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Competition between mixo- and heterotrophic ciliates under dynamic resource supply 动态资源供给下的混养和异养纤毛虫之间的竞争
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-16 DOI: 10.1002/ecs2.4950
Sabine Flöder, Toni Klauschies, Moritz Klaassen, Tjardo Stoffers, Max Lambrecht, Stefanie Moorthi

The outcome of species competition strongly depends on the traits of the competitors and associated trade-offs, as well as on environmental variability. Here, we investigate the relevance of consumer trait variation for species coexistence in a ciliate consumer–microalgal prey system under fluctuating regimes of resource supply. We focus on consumer competition and feeding traits, and specifically on the consumer's ability to overcome periods of resource limitation by mixotrophy, that is, the ability of photosynthetic carbon fixation via algal symbionts in addition to phagotrophy. In a 48-day chemostat experiment, we investigated competitive interactions of different heterotrophic and mixotrophic ciliates of the genera Euplotes and Coleps under different resource regimes, providing prey either continuously or in pulses under constant or fluctuating light, entailing periods of resource depletion in fluctuating environments, but overall providing the same amount of prey and light. Although ultimate competition results remained unaffected, population dynamics of mixotrophic and heterotrophic ciliates were significantly altered by resource supply mode. However, the effects differed among species combinations and changed over time. Whether mixotrophs or heterotrophs dominated in competition strongly depended on the genera of the competing species and thus, species-specific differences in the minimum resource requirements that are associated with feeding on shared prey, nutrient uptake, light harvesting, and access to additional resources such as bacteria. Potential differences in the curvature of the species' resource-dependent growth functions may have further mediated the species-specific responses to the different resource supply modes. Overall, our study demonstrates that genus- or species-specific traits other than that related to nutritional mode may override the relevance of acquired phototrophy by heterotrophs in competitive interactions, and that the potential advantage of photosynthetic carbon fixation of symbiont-bearing mixotrophs in competition with pure heterotrophs may differ greatly among different mixotrophs, playing out under different environmental conditions and depending on the specific requirements of the species. Complex trophic interactions determine the outcome of competition, which can only be understood by taking on a multidimensional trait perspective.

物种竞争的结果在很大程度上取决于竞争者的性状、相关权衡以及环境变化。在此,我们研究了纤毛虫消费者-微藻类猎物系统在资源供应波动制度下,消费者性状变异与物种共存的相关性。我们重点研究了消费者的竞争和摄食特征,特别是消费者通过混合营养体克服资源限制期的能力,即除吞噬作用外通过藻类共生体进行光合碳固定的能力。在一个为期 48 天的恒温箱实验中,我们研究了在不同的资源制度下,不同的异养纤毛虫和混养纤毛虫属(Euplotes 和 Coleps)之间的竞争性相互作用,在恒定或波动的光照下连续或脉冲地提供猎物,在波动的环境中造成资源枯竭期,但总体上提供相同数量的猎物和光照。虽然最终的竞争结果未受影响,但混养和异养纤毛虫的种群动态受资源供应模式的影响很大。不过,不同物种组合的影响不同,而且随着时间的推移而变化。在竞争中是混养纤毛虫占优势还是异养纤毛虫占优势,在很大程度上取决于竞争物种的属,因此也取决于物种在最低资源要求方面的差异,这些最低资源要求与摄食共同的猎物、吸收营养物质、采光以及获取额外资源(如细菌)有关。物种依赖资源的生长函数曲率的潜在差异可能进一步介导了物种对不同资源供应模式的特异性反应。总之,我们的研究表明,除了与营养模式有关的特征外,属或物种特有的特征可能会超越异养生物在竞争性相互作用中获得的光营养的相关性,而且在不同的环境条件下,根据物种的具体要求,不同的混养生物在与纯异养生物的竞争中光合作用碳固定的潜在优势可能会有很大的不同。复杂的营养相互作用决定了竞争的结果,只有从多维性状的角度才能理解竞争的结果。
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引用次数: 0
Recovery of metabolites via subnivean photosynthesis in Arctic tundra plants: Implications for climate change 北极苔原植物通过叶下光合作用恢复代谢物:对气候变化的影响
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4936
Nicholas Wright-Osment, Christina Lynn Staudhammer, Steve Oberbauer, Behzad Mortazavi, Gregory Starr

Plants have evolved numerous strategies for surviving the harsh conditions of the Arctic. One strategy for Arctic evergreen and semi-evergreen species is to photosynthesize beneath the snow during spring. However, the prevalence of this photosynthesis and how recent photosynthates are used is still unknown. Here we ask, how is newly acquired carbon beneath the snow allocated? To answer this question, we delivered isotopically labeled 13CO2 to tussock tundra plants before snowmelt. Soluble sugars and starches were preferentially enriched with 13C in all five species tested, with lipids having comparatively low 13C enrichment. These results provide evidence of the recovery of metabolites used over the long winter. Additionally, these new soluble sugars may function in photoprotection and cold tolerance as plants release from snow cover. Climate change, by reducing the duration of subnivean photosynthesis of these species, will limit metabolite production before snowmelt, which may lead to a reduction in the ability of these species to compete effectively during the growing season, potentially leading to changes in community structure.

植物进化出了许多在北极恶劣条件下生存的策略。北极常绿和半常绿物种的一种策略是在春季的积雪下进行光合作用。然而,这种光合作用的普遍程度以及如何利用新近获得的光合作用物仍是未知数。在这里,我们要问的是,雪下新获得的碳是如何分配的?为了回答这个问题,我们在融雪前向苔原植物输送了同位素标记的 13CO2。在所有五个测试物种中,可溶性糖和淀粉都优先富集了 13C,而脂类的 13C 富集程度相对较低。这些结果证明,经过漫长的冬季,代谢物得到了恢复。此外,这些新的可溶性糖可能会在植物从积雪覆盖中释放出来时起到光保护和耐寒的作用。气候变化会缩短这些物种的叶下光合作用持续时间,从而限制融雪前代谢物的产生,这可能会导致这些物种在生长季节的有效竞争能力下降,进而可能导致群落结构发生变化。
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引用次数: 0
Turnover of bird species along the Nullarbor Plain: Insights from taxonomic, phylogenetic, and functional beta diversity 纽伦堡平原鸟类物种的更替:从分类学、系统发生学和功能贝塔多样性中获得的启示
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4910
Vicente García-Navas, Carlos Martínez-Núñez, Les Christidis, Arpat Ozgul

The Nullarbor Plain constitutes one of the main biogeographic barriers of Australia, and it has been suggested to have played a key role in the disjunct distribution of numerous southern Australian species. Although previous research has shown that the origin of this barrier coincides with the timing of the speciation events in some plant lineages, it is not clear whether the uplift of this barrier promoted divergence events in vertebrates. We addressed the role of the Nullarbor barrier and its fringing semiarid habitats as drivers of beta diversity in bird assemblages. Specifically, we determined the effect of distance from the Nullarbor barrier, environmental conditions, and isolation by distance on the composition of local communities on both sides of the plain. We measured beta diversity using taxonomic, phylogenetic, and functional metrics of composition. The influence of precipitation, geographic distance, and distance to the Nullarbor barrier on these metrics was addressed using generalized dissimilarity models and a moving-window approach. We also tested for differences in local extinction, dispersal and speciation rates, and lineage diversity between two regions, southeastern (SE) and southwestern (SW) Australia. Geological and orogenetic dynamics linked to the appearance of the Nullarbor Plain may have spurred speciation events in SE. However, evidence suggests that subsequent periods in which this region was wetter and forested favored dispersal, mainly from SE to SW. Accordingly, observed dissimilarity in species composition was lower than expected at random, suggesting the existence of considerable turnover between regions. Our results suggest that precipitation deficit (and the xeric vegetation that it promotes) was the most important predictor of beta diversity, whereas the distance to the barrier explained some variation in terms of phylogenetic composition. This study shows that the uplift of the Nullarbor barrier played a minor role in shaping present-day bird diversity in southern Australia. Recent speciation events coupled with historical connectivity can explain the observed patterns.

纽拉伯平原是澳大利亚主要的生物地理屏障之一,有人认为它在澳大利亚南部众多物种的分离分布中起到了关键作用。尽管之前的研究表明,这一屏障的起源与一些植物种系的物种分化事件的时间相吻合,但目前还不清楚这一屏障的隆起是否促进了脊椎动物的分化事件。我们研究了纽伦堡屏障及其边缘半干旱栖息地作为鸟类群落贝塔多样性驱动因素的作用。具体来说,我们确定了与努拉伯屏障的距离、环境条件和距离隔离对平原两侧当地群落组成的影响。我们使用分类学、系统发生学和功能性组成指标来测量贝塔多样性。我们使用广义异质性模型和移动窗口方法,研究了降水、地理距离和与努拉伯屏障的距离对这些指标的影响。我们还检验了澳大利亚东南部(SE)和西南部(SW)两个地区在当地灭绝、扩散和物种形成率以及种系多样性方面的差异。与纳拉伯平原的出现有关的地质和造山动力学可能刺激了东南部的物种分化。然而,有证据表明,在随后的时期,该地区更加潮湿,森林覆盖率更高,有利于物种的扩散,主要是从东南部扩散到西南部。因此,观察到的物种组成差异低于随机预期,这表明区域间存在相当大的更替。我们的研究结果表明,降水不足(及其促进的干旱植被)是预测贝塔多样性的最重要因素,而与屏障的距离则解释了系统发育组成方面的一些差异。这项研究表明,纽伦堡屏障的隆起在塑造澳大利亚南部现今的鸟类多样性方面发挥了微不足道的作用。最近的物种分化事件加上历史上的连通性可以解释观察到的模式。
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引用次数: 0
Thirty years of forest productivity in a mountainous landscape: The Yin and Yang of topography 山地三十年的森林生产力:地形的阴与阳
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4865
David A. Perry, Doug R. Oetter

We measured light-related patterns of primary productivity within a topographically complex Oregon watershed over a 30-year period. Second-growth conifer densities were experimentally altered in 1981. Plots receiving at least 3434 MJ m−2 over a 6-month growing season averaged 40% greater aboveground net primary productivity (ANPP) than those receiving less light (p = 0.000). Unthinned stands potentially built enough LAI to compensate for low light, but risked mortality that exceeded resilience. The two light levels acted as basins of attraction for other physiological and ecological processes, including size–density relationships and limiting foliar nutrients. Initial (1981) LAI and the irradiation step (above or below 3434 MJ m−2) explained 60% of variation in a 30-year ANPP. Irradiation within each light group did not affect ANPP. At high irradiation, foliar N/Ca and slope steepness (both negative) explained 58% of the variation in residuals from the initial models, while at low irradiation on north, east, and west aspects, 83% of residual variation was explained by foliar Mg (+), understory cover (+), and 30-year mortality (−). Light use efficiency (LUE) of fully stocked stands correlated with LAI and foliar N/K. Results suggest that understory influence on tree foliar N (+ or −) enhances ANPP by regulating critical nutrient ratios. Mortality reduced or eliminated differences among thinning levels, which did not vary at low light and only between unthinned and heavily thinned at high light. Values associated with relatively open forests (biodiversity, resilience) may be attained without large sacrifice of long-term carbon sinks. In our study, light interacts with topography to produce nonlinear dynamics in which small changes in irradiation can have large consequences. Reduced sunlight has been suggested as a geoengineering option to combat global warming. Ecological changes out of proportion to lowered irradiation are a distinct possibility, including sharp reductions in terrestrial carbon sinks.

我们测量了俄勒冈州一个地形复杂的流域 30 年间与光有关的初级生产力模式。1981 年,通过实验改变了第二生长针叶树的密度。在 6 个月的生长季中,接受至少 3434 兆焦耳/平方米-2 光照的地块比接受较少光照的地块平均高出 40% 的地上净初级生产力(ANPP)(p = 0.000)。未疏伐的林分有可能建立足够的 LAI 来补偿低光照,但有可能导致死亡率超过恢复能力。两种光照水平对其他生理和生态过程(包括大小-密度关系和限制性叶片养分)起着吸引作用。最初(1981 年)的 LAI 和辐照阶跃(高于或低于 3434 兆焦耳/平方米-2)解释了 30 年 ANPP 变化的 60%。每个光照组内的辐照对 ANPP 没有影响。在高辐照条件下,叶片 N/Ca 和坡度(均为负值)解释了初始模型残差变化的 58%,而在北面、东面和西面的低辐照条件下,叶片 Mg(+)、林下植被覆盖度(+)和 30 年死亡率(-)解释了残差变化的 83%。完全放养林分的光利用效率(LUE)与 LAI 和叶面 N/K 相关。结果表明,林下植物对树木叶面氮的影响(+或-)可通过调节关键的养分比率来提高ANPP。死亡率缩小或消除了不同疏伐水平之间的差异,在光照不足时差异不大,只有在光照充足时,未疏伐和大量疏伐之间才会有差异。与相对开放的森林相关的价值(生物多样性、恢复力)可以在不大量牺牲长期碳汇的情况下实现。在我们的研究中,光照与地形相互作用,产生了非线性动态变化,其中辐照的微小变化就会产生巨大的后果。减少日照被认为是应对全球变暖的一种地球工程选择。与辐照减少不成比例的生态变化是完全可能的,包括陆地碳汇的急剧减少。
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引用次数: 0
Stream size-dependent effect of urban land use on occupancy of an apex freshwater carnivore recolonizing past ranges 城市土地使用对一种顶级淡水食肉动物重新定居过去分布区的影响与溪流大小有关
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4937
Manlio Marcelli, Giuseppe Luzzi, Romina Fusillo

Accurate assessment of population trends and factors that limit distributions of threatened species is key to conserving biodiversity. A reduction in impacts of human land use on species habitats may be one of the factors involved in the recolonization of former ranges by native species. The signature of this process could be detected as a temporal reduction of land use effects on species distributions, or as a spatial reduction, with effects persisting only in habitats more sensitive to anthropogenic stressors. We explored these hypotheses in a recolonizing semiaquatic carnivore. Our species of interest was the Eurasian river otter (Lutra lutra) in Italy, a nationally vulnerable species with a restricted but expanding range. Human land use is likely to strongly affect riparian and stream communities through habitat degradation. We used three independent survey datasets collected in 2003, 2009, and 2019 at the southern range periphery, and unpaired-site occupancy models to account for imperfect detection in otter surveys. To assess how land use affects recolonization by otters, we tested three main model predictions: (1) occupancy increased over years, (2) effects of agricultural and urban land cover on occupancy decreased over years, (3) effects of agricultural and urban land cover were constant across years and changed with stream size and elevation. We found evidence that otter occupancy increased over years, with predicted mean occupancy of 0.27 in 2003 and 0.65 in 2019. An interaction effect of urban land cover with stream size was the strongest predictor of otter occupancy. Interestingly, a higher percentage of urban land cover around streams was predicted to reduce the probability of occupancy at smaller streams, but did not influence occupancy at larger streams. Despite a large increase in occupancy, otters at the southern periphery of the Italian range are still unable to colonize small rivers in urbanized areas. This pattern supports our hypothesis that human land use can affect recolonizing species at sensitive habitats, considering the intrinsic vulnerability of small stream ecosystems to anthropogenic stressors. Restoring small streams impacted by urban areas can be a valuable conservation action to increase habitat connectivity and favor recolonization of otters.

准确评估种群趋势和限制受威胁物种分布的因素是保护生物多样性的关键。减少人类使用土地对物种栖息地的影响,可能是本地物种重新拓殖原生地的因素之一。这一过程的特征可能表现为土地利用对物种分布的影响在时间上的减弱,也可能表现为空间上的减弱,即只有在对人为压力更敏感的栖息地上,影响才会持续存在。我们在一种重新定居的半水生食肉动物身上探索了这些假设。我们关注的物种是意大利的欧亚河獭(Lutra lutra),它是国家级易危物种,分布范围有限但在不断扩大。人类对土地的使用可能会导致栖息地退化,从而对河岸和溪流群落造成严重影响。我们使用了 2003 年、2009 年和 2019 年在南部分布区外围收集的三个独立调查数据集,并使用非配对地点占据模型来考虑水獭调查中的不完全检测。为了评估土地利用如何影响水獭的重新定居,我们检验了三个主要的模型预测:(1)水獭占据率逐年增加;(2)农业和城市土地覆盖对水獭占据率的影响逐年减少;(3)农业和城市土地覆盖的影响在不同年份保持不变,并随溪流大小和海拔高度的变化而变化。我们发现有证据表明,水獭的栖息率逐年增加,2003 年的预测平均栖息率为 0.27,2019 年为 0.65。城市土地覆盖与溪流大小的交互效应是水獭栖息率的最强预测因子。有趣的是,溪流周围城市土地覆盖率越高,预测占用较小溪流的概率越低,但不会影响占用较大溪流的概率。尽管占用率大幅增加,意大利南部边缘地区的水獭仍然无法在城市化地区的小河流中定居。考虑到小溪流生态系统在人为压力下的内在脆弱性,这种模式支持了我们的假设,即人类的土地使用会影响物种在敏感栖息地的重新定居。恢复受城市影响的小溪流是一项有价值的保护措施,可以增加栖息地的连通性,有利于水獭的重新定居。
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引用次数: 0
Parasites as indicators of biodiversity and habitat complexity in coastal ecosystems 寄生虫是沿海生态系统生物多样性和生境复杂性的指标
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4928
Christopher S. Moore, Rachel K. Gittman, April M. H. Blakeslee

Researchers often use surrogate species for assessing biodiversity—organisms that can indicate the presence of additional taxa or provide insight into environmental processes. As indicators of anthropogenic impact, “cross-taxon” surrogates are theorized to be effective shortcuts for determining how communities respond to environmental change. However, few studies have implemented cross-taxon surrogates given the challenge of validating the strength of the relationship between surrogates and their target taxa. Trophically transmitted parasites require multiple invertebrate and vertebrate taxa to complete their life cycles (e.g., annelids, mollusks, fishes, shorebirds), making them ideal cross-taxon surrogates of community diversity. By sampling for these parasite surrogates, it is theoretically possible to infer the composition of the overall host community based on the species of parasites present. In our study, we tested the use of parasites as cross-taxon surrogates of biodiversity by sampling for digenetic trematodes in the mudsnail Ilyanassa obsoleta, collected from coastal shoreline environments with or without artificial structures (e.g., bulkheads, seawalls). We found that trematode richness, evenness, and diversity were all greater in snails sampled from natural shorelines versus those with artificial structures. While parasite communities clustered by shoreline type (with vs. without artificial structures), we found no differences in multivariate dispersion, or beta-diversity, between groups in our system. At the species level, trematodes requiring polychaetes and estuarine fishes as downstream hosts dominated parasite communities at shorelines with artificial structures. These taxa are ubiquitous but more abundant in degraded environments. In contrast, trematode species requiring mollusks and shorebirds as hosts was only documented from shorelines without artificial structures (i.e., natural), which may indicate that these areas are less degraded and have greater overall host diversity. High parasite diversity in easily collected hosts (e.g., mudsnails) provides evidence that the secondary (polychaetes, crustaceans) and tertiary (fishes, shorebirds) hosts required by the parasites are present in the system. Our study also helps validate the concept of surrogate species by demonstrating how a single species can represent broader taxonomic groups.

研究人员经常使用代用物种来评估生物多样性--这些生物可以表明其他类群的存在,或提供对环境过程的洞察力。作为人为影响的指标,"跨类群 "代用物种被认为是确定群落如何应对环境变化的有效捷径。然而,鉴于验证代用物与其目标类群之间关系的强度是一项挑战,很少有研究采用跨类群代用物。滋养传播的寄生虫需要多个无脊椎动物和脊椎动物类群(如无脊椎动物、软体动物、鱼类、海岸鸟类)来完成其生命周期,因此它们是群落多样性的理想跨类群替代品。通过对这些寄生虫替代物进行取样,理论上可以根据寄生虫的种类推断整个宿主群落的组成。在我们的研究中,我们通过对泥螺 Ilyanassa obsoleta 中的二齿吸虫取样,测试了将寄生虫作为生物多样性的跨类群替代物的用途,这些泥螺是从有或没有人工结构(如隔板、海堤)的海岸线环境中采集的。我们发现,在自然海岸线与人工结构海岸线采样的蜗牛中,吸虫的丰富度、均匀度和多样性都更高。虽然寄生虫群落按海岸线类型(有人工结构与无人工结构)进行了聚类,但我们发现在我们的系统中,不同群落之间的多元分散性或贝塔多样性并无差异。在物种水平上,需要多毛目环节动物和河口鱼类作为下游宿主的吸虫在有人工结构的海岸线寄生虫群落中占主导地位。这些类群无处不在,但在退化环境中更为丰富。相比之下,需要软体动物和海岸鸟类作为宿主的颤形目物种只出现在没有人工结构的海岸线(即自然海岸线)上,这可能表明这些地区的环境退化程度较低,宿主的整体多样性较高。易于采集的寄主(如泥螺)中寄生虫的多样性较高,这证明寄生虫所需的二级(多毛目环节动物、甲壳类)和三级(鱼类、岸鸟)寄主在该系统中存在。我们的研究还通过展示单一物种如何代表更广泛的分类群,帮助验证了代用物种的概念。
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引用次数: 0
Using integrated step selection to determine effects of predation risk on bison habitat selection and movement 利用综合步骤选择确定捕食风险对野牛栖息地选择和移动的影响
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4909
S. Salganek, K. A. Schoenecker, M. L. N. Terwilliger

Animal movement is a fundamental mechanism that shapes communities and ecosystems. Ungulates alter the ecosystems they inhabit and understanding their movements and distribution is critical for linking habitat with population dynamics. Predation risk has been shown to strongly influence ungulate movement patterns, such that ungulates may select habitat where predation risk is lower (refugia), adjust movement rates, temporal patterns, or selection of cover variables in areas with greater predation risk. We evaluated potential predation avoidance behavior in a population of plains bison inhabiting the north rim of Grand Canyon National Park (GRCA) and adjacent Kaibab National Forest (KNF). The KNF has year-round hunting managed by Arizona Game and Fish Department, whereas hunting is not allowed in GRCA. Human-maintained water sources on the KNF are particularly important resources for bison wherein they may be exposed to higher predation risk to access these resources. We used 2-h GPS locations for three years from 31 bison (n = 9 males; n = 22 females), and integrative step selection analysis to test four hypotheses about the potential for bison to reduce their risk from human predation by avoiding areas of high predation risk; moving faster in areas with high predation risk; entering high-risk areas at night when risk is reduced; and entering high-risk areas in habitats that provide cover (coniferous forest). The highest performing model indicated bison movement was 1.3 times faster per 2-h step interval than in areas with no hunting across all vegetation classes (coniferous forest, shrub, quaking aspen, grass-forb meadow) and across all topography classes (valley, slope, ridge). Bison moved more slowly in grass-forb meadows than all other vegetation types, and in valleys relative to slopes and ridges. Several radio-collared individuals had no GPS locations in KNF for the duration of the study. Bison avoided predation risk using two strategies: moving faster while in the KNF, and fully avoiding high-risk areas by remaining within GRCA. Management that manipulates or reduces timing of hunting seasons may reduce perceived predation risk and encourage bison to distribute into the KNF and across a broader range of available habitat.

动物运动是塑造群落和生态系统的基本机制。有蹄类动物会改变它们栖息的生态系统,因此了解它们的运动和分布对于将栖息地与种群动态联系起来至关重要。捕食风险对有蹄类动物的运动模式有很大影响,有蹄类动物可能会选择捕食风险较低的栖息地(避风港),在捕食风险较高的地区调整运动速度、时间模式或选择覆盖变量。我们对栖息在大峡谷国家公园(Grand Canyon National Park,GRCA)北缘和邻近的凯巴布国家森林公园(Kaibab National Forest,KNF)的平原野牛的潜在捕食规避行为进行了评估。KNF 由亚利桑那州狩猎和渔业部管理,全年狩猎,而 GRCA 不允许狩猎。KNF 上由人类维护的水源对野牛来说是特别重要的资源,野牛为了获得这些资源可能会面临更高的捕食风险。我们利用 31 头野牛(n = 9 头雄性;n = 22 头雌性)三年的 2 小时 GPS 定位和综合步长选择分析,检验了野牛通过以下方式降低人类捕食风险的可能性的四个假设:避开捕食风险高的地区;在捕食风险高的地区移动得更快;在夜间风险降低时进入风险高的地区;在提供覆盖物(针叶林)的栖息地进入风险高的地区。表现最好的模型表明,在所有植被等级(针叶林、灌木、柞树、草-草甸)和所有地形等级(山谷、斜坡、山脊)中,野牛每 2 小时的移动间隔比没有狩猎的地区快 1.3 倍。野牛在禾本科草甸中的移动速度慢于其他所有植被类型,在山谷中的移动速度也慢于山坡和山脊。在研究期间,有几只被无线电追踪的野牛在KNF没有GPS定位。野牛使用两种策略规避捕食风险:在 KNF 内加快移动速度,以及留在 GRCA 内完全避开高风险区域。控制或减少狩猎季节时间的管理方法可能会降低捕食风险,并鼓励野牛分布到 KNF 和更广泛的可用栖息地。
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引用次数: 0
Fruiting trees provide fruit and insect resources for four tropical deer species 果树为四种热带鹿提供水果和昆虫资源
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4889
Balram Awasthi, Jin Chen, Kim R. McConkey

Fruiting trees provide important fruit and seed resources for various animal species, but rarely are they considered to be rich sources of insects as well. During a study of seed dispersal of Trewia nudiflora (Euphorbiaceae) using camera traps in Nepal, we observed four tropical deer species (Axis axis, Muntiacus vaginalis, Rusa unicolor, Axis porcinus) foraging for insects, rather than fruits under the trees. These herbivorous deer are proven seed dispersers of Trewia, but 8%–38% of video captures (across each species) were of insectivory, rather than frugivory. The deer chased and consumed red cotton bugs (Dysdercus sp. family Pyrrhocoridae), which were seed predators that hoarded Trewia seeds. It is likely that other unidentified insect species were also consumed. Tropical deer species are considered to be fully herbivorous, so our observations extend their known diets and possibly indicate a seasonal requirement for protein. These findings also highlight tri-trophic interactions among deer, insects, and fruits that could have important implications for seedling recruitment if seed predators are being consumed by seed dispersers (in addition to fruit consumption).

果树为各种动物提供了重要的果实和种子资源,但很少有人认为它们也是昆虫的丰富来源。在尼泊尔利用相机陷阱对裸花翠菊(大戟科)的种子传播进行研究期间,我们观察到四种热带鹿(Axis axis、Muntiacus vaginalis、Rusa unicolor、Axis porcinus)在树下觅食昆虫而非果实。这些食草鹿是经证实的 Trewia 种子传播者,但 8%-38%的视频捕获(每个物种)是捕食昆虫,而不是觅食。这些鹿追逐并吃掉了红棉虫(Dysdercus sp.很可能还吃了其他不明昆虫物种。热带鹿类被认为是完全的草食性动物,因此我们的观察结果扩展了它们已知的食谱,并可能表明它们对蛋白质的季节性需求。这些发现还突显了鹿、昆虫和果实之间的三营养交互作用,如果种子散播者消耗的是种子捕食者(除了消耗果实之外),这些发现可能会对幼苗新陈代谢产生重要影响。
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引用次数: 0
Symbiotic species diversity can explain invasion success and host–parasite system stability: The case of gammarid hosts 共生物种多样性可以解释入侵的成功率和宿主-寄生系统的稳定性:伽马类宿主的案例
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4946
Volodimir Sarabeev, Juan Antonio Balbuena, Mikuláš Oros, Valerii Domnich, Rosa Ana Sueiro, Jose Manuel Leiro, Mykola Ovcharenko

A major current challenge related to invasions is the absence of a comprehensive theoretical basis for preventing the introduction of alien species and controlling their populations. By using a macroecological framework, we aim to examine patterns of symbiotic species diversity across native and invasive hosts to understand the mechanisms underlying the host–parasite system stability. The symbiotic communities of seven gammarid species, two native and five invasive, were analyzed at 16 fresh and brackish water sites along the Baltic coast of Poland. We investigated the influence of four factors—locality, habitat, host species, and host origin—on diversity patterns and assessed their relative contribution to diversity variation. Our results indicate that all factors are crucial in determining the composition and abundance of symbiotic communities in gammarids. Among these factors, locality and host species apparently have a greater influence on symbiotic communities than habitat conditions and host origin. Comparative analysis of diversity indexes of symbiotic organisms from native and invasive hosts showed that the richer communities of native gammarids were paradoxically less diverse. We assume that these rich and uneven symbiotic communities keep the host–parasite system of native gammarids in equilibrium. Highly dominant symbiotic species with a high load per host individual may stabilize the growth of the host population. Symbiotic communities of the invasive host exhibited lower species richness but displayed a relatively even distribution of species with moderate loads per individual, resulting in a scarcity of heavily infected gammarids within the population. Thus, the survival rate of invasive gammarids is expected to be relatively high, facilitating their population growth and further spread. We conclude that complex communities of native gammarids constructed from many symbiotic species may prevent host populations from undergoing explosive growth, while such mechanisms may be completely or partially reduced in invasive hosts.

目前与入侵有关的一个主要挑战是缺乏防止外来物种引入和控制其数量的全面理论基础。通过使用宏观生态学框架,我们旨在研究原生宿主和入侵宿主的共生物种多样性模式,以了解宿主-寄生系统稳定的内在机制。我们在波兰波罗的海沿岸的16个淡水和咸水地点分析了7种伽马类(2种原生种和5种入侵种)的共生群落。我们研究了四个因素--地点、栖息地、宿主种类和宿主来源--对多样性模式的影响,并评估了它们对多样性变化的相对贡献。我们的研究结果表明,所有因素都对决定伽马类共生群落的组成和丰度至关重要。在这些因素中,地点和宿主种类对共生群落的影响显然大于生境条件和宿主来源。对本地宿主和外来宿主共生生物多样性指数的比较分析表明,本地伽马类的共生群落更为丰富,但其多样性却较低。我们认为,这些丰富而不均衡的共生生物群落使本地伽马类的寄主-寄生系统保持平衡。优势共生物种对宿主个体的负荷较高,可能会稳定宿主种群的增长。入侵宿主的共生群落物种丰富度较低,但物种分布相对均匀,每个宿主个体的负载量适中,导致种群中受严重感染的伽马类数量稀少。因此,入侵伽马虫的存活率相对较高,有利于其种群增长和进一步扩散。我们的结论是,由许多共生物种组成的复杂的本地伽马虫群落可能会阻止宿主种群的爆炸性增长,而入侵宿主的这种机制可能会完全或部分减弱。
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引用次数: 0
Human footprint and rainfall shape Masai giraffe's habitat suitability and connectivity in a multiple-use landscape 人类足迹和降雨决定了马赛长颈鹿在多用途景观中的栖息地适宜性和连通性
IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY Pub Date : 2024-07-15 DOI: 10.1002/ecs2.4933
Amos C. Muthiuru, Ramiro D. Crego, Jemimah A. Simbauni, Philip M. Muruthi, Grace Waiguchu, Fredrick Lala, James D. A. Millington, Eunice W. Kairu

Giraffe populations have declined by around 40% in the last three decades. Climate change, poaching, habitat loss, and increasing human pressures are confining giraffes to smaller and more isolated patches of habitats. Masai giraffes (Giraffa tippelskirchi) have been subjected to habitat loss and fragmentation, diseases, poaching, and unpredictable calamities such as wildfires and climate change. In this study, we aimed to identify (1) suitable Masai giraffe habitats within the transboundary landscape of Tsavo-Mkomazi in Southern Kenya and Northern Tanzania; and (2) key connecting corridors in a multiple-use landscape for conservation prioritization. We combined Masai giraffe presence data collected through a total aerial survey with moderate resolution satellite data to model habitat suitability at 250 m resolution using species distribution models (SDMs) implemented in Google Earth Engine (GEE). Model accuracy was assessed using area under precision recall curve (AUC-PR). We then used the habitat suitability index as a resistance surface to model functional connectivity using Circuitscape theory and cost-weighted distance pairwise methods. Human habitat modification, rainfall, and elevation were the main model predictors of Masai giraffe habitat and corridors. On average, our 10-fold model fitting attained a good predictive performance with an average AUC-PR = 0.80 (SD = 0.01, range = 0.79–0.83). The model predicted an area of 15,002 km2 as potential suitable Masai giraffe habitat with over 17% outside protected areas within the landscape. Although Tsavo West National Park formed a key habitat and a key connecting corridor, nonprotected community ranches connecting Tsavo West and Tsavo East National Parks are equally important in maintaining landscape connectivity joining more than two Masai giraffe core areas with low resistance and high permeability. To maintain critical Masai giraffe's habitats and landscape functional connectivity, especially in multiple-use landscapes, conservation-compatible land use practices, capacity building, and land use planning should be considered at the outset of any new infrastructure development and land use changes. This modeling shows the potential of utilizing remotely sensed information and ground surveys to guide the management of habitats and their connecting corridors across important African landscapes, complementing existing efforts to identify, conserve, and protect wildlife habitats and their linkage zones.

在过去的三十年里,长颈鹿的数量减少了约 40%。气候变化、偷猎、栖息地丧失以及日益增长的人类压力正在将长颈鹿限制在更小、更孤立的栖息地上。马赛长颈鹿(Giraffa tippelskirchi)一直受到栖息地丧失和破碎化、疾病、偷猎以及野火和气候变化等不可预测灾害的影响。在这项研究中,我们旨在确定:(1)肯尼亚南部和坦桑尼亚北部跨境景观 Tsavo-Mkomazi 中合适的马赛长颈鹿栖息地;(2)多用途景观中的关键连接走廊,以确定保护的优先次序。我们将通过全面航空调查收集到的马赛长颈鹿存在数据与中等分辨率卫星数据相结合,利用谷歌地球引擎(GEE)中的物种分布模型(SDM),以 250 米的分辨率建立栖息地适宜性模型。使用精确度召回曲线下面积(AUC-PR)评估模型的精确度。然后,我们将栖息地适宜性指数作为阻力面,利用环景理论和成本加权距离配对法建立功能连接模型。人类栖息地改造、降雨量和海拔高度是马赛长颈鹿栖息地和走廊的主要模型预测因素。平均而言,我们的 10 倍拟合模型具有良好的预测性能,平均 AUC-PR = 0.80(SD = 0.01,范围 = 0.79-0.83)。该模型预测适合马赛长颈鹿栖息的潜在区域面积为 15,002 平方公里,其中超过 17% 位于景观保护区之外。虽然沙窝西国家公园是马赛长颈鹿的主要栖息地和关键连接走廊,但连接沙窝西国家公园和沙窝东国家公园的非保护区社区牧场对于维持两个以上马赛长颈鹿核心区的景观连通性同样重要,具有低阻力和高渗透性。为了保持马赛长颈鹿的重要栖息地和景观功能的连通性,尤其是在多用途景观中,在任何新的基础设施开发和土地使用变化之初,都应考虑与保护相容的土地使用实践、能力建设和土地使用规划。该模型显示了利用遥感信息和地面勘测指导非洲重要地貌中栖息地及其连接走廊管理的潜力,是对现有识别、养护和保护野生动物栖息地及其连接区工作的补充。
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引用次数: 0
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Ecosphere
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