Regional persistence of an endemic plant, Erigeron acer subsp. decoloratus, in disturbed riparian habitats

Regional persistence of species requires a positive balance between colonizations and local extinctions. In this study, we examined the amount of colonizations and extinctions and their likelihood as a function of patch size, isolation, and habitat characteristics of a riparian perennial plant, Erigeron acer subsp. decoloratus. We also studied the importance of patch dynamics to the regional population growth. Over five successive years, we counted the number of plant patches along 43 km of riverside. Most patches were small in area and population size. The annual finite growth rate in the number of patches varied between years, but the geometric mean was close to 1.0, indicating a viable patch network in spite of local extinctions. Extinction rate was highest on steep slopes and for small patches with few individual plants and a small patch area. When the patches were classified into different stage classes, the most common fate was stasis, i.e., the patch remained at the same stage. Patch survival and local, within-patch dynamics were most important during this five-year period. Between-patch dynamics (including colonization for example) accounted for 5–10% of annual transitions. The overall dynamics were relatively similar to those of other plant species subjected to riparian disturbance regimes. In the long run, the survival of the species depends on how well it is able to escape from competition from forest and meadow species and track the availability of suitable habitats. This kind of habitat tracking differs from classical metapopulation dynamics. In the former, local extinctions occur as a consequence of adverse changes in the habitat and recolonizations are rare, whereas metapopulation models assume a highly persistent habitat structure with frequent recolonizations. In this respect, the regional dynamics of perennial plants in disturbed riparian habitats may differ from classical metapopulations.     

Spatial dynamics of plant species in an agricultural landscape in the Netherlands

This study examined the changes in distribution patterns of 13 herbaceous plant species from 1998 to 2000 in ditch banks along the edges of arable fields in the Netherlands. The objective was to test if spatial dynamics could be related to spatial isolation and disturbance of habitat and to the dispersal and seed bank characteristics of the species. Knowledge of these relations should be used to increase the effectivity of agri-environmental schemes aiming at an increase of botanical diversity. All species frequently colonized empty patches and populations in occupied patches frequently went extinct. Most colonization events occurred within 50 m of conspecific source patches in the preceding year, but colonization events in patches at distances more than 200 m from conspecific source patches were also observed. The colonization probabilities decreased with isolation distance. For nine species this relation was statistically significant, after correction for year and habitat. The extinction probabilities increased with isolation. For only four species this relation was statistically significant. Both colonization and extinction probabilities were more often statistically significant related to isolation for species with transient seed banks than species with persistent seed banks. Implications for management options aiming at survival of plant species in fragmented landscapes are discussed.     

复合荔枝园节肢动物群落动态的研究

对单一荔枝和复合荔枝园节肢动物群落进行了调查、分析,结果表明：复合园的捕食性、寄生性昆虫以及蜘蛛类群的数量和丰富度明显高于单一园,而植食性类群的数量和主要害虫发生数量明显少于单一园。复合园各种类型的多样性指数季节变化,其总趋势比单一园大,波动程度比单一园低。复合园的均匀度全年维持在０．８以上,而单一园的则波动很大。     

Eight-legged swimmers: Behavioral responses to floods in two South American spiders

Arthropods inhabiting floodplains have to cope with regular cycles of wet and dry conditions. Allocosa senex and Allocosa marindia are two sympatric and synchronic sand-dwelling wolf spiders that construct burrows along South American coasts and are subject to periodic floods. Our objective was to study tolerance to immersion and describe the behavioral responses to that event in A. senex and A. marindia. We placed each spider in a terrarium with sand as substrate to allow burrow construction. Then, we gradually increased water levels and recorded the behavioral responses for 30 min. None of the individuals died during the artificial flood. More adults of A. senex performed “dives” and “floats” compared to A. marindia. Also, A. senex showed higher occurrences of “floats,” “swims,” and swam for longer than A. marindia. Finally, females of both species swam more frequently than males. Our findings indicate that both Allocosa are able to withstand floods, showing differential tactics according to the life histories of each sex and species.     

Facies dynamics in Eocene to Oligocene circumalpine carbonates

A new concept, termed ‘Facies Dynamics’ (defined as changes of specific carbonate facies types in time and space, which are controlled by phylogenetic, ecological and geological parameters), is introduced. This concept aims to define and interpret spatial and temporal changes of carbonate facies patterns. It is based on Middle Eocene to Early Oligocene shallow-water carbonate facies types from the circumalpine area (north-eastern Italy, northern Slovenia, Austria and southern Bavaria), which are compared with respect to dominating biogenic components and their distributions along a shelf gradient. This comparison has lead to the distinction and definition of 14 Major Facies Types (MFTs), which are dominated by coralline algae, larger and smaller foraminifera, corals and bryozoans. The presence and distribution of these MFTs from three different time slices (Middle Eocene, Late Eocene and Early Oligocene) is compared. Nine aspects of facies dynamics are distinguished: origination, extinction, immigration, emigration, expansion, reduction, stasis, shift, and replacement of MFTs. These changes are controlled by regional changes in ecological parameters, but also by global events, especially extinction patterns at the Middle/Late Eocene boundary and at the Eocene/Oligocene boundary.     

Habitat utilization by Hawaiian stream fishes with reference to community structure in oceanic island streams

Synopsis Much of the freshwater biota on high Pacific islands is derived from marine ancestors. Traces of this marine origin are seen in the amphidromous life history patterns of these species. Investigation of the habitat utilization of an assemblage of freshwater gobies in the Hawaiian Islands indicates some resource partitioning within this group. The three major stream species appear to exhibit distinct habitat preferences, which in conjunction with their longitudinal zonation in streams may have served to facilitate their colonization or co-existence.     

Macrofaunal responses to pit-mound patch dynamics in an intertidal mudflat: local versus patch-type effects

Biogenic structures created via feeding activities have varying effects on soft sediment communities, altering population dynamics, creating a temporal mosaic of successional patches, and ultimately increasing variation at different spatial scales. This study focused on assessing population responses to pits (P) and mounds (M) in an intertidal mudflat (River Plym, England) in order to determine (a) how these structures (max size 1400 cm²), and their formation, affected infauna and (b) to what extent local variations in ambient communities may have affected infaunal responses. Densities in 0- and 1-week-old pits were significantly lower than in ambient and mound areas for most of the dominant infauna over the study period. Abundances were higher in mounds for some species and responses to both structures differed among juveniles and adults. Recovery to ambient levels in P-M systems took about 3 weeks, although their physical characteristics only lasted about 2 weeks. Correlations among ambient densities and adjacent P-M systems were mixed, but suggested decoupling between local ambient and P-M dynamics for some taxa either in relation to age of the patch and/or size of the individuals. At the community level, local differences appeared to be a significant source of variation in new pits, but differences were swamped out when recruitment was high. Differences were more evident in older P-M systems. These results show that sources of local variation in infaunal dynamics can be attributed to a combination of small-scale disturbance/recovery processes and spatially and temporally changing ambient conditions. Identifying extant spatial and temporal small-scale variation can be a critical component of understanding and interpreting larger-scale dynamics of soft-sediment systems.     

Comparison of the trophic niches between two planktivorous fishes in two large lakes using stable isotope analysis

This paper studied the sources of food and the trophic levels of silver and bighead carps using stable isotopes (δ¹³C and δ¹⁵N) analysis in Lake Qiandao and Lake Taihu. The δ¹³C values of POM and phytoplankton indicated that Particulate Organic Matter (POM) is of terrestrial origin in LQ and phytoplankton origin in LT. The different signature of δ¹⁵N of phytoplankton and POM also showed the different extent of anthropogenic impacts on the two lakes, with higher impacts in LT than in LQ. In LQ the trophic levels of silver and bighead carps were significantly different (2.48 ± 0.19 and 2.66 ± 0.19, respectively), while in LT the difference was not significant (2.15 ± 1.54 and 2.36 ± 0.38, respectively). Using a mixing model, we found that silver and bighead carps consumed a major proportion on phytoplankton and/or POM in both lakes with higher contribution of phytoplankton in more eutrophic lake. Silver and bighead carps had clear differentiation in food resources with silver carp more on POM and bighead more on zooplankton in deep and mesotrophic lakes. Contrary to this, both carps fed primarily on phytoplankton (and POM) and may have more niche overlaps in shallow and eutrophic lakes.     

Functional traits of tree species with phylogenetic signal co-vary with environmental niches in two large forest dynamics plots

Aims While using phylogenetic and functional approaches to test the mechanisms of community assembly, functional traits often act as the proxy of niches. However, there is little detailed knowledge regarding the correlation between functional traits of tree species and their niches in local communities. We suggest that the co-varying correlation between functional traits and niches should be the premise for using phylogenetic and functional approaches to test mechanisms of community assembly. Using functional traits, phylogenetic and environmental data, this study aims to answer the questions: (i) within local communities, do functional traits of co-occurring species co-vary with their environmental niches at the species level? and (ii) what is the key ecological process underlying community assembly in Xishuangbanna and Ailaoshan forest dynamic plots (FDPs)?Methods We measured seven functional traits of 229 and 36 common species in Xishuangbanna and Ailaoshan FDPs in tropical and subtropical China, respectively. We also quantified the environmental niches for these species based on conditional probability. We then analyzed the correlations between functional traits and environmental niches using phylogenetic independent contrasts. After examining phylogenetic signals of functional traits using Pagel's λ, we quantified the phylogenetic and functional dispersion along environmental gradients within local tree communities.Important findings For target species, functional traits do co-vary with environmental niches at the species level in both of the FDPs, supporting that functional traits can be used as a proxy for local-scale environmental niches. Functional traits show significant phylogenetic signals in both of the FDPs. We found that the phylogenetic and functional dispersion were significantly clustered along topographical gradients in the Ailaoshan FDP but overdispersion in the Xishuangbanna FDP. These patterns of phylogenetic and functional dispersion suggest that environmental filtering plays a key role in structuring local tree assemblages in Ailaoshan FDP, while competition exclusion plays a key role in Xishuangbanna FDP.     

Spatial and temporal colonization dynamics of segmented filamentous bacteria is influenced by gender,age and experimental infection with Helicobacter hepaticus in Swiss Webster mice

In this study, we examined colonization dynamics of segmented filamentous bacteria (SFB) in intestine of Swiss Webster (SW) mice infected with Helicobacter hepaticus (Hh). At 8 weeks post-inoculation with Hh (WPI), cecal and colonic SFB levels in the control males were significantly lower compared to those at 16 WPI. Hh infection in both genders did not alter SFB levels in the jejunum and ileum, but increased SFB levels in the cecum and colon of males compared to the controls (P < 0.05) at 8 WPI. At 16 WPI, the Hh-infected females contained lower levels of SFB in the jejunum, cecum and colon compared to the female controls. Irrespective of gender, aging and Hh infection, the Il-17A mRNA levels decreased from the small intestine to the cecum and then to the colon, whereas the Foxp3 mRNA levels were comparable in these intestinal regions. There were significant differences in Il-17A mRNA levels in the ileum (P < 0.05, R² = 0.31), with females having greater Il-17A mRNA levels than males, and higher SFB colonization levels related to more Il-17A mRNA. These results indicate that aging and gender play an important role in colonization dynamics of intestinal SFB and ileal SFB-associated Th17 response.     

Egg size in relation to fertilization dynamics in free-spawning tropical reef fishes

In marine invertebrates that spawn by simply releasing their gametes into the water (free-spawning), fertilization success likely is often limited by low sperm concentrations, due to dispersion of mates and dispersal of gametes by water movements. Production of large, low density eggs might be advantageous when sperm concentrations consistently are low, because large target size might increase egg/sperm encounters, and more low than high density eggs could be produced per clutch. Although average fertilization success in the labrid Thalassoma bifasciatum is 95% in both group spawns (in which multiple males compete for fertilizations by producing large quantities of sperm) and pair (mono-male) spawns, it is slightly lower in pair spawns, due to low level sperm limitation that arises because pair-spawning males release near the minimum number of sperm necessary for maximum fertilization. I examined whether variation in egg size and content in T. bifasciatum and other free-spawning fishes is related to variation in spawning mode, to assess whether compensatory production of large, low-density eggs might be contributing to high fertilization success in pair spawns. I found no difference between the volume or density of eggs of (1) pair- and group-spawning females of T. bifasciatum, or (2) pair-and group-spawning congeneric species of labrids, scarids, and serranids, or (3) labrids and scarids with vigorous, rapid spawning movements (which could turbulently diffuse gamete clouds) and those with slow movements. Further, egg density does not decline with increasing egg volume among those fishes. Assuming that egg size can affect fertilization success, then sperm limitation seems unlikely to represent a significant problem for pair-spawning T. bifasciatum, probably because mates place their vents close together during gamete release. The situation regarding sperm limitation in other fishes, and effects of environmentally generated water turbulence on it, are less clear. Interspecific variation in the size and content of these fishes' eggs may relate to provisioning of offspring for different larval life-histories.     

Effects of habitat fragmentation by damming on salmonid fishes: lessons from white-spotted charr in Japan

Dam construction has serious consequences, and one of the most serious concerns is the fragmentation of riverine ecosystems. We reviewed the influence of habitat fragmentation on white-spotted charr Salvelinus leucomaenis populations. First, habitat fragmentation by damming has serious consequences in terms of alternative life-history strategies. Most fish in dammed-off areas do not migrate to the sea and instead become resident forms. This loss of the anadromous form negatively affects populations through decreased spawning biomass. In addition, the smaller population sizes in dammed-off habitats can negatively affect population dynamics through demographic, environmental, and genetic stochasticity. Therefore, the population viability is reduced in small, dammed-off habitats. White-spotted charr populations also likely experience different selection pressures after damming. Many of these effects of habitat fragmentation due to damming are not immediate but rather occur gradually over several generations. Because most Japanese dams were constructed after 1970, some effects of damming may not yet be obvious. Kentaro Morita is the recipient of the 12th Denzaburo Miyadi Award.     

Differential responses to predator cues between two mosquito species breeding in different habitats

1. Natural selection favours females who can correctly assess the predation risk and hence avoid high‐risk oviposition sites and reduce the mortality rate of their offspring. In spite of the potential significance of such behaviour, relatively few studies have assessed the relationship between oviposition behaviour and predation risk. 2. The present study aimed to determine the sublethal effects of predators on oviposition site selection by gravid females, the foraging activity of larvae, and the life history traits of two mosquito species that breed in different habitats, Aedes albopictus Skuse (container breeder) and Culex tritaeniorhynchus Giles (wetland breeder). 3. Female C. tritaeniorhynchus avoided laying eggs at oviposition sites in the presence of a predator cue. In contrast, female A. albopictus laid eggs in both the absence and presence of the predator cue. 4. To examine the effects of predator cues on larval behaviour, experiments were conducted in the absence and presence of a predator cue. Although larval activity was lower in the presence of the predator cue than that in its absence in both species, C. tritaeniorhynchus responded to the predator cue more strongly than A. albopictus. Female A. albopictus that had been reared with caged predators exhibited an extended larval development period, whereas the adult C. tritaeniorhynchus reared in the presence of predators were smaller than those reared in their absence. 5. This finding might explain why C. tritaeniorhynchus avoid laying eggs in predator‐conditioned water, for example to increase the fitness of their offspring, but A. albopictus either cannot detect predator cues or are not sensitive to them.     

新薛河溪流生境底栖动物群落结构季节动态

明确底栖动物在时空尺度上的自然变化规律对有效评估和保护水生态系统十分重要。基于2012年季节调查数据,对新薛河典型生境底栖动物群落季节动态进行了研究。共鉴定底栖动物108种,隶属5门10纲74属。短脉纹石蛾、长钝直突摇蚊、拟长跗摇蚊、Neozarelia sp.为研究区域优势分类单元,相对丰度分别为25.1%、9.8%、9.0%、8.6%;各季节间优势分类单元组成差异较大,3个季度共同优势物种仅短脉纹石蛾1种。密度、物种丰度、香农指数表现为4月和12月显著高于10月;均匀度指数10月份最高。非度量多维标度排序表明,不同季节底栖动物群落结构差异显著;对照河段(D河段)群落结构季节间差异相对较小。指示物种法分离出了新薛河及各河段代表性物种41种,但B河段未分离出指示物种;双向聚类分析进一步明确了指示物种的指示属性(特有或者相对丰度最高)。     

Determination of digestive enzyme kinetics: a new method to define trophic niches in freshwater snails

 Fluorogenic substrate analogues (MUF substrates) are very sensitive in detecting hydrolytic enzymes. This method was adapted for the quantitative analysis of extracellular enzymes in snails and other animals. It was then used to determine cellobiase, chitobiase, protease, esterase, phosphatase and lipase in the digestive tract of Radix peregra and Bithynia tentaculata. The method was sensitive enough to determine the complete enzyme kinetics (K _m, V _max values) in the esophagus, stomach, digestive gland and intestine of single animals adapted to various natural foods. With the exception of lipase and phosphatase, K _m values were between 15 and 30 mmol l^–1, independent of prefeeding. Enzyme activities, in contrast, changed with food conditions: cellobiase-activities ranged from 80 to 8000 picokatal, esterase from 500 to 3000 pKat, chitobiase from 150 to 750 pKat and protease from 100 to 1100 pKat per animal. R. peregra had cellobiase activities 10 times higher than B. tentaculata. For chitobiase, esterase and protease the enzyme activities were in the same order of magnitude in both species. All enzymes differed significantly in activity between prefeeding regimes. This variability with prefeeding was much higher in Bithynia than in Radix. These results help to better define the trophic niches and feeding specializations of the two species studied. Received: 12 April 1996 / Accepted: 26 June 1996     

An approach to analysis of colonization dynamics in community functioning of protozoa for bioassessment of marine pollution

Biological trait analysis is a powerful tool to summarize the spatial/temporal patterns of community functioning and ecosystem process at taxon-free resolutions. To identify the optimal colonization period with high homogeneity in functional patterns of protozoa for bioassessment, 1-month baseline colonization survey was conducted in coastal waters of the Yellow Sea. A fuzzy-coding functional trait system was used to summarize the functional structure of protozoan communities during the colonization process. The functional patterns showed a low homogeneity during the early stage (3–7 days), followed by a stable stage (10–14 days) with high homogeneity, and the last stage (21–28 days) with high heterogeneity. The functional richness showed a low variability, while the functional evenness and divergence generally showed a decreasing trend during the whole colonization process. Furthermore, the functional dispersion and RaoQ indices generally leveled off only during the stable stage. These results suggest that it is necessary to determine the optimal exposure time period with high homogeneity of community functioning for bioassessment using protozoan colonization in marine ecosystems.     

北京地区韭菜迟眼蕈蚊种群动态及越夏越冬场所调查研究

【目的】为明确北京地区不同栽培管理模式下韭菜田全年韭菜迟眼蕈蚊Bradysia odoriphaga种群动态的发生规律及其越夏越冬场所。【方法】分别在2014—2015年通过黄色板对露地和温室韭菜田块的韭菜迟眼蕈蚊成虫进行了监测,并通过挖根和网捕的方式调查韭菜迟眼蕈蚊的越夏越冬场所及虫态。【结果】北京地区,露地韭菜田块韭菜迟眼蕈蚊每年发生3~4代,温室内可全年发生,主要为害高峰期在春秋两季;韭菜迟眼蕈蚊幼虫主要分布在0~5 cm的土壤深处;夏季韭菜迟眼蕈蚊虫口基数偏低,但主要在本地韭菜田块越夏;冬季韭菜迟眼蕈蚊主要以4龄老熟幼虫在鳞茎内或鳞茎附近的土壤中越冬。【结论】本研究阐明了北京地区不同栽培管理模式下,韭菜迟眼蕈蚊周年发生的种群动态规律及越夏越冬生物学特性,为韭菜迟眼蕈蚊的预测测报和综合防治提供理论参考依据。     

Modeling the flocking propensity of passerine birds in two Neotropical habitats

We examined the importance of mixed-species flock abundance, individual bird home range size, foraging height, and foraging patch characteristics in predicting the propensity for five Neotropical passerine bird species (Slaty Antwren, Myrmotherula schisticolor; Golden-crowned Warbler, Basileuterus culicivorus; Slate-throated Redstart, Myioborus miniatus; Wilson’s Warbler, Wilsonia pusilla; and Black-and-white Warbler, Mniotilta varia) to forage within flocks, rather than solitarily. We used study plots in primary mid-elevation forest and in shade coffee fields in western Panama. We expected that all species would spend as much time as possible flocking, but that the social and environmental factors listed above would limit compatibility between flock movements and individual bird movements, explaining variability in flocking propensity both within and among species. Flocking propensity was well predicted by home range size and flock abundance together, for four of the five species. While flock abundance was uniform across plots, home range sizes varied among species and plots, so that home range size appeared to be the principle factor limiting flocking propensity. Estimates of flock abundance were still required, however, for calculating flocking propensity values. Foraging height and patch characteristics slightly improved predictive ability for the remaining species, M. miniatus. In general, individual birds tended to join flocks whenever one was available inside their home range, regardless of a flock’s specific location within the home range. Flocking propensities of individual species were lower in shade coffee fields than in forests, and probably vary across landscapes with variations in habitat. This variability affects the stability and species composition of flocks, and may affect survival rates of individual species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.