浙江披山海域主要鱼类时空生态位

依据2015年11月(秋)、2016年2月(冬)、5月(春)、8月(夏)4个航次的渔业资源底拖网调查数据,运用相对重要性指数(IRI)、Shannon指数和Pianka指数对浙江披山海域主要鱼类的时空生态位宽度和重叠进行分析,并结合冗余分析和种间竞争系数研究了主要鱼类间的竞争共存关系及生态位分化.结果 表明:研究期间共...     

闽江口主要渔获鱼类的生态位宽度与重叠

根据2015年闽江口4个季度月(1、5、8、11月)的渔业资源底拖网调查资料,通过相对重要性指数确定主要渔获鱼类,对主要渔获鱼类的生态位宽度、生态位重叠进行分析.结果表明: 4个航次总共渔获鱼类137种,隶属16目37科,以鲈形目、鲱形目、鲽形目和鲀形目等为主.主要渔获鱼类有15种,其中优势种6种,分别为六指马鲅、龙头鱼、白姑鱼、鹿斑仰口鲾、短舌鳎和凤鲚,其余9种为重要种.时空生态位宽度值达到1以上的种类有7种,从大到小依次为短舌鳎、棘头梅童鱼、鹿斑仰口鲾、六丝钝尾虾虎鱼、赤鼻棱鳀、凤鲚、龙头鱼.主要渔获鱼类的生态位变动在闽江口受季节变化的影响比较明显.闽江口主要渔获鱼类种对的时空生态位重叠达有意义水平的种对占比较高,达81.9%,其中重叠显著的有6个种对,说明闽江口主要渔获鱼类间在时空二维上的分布普遍相似,在资源利用上存在竞争关系.时空生态位重叠值最大的种对为日本绯鲤-沙带鱼,重叠值最小的种对为日本绯鲤-棘头梅童鱼,时空生态位重叠受季节变化的影响比较明显.     

云南省玉龙鼠疫疫源地小型兽类垂直空间与季节生态位分析

2015年4至12月,以玉龙鼠疫疫源地的核心区域文笔山为样区,在2 400 m以上海拔区间划分4个垂直生态带,采用夹夜法进行四个季节的小型兽类调查.根据生态位宽度指数(Bi)和生态位重叠指数(Cih)对该地区小型兽类垂直空间与季节生态位特征进行分析.调查共布鼠夹8 028次,捕获小型兽类1 583只,包括4目6科12属...     

南海北部近海头足类优势种及其生态位特征

为了解南海北部近海头足类优势种的种间关系,根据2014—2015年该海域4个季节底拖网渔业资源调查,应用相对重要性指数、生态位宽度和重叠指数从时空维度分析头足类优势种的生态位特征。结果表明: 该海域4个季节的头足类优势种共5种,分别为剑尖枪乌贼、中国枪乌贼、火枪乌贼、金乌贼和杜氏枪乌贼,前两种是4个季节的共同优势种。与历史数据相比,头足类优势种的种类组成已发生改变。头足类资源时空分布格局明显,海南岛南部至粤东海域资源密度高于北部湾,季节变化呈夏季高而冬季低特征。时空生态位分析表明,优势种的时间和空间生态位宽度没有一致位序,剑尖枪乌贼和中国枪乌贼分别占据最大的时间(1.32)和空间生态位宽度(3.90),而时间和空间生态位宽度最小的物种分别是金乌贼(0.98)和杜氏枪乌贼(2.04)。虽然时间生态位重叠在数值上显著高于空间生态位重叠,但二者均是在中国枪乌贼、剑尖枪乌贼、火枪乌贼等种对间有较高重叠,而杜氏枪乌贼与其余4个优势种的重叠较低。相关分析表明,在时空尺度上生态位宽度与丰度的变化均呈极显著负相关。生态位可反映物种资源量时空变化信息,丰富了传统渔业群落研究方法。     

Phenological asynchrony in plant–butterfly interactions associated with climate: a community‐wide perspective

Although much information has been accumulated on the effects of climate change on particular species worldwide, research aimed at assessing how such change influences biotic interactions from a community‐wide perspective is still in its infancy. We contribute to filling in this gap by analyzing a 17‐year (1996–2012) dataset that includes records of flower‐visitation interactions between 12 butterfly species and 17 plant species in a coastal wetland area in northeastern Iberian Peninsula. We assessed the extent to which temporal asynchronies between plants and adult butterflies are influenced by different climatic variables that affect both plant and insect phenologies. Temperature and degree of aridity at various monthly summaries were used as predictors of the plant–butterfly phenological asynchrony. We identified the seasonal window with the greatest effect on asynchronies for two butterfly generations (spring and summer), and assessed whether the magnitude of asynchrony is associated with the level of butterfly specialization. We used generalized linear mixed models considering a total of 39 plant–butterfly interactions. Average asynchrony was higher in the spring generation and dry conditions during winter lead to decreased temporal overlap with flowers in this butterfly generation, whereas dry conditions in the spring lead to decreased temporal overlap in the summer butterfly generation. The magnitude of the effect was consistently small at the community level (all interactions pooled). Moreover, no clear climatic trend over the study time frame was detected. Finally, specialized and generalized butterflies in their resource use as adults were similarly vulnerable to asynchronies, in contrast to previous predictions of greater mutualistic disruptions in species with narrower niches. We conclude that a least in the Mediterranean region, phenological asynchronies might be more affected by aridity level than by temperature itself, and thus the former can be a key climatic trait to make better predictions in this region.     

Coexistence of cryptic rotifer species: ecological and genetic characterisation of Brachionus plicatilis

1. The coexistence of five cryptic species of the rotifer species complex Brachionus plicatilis was investigated in four coastal Mediterranean ponds. Monthly sampling was undertaken for 15 months and species were characterised using allozyme electrophoresis. 2. We describe species‐diagnostic allozyme loci that can be used for rapid identification of these species. 3. The five species overlapped to some extent in their temporal use of the ponds, although some seasonal segregation was observed. 4. The match between temporal and spatial distribution and limnological conditions suggested ecological specialisation in some cases, although we found striking examples of extensive seasonal overlap. 5. Our results indicate that sympatry of cryptic rotifer species is largely because of seasonal ecological specialisation, which allows seasonal succession and partitioning of resources. The processes that might be involved in the long periods of overlapping seasonal distributions of species which are potentially competitors are discussed. This example illustrates that the ‘paradox of the plankton’ is more the rule than the exception.     

Niche Overlap and Network Specialization of Flower-Visiting Bees in an Agricultural System

Different resource use strategies manifest as differences in the realized niches of species. Niche segregation may involve several dimensions of the niche, such as diet, space, and time. We measured the level of redundancy and complementarity of a bee–plant interaction network in an agricultural system. Because flower resource diversity is high and resource abundance associated with flowering phenology varies throughout the year, we hypothesized that trophic overlap in the community would be low (i.e., high niche complementarity). In contrast, we expected a combination of physiological constraints and exploitation competition to create high temporal overlap, leading to high redundancy in the time of use of floral resources. Dietary overlap was low (NO_ih?=?0.18): niches of 88% of species pairs had less than 30% overlap. In contrast, temporal overlap was intermediate (NO_ih?=?0.49): niches of 65% of species pairs had 30% to 60% overlap. Network analysis showed that bees separated their dietary niches and had intermediate complementary specialization (H₂′?=?0.46). In terms of their temporal niches (H₂′?=?0.12), bees were generalists, with high temporal redundancy. Temperature was not a key factor in the determination of niche overlap, suggesting that environmental factors do not likely have a primary role in determining high redundancy in the temporal use of floral resources. Rather, temporal overlap is likely associated with the timing of nectar production by flowers. Our results suggest that bees partition a wide variety of available floral resources, resulting in low dietary overlap and intermediate temporal overlap.     

Ecological comparisons of robber fly species (Diptera: Asilidae) coexisting in a neotropical forest

Summary Data regarding seasonal abundance, microhabitat preference, and diet were collected over 3 field seasons for adults of 15 robber fly species on Barro Colorado Island, Panama. The species comprised 2 distinct thermal guilds; light-seeking (hereafter LS) species foraged in sunlit areas, while shade-seeking (SS) species foraged only in deep shade. All species were rare during the dry season. During the rainy months, most SS species had flight periods of 2–3 months, and no temporal segregation was apparent. In contrast, most LS species had flight periods of only 4–6 weeks, and a distinct sequence of occurrence was evident during 2 years of censusing. Most SS and LS species displayed a pronounced specificity for perches of a particular substrate type. However, the ranges of perching heights utilized varied considerably among species. Dietary comparisons revealed that mean and maximum prey sizes increased with increasing robber fly size, while minimum prey sizes were constant. Robber fly species <20 mg fed primarily upon nematocerous Diptera, whereas larger species generally fed upon a wide variety of prey types. For each thermal guild, the actual mean overlap for a particular niche dimension was compared to mean overlaps generated by randomly assigning species to thermal guilds. No significant differences from the random null hypothesis were found for the SS guild. However, niche complementarity between dietary and spatial overlaps and dietary overlap was apparent among the 5 large LS species.     

Dietary shifts,niche relationships and reproductive output of coexisting Kestrels and Long-eared Owls

Summary Food samples of breeding Kestrels (Falco tinnunculus) and Long-eared Owls (Asio otus) were collected in the peak and low phase of their preferred prey (Microtus voles) in western Finland. Diets of pairs that bred as neighbours (1 km) with interspecifics were compared with those of non-neighbours. In both species, neighbouring pairs fed less on Microtus voles and more on alternative prey than did non-neighbours. Competition theory predicts that diet overlap should be lower during prey shortage and that diet similarity should be especially reduced in neighbouring pairs. Observations were consistent with expectations: diet similarity was lower in the low vole years and neighbouring pairs showed less diet overlap that non-neighbours. Differences in habitat composition and prey availability at the sample sites should not confuse the results. In addition to the high diet similarity, hunting habitats and nest sites of the species overlapped almost completely; they only showed clear temporal segregation in hunting. Probably because of food competition, the neighbouring pairs of both species produced significantly fewer young than the non-neighbours. These results contrast with the view that the diet composition and dietary shift of rodent-feeding predatory birds can be interpreted in terms of simple opportunistic foraging. In the breeding season, interspecific competition for food seems to be an important factor that affects the niches of these species, especially in northern areas, where the seasonal low phase of voles in spring and the number of alternative prey are lower than in more southern areas.     

Seasonal climatic niches diverge in migratory birds

Migratory birds occupy different geographical areas during breeding and non-breeding periods, and thus different factors may determine their range limits depending on each season. One such factor is the spatial climatic component of the niche, which is widely used to model species distributions, yet the temporal component is often neglected and is generally assumed to be constant. We tested the hypothesis that the climatic niche is conserved between breeding and non-breeding areas in 355 bird species migrating through Eurasian–African flyways. For this, we performed niche overlap analyses and compared niche differences between sister or phylogenetically closely related species, as well as linking the differences to migratory distances. For more than 80% of the species, there was no or very little overlap between their breeding and non-breeding climatic niches. For most closely related species, the degree of overlap of their breeding climatic niches was larger than the overlap observed within each species, but not for their wintering climatic niches, suggesting a phylogenetic conservation of breeding climatic niches. Finally, there was a clear negative relationship between migratory distances and climatic niche overlap within each species. Our results confirmed that the climatic niche of most Eurasian–African migratory species differs between both breeding and non-breeding ranges, suggesting distinctive seasonal climatic requirements. Given these results and the geographically uneven effects of climate change, the impact of global change is likely to have different effects in each seasonal range. Hence, both breeding and non-breeding climatic data need to be considered when using species distribution models.     

Seasonal patterns of reproductive activities among deep-sea benthic copepod species in the bathyal Sagami Bay, central Japan

Little is known about the life histories of the deep-sea metazoan meiobenthos. At a bathyal site (depth 1430 m) in Sagami Bay, central Japan, temporal changes in abundance and reproductive activity of deep-sea benthic copepods were investigated for eight abundant species that composed about 50% of total individuals, based on samples collected before fresh organic matter increased in the sediment (December 1996 and 1997), 1 month thereafter (June 1997 and May 1998), and a few months after the event (August 1997 and 1998). Densities of adults of these species fluctuated among samples (the total abundance was 5–30 individuals/10 cm²), but did not show any seasonal trend. Strong evidence for competitive relationships among species could not be detected, and there was no significant negative correlation in abundance between any species pair. The percentage of ovigerous females among total adult females of Schizopera sp. 1 differed significantly by month. Furthermore, the adult sex ratio of the species appeared to fluctuate temporally. These suggest a temporal change in reproductive activity and synchronized growth of Schizopera sp. 1. There was no temporal trend, however, in any parameter for the other species. Mean egg number per brood and egg diameter differed among species, but did not change seasonally in any species. Our study suggests the rarity of seasonal breeding species among the deep-sea benthic copepods, one of the major metazoan meiofaunal groups, as well as among other macro-megafaunal metazoans.     

Acoustic niche partitioning among seven cuckoo species in a forest in eastern China

Acoustic communication among birds plays an important role in attracting mates and defending territories. For the successful transmission of songs, individuals of different species often avoid singing at the same time to reduce acoustic interference from background noise and overlapping signals from heterospecifics. Such behavioural acoustic niche partitioning may occur especially among closely related species due to their ecological similarities. In this study, we recorded bird sounds in a subtropical forest in China in May–June 2019 and detected seven cuckoo species. Extracting characteristics of the cuckoo calls, we found that only four of the 21 pairs of species overlapped in frequency range, and 19 pairs were classified accurately using a linear discriminant analysis classifier based on their features. The remaining two species pairs could be separated based on temporal or spatial distribution patterns. We also analysed the temporal distribution patterns and overlap time of the calls, finding that the seven species exhibit partitioning in at least one of three acoustic dimensions (site, frequency, activity time). We conclude that the seven sympatric cuckoo species were strongly partitioned in acoustic signal space and minimally masked each other's signals.     

Seasonal dietary niche contraction in coexisting Neotropical frugivorous bats (Stenodermatinae)

Tropical dry forests are characterized by punctuated seasonal precipitation patterns that drive primary production and the availability of fruits, seeds, flowers, and insects throughout the year. In environments in which the quantity and quality of food resources varies seasonally, consumers should adjust their foraging behavior to maximize energy intake while minimizing overlap with competitors during periods of low food availability. Here, we investigated how the diets of frugivorous bats in tropical dry forests of NW Mexico varied in response to seasonal availability and how this affected dietary overlap of morphologically similar species. We performed stable isotope analyses to understand temporal and interspecific patterns of overall isotopic niche breadth, trophic position, and niche overlap in the diet of six frugivorous species of closely related New World leaf-nosed bats (family Phyllostomidae, subfamily Stenodermatinae). We estimated seasonal changes in resource abundance in two complementary ways: (a) vegetative phenology based on long-term remote sensing data and (b) observational data on food availability from previously published insect and plant fruiting surveys. In all species, there was a consistent pattern of reduced isotopic niche breadth during periods of low food availability. However, patterns of niche overlap varied between morphologically similar species. Overall, results from our study and others suggest that seasonal food availability likely determines overall dietary niche breadth in Phyllostomidae and that despite morphological specialization, it is likely that other mechanisms, such as opportunistic foraging and spatiotemporal niche segregation, may play a role in maintaining coexistence rather than simply dietary displacement.     

Feeding of an Iberian stream cyprinid assemblage: seasonality of resource use in a highly variable environment

Food resource use by seven cyprinids from an Iberian stream was analysed over 9 months. Differences in food resource use were found both between species and within species between seasons. Plant material was a more important food for carp, nase, goldfish and barbel than for gudgeon, roach and chub, irrespective of the season. Chironomid larvae were the staple animal food for the former five species throughout the year. Roach and chub, especially the latter, displayed large seasonal variations in prey use, with chironomid larvae only being important during autumn. Ephemerellid nymphs and ephemeropteran imagos dominated the animal diet of chub during spring and summer, respectively. Dipteran adults and Formicidae were the most important prey for roach during spring and summer, with other common prey being ephemerellid nymphs and hydropsychid larvae. Food resource overlap among the three dominant species (roach, barbel and chub) displayed a large seasonal variation. High overlaps were observed during autumn when these species used the same resources. During summer overlaps were much lower with each species specialising on different prey. The remaining less abundant species had large diet overlaps amongst themselves and with barbel, over all seasons. It is suggested that morphological constraints, habitat partitioning and temporal changes in food resource limitation may be involved in producing these patterns of food resource use.     

Development of dietary specializations in a summer community of juvenile fishes

Synopsis Patterns of food use and food availability were analysed in a species rich summer weedbed community of juvenile lake fish to elucidate ontogenetic and ecological adaptations facilitating species co-existence and rapid growth. It was found that: (a) the community was based on the period of high seasonal invertebrate abundance linked to the spring-summer proliferation of macrophytes: food was not limiting; (b) diet separations of individual fish species were high. In mid-July when nine species were present, Schoener diet overlap values exceeded 0.25 in only ten of 36 pairs of combinations. This contrasted with findings from a preceding May-June community of larval fish (Keast 1980); (c) mouth size helped channel the species towards different diets; and (d) diets of the early juveniles were distinct from those of the larvae, and late juveniles and adults of their species. At both the species and community level, ontogenetic and ecological developments have evolved in response to the opportunities created by an annually repetitive resource base.     

浙江南部近海主要虾类的时空生态位及种间联结性

根据2015年11月(秋季)、2016年2月(冬季)、5月(春季)、8月(夏季)在浙江南部近海的调查数据,运用生态位宽度、生态位重叠值、方差比率法、卡方检验、联结系数以及种对共同出现百分率对主要虾类间的关系进行研究.结果表明:1)在时间维度上,扁足异对虾的生态位宽度值最大;在空间维度上,中华管鞭虾的生态位宽度值最大;在时空二维上,扁足异对虾的生态位宽度值最大;2)在时间维度上,假长缝拟对虾和细巧仿对虾的生态位重叠值最高,拥有最大的时间生态位重叠值(>0.99);在空间维度上,凹管鞭虾、中国对虾、假长缝拟对虾和滑脊等腕虾的生态位重叠值最高(0.96);在时空二维上,中国对虾和凹管鞭虾的生态位重叠值最高;3)方差比率法分析表明,主要虾类总体呈显著正关联,其中有13个种对间的联结性达到显著水平(χ²≥3.841),联结系数(AC)和共同出现百分率(PC)表明种间联结性趋于正相关.本研究结果为探讨虾类的生态位分化、种间竞争及对环境的适应性研究提供了数据资料.     

Competition between mullet fry

The fry of Liza ramada, L. aurata, L. saliens, Chelon labrosus and Mugil cephalus in a lagoon in NE Spain fed mainly on zooplanktonic crustacea, such as cyclopoids, calanoids and cladocerans, but adult chironomids were also important. A high trophic and temporal overlap was found between the fry of several of these species. Trophic overlap was asymmetrical for almost all the species pairs and niche breadth expanded for the less competitive species when they were alone in the estuary. In contrast, niche breadth did not expand for the most competitive species ( L. ramada ) when it was alone. These results suggest that competition was occurring among these species, but experimental evidence is needed to prove its existence.     

Flowering phenologies of hummingbird plants from the temperate forest of southern South America: is there evidence of competitive displacement?

Plant species sharing pollinators may compete through pollination. This type of competition may lead to overdispersed flowering phenologies. However, phenological segregation is difficult to detect in seasonal climates. We compared patterns of phenological overlap in assemblages of ornithophilous plants from three localities of the temperate forest of southern South America with those generated by four different null models. These species were all visited and presumably pollinated by a single species, the hummingbird Sephanoides sephaniodes, which makes this situation ideal to evaluate the role of pollination‐mediated competition. For one site, we compiled data on flowering phenologies for three different years. Three models considered the flowering period of the whole assemblage of ornithophilous plants as the phenological window within which flowering phenologies were randomized, but made no further assumptions on how species should be distributed within that temporal frame. The fourth model assigned differential probabilities to different time intervals based on the flowering onset of non‐ornithophilous plant species. Observed mean pairwise overlaps for all localities and years were well within the interval defined by the 2.5 and 97.5% percentiles of the randomized distribution of expected mean pairwise overlaps according to models 1–3. However, model 4 showed a consistent trend towards overdispersion of ornihophilous phenologies, which show a shift towards mid‐ to late‐summer flowering. Thus, to the extent that the distribution of flowering of non‐ornithophilous species reflects the constraints imposed by a highly seasonal climate, our results provide support to the proposal that pollinator sharing may cause evolutionary displacement or ecological sorting of flowering phenologies. Other factors, such as phylogenetic inertia, could also contribute to explain extant phenological patterns in the highly endemic ornithophilous flora of the temperate forest of southern South America.     

The effect of mean and variance in resource supply on survival of annuals from Mediterranean and desert environments

Resource availability is often characterized by mean annual amounts, while ignoring the spatial variation within habitats and the temporal variation within a year. Yet, temporal and spatial variation may be especially important for identifying the source of stress in low productivity environments such as deserts where resources are often pulsed and resource renewal events are separated by long periods of low resource availability. Therefore, the degree of stress will be determined in part by the length of time between recharge events. Here, we investigated the effect of timing and total amount of water application on two congeneric pairs, each with a population from a low (desert) and a high (Mediterranean) productivity habitat. As expected, highest survival and greatest growth were found at low or intermediate recharge intervals, and the magnitude of response to increases in total seasonal amounts was greater for Mediterranean species than desert species. The species that had greater survival switched in the hierarchy under high total water depending on interval length. These results demonstrate that temporal variation in resource availability can be as important as annual total amounts for plant performance and that response to temporal dynamics can vary between species. This has implications for community-level processes, as competitive hierarchies may switch based on resource dynamics rather than only total availability.     

Home range of the raccoon dog (Nyctereutes procyonoides) in southern Finland

Home ranges, relationships between individuals and dispersal among raccoon dogs ( Nyctereutes procyonoides ) were studied in southern Finland in 1989-91. The average maximum home range, calculated by the harmonic mean method. was 9·5 km² and the core area (85% utilization) 3·4 km². There were no statistically significant annual. seasonal or sexual differences in the size of the average core area of adults, but the home ranges of juveniles in autumn were larger than those of adults. However. the maximum home ranges of adults were larger in autumn than in summer, especially those of males, which were conspicuously small in summer and large in autumn. The core areas of adjacent pairs did not usually overlap in the pup-rearing season. but in autumn some home ranges shifted and there was much more overlap. The home ranges of the male and female of a pair overlapped almost totally, and a male and a female sharing the same home range also travelled together or close to each other, thus supporting the idea that the raccoon dog is monogamous in Finland. None of the adults left the study area, but 38% of the juveniles were recovered further than 10 km from the marking place during the first autumn.