Spatial patterns of hypolithic cyanobacterial diversity in Northern Australia

Photosynthetic microbial communities under translucent rocks (hypolithic) are found in many arid regions. At the global scale, there has been little intercontinental gene flow, and at a local scale, microbial composition is related to fine‐scale features of the rocks and their environment. Few studies have investigated patterns of hypolithic community composition at intermediate distances. We examined hypolithic cyanobacterial diversity in semi‐arid Australia along a 10‐km transect by sampling six rocks from four adjacent 1 m² quadrats (“distance zero”) and from additional quadrats at 10, 100, 1,000, and 10,000 m to test the hypothesis that diversity would increase with the number of rocks sampled and distance. A total of 3,108 cyanobacterial operational taxonomic units (OTUs) were detected. Most were neither widespread nor abundant. The few that were widespread tended to be abundant. There was no difference in the community composition between the four sites at distance zero, but the samples 10 m away were significantly different, as were those at all other distances compared to distance zero. Many additional OTUs were recorded with increasing distance up to 100 m. These patterns of distribution are consistent with a colonization model involving dispersal from rock to rock. Our results indicate that distance was a significant factor that can be confounded by interrock differences. Most diversity was represented in the first 100 m of the transect, with an additional 1.5% of the total diversity added by the sample at 1 km, but only 0.2% added with the addition of the 10‐km site.     

Distinguish water utilization strategies of trees growing on earth‐rocky mountainous area with transpiration and water isotopes

Water stress is regarded as a global challenge to forests. Unlike other water‐limited areas, the water use strategies of rocky mountainous forests, which play an important ecohydrological role, have not received sufficient attention. To prove our hypothesis that species adopt different water use strategies to avoid competition of limited water resources, we used site abiotic monitoring, sap flow and stable isotope method to study the biophysiological responses and water use preferences of two commonly distributed forest species, Pinus tabuliformis (Pt) and Quercus variabilis (Qv). The results showed that Pt transpired higher than Qv. Pt was also prone to adopt isohydric water use strategy as it demonstrated sensitive stomatal control over water loss through transpiration. Qv developed cavitation which was reflected by the dropping E_c in response to high vapor pressure deficit, concentrated peak sap flux density (J_s), and enlarged hysteresis loop. Considering the average soil depth of 52.8 cm on the site, a common strategy shared by both species was the ability to tap water from deep soil layers (below 40 cm) when soil water was limited, and this contributed to the whole growing season transpiration. The contribution of surface layer water to plant water use increased and became the main water source for transpiration after rainfall. Qv was more efficient at using water from surface layer than Pt due to the developed surface root system when soil water content was not stressed. Our study proves that different water‐using strategies of co‐occurring species may be conducive to avoid competition of limited water resources to guarantee their survival. Knowledge of water stress‐coping strategies of trees has implications for the understanding and prediction of vegetation composition in similar areas and can facilitate forest management criteria for plantations.     

Contrasting behavior between two populations of an ice‐obligate predator in East Antarctica

The Austral autumn–winter is a critical period for capital breeders such as Weddell seals that must optimize resource acquisition and storage to provision breeding in the subsequent spring. However, how Weddell seals find food in the winter months remains poorly documented. We equipped adult Weddell seals after their annual molt with satellite‐relayed data loggers at two sites in East Antarctica: Dumont D'Urville (n = 12, DDU) and Davis (n = 20). We used binomial generalized mixed‐effect models to investigate Weddell seals’ behavioral response (i.e., “hunting” vs. “transit”) to physical aspects of their environment (e.g., ice concentration). Weddell seal foraging was concentrated to within 5 km of a breathing hole, and they appear to move between holes as local food is depleted. There were regional differences in behavior so that seals at Davis traveled greater distances (three times more) and spent less time in hunting mode (half the time) than seals at DDU. Despite these differences, hunting dives at both locations were pelagic, concentrated in areas of high ice concentration, and over areas of complex bathymetry. There was also a seasonal change in diving behavior from transiting early in the season to more hunting during winter. Our observations suggest that Weddell seal foraging behavior is plastic and that they respond behaviorally to changes in their environment to maximize food acquisition and storage. Such plasticity is a hallmark of animals that live in very dynamic environments such as the high Antarctic where resources are unpredictable.     

2010年来黄土高原景观生态研究进展

严重的水土流失以及不合理的土地利用加剧了黄土高原土地资源的退化,导致该地区生态环境脆弱、生态系统服务不断下降。针对黄土高原地区存在的问题,我国学者基于景观生态学原理和方法,围绕"景观格局演变-驱动机制-水土流失过程-生态系统服务"的框架开展了大量研究,取得了一系列研究成果。通过梳理和总结2010年以来黄土高原地区景观生态学研究的现状和特点,指出了目前研究中存在的问题和不足,突出表现在区域比较研究、景观格局与生态过程耦合研究、生态服务权衡方法和模型构建等方面比较缺乏。建议未来黄土高原的景观生态学研究应加强区域尺度上的综合研究和不同地区之间的比较研究,深化景观格局演变的形成机理;进一步开展景观格局与过程的定量识别方法学研究,开发格局-过程耦合模型;加强生态系统过程与服务研究,同时开展相应的实证性研究,研发适宜的生态服务权衡模型,进而深入探讨区域生态系统服务的权衡机制。     

Investigating the genomic basis of discrete phenotypes using a Pool‐Seq‐only approach: New insights into the genetics underlying colour variation in diverse taxa

While large‐scale genomic approaches are increasingly revealing the genetic basis of polymorphic phenotypes such as colour morphs, such approaches are almost exclusively conducted in species with high‐quality genomes and annotations. Here, we use Pool‐Seq data for both genome assembly and SNP frequency estimation, followed by scanning for F_ST outliers to identify divergent genomic regions. Using paired‐end, short‐read sequencing data from two groups of individuals expressing divergent phenotypes, we generate a de novo rough‐draft genome, identify SNPs and calculate genomewide F_ST differences between phenotypic groups. As genomes generated by Pool‐Seq data are highly fragmented, we also present an approach for super‐scaffolding contigs using existing protein‐coding data sets. Using this approach, we reanalysed genomic data from two recent studies of birds and butterflies investigating colour pattern variation and replicated their core findings, demonstrating the accuracy and power of a Pool‐Seq‐only approach. Additionally, we discovered new regions of high divergence and new annotations that together suggest novel parallels between birds and butterflies in the origins of their colour pattern variation.     

Nearly a decade‐long repeatable seasonal diversity patterns of bacterioplankton communities in the eutrophic Lake Donghu (Wuhan,China)

Uncovering which environmental factors govern community diversity patterns and how ecological processes drive community turnover are key questions related to understand the community assembly. However, the ecological mechanisms regulating long‐term variations of bacterioplankton communities in lake ecosystems remain poorly understood. Here we present nearly a decade‐long study of bacterioplankton communities from the eutrophic Lake Donghu (Wuhan, China) using 16S rRNA gene amplicon sequencing with MiSeq platform. We found strong repeatable seasonal diversity patterns in terms of both common (detected in more than 50% samples) and dominant (relative abundance >1%) bacterial taxa turnover. Moreover, community composition tracked the seasonal temperature gradient, indicating that temperature is a key environmental factor controlling observed diversity patterns. Total phosphorus also contributed significantly to the seasonal shifts in bacterioplankton composition. However, any spatial pattern of bacterioplankton communities across the main lake areas within season was overwhelmed by their temporal variabilities. Phylogenetic analysis further indicated that 75%–82% of community turnover was governed by homogeneous selection due to consistent environmental conditions within seasons, suggesting that the microbial communities in Lake Donghu are mainly controlled by niche‐based processes. Therefore, dominant niches available within seasons might be occupied by similar combinations of bacterial taxa with modest dispersal rates throughout different lake areas.     

Gene expression and molecular characterization of a novel C-type lectin,encapsulation promoting lectin (EPL), in the rice armyworm,Mythimna separata

Insect cellular immune reactions differ depending on the target species. Phagocytosis is activated to scavenge microorganisms such as bacteria and fungi. On the other hand, larger invaders such as parasitoid wasps are eliminated by activation of encapsulation. In this study, we hypothesized that novel determinants regulate cellular immunities independent of surface molecular pattern recognition involving pattern recognition receptors (PRRs). Immune-related genes differentially expressed depending on the treated material size were screened in larval hemocytes of the rice armyworm, Mythimna separata. Consequently, we identified a novel C-type lectin gene up-regulated by injection of large beads but not small beads of identical material. Examination of in vitro effect of the recombinant protein on the immune reactions clarified that the protein activated encapsulation reaction, while it suppressed phagocytosis. These results suggest that this novel C-type lectin designated “encapsulation promoting lectin (EPL)” regulates cellular immunity by a novel immune target size-recognition mechanism.     

应用高频观测探讨不同森林经营方式下矿质土壤呼吸的昼夜动态特征

矿质土壤呼吸是森林生态系统土壤碳库损失的重要途径之一,也是森林生态系统碳(C)平衡估算中的关键因子。了解矿质土壤呼吸在不同时间尺度上的变化,对理解森林生态系统C循环应对全球变化的响应至关重要,而高频观测是探讨矿质土壤呼吸在不同时间尺度变化的重要手段之一。通过高频自动观测系统与Li-8100土壤CO2通量测量系统,对福建省三明市陈大镇国有林场的米槠(Castanopsis carlesii)次生林在不同森林经营方式下(CK对照,RR皆伐,RB火烧)的矿质土壤呼吸与土壤温度和含水量的昼夜动态进行分析,并比较2种采样策略下矿质土壤呼吸的年、日均通量差异。结果表明:1)不同森林经营方式的矿质土壤呼吸与土壤温度和土壤含水量均存在着明显的季节动态,矿质土壤呼吸速率年均值表现为CK(2.18μmol m~(-2)s~(-1))RB(1.93μmol m~(-2)s~(-1))RR(1.89μmol m~(-2)s~(-1))。2)在不同森林经营方式下,采用手动观测的矿质土壤呼吸年平均日通量显著低于高频观测结果,而采用高频观测09:00—11:00时间段内观测数据计算日通量与高频自动观测系统全天(24h)结果无显著差异;3)不同森林经营方式下的林地,土壤水热条件的变化是影响矿质土壤呼吸的重要因素之一。双因子模型拟合结果表明,土壤温度和含水量共同解释了CK、RR和RB矿质土壤呼吸速率的年变化的96.8%,62.8%,95.4%,拟合结果明显优于以温度为单因子的指数模型。因此,未来气候变化背景下,为准确评估和预测不同森林经营方式对土壤与大气间碳通量交换的影响,采用高频自动观测技术观测矿质土壤呼吸,将有利于提高碳通量估算精度。     

基于生态重要性和敏感性的西南山地生态安全格局构建——以云南省大理白族自治州为例

生态安全格局构建是快速城市扩张背景下缓解生态保护和土地开发矛盾、保证区域生态安全的有效途径。源地和阻力面是生态安全格局构建的重要基础,当前阻力面构建多关注生态要素而忽视与区域典型生态问题相对应的生态过程表征。以西南山地地区--云南省大理白族自治州为研究区,选取生物资源保护、水资源安全和营养物质保持等生态系统服务评估生态重要性从而识别源地,基于地质灾害、土壤侵蚀、石漠化等生态敏感性构建生态阻力面,并运用最小累积阻力模型识别组团廊道和景观廊道,从而构建山地生态安全格局。研究表明,大理州生态安全源地总面积14416.64 km~2,占全州土地总面积的50.93%;关键生态廊道分为组团廊道和景观廊道两类,分别长404.7 km和208.4 km,以"一轴三带"形式呈树状辐射分布。生态安全格局中的生态源地和廊道应成为低丘缓坡土地资源开发中的禁止开发区。生态重要性源地识别和生态敏感性阻力面分析方法可为生态安全格局构建提供新思路,研究结果对于大理州山地城镇建设的用地选择和空间扩张提供定量指引。