摘要: Although food availability and the abundance of seed predators have been postulated to affect seed dispersal, it is not clear how seed-eating animals modify their scatter-hoarding strategies in response to different levels of interspecific competition. We placed paired germinated and ungerminated acorns of Quercus mongolica on 30-cm high platforms to exclude potential interspecific competition of the predominant larder hoarders Apodemus peninsulae and Myodes rufocanus, to investigate seed dispersal by a predominant scatter-hoarder, Tamias sibiricus, in the field in north-eastern China. Our results showed that T. sibiricus ate more acorns in situ in the absence of interspecific competition. In the presence of interspecific competition of A. peninsulae and C. rufocanus, however, more acorns were scatter-hoarded by T. sibiricus. Regardless of interspecific competition, germination of acorns showed no significant effects on seed dispersal patterns, inconsistent with the seed perishability hypothesis that animals avoid hoarding seeds with high perishability. Exclusion of interspecific competition, though relatively increasing the per capita seed abundance, appears to reduce seed dispersal, scatter-hoarding and seedling establishment. Therefore, we propose that moderate interspecific competition rather than competition exclusion may benefit seed scatter-hoarding and seedling establishment.

摘要: Neighborhood effects on seed predation and dispersal processes are usually seed-characteristic-dependent; however, how seeds with certain characteristics affect the foraging behavior of rodents in relation to other seeds nearby is unclear. Because large differences in seed characteristics between neighboring seeds may lead to significant differences in rodent foraging preferences, we hypothesized that neighborhood effects were more likely to be detected when paired seeds differed in seed characteristics. We investigated the foraging decisions of two rodent species, the red spiny ratMaxomys suriferand the Chinese white-bellied ratNiviventer confucianus, in semi-natural enclosures by presenting them with artificial seeds containing different levels of tannin (0, 3%, and 6% tannin). Both rodents showed similar preferences and preferentially consumed high-tannin seeds (6% tannin) and scatter hoarded low-tannin seeds (0 tannin). The scatter hoarding of low-tannin (0 tannin) and high-tannin (6% tannin) seeds was significantly higher when these seeds were neighboring higher-tannin seeds than when they neighbored lower-tannin seeds, whereas the scatter hoarding of intermediate-tannin seeds (3% tannin) varied little when they had different neighbors. High-tannin-seed (6% tannin) scatter hoarding was lowest when they neighbored low-tannin seeds (0 tannin), while low-tannin-seed (0 tannin) scatter hoarding was highest when they neighbored high-tannin seeds (6% tannin). Therefore, the seeds that the rodents scatter hoarded were next to (neighbored) seeds that they preferred to eat immediately, and vice versa. Our findings suggest that seed neighborhood effects affect rodent foraging behavior and the relationship between plants and rodents, and may have a profound effect on the regeneration and spatial structure of plant communities.

摘要: In this study, the lateral line systems in Chinese cavefish eyeless Sinocyclocheilus tianlinensis and eyed Sinocyclocheilus macrophthalmus were investigated to reveal their morphological changes to survive in harsh environments. Compared with the eyed cavefish S. macrophthalmus (atypical), the lateral line system in the eyeless cavefish S. tianlinensis (typical) has certain features to adapt to the dark cave environments: the superficial lateral line system in the eyeless species possesses a higher number of superficial neuromasts and more hair cells within an individual neuromast, and the trunk lateral line canal system in S. tianlinensis exhibits larger canal pores, higher canal diameter and more pronounced constrictions. Fluid-structure interaction analysis suggested that the trunk lateral line canal system in the eyeless S. tianlinensis should be more sensitive than that in the eyed S. macrophthalmus. These morphological features of the lateral line system in the eyeless S. tianlinensis probably enhance the functioning of the lateral line system and compensate for the lack of eyes. The revelation of the form-function relationship in the cavefish lateral line system provides inspiration for the design of sensitive artificial flow sensors.

摘要: Superior species may have distinct advantages over subordinates within asymmetrical interactions among sympatric animals. However, exactly how the subordinate species coexists with superior species is unknown. In the forests west of Beijing City, intense asymmetrical interactions of food competition exist among granivorous rodents (e.g. Apodemus peninsulae, Niviventer confucianus, Sciurotamias davidianus and Tscherskia triton) that have broadly overlapping habitats and diets but have varied body size (range 15-300 g), hoarding habits (scatter vs larder) and/or daily rhythm (diurnal vs nocturnal). The smallest rodent, A. peninsulae, which typically faces high competitive pressure from larger rodents, is an ideal model to explore how subordinate species coexist with superior species. Under semi-natural enclosure conditions, we tested responses of seed-hoarding behavior in A. peninsulae to intraspecific and interspecific competitors in the situations of pre-competition (without competitor), competition (with competitor) and post-competition (competitor removed). The results showed that for A. peninsulae, the intensity of larder-hoarding increased and the intensity of scatter-hoarding declined in the presence of intraspecifics and S. davidianus, whereas A. peninsulae ceased foraging and hoarding in the presence of N. confucianus and T. triton. A. peninsulae reduced intensity of hoarding outside the nest and moved more seeds into the nest for larder-hoarding under competition from intraspecific individuals and S. davidianus. In most cases, the experimental animals could recover to their original state of pre-competition when competitors were removed. These results suggest that subordinate species contextually regulate their food-hoarding strategies according to different competitors, promoting species coexistence among sympatric animals that have asymmetrical food competition.

摘要: Little is known about how seed defense and seed abundance interact with behavioral responses of seed dispersers to predict dispersal and survival dynamics in animal-dispersed plants. By tracking the fate of individual seeds in Camellia stands with high and low seed abundance in Southwest China in 2007, we investigated the dispersal and survival of 2 high-saponin Camellia species (Camellia oleifera and Camellia sinensis and 1 non-saponin species (peanut Arachis hypogaea) as a control. Saponins in Camellia seeds are chemical compounds that act as seed defense. Our results were most consistent with the predictions based on the predator satiation hypothesis and the plant defense hypothesis. At the abundant Camellia stand (predators and dispersers were satiated), more Camellia seeds survived at the source but fewer were hoarded and survived at cache sites. At the sparse Camellia stand (predators and dispersers were not satiated), no Camellia seeds survived at the source, but more Camellia seeds were hoarded and survived at cache sites. Unlike Camellia seeds, no peanuts survived at the source at both stands, while more peanuts were hoarded and then survived at cache sites in the abundant Camellia stand compared to none at the sparse Camellia stand. In addition, the 2 Camellia species showed similar trends for seed fates across different dispersal stages. Our study indicates that the combined effects of seed abundance and seed defense, compared to their separate effects, provide a more accurate prediction for dispersal and survival patterns in animal-dispersed Camellia species.