Contribution of peeling host for epiphyte abundance in two tropical dry forests in the “El Cielo Biosphere Reserve”, Mexico

Host traits partly determine the abundance and species richness of epiphytes in tropical forests. It has been proposed that older trees with rough bark and evergreens often house more individuals and more epiphytic species than those with thin, smooth, and peeling bark, which harbor few epiphytes. We hypothesize (i) that epiphytes are more abundant and species-rich in the more shaded forest, which is related to bark roughness, and (ii) that epiphytes are distributed in the middle of the host, where microenvironmental conditions are more favorable to survival. We evaluated abundance, species richness, and vertical distribution of epiphytes in two tropical dry forests, according to the deciduousness and basal area of the trees. Moreover, we selected the most abundant epiphytes to test whether their distribution is related to a specific bark type and examine their vertical distribution in two dry forests. We distinguished a high abundance and species richness of epiphytes in the deciduous forest, although basal area and host species richness were higher in the semi-deciduous forest. In both forests, we found a positive relationship between epiphyte abundance and basal area. Higher abundance of epiphytes was related to the predominance of Tillandsia schiedeana, a drought-adapted species, in both forests. Unexpectedly, epiphytes abundantly colonized Bursera simaruba, a host with peeling bark and a very branched crown, where small individuals of T. schiedeana colonized abundantly toward the top of the crown. Our results show the importance of the tropical dry forest, particularly, B. simaruba, in maintaining epiphyte diversity in terms of T. schiedeana colonization.     

Inconsistent detection of extinction debts using different methods

The extinction debt, delayed species extinctions following landscape degradation, is a widely discussed concept. But a consensus about the prevalence of extinctions debts is hindered by a multiplicity of methods and a lack of comparisons among habitats. We applied three contrasting species–area relationship methods to test for plant community extinction debts in three habitats which had different degradation histories over the last century: calcareous grassland, heathland and woodland. These methods differ in their data requirements, with the first two using information on past and current habitat area alongside current species richness, whilst the last method also requires data on past species richness. The most data‐intensive, and hence arguably most reliable method, identified extinction debts across all habitats for specialist species, whilst the other methods did not. All methods detected an extinction debt in calcareous grassland, which had undergone the most severe degradation. We conclude that some methods failed to detect an extinction debt, particularly in habitats that have undergone moderate degradation. Data on past species numbers are required for the most reliable method; as such data are rare, extinction debts may be under‐reported.     

Can we manage fisheries with the inherent uncertainty from eDNA?

Environmental (e)DNA, as a general approach in aquatic systems, seeks to connect the presence of species' genetic material in the water and hence to infer the species' physical presence. However, fisheries managers face making decisions with risk and uncertainty when eDNA indicates a fish is present but traditional methods fail to capture the fish. In comparison with traditional methods such as nets, electrofishing and piscicides, eDNA approaches have more sources of underlying error that could give rise to false positives. This has resulted in some managers to question whether eDNA can be used to make management decisions because there is no fish in hand. As a relatively new approach, the methods and techniques have quickly evolved to improve confidence in eDNA. By evaluating an eDNA based research programmes through the pattern of the eDNA signal, assay design, experimental design, quality assurance and quality control checks, data analyses and concurrent search for fish using traditional gears, the evidence for fish presence can be evaluated to build confidence in the eDNA approach. The benefits for fisheries management from adopting an eDNA approach are numerous but include cost effectiveness, broader geographic coverage of habitat occupancy, early detection of invasive species, non-lethal stock assessments, exploration of previously inaccessible aquatic environments and discovery of new species hidden beneath the water's surface. At a time when global freshwater and marine fisheries are facing growing threats from over-harvest, pollution and climate change, we anticipate that growing confidence in eDNA will overcome the inherent uncertainty of not having a fish in hand and will empower the informed management actions necessary to protect and restore our fisheries.     

At Palmyra Atoll,the fish-community environmental DNA signal changes across habitats but not with tides

At Palmyra Atoll, the environmental DNA (eDNA) signal on tidal sand flats was associated with fish biomass density and captured 98%–100% of the expected species diversity there. Although eDNA spilled over across habitats, species associated with reef habitat contributed more eDNA to reef sites than to sand-flat sites, and species associated with sand-flat habitat contributed more eDNA to sand-flat sites than to reef sites. Tides did not disrupt the sand-flat habitat signal. At least 25 samples give a coverage >97.5% at this diverse, tropical, marine system.     

Trade-off between number and length of remote videos for rapid assessments of reef fish assemblages

Remote underwater videos are widely employed to assess the structure and composition of reef fish assemblages but the sampling effort employed on each survey differs considerably, indicating that both the number of assessments and video length could be optimized. We searched for this optimal sampling effort in remote video samples to conduct rapid assessments of community composition and discussed the relation between number of replicates and video length, and how it impacts the method's efficiency to characterize species assemblages. Remote video recordings from tropical reefs in northeastern Brazil were used to investigate how fish species richness and composition builds across time and number of assays. Videos as short as 5 min successfully recorded species richness, requiring about five repetitions to record most species that compose 80% of the total biomass. Recording species composition required even less time in these reefs, setting a minimum of 3 min with the same five videos. By comparing the detected richness per analysed time unit, we found several shorter videos recorded for more species than a few longer videos, indicating that increasing the sampling coverage in the reef area might be better than just extending the video length for rapid assessments.     

西南地区壳斗科物种丰富度和特有性分布格局模拟及其环境解释

如何准确地模拟物种宏观丰富度格局和特有性中心是生物多样性保护工作的重点,也是生物地理学的热点话题。西南地区是我国壳斗科植物最丰富的地区之一,但物种多样性格局及环境驱动机制尚不清楚。本研究基于西南地区161种壳斗科植物7258个分布点位数据,利用点格局法和物种分布模型两种方式构建了物种丰富度、加权特有性指数和校正加权特有性指数的分布格局,并采用空间自回归模型(SAR)分析上述3个多样性指数与环境因子间的关系。总体上看,物种分布模型模拟的3个指数在空间上比点格局法更为连续,但数值高低分布情况具有相似性: 两种方式模拟的物种丰富度高值区主要分布在滇南边缘、桂北部和桂西南部地区(62～89种);加权特有性指数最大值集中在滇南和桂西地区(1.77～5.02);藏东南、秦岭-大巴山、桂西南部和滇东南地区具有最高的校正加权特有性指数(0.07～0.17)。SAR模型结果显示:最干月降雨量、温度季节性变化标准差、海拔变幅和土壤有机碳含量对物种丰富度的影响均显著,最干月降雨量、温度季节性变化标准差、潜在蒸散量和海拔变幅对加权特有性有着显著影响,温度季节性变化标准差、最干月降雨量、历史温度变化、增强型植被指数变异系数和海拔变幅对校正加权特有性的影响显著;SAR模型对物种丰富度、特有性指数和加权特有性指数的拟合效果(R²=0.857、0.733、0.593)分别优于普通线性模型(R²=0.689、0.425、0.422)。综上,水分可获得性、气候季节性、生境异质性、历史气候变化和土壤状况是制约西南地区壳斗科丰富度和特有性分布的最重要因素。滇南、滇东南、桂西南、桂西、秦岭-大巴山以及藏东南地区是壳斗科物种丰富度中心或特有性中心,应受到重点关注和保护。     

中条山油松人工林下物种对群落物种丰富度分布格局的贡献

该研究以中条山油松人工林群落为研究对象,研究林下不同大小的子群落对群落物种丰富度分布格局的贡献,并确定影响该区域群落物种丰富度分布格局的关键种,为区域物种多样性保护提供理论依据。结果表明:(1)该地区林下物种频度分布格局呈明显右偏,且不同样方物种丰富度存在明显差异。(2)常见种对群落丰富度分布格局的贡献大于稀有种。(3)最常见的物种解释了整个群落物种丰富度格局的88.4%(P0.01),而最稀有物种仅解释了24.5%(P0.05),去除最稀有物种后,最常见物种可以解释剩余物种的90.8%(P0.01),而去除最常见物种后,最稀有物种仅能解释剩余物种的48.6%(P0.01)。(4)当子群落中常见种越多时,子群落与整个群落的丰富度分布格局相关性越高。(5)连翘(Forsythia suspensa)、太平花(Philadelphus pekinensis)、鞘柄菝葜(Smilax stans)、多歧沙参(Adenophora wawreana)、金花忍冬(Lonicera chrysantha)等对群落物种丰富度分布格局的贡献最大,但并非越常见的物种对群落丰富度格局贡献越大。(6)与频度较高物种的种间关联度低的物种对于群落物种的分布格局贡献较大,但此解释并不适用于稀有种。研究发现,稀有种对中条山油松人工林群落物种丰富度分布格局存在较大的贡献,所以在油松人工林物种多样性保护过程中并不能只关注常见种而忽视稀有种。     

Congruent spatial patterns of species richness and phylogenetic diversity in karst flora: Case study of Primulina (Gesneriaceae)

The karst landform in southern China is renowned for its high levels of species diversity and endemism. Globally, karst ecosystems are under threat from unsustainable anthropogenic disturbance and climate changes and are among the most threatened ecosystems worldwide. In this study, we used the typical karst endemic genus in southern China, Primulina Hance, as a model to identify areas within the karst landform with high diversity and to investigate congruence between phylogenetic and species‐based measures of diversity. Using phylogenetic information and species distribution data, we measured geographical patterns of diversity with four metrics: species richness (SR), corrected weighted endemism (CWE), phylogenetic diversity (PD), and phylogenetic endemism (PE). Our results revealed a high spatial congruence among SR, PD, and PE, with hotspot areas identified in the Nanling Mountains (i.e., north Guangdong and northeast Guangxi) and southeast Yungui Plateau (i.e., north and southwest Guangxi), whereas the hotspots of CWE are comparatively uniform throughout the geographic extent. The categorical analysis of neo‐ and paleoendemism identified a pattern of mixed neo‐ and paleoendemism in numerous grid cells, suggesting that karst areas in southern China have acted as both “museums” and “cradles” of plant evolution. Conservation gap analysis of hotspots revealed that the majority of prioritized hotspots (>90%) of the genus are outside of protected areas, therefore indicating the limited effectiveness of national nature reserves for the karst flora. Overall, our results suggest that the karst flora merits more conservation attention and SR can be an effective surrogate to capture PD in conservation planning.     

生态系统多功能性的指标选择与驱动因子: 研究现状与展望

全球变化和人类活动正以空前的速度在世界范围内改变着生物多样性, 这导致了全球生物多样性的锐减以及生产力的下降、病虫害的增加和抗入侵能力的减弱等生态问题。近30年来, 生态学家开始对于生物多样性的持续丧失是否以及如何影响生态系统功能的问题越来越感兴趣, 生物多样性与生态系统功能(biodiversity and ecosystem functioning, BEF)关系的研究应运而生, 并成为生态学研究的热点之一。但长期以来, 研究者更多地关注单一生态系统功能, 而忽略了生态系统能够同时提供多种生态系统功能的能力, 即生态系统多功能性(ecosystem multifunctionality, EMF)。本文综述了EMF研究中功能指标的选择、生物多样性的不同维度、微生物多样性对EMF的影响以及其他非生物因子对EMF的驱动等进展。因只考虑单一功能可能会低估生物多样性对整体生态系统功能的影响, 故生物多样性与生态系统多功能性(BEMF)关系的研究成为BEF关系研究的重点。近年来, BEMF关系的研究发展较快, 在不同生态系统(包括水生、草地、森林、旱地、农业等)、不同研究尺度(从区域到全球尺度)、BEMF关系的驱动机制(从单一驱动机制到多种驱动机制共同作用)、研究方法(包括新概念以及新的量化方法的提出和应用)等方面均取得了新的进展。但仍有不足之处, 如对于EMF研究中功能指标的选取没有统一的标准、对地下微生物多样性的关注度不够、涉及多营养级水平下的BEMF关系研究较少、驱动EMF的机制仍存在争论等。未来应加强对于功能指标选取的标准研究, 综合分析地上、地下生物多样性以及非生物因子对EMF的整体影响, 加强生态系统多服务性(ecosystem multiserviceability, EMS)方法的研究和应用。     

贵州花溪大学城破碎化林地鸟类多样性与嵌套分布格局

为揭示城镇化进程中生境破碎化对鸟类多样性及分布格局的影响, 本研究于2017-2019年每年的4-8月使用样线法对贵州花溪大学城26块破碎化林地(面积介于0.3-290.4 ha)中的鸟类群落进行了10次调查。共记录到鸟类78种, 隶属于11目37科。其中, 东洋界物种数占56.4%, 古北界物种数占32.1%, 广布种占11.5%; 有中国特有种1种。剔除高空飞行、非森林鸟类及偶然出现物种后, 不同斑块中的鸟类物种数介于12-55之间, 平均每个斑块有23.2 ± 10.5种。线性回归分析显示, 鸟类物种丰富度与林地斑块的面积有显著相关性, 斑块面积越小, 鸟类物种丰富度越低; 斑块隔离度对物种丰富度没有显著影响。基于物种多度分布矩阵的WNODF (weighted nestedness metric based on overlap and decreasing fill)嵌套分析显示, 不同斑块中鸟类群落呈现出反嵌套结构。小斑块中鸟类物种丰富度较低可能与植物丰富度较低、食物资源稀缺和繁育条件不足有关, 但短距离的隔离对鸟类迁入或扩散影响有限。环境过滤效应、种间竞争或优先效应可能导致不同斑块间存在较大的物种组成差异, 从而导致反嵌套格局。因此, 本研究建议在城市规划建设中应注重维持栖息地的完整性, 对不同面积大小的破碎化斑块都应加以保护。