Search Results (7)

Three rodent species with similar characteristics coexist in the centre of the Iberian Peninsula (Wood mouse Apodemus sylvaticus, Algerian mouse Mus spretus and Common vole Microtus arvalis). This study examines if habitat segregation exists between the species, as a means of preventing the intense competition that may exclude any of these species. One of the three species recently arrived in the area. The other two have been consuming resources for a long time. Our aim is to check whether adaptations have been acquired during this time. To do this, we placed the three rodent species in semi-wild enclosures consisting of three different habitats and fed them acorns from the two most abundant oak species of the area for one week. We estimated the number of acorns and the mass per acorn that each species consumed in each habitat. It was found that each species prefers different habitats. The two species that were first installed in the area participated in acorn dissemination through transport and storage. They also conserved the embryos of the acorns consumed. The newly arrived species did not transport acorns and destroys them during consumption, behaving as a true predator species. The three species segregate their habitats to avoid competition. The two species that have been in the area for a longer time exhibit a relationship with the oaks that is akin to mutualism. Full article

Seed hardness has been acknowledged as one of the most significant physical traits influencing seed consumption and caching by animals. From an evolutionary perspective, a hard seed shell should potentially be regarded as a dispersal and predator escape strategy rather than a maladaptive trait of plants. However, to our knowledge, this prediction has not been adequately tested in the context of seed dispersal. Here, we offered seeds with hard shells to the main seed consumers widely distributed in two distinct forest ecosystems to test our hypothesis that a hard seed shell might act as an ecological filter to deter predators but attract obligatory seed dispersers. Our studies demonstrated that seeds with the hardest shells consistently and directly deterred small-bodied seed consumers that have been proven to be either larder-hoarders or scatter-hoarders in the two forests. Nevertheless, rodents with the largest body size and seed handling capacity seemed to be effective seed dispersers targeting hard seed shells. The deterrence to seed predators and the attraction to an effective seed disperser reflects the evolutionary significance of seed hardness in the seed dispersal syndrome. Our studies in different forest ecosystems strongly suggest that a hard seed shell is not an evolutionary dead end in plant–animal interactions. On the contrary, the outcome of a hard seed shell in the seed dispersal syndrome is of evolutionary importance for plant–animal mutualistic interactions in various forest ecosystems. Full article

Frequency-dependent predation is common in predator–prey interactions. Size is an important characteristic of seeds and is crucial in the regeneration stage of plant seeds. However, the frequency dependence of animal predation on seed size has not been reported. In this study, we conducted a field experiment and used different sizes of Liaodong oak (Quercus wutaishanica) seeds to test the frequency dependence of intraspecific seed size selection in rodents. We used the number ratio of large to small seeds as the frequency. The results show that the rate of small seeds being eaten in situ was significantly higher than that of large seeds (p < 0.05). The rates of different-sized seeds being eaten after removal decreased with increasing frequencies, and there was no significant difference between frequencies except for 1:9 and 9:1. The rates of large seeds being scatter-hoarded were significantly higher than those of small seeds at different frequencies (p < 0.05). The eating distances after removal of large seeds were significantly longer than those of small seeds at the same frequencies (p < 0.05). Furthermore, the scatter-hoarding distances of large seeds were significantly longer than those of small seeds at three frequencies (1:9, 3:7, and 9:1) (p < 0.05). That is, rodents consumed more small seeds in situ, dispersed and scatter-hoarded more large seeds, and dispersed large seeds over longer distances. Rodents exhibited a negative frequency dependence for small seeds and a positive frequency dependence for large seeds on being eaten in situ. Moreover, rodents exhibited a negative frequency dependence for large seeds and a positive frequency dependence for small seeds on being eaten after removal and scatter-hoarding. These results reveal the frequency dependence of rodent selection on seed size and provide new insights into animal-mediated seed dispersal and the regeneration of plant populations. Full article

Animal-mediated seed dispersal is very important for plant population regeneration and the stability of forest ecosystems. Seed size and cache density are important factors for seed dispersal, but we still know little about seed size selection at different cache densities. Here, we conducted field experiments in a Larix principis-rupprechtii plantation in the Liupan Mountains in Ningxia province to investigate the effects of tag-marked Quercus wutaishanica seeds of different sizes and cache densities on predation and the scatter-hoarding behavior of rodents. The results showed lower proportions of intact in situ (IIS) and eaten in situ (EIS) large seeds than small seeds at all levels of cache density, with the exception of IIS seeds at a 6.25 seed·m⁻² cache density. A higher proportion of small seeds were eaten after removal (EAR), but a higher proportion of large seeds were scatter-hoarded (SH) by rodents at most cache densities. Furthermore, rodents preferentially removed large seeds farther away for eating or scatter-hoarding. The IIS and EIS proportions of both large and small seeds declined, but the proportion of the two types of seeds that were EAR fluctuated, increasing with increasing cache density. Rodents preferred to increase the proportion of scatter-hoarding of large seeds with increasing cache density, whereas the proportion of scatter-hoarding of small seeds was maximized at a cache density of 6.25 seed·m⁻². Both the eaten distance after removal (EDAR) and scatter-hoarded distance (SHD) increased with increasing cache density. These results suggest that large seeds are more likely to be scatter-hoarded and removed to longer distances than small ones. Rodents tended to reduce the seed proportion of EIS seeds and increased the proportion of seeds EAR and SH, and accordingly increased EDAR and SHD with increasing cache density. This study provides some scientific basis for animal-mediated seed dispersal. Full article

The predation and/or dispersal of Quercus seeds by rodents play an important role in the creation of the tree species. The present study examined the effects of community habitats on the predation and dispersal of Quercus wutaishanica seeds by rodents. We released seeds with densities set at 2, 4, 8, 16, and 32 seed square meter with litter cover, soil burial, and bare ground in the Liupan Mountains National Nature Reserve in the Ningxia Hui Autonomous Region, northwest China. The results showed that (1) the litter cover and soil burial significantly increased the seed survival probability compared with bare ground treatments, especially the predation in situ (PIS) (p < 0.05). Both the scatter hoarding (SH) and larder hoarding (LH) for litter cover and soil burial were significantly increased compared with bare ground (p < 0.05). (2) The large seeds are preferentially predated after dispersal and their long-distance dispersal (>5 m) was significantly greater than that of small seeds (p < 0.05), while small seeds are more likely to be preyed on in situ or during short-distance dispersal (<3 m). (3) The Q. wutaishanica seed predation by rodents increased at a high density rather than at a low density, indicating a negative density-dependent predation. These findings provide insights into the ecological characteristics of Quercus tree regeneration and shed light on the coexistence between rodents and different-sized seeds. Full article

Although dispersal is critical to plant life history, the relationships between seed traits and dispersal success in animal-dispersed plants remain unclear due to complex interactions among the effects of seed traits, habitat structure, and disperser behavior. We propose that in plants dispersed by scatter-hoarding granivores, seed trait evolution may have been driven by selective pressures that arise from interactions between seedling shade intolerance and predator-mediated caching behavior. Using an optimal foraging model that accounts for cache concealment, hoarder memory, and perceived predation risk, we show that hoarders can obtain cache-recovery advantages by placing caches in moderately risky locations that force potential pilferers to engage in high levels of vigilance. Our model also demonstrates that the level of risk needed to optimally protect a cache increases with the value of the cached food item. If hoarders perceive less sheltered, high-light conditions to be more risky and use this information to protect their caches, then shade-intolerant plants may increase their fitness by producing seeds with traits valued by hoarders. Consistent with this hypothesis, shade tolerance in scatter-hoarded tree species is inversely related to the value of their seeds as perceived by a scatter-hoarding rodent. Full article

Larch (Larix spp.) is planted after a clear-cut of secondary forests (SFs) to meet the timber demand of Northeast China. However, the declination of soil fertility and the acidification of surface runoff in larch plantations (LPs) resulting from mono-species composition have threatened the sustainable development of LPs. Converting pure LPs into larch-walnut mixed forests can solve those problems, in which it is crucial to promote the seed regeneration of Juglans mandshurica in LPs. The success of walnut seed regeneration is dependent on rodent removing seed away from mother trees and the dispersal processes rely on the stand structure. The spatial distribution pattern between LPs and SFs is a type of stand structure that might affect seed dispersal. There are two typical spatial patterns in Northeast China due to different topographical conditions, that is, contour type (C-T, LPs and SFs located at the same slope position and aspect) and downslope type (D-T, LPs located at the down slope of the adjacent SF in the same aspect). The objectives of our study were to verify the effects of the spatial distribution pattern of LPs on rodent-mediated seed dispersal and to determine the optimal spatial distribution type for seed dispersal. The field trial was conducted by releasing tagged J. mandshurica seeds at three stages of seed rain during two continuous growing seasons in two types of spatial distribution patterns for LPs. We found that contour type had a substantial advantage in the rodent-mediated seed dispersal, that is, the dispersal rate and the proportion of scatter-hoarded seeds in LPs of C-T stands were much higher than in D-T stands, respectively. These differences may be caused by the variation in the topographic factor for these two types of spatial distribution pattern of LPs. In the C-T stands, it was a translational motion for rodents to remove walnuts from SFs to LPs, which would be an energy efficient and favorable method of seed dispersal. Fluctuation of seed abundance had an effect on rodent behaviors and seed fates, that is, there was a faster dispersal rate and lower proportion of seeds in situ in the non-masting year of 2015 than in the masting year of 2016 and proportion of scatter-hoarded seeds reached the highest during the early stage and lowest at the middle stage of seed rain. Thus, the contour type of LPs with a favorable terrain advantage is potentially conducive to dispersing walnut seeds by rodents during early stage of seed rain and converting larch plantations into larch-walnut mixed forests. Full article