visit, although negatively related to seed size. The life‐form of plants was the only factor explaining the germination of seeds after gut passage. Yet, the body mass of birds was positively related to the gut retention time of seeds. Small and medium birds have a relatively higher SDE than large birds. These results differ from the assertion that large birds are more effective dispersers of plants. Small and medium birds are also effective dispersers of plants that should be preserved and protected from the impact of human activities.