Background:Disentangling the relative importance of environmental variables and interspecific interaction in modulating co-occurrence patterns of sympatric species is essential for understanding the mechanisms of comm...Background:Disentangling the relative importance of environmental variables and interspecific interaction in modulating co-occurrence patterns of sympatric species is essential for understanding the mechanisms of community assembly and biodiversity. For the two sympatric Galliformes, Silver Pheasants (Lophura nycthemera) and Whitenecklaced Partridges (Arborophila gingica), we know little about the role of habitat use and interspecific interactions in modulating their coexistence. Methods:We adopted a probabilistic approach incorporating habitat preference and interspecific interaction using occupancy model to account for imperfect detection,and used daily activity pattern analysis to investigate the cooccurrence pattern of these two sympatric Galliformes in wet and dry seasons. Results: We found that the detection probability of Silver Pheasant and White-necklaced Partridge were related to habitat variables and interspecific interaction. The presence of Silver Pheasant increases the detection probability of White-necklaced Partridge in both the wet and dry season. However, the presence of White-necklaced Partridges increases the detection probability of Silver Pheasants in the wet season, but decreases the probability in the dry season. Further, Silver Pheasants were detected frequently in the sites of high values of enhanced vegetable index (EVI) in both the wet and dry season, and in sites away from human residential settlement in the wet season. Whitenecklaced partridges were mainly detected in low EVI sites. The site use probabilities of two Galliformes were best explained by habitat variables, Silver Pheasants and White-necklaced Partridges preferred steeper areas during the wet and dry season. Both species mainly occurred in low EVI areas during the wet season and occupied sites away from the resident settlement during the dry season. Moreover, the site use probabilities of two species had opposite relationships with forest canopy coverage. Silver Pheasants preferred areas with high forest canopy coverage whereas White-necklaced Partridges preferred low forest canopy coverage in the dry season, and vice versa in the wet season. Species interaction factor (SIF)corroborated weak evidence of the dependence of the site use of one species on that of the other in the either dry or wet season.Temporally, high overlapping of daily activity pattern indicated no significantly temporal niche differentiation between sympatric Galliformes in both wet and dry seasons. Conclusions:Our results demonstrated that the presence of two species influenced the detection probability interactively and there was no temporal partitioning in activity time between Silver Pheasants and White-necklaced Partridges in the wet and dry seasons.The site use probability of two Galliformes was best explained by habitat variables, especially the forest canopy coverage.Therefore, environmental variables and interspecific interaction are the leading drivers regulating the detection and site use probability and promoting co-occurrence of Silver Pheasants and White-necklaced Partridges.展开更多
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 indiv...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.展开更多
Beyond direct species interactions,seed dispersal is potentially affected by indirect seed–seed interactions among co-occurring nut-bearing trees which are mediated by scatter-hoarding animals as shared seed disperse...Beyond direct species interactions,seed dispersal is potentially affected by indirect seed–seed interactions among co-occurring nut-bearing trees which are mediated by scatter-hoarding animals as shared seed dispersers.A relevant question in such systems is to what extent different functional traits related to food palatability and profitability affect the kinds of indirect interactions that occur among co-occurring seeds,and the consequences for seed dispersal.We used field experiments to track seed dispersal with individually tagged seeds in both monospecific and mixed seed communities.We measured indirect effects based on 3 seed–seed species pairs from the family Fagaceae with contrasting seed size,tannin level,and dormancy in a subtropical forest in Southwest China.When all else was equal,the presence of adjacently placed seeds with contrasting seed traits created different indirect effects measured through a variety of dispersal-related indicators.Apparent mutualism was reciprocal due to increasing seed dispersal in mixed seed patches with mixed differences in seed tannins and dormancy.However,differences in either seed size or dormancy in co-occurring adjacently placed seeds caused apparent competition with reduced seed removal or seed dispersal(distance)in at least one species.Our study supports the hypothesis that different functional traits related to food palatability and profitability in co-occurring seeds modify foraging decisions of scatter-hoarding animals,and subsequently cause indirect effects on seed dispersal among rodent-dispersed trees.We conclude that such indirect effects mediated by shared seed dispersers may act as an important determinant of seed dispersal for co-fruiting animal-dispersed trees in many natural forests.展开更多
基金supported by the National Key Research and Development Program of China(2017YFC0503802)China Postdoctoral Science Foundation(2017M 620905)
文摘Background:Disentangling the relative importance of environmental variables and interspecific interaction in modulating co-occurrence patterns of sympatric species is essential for understanding the mechanisms of community assembly and biodiversity. For the two sympatric Galliformes, Silver Pheasants (Lophura nycthemera) and Whitenecklaced Partridges (Arborophila gingica), we know little about the role of habitat use and interspecific interactions in modulating their coexistence. Methods:We adopted a probabilistic approach incorporating habitat preference and interspecific interaction using occupancy model to account for imperfect detection,and used daily activity pattern analysis to investigate the cooccurrence pattern of these two sympatric Galliformes in wet and dry seasons. Results: We found that the detection probability of Silver Pheasant and White-necklaced Partridge were related to habitat variables and interspecific interaction. The presence of Silver Pheasant increases the detection probability of White-necklaced Partridge in both the wet and dry season. However, the presence of White-necklaced Partridges increases the detection probability of Silver Pheasants in the wet season, but decreases the probability in the dry season. Further, Silver Pheasants were detected frequently in the sites of high values of enhanced vegetable index (EVI) in both the wet and dry season, and in sites away from human residential settlement in the wet season. Whitenecklaced partridges were mainly detected in low EVI sites. The site use probabilities of two Galliformes were best explained by habitat variables, Silver Pheasants and White-necklaced Partridges preferred steeper areas during the wet and dry season. Both species mainly occurred in low EVI areas during the wet season and occupied sites away from the resident settlement during the dry season. Moreover, the site use probabilities of two species had opposite relationships with forest canopy coverage. Silver Pheasants preferred areas with high forest canopy coverage whereas White-necklaced Partridges preferred low forest canopy coverage in the dry season, and vice versa in the wet season. Species interaction factor (SIF)corroborated weak evidence of the dependence of the site use of one species on that of the other in the either dry or wet season.Temporally, high overlapping of daily activity pattern indicated no significantly temporal niche differentiation between sympatric Galliformes in both wet and dry seasons. Conclusions:Our results demonstrated that the presence of two species influenced the detection probability interactively and there was no temporal partitioning in activity time between Silver Pheasants and White-necklaced Partridges in the wet and dry seasons.The site use probability of two Galliformes was best explained by habitat variables, especially the forest canopy coverage.Therefore, environmental variables and interspecific interaction are the leading drivers regulating the detection and site use probability and promoting co-occurrence of Silver Pheasants and White-necklaced Partridges.
基金We thank Xunlong Wang for help with field The National Key Research and Development Program of China(2017YFC0503802,2016YFC0500105)the National Natural Science Foundation of China(31770565,31270470)The State Key Laboratory of Integrated Management of Pest Insects and Rodents(ChineseIPM1718).
文摘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.
基金This research was supported by the National Key Research and Development Program of China(2016YFC0500105,2017YFC0503802)the National Natural Science Foundation of China(31971441,31770565)The State Key Laboratory of IntegratedManagement of Pest Insects and Rodents(ChineseIPM1718).
文摘Beyond direct species interactions,seed dispersal is potentially affected by indirect seed–seed interactions among co-occurring nut-bearing trees which are mediated by scatter-hoarding animals as shared seed dispersers.A relevant question in such systems is to what extent different functional traits related to food palatability and profitability affect the kinds of indirect interactions that occur among co-occurring seeds,and the consequences for seed dispersal.We used field experiments to track seed dispersal with individually tagged seeds in both monospecific and mixed seed communities.We measured indirect effects based on 3 seed–seed species pairs from the family Fagaceae with contrasting seed size,tannin level,and dormancy in a subtropical forest in Southwest China.When all else was equal,the presence of adjacently placed seeds with contrasting seed traits created different indirect effects measured through a variety of dispersal-related indicators.Apparent mutualism was reciprocal due to increasing seed dispersal in mixed seed patches with mixed differences in seed tannins and dormancy.However,differences in either seed size or dormancy in co-occurring adjacently placed seeds caused apparent competition with reduced seed removal or seed dispersal(distance)in at least one species.Our study supports the hypothesis that different functional traits related to food palatability and profitability in co-occurring seeds modify foraging decisions of scatter-hoarding animals,and subsequently cause indirect effects on seed dispersal among rodent-dispersed trees.We conclude that such indirect effects mediated by shared seed dispersers may act as an important determinant of seed dispersal for co-fruiting animal-dispersed trees in many natural forests.
