Trophic flexibility and opportunism in pike Esox lucius

The first comprehensive investigation of pike Esox lucius trophic ecology in a region (Ireland) where they have long been thought to be a non‐native species is presented. Diet was investigated across habitat types (lake, river and canal) through the combined methods of stable‐isotope and stomach content analyses. Variations in niche size, specialization and the timing of the ontogenetic dietary switch were examined, revealing pronounced opportunism and feeding plasticity in E. lucius, along with a high occurrence of invertivory (up to 60 cm fork length, L_F) and a concomitant delayed switch to piscivory. Furthermore, E. lucius were found to primarily prey upon the highly available non‐native roach Rutilus rutilus, which may alleviate predation pressure on brown trout Salmo trutta, highlighting the complexity of dynamic systems and the essential role of research in informing effective management.     

Widespread supplementary feeding in domestic gardens explains the return of reintroduced Red Kites Milvus milvus to an urban area

Reintroductions are commonly used to mitigate biodiversity loss. One prominent example is that of the Red Kite Milvus milvus, a charismatic raptor of conservation concern. This species has been reintroduced across the UK over the last 25 years following its near extinction after centuries of persecution. The species was not expected to recolonize urban areas; its historical association with human settlements is attributed to scavenging on human waste and refuse, a resource now greatly reduced on the streets of modern European cities. However, the species has become a common daytime visitor to a large conurbation centred on the town of Reading, southern England, approximately 20 km from the first English reintroduction site. Given a near‐absence of breeding and roost sites, we investigated foraging opportunities and habitat associations that might explain use by Red Kites of this urban area. Surveys of discarded human foods and road‐kill suggested that these could support at most 13–29 Kites per day. Face‐to‐face surveys of a cross‐section of residents revealed that 4.5% (equivalent to 4349 households) provided supplementary food for Red Kites in their gardens. Using estimates of per‐household resource provision from another study, we calculated that this is potentially sufficient to feed 142–320 Kites, a substantial proportion of the total estimated to visit the conurbation each day (between 140 and 440). Road transects found positive associations between Red Kites and residential areas. We suggest that the decision made by thousands of householders to provide supplementary food for Red Kites in their gardens is the primary factor explaining their daytime abundance in this urban area.     

Litter‐trapping plants: filter‐feeders of the plant kingdom

Litter‐trapping plants have specialized growth habits and morphologies that enable them to capture falling leaf litter and other debris, which the plants use for nutrition after the litter has decayed. Litter is trapped via rosettes of leaves, specially modified leaves and/or upward‐growing roots (so‐called ‘root baskets’). Litter‐trappers, both epiphytic and terrestrial, are found throughout the tropics, with only a few extra‐tropical species, and they have evolved in many plant families. The trapped litter mass is a source of nutrients for litter‐trapping plants, as well as food and housing for commensal organisms. Despite their unique mode of life, litter‐trapping plants are not well documented, and many questions remain about their distribution, physiology and evolution.–© 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 554–586.     

The dynamics of coexistence: habitat sharing versus segregation patterns among three sympatric montane vipers

Contact zones of closely related and ecologically similar species constitute rare opportunities to study the evolutionary consequences of past speciation processes. They represent natural laboratories in which strong competition could lead to the exclusion of one species, or the various species may switch into distinct ecological niches. Alternatively, if reproductive isolation has not yet been achieved, they may hybridize. We elucidate the degree of taxon integrity by comparing genetics and habitat use of three similar‐sized congeneric viper species, Vipera ammodytes, Vipera aspis, and Vipera berus, of Nadiza Valley in western Slovenia. No hybridization was detected for either mitochondrial or nuclear genomes. Similarly, external intermediacy by a single prestudy viper (probably V. ammodytes × V. aspis) indicates that hybridization occasionally occurs, but should be very rare. Populations of the three related viperids are partially allopatric in Nadiza Valley, but they also coexist in a narrow contact zone in the montane grassland along the south‐exposed slope of Mount Stol (1673 m a.s.l.). Here, the three species that occupy areas in or near patches of rocky microhabitats (e.g. stone piles, slides, and walls) live in syntopy. However, fine‐scale measurements of structural components show partial habitat segregation, in which V. berus becomes more dominant at elevations above 1400 m and occupies mostly the mountain ridge and north‐exposed slopes of Mount Stol, V. aspis occurs below 1300 m and is the only species to inhabit stoneless patches of grass and bushes around 1000 m and lower, and V. ammodytes occurs at all elevations up to 1500 m, but is restricted to a rocky microhabitat. We suggest that a high degree of microstructure divergence, slightly different environmental niches, and a generally favourable habitat for all three viper species, keep the pressure for mis‐mating and hybridization low, although mechanisms such as reduced hybrid inferiority and temporal mating segregation cannot yet be excluded.     

Into the light: diurnality has evolved multiple times in geckos

Geckos are the only major lizard group consisting mostly of nocturnal species. Nocturnality is presumed to have evolved early in gecko evolution and geckos possess numerous adaptations to functioning in low light and at low temperatures. However, not all gecko species are nocturnal and most diurnal geckos have their own distinct adaptations to living in warmer, sunlit environments. We reconstructed the evolution of gecko activity patterns using a newly generated time‐calibrated phylogeny. Our results provide the first phylogenetic analysis of temporal activity patterns in geckos and confirm an ancient origin of nocturnality at the root of the gecko tree. We identify multiple transitions to diurnality at a variety of evolutionary time scales and transitions back to nocturnality occur in several predominantly diurnal clades. The scenario presented here will be useful in reinterpreting existing hypotheses of how geckos have adapted to varying thermal and light environments. These results can also inform future research of gecko ecology, physiology, morphology and vision as it relates to changes in temporal activity patterns. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.     

北京城市景观格局时空变化及驱动力

2004—2020年城市总体规划以来,北京经历了快速的城市化发展期,城市景观格局发生了很大变化。采用TM遥感影像为信息源,通过RS解译建立了2003、2007和2011年北京市土地利用覆盖空间数据,利用Fragstats对景观格局特征指数进行了计算和分析,分别从全市域和六环内城市化典型地区两个尺度研究了北京市城市景观格局时空变化特征,结合社会经济、城市总体规划和城市发展政策因素,分析了北京城市景观格局变化的驱动力因素。研究结果表明,过去近10年,市域景观特征发生了深刻变化,建设用地保持较快的增长速度,其比例由15.0%上升至18.0%,相反耕地面积比例由21.3%下降至18.8%。林地一直是市域的优势景观类型,比例维持在51%以上。而六环内城市化典型地区的景观变化更加明显,建设用地比例增加近10%,是六环地区的优势景观类型,耕地比例相应减少10%。建设用地的增长主要以耕地占用为主。景观格局指数的分析表明,大尺度和小尺度的景观格局变化表现出不同的特征,市域大尺度建设用地斑块破碎化程度高,景观蔓延度、聚合度下降,景观多样性增加;而小尺度六环内的建设用地斑块破碎化趋势降低,景观蔓延度和聚合度上升,但景观多样性下降迅速。大小两个尺度的景观空间形态均表现出复杂性增加的趋势。通过景观格局变化的驱动因素分析,人口规模的增加、产业结构调整、城市总体规划的实施以及城市发展政策的变化是导致景观格局变化的主要因素。     

川西亚高山-高山森林土壤养分动态及其对季节性冻融的响应

为深入了解川西亚高山-高山森林冬季生态学过程,于2008年11月—2009年10月,在土壤冻结初期、冻结期和融化期及植被生长季节,研究了不同海拔(3582 m、3298 m和3023 m)岷江冷杉林土壤养分动态及其对季节性冻融的响应。3个海拔森林土壤冬季具有较高养分含量,且随土壤冻融过程不断变化。土壤有机层可溶性碳和氮、铵态氮、硝态氮含量在冻结初期显著增加后快速降低,并随融化过程迅速增加后再次降低,而土壤可溶性碳和氮、硝态氮含量在冻结期变化不明显,铵态氮显著增加。矿质土壤层可溶性碳和氮、铵态氮含量也在冻结初期显著增加后降低,而土壤可溶性氮、铵态氮和硝态氮在冻结期显著增加,并在融化期经历一个明显的含量高峰。海拔和土层的交互作用显著影响土壤可溶性碳和硝态氮含量,土壤养分含量与土壤温度的相关性随海拔差异而不同。这表明季节性冻融期是土壤生态过程的重要时期,土壤冻融格局显著影响川西亚高山-高山森林土壤养分动态。     

环境DNA技术在地下生态学中的应用

地下生态过程是生态系统结构、功能和过程研究中最不确定的因素。由于技术和方法的限制,作为"黑箱"的地下生态系统已经成为限制生态学发展的瓶颈,也是未来生态学发展的主要方向。环境DNA技术,是指从土壤等环境样品中直接提取DNA片段,然后通过DNA测序技术来定性或定量化目标生物,以确定目标生物在生态系统中的分布及功能特征。环境DNA技术已成功用于地下生态过程的研究。目前,环境DNA技术在土壤微生物多样性及其功能方面的研究相对成熟,克服了土壤微生物研究中不能培养的问题,可以有效地分析土壤微生物的群落组成、多样性及空间分布,尤其是宏基因组学技术的发展,使得微生物生态功能方面的研究成为可能;而且,环境DNA技术已经在土壤动物生态学的研究中得到了初步应用,可快速分析土壤动物的多样性及其分布特征,更有效地鉴定出未知的或稀少的物种,鉴定土壤动物类群的幅度较宽;部分研究者通过提取分析土壤中DNA片段信息对生态系统植物多样性及植物分类进行了研究,其结果比传统的植物分类及物种多样性测定更精确,改变了以往对植物群落物种多样性模式的理解。同时,环境DNA技术克服传统根系研究方法中需要洗根、分根、只能测定单物种根系的局限,降低根系研究中细根区分的误差,并探索性地用于细根生物量的研究。主要综述了基于环境DNA技术的分子生物学方法在土壤微生物多样性及功能、土壤动物多样性、地下植物多样性及根系生态等地下生态过程研究中的应用进展。环境DNA技术对于以土壤微生物、土壤动物及地下植物根系为主体的地下生态学过程的研究具有革命性意义,并展现出良好的应用前景。可以预期,分子生物学技术与传统的生态学研究相结合将成为未来地下生态学研究的一个发展趋势。     

不同放牧制度下呼伦湖流域草原植被冠层截留

冠层截留是降雨过程中的水量分配和流域水平衡的一个重要组成部分,通过水浸泡法和降雨模拟实验研究呼伦湖流域草原3种放牧制度下(休牧、轮牧、自由放牧(超载放牧))植被冠层截留量的变化规律,并利用遥感解译植被归一化指数(NDVI),确定3种放牧制度下草原面积,估算呼伦湖流域草原降雨截留量。研究表明:在休牧、轮牧、自由放牧3种制度下,水浸泡法测定的截留量分别是0.468、0.320、0.271 mm。降雨模拟实验法测得的结果分别是0.957、0.613、0.431 mm。休牧、轮牧、自由放牧草场叶面积指数、盖度、容重、生物量等指标差异显著(P0.05),且单株植被高度、鲜重对截留量影响显著呈线性正相关关系。呼伦湖流域草原一次降雨量为大于等于30 mm全流域降雨,其植被截留量为6.462×106m3。