Combined effects of habitat and interspec ificinteraction define co-occurrence patterns of sympatric Galliformes

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.

基于标记–重捕模型开展野生动物红外相机种群监测的方法及案例

红外相机技术的广泛应用推动了动物种群生态学研究方法的发展和革新,特别是基于标记–重捕模型框架通过非损伤取样方式对物种数量和密度等种群参数的可靠估计,为保护濒危物种和评估保护成效提供了有力的科学依据。对于身体上具有独特天然标记的动物(如多数猫科动物),可依据红外相机拍摄身体上的独特斑点或条纹鉴别个体,再运用标记–重捕模型,估计动物种群数量、密度等参数。本文概述了标记–重捕模型的基本原理、特点以及国内外的应用,特别是近年来发展出的空间标记–重捕模型。总结了从相机布设到数据分析的具体流程、操作原则,并以青城山家猫为实例,展示了应用红外相机数据通过空间标记–重捕模型估计种群密度和数量的基本步骤。最后展望了该模型在种群动态、景观廊道设计、资源选择等方面的应用和发展趋势。

河南内乡宝天曼国家级自然保护区豹猫及其潜在猎物之间日活动节律的季节性

日活动节律是动物应对食物可利用性、天敌捕食风险和环境条件等变化的适应性特征。阐明捕食者与猎物之间的日活动节律以及相关影响因素,对于理解不同物种的生存策略、指导保护对策至关重要。然而,由于采样方法的限制和人类干扰下的快速环境变化,人们对许多野生动物日活动节律的了解并不全面,甚至与实际情况存在偏差。以往认为夜行性的豹猫(Prionailurusbengalensis)被发现有一定程度的日间活动,并增加晨昏活动,这说明有必要深入调查豹猫等野生动物的昼夜节律为何存在这些变化。本研究在河南内乡宝天曼国家级自然保护区通过红外相机技术对豹猫及其潜在猎物进行调查,基于核密度函数比较分析了豹猫与其潜在猎物在冷、暖季节的日活动节律。2016年全年设置了55个红外相机位点,累计14,972个相机工作日,获得豹猫及其潜在猎物的独立有效照片1,343张。结果显示,该保护区内豹猫、蒙古兔(Lepus tolai)和鼠类以夜间活动为主,其中豹猫有明显的晨昏活动高峰,而赤腹松鼠(Callosciurus erythraeus)、岩松鼠(Sciurotamias davidianus)、红腹锦鸡(Chrysolophus pictus)和勺鸡(Pucrasia macrolopha)均在昼间活动。活动重叠度分析结果显示,豹猫与夜行性的蒙古兔和鼠类在冷季和暖季均有较高重叠度(Δ≥0.50),但与其他猎物之间的重叠度均相对较低(Δ≤0.40)。本研究显示豹猫及其猎物的昼夜节律既有保守性,也具有一定的季节可塑性,可能受到季节性猎物分布和环境变化的影响。因此,需要加强调查研究来充分认识不同物种日活动节律的季节性变化规律及其驱动因素。

How seed defense and seed abundance predict dispersal and survival patterns in Camellia

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.

Palatability and profitability of co-occurring seeds alter indirect interactions among rodent-dispersed trees

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.