Effects of newly planted hedges on ground-beetle diversity (Coleoptera, Carabidae) in an agricultural landscape

The diversity of ground-beetle communities (Coleoptera. Carabidae) was studied to assess the short-term impact of new hedges planted in an intensive agro-ecosystem. Hedges represent a new and undisturbed habitat for those polyphagous predators and may provide increased prey availability. Carabids were sampled with pitfall traps in a hedge and an adjacent cultivated field during the whole activity period of these insects to assess the effect of distance from the hedge on species diversity. Fenced pitfall traps were also used to estimate absolute population densities. Several diversity indices were calculated at various sampling levels (total area, distance treatment, trap). Kendall's coefficient of rank correlation between communities at adjacent distances showed that the greatest changes in species relative abundances occurred close to the hedge. Indices of species richness, dominance concentration, equitability and Fisher's a all indicated a significant decrease in species diversity with increasing distance from the hedge. These trends are explained by two complementary factors. First, the number of species decreased significantly with distance from the centre of the hedge. Second, the various species had different spatial patterns of total capture and absolute density. Four groups of species can thus be distinguished: species restricted to the hedge, species preferring the hedge, species preferring the crop, and species unaffected by the hedge. The respective roles of small-scale abiotic changes in habitat structure and differences in prey availability are discussed.     

Fragmentation in calcareous grasslands: species specialization matters

Habitat fragmentation resulting from anthropogenic land-use change may negatively affect both biodiversity and ecosystem structure and function. However, susceptibility to fragmentation varies between species and may be influenced by for instance specialization, functional traits and trophic level. We examined how total and specialist species richness, species composition and functional trait composition at two trophic levels (vascular plants and sap-feeding hoppers) vary with habitat fragmentation (patch size and connectivity) in dry calcareous grasslands in southeast Norway. We found that fragmentation affected plant and hopper species composition both totally and of habitat specialists, but with a net species loss only for the specialists, indicating greater susceptibility of specialized species. Reductions in patch size and increasing isolation negatively affected plant specialists with different sets of traits, effectively reducing the number of species with trait combinations suitable to persist in small and isolated patches. Fragmentation influenced trait composition of the total hopper community, but not of habitat specialists. A lesser degree of habitat association could explain why hoppers, despite belonging to a higher tropic level, seemed to be less susceptible to fragmentation than plants. Nonetheless, our study shows that habitat fragmentation affects both species richness, species composition and trait composition of plants and hoppers, indicating that fragmentation leads not only to a loss of species, but also alters dominance hierarchies and the functionality of grassland communities.     

The Bromeliad Microcosm and the Assessment of Faunal Diversity in a Neotropical Forest1

The faunas of tank bromeliads were sampled over two years in three forest types at different elevations in the Luquillo Experimental Forest, Puerto Rico, and the diversity of their animal communities compared. Bromeliad plants behaved as islands in that, within forests, the species richness and abundance of their animal communities were significantly and positively correlated with increase in plant size. The amount of canopy debris they accumulated was similarly correlated with increase in plant size. Overall diversity was lowest in the dwarf forest, where plants were uniformly small. Animal communities were stable from year to year, and could be characterised for each forest type and for compartments within the plant. They showed a pattern of high dominance, which increased with elevation (Mc-Naughton index 37, 54, and 73, respectively, for the tabonuco, palo Colorado, and dwarf forest). Alpha-diversity for sites sampled in each year reflected net primary productivity (NPP) of the forest, declining with increasing elevation when animal abundance measures were used (jackknife estimates of Simpson's diversity index 6.54 & 11.04 [tabonuco], 3.53 & 6.22 [palo Colorado], and 2.75 & 2.17 [dwarf forest]). Species richness over the two years, however, was highest in the intermediate palo Colorado forest (187 species), compared to 146 and 88 in the tabonuco and dwarf forests, respectively. These figures were close to jackknife estimates of maximum species richness. The difference in species richness between tabonuco and palo Colorado forests was significant in one year only. In addition to NPP, other factors, such as litter quality and the structural complexity of the habitat in the palo Colorado forest, may have influenced species richness. The most abundant species in individual plants were also the most widely occurring, confirming known patterns of abundance and distribution in other functional groups. Diversity within bromeliad microcosms at different elevations supported known relationships between diversity, productivity, and habitat complexity along gradients and was not related to differences in the total bromeliad habitat available for colonization.     

Measuring the effects of invasive species on the demography of a rare endemic plant

The impacts of invasive species are among the greatest threats to the persistence of native species and communities. Yet most work on rare plants has focused on issues such as habitat fragmentation and genetic diversity, while few studies have quantified the impacts of invasive plants on native ones or investigated the underlying mechanisms of those impacts. I used removal experiments to assess the effects of invasive grasses on the seedling and adult demography of an endangered California endemic, Oenothera deltoidesssp. howellii. Invasive plant removal significantly increased O. deltoides seedling recruitment, but had no effect on adult plants. Differences in seedling recruitment were primarily driven by greatly increased seedling emergence rates in removal plots, although there was also some evidence of higher seedling survivorship with invasives removal. Differences in habitat type strongly influenced both the effects of removal treatments and O. deltoides demography, with areas that support natural recruitment showing weaker treatment effects and higher overall recruitment, but lower adult survivorship, compared to those under restoration through planting. These results indicate that inhibition of germination due to reduced soil disturbance, rather than resource competition, appears to be the strongest impact of invasive plants on this rare endemic. Although previous work has documented the importance of changed disturbance regimes in generating invasion impacts, invader effects on rare plants are generally presumed to result from resource competition. Studies like this one highlight the need for a greater emphasis on understanding the mechanisms by which invasive plants impact native ones, and the importance of such information in designing conservation and management strategies.     

Testing simple indices of habitat proximity

Simple measures of habitat proximity made primarily on the basis of land cover are widely used in the ecological literature to infer habitat connectivity, or the potential for animal movement among resource patches. However, such indices rarely have been tested against observations of animal movement or against more detailed biological models. We developed a priori expectations as to the types of study systems and organisms for which various habitat proximity indices would be best suited. We then used data from three study systems and four species to test which, if any, of the indices were good predictors of population-level responses. Our a priori expectations about index performance were not upheld. The indices that consider both habitat area and distance from the focal patch were highly correlated with each other, suggesting that they do index similar quantities. However, none of the indices performed well in predicting population response variables. The results suggest that the pattern of habitat cover alone may be insufficient to predict the process of animal movement.     

Temperature relations of photosynthetic response in populations of Verbascum thapsus L.

Summary Seedlings representative of Verbascum thapsus L. populations from thermally diverse habitats were grown under uniform, controlled conditions. The plants were used to obtain temperature response curves for net photosynthesis over a range of 15–40°C. In general, all experimental plants exhibited similar rates of net photosynthesis at 20, 25, 30, and 35°C. Plants representative of cool habitat populations (high-latidude and high-altitude) had greatest rates of net photosynthesis at the lower temperatures and much lower rates at 40°C. Plants representative of warm habitat populations (low-latitude and low-altitude) exhibited rates of net photosynthesis at 40°C which were nearly twice those of plants representative of cool habitat populations. Carbon dioxide transfer resistances are discussed with reference to plant control of photosynthesis at different temperatures. Patterns of photosynthesis and resistance response among plants representative of different habitats suggest ecotypic variation has occurred only to a very limited extent. Therefore, the patterns exhibited by experimental plants suggest that Verbascum thapsus' success in a number of diverse sites is related to the ability of all members of the species to photosynthesize over a broad range of temperatures.     

Habitat preferences of small mammals in tropical open-forest of the Northern Territory

Pattern analysis was used to investigate the habitat preferences of five small mammal species in tropical open-forest of the Northern Territory. Fifty-one sites were classified by faunal abundance and the groups examined for significant differences in vegetation structural attributes and plant species in both dry and wet seasons. The omnivore Isoodon macrourus showed strong association with floristic and vegetation structural attributes only in the dry season, when areas with a dense understorey of small trees and shrubs and a high percentage of leaf litter cover were favoured. Of the two primarily carnivorous species, Antechinus bellus was related strongly with floristic and structural attributes in both seasons and showed a consistent preference for areas with relatively dense low-level foliage (< 2m). By contrast, Dasyurus hallucatus was associated more with the structurally simple open-forest types. Of the two mainly herbivorous species Mesembdomys gouldii showed associations only withfioristics in both seasons, while the habitat relationships of Trichosurus arnhemensis were very weak due to its low abundance in the study area. The number and strength of animal/habitat relationships were greatest in the dry season. Forest types with dense mid-level foliage and abundant hollow logs and leaf litter had the greatest mammal richness and abundance; these areas may be critical to the survival of local mammal populations. A comparison of site-groups, defined independently on the basis of fauna, floristics or structure, showed that animal groups overlapped one to six of the habitat groups. The animal's perception of s‘habitat’ may thus differ from that of humans, or that defined by measurement of habitat attributes.     

Comparisons of butterfly richness and abundance measures in prairie and barrens

Transect surveys of adult butterflies were conducted along fixed routes at 27 study sites grouped into three subregions of tallgrass prairie and one subregion of pine-oak barrens in the midwestern USA. Within subregion, each site was visited the same number of times over 5–7 years on similar dates with similar weather. For each site, five indices of species richness and/or abundance were calculated both for total butterflies and for specialist species primarily restricted to native herbaceous vegetation. These indices were then analysed as to how much they agreed or conflicted in site ranking and how site rankings based on total butterflies compared to those based on specialists. Variation in site ranking by different indices was relatively low. Mean site rank by specialist indices covaried significantly with mean site rank by indices for total butterflies. Numerous studies have shown that on a regional scale, areas of higher richness for all species in a taxonomic group are different habitat types (based on amount of canopy or degree of degradation) from hotspots for that taxon's subset of species of conservation concern (endemics or specialists). But in this study, within a habitat type, site rankings based on total butterflies significantly tended to agree with site rankings based on specialist butterflies. This suggests that site prioritization and management favouring specialist butterflies would also favour the overall butterfly fauna possible in the same habitat.     

Seasonal and spatial patterns of population density in the marine macroalga Mazzaella splendens (Gigartinales, Rhodophyta)

Insight into demographic processes that operate at larger spatial scales can be achieved through studying local populations when a particular species of interest is examined over time, by many investigators, in a variety of locations. On the west coast of North America, Mazzaella splendens (Setchell et Gardner) Fredericq is such a species of interest. A synthesis of local demographic studies of M. splendens from the late 1960s to the present reveals a pattern that is potentially common to the larger natural populations. This is the pattern: population density is high in summer and low in winter for both alternate free‐living life history phases of M. splendens. The magnitude of this seasonal change decreases in increasingly wave‐exposed habitats. In wave‐sheltered habitats there is a seasonal alternation from summer haploid to winter diploid dominance. This alternation gradually changes to constant diploid dominance as wave exposure in the habitat increases. Changes in population density are primarily a function of appearances and disappearances of perennating basal crusts (genets), as modules are produced or lost, rather than differential module production by genets of one phase over those of the other. To test the generality of this pattern, we examined seasonal changes in density, in local populations of M. splendens, in both a wave‐sheltered and a wave‐exposed habitat at Second Beach, Barkley Sound. Greater seasonal fluctuation in population density at wave‐sheltered, compared to wave‐exposed habitats is supported as a pattern potentially common to the natural populations of M. splendens. A change from summer haploid dominance in wave‐sheltered areas to summer diploid dominance in wave‐exposed areas is similarly supported. All changes in population density were the result of appearances and disappearances of genets rather than differential module production by haploid versus diploid basal crusts, also consistent with previous observations. A seasonal alternation in phase dominance, however, was absent from the wave‐sheltered site at Second Beach, Barkley Sound for 3 consecutive years. Seasonal alternation in phase dominance of M. splendens appears dependent on local conditions and is not common to all natural populations.     

Temperature and salinity regulation of growth and gas exchange of Salicornia fruticosa (L.) L.

Summary Salicornia fruticosa was collected from a salt marsh on the Mediterranean sea coast in Libya. Growth and gas exchange of this C₃ species were monitered in plants pretreated at various NaCl concentrations (0, 171, 342, 513 and 855 mM). Maximum growth was at 171 mM NaCl under cool growth conditions (20/10° C) and at 342 mM NaCl under warm growth conditions (30/15° C) with minimum growth at 0 mM NaCl (control). Net photosynthesis (Pn) was greatest in plants grown in 171 mM NaCl with plants grown at 513 and 855 mM having lowest rates. Maximum Pn was at 20–25° C shoot temperatures with statistically significant reductions at 30° C in control plants while salt treated plants showed such reductions at 35° C. Salt treatments increased dark respiration over the control at 171 and 342 mM but reduced it at higher concentrations. Photorespiration was reduced by salt treatment and increased by increasing shoot temperature. Greatest transpiration was in 171 mM NaCl treated plants and increasing shoot temperature increased transpiration in all treatments. Stomatal resistance to CO₂ influx was influenced only moderately by temperature while increasing salinity resulted in increased stomatal resistance. In general both temperature and salinity increased the mesophyll resistance to CO₂ influx. The species seems adapted to the warm saline habitat along the Mediterranean sea coast, at least partially, by its ability to maintain relatively high Pn at moderate NaCl concentrations over a broad range of shoot temperatures.     

塔里木荒漠河岸林异质生境物种多样性比较与其测度指标筛选及评价

选择合适的物种多样性测度指标与多样性指数是进行群落多样性研究的基础工作。依据塔里木河上游荒漠河岸林样地调查资料,分别采用重要值、盖度和多度为测度指标比较了反映群落物种丰富度、多样性、均匀度和优势度12种多样性指数与异质生境群落多样性特征,并对多样性指数进行了相关分析与评价。结果表明,荒漠河岸林异质生境群落物种组成种类差异明显,轮南镇胡杨群落物种丰富度与多样性指数最高,水工三连灰胡杨群落多样性最低,土壤水盐的空间异质性是引起荒漠植被空间分布与群落多样性差异的主导因子。表征荒漠群落多样性以重要值和盖度为测度指标优于多度指标,其中以重要值为测度指标来反映群落多样性更为合理。相关与主成分分析表明,均匀度与多样性指数间的相关性高于丰富度与多样性指数,且多样性指数受均匀度、优势度指数受丰富度影响较大,反映出荒漠河岸林群落多样性主要决定于物种分布的均匀程度。12种多样性指数中Margalef丰富度指数（Ma）、Shannon-Weiner多样性指数（H）与Simpson多样性指数（D）能客观真实地反映异质生境荒漠植物群落多样性。同时,针对高度生境异质性的荒漠植物群落,还应综合考虑群落物种组成与生境特征,选择合适的多样性指数组合可更客观地反映荒漠河岸林群落多样性变化。     

Green Plants in the Red: A Baseline Global Assessment for the IUCN Sampled Red List Index for Plants

Plants provide fundamental support systems for life on Earth and are the basis for all terrestrial ecosystems; a decline in plant diversity will be detrimental to all other groups of organisms including humans. Decline in plant diversity has been hard to quantify, due to the huge numbers of known and yet to be discovered species and the lack of an adequate baseline assessment of extinction risk against which to track changes. The biodiversity of many remote parts of the world remains poorly known, and the rate of new assessments of extinction risk for individual plant species approximates the rate at which new plant species are described. Thus the question ‘How threatened are plants?’ is still very difficult to answer accurately. While completing assessments for each species of plant remains a distant prospect, by assessing a randomly selected sample of species the Sampled Red List Index for Plants gives, for the first time, an accurate view of how threatened plants are across the world. It represents the first key phase of ongoing efforts to monitor the status of the world’s plants. More than 20% of plant species assessed are threatened with extinction, and the habitat with the most threatened species is overwhelmingly tropical rain forest, where the greatest threat to plants is anthropogenic habitat conversion, for arable and livestock agriculture, and harvesting of natural resources. Gymnosperms (e.g. conifers and cycads) are the most threatened group, while a third of plant species included in this study have yet to receive an assessment or are so poorly known that we cannot yet ascertain whether they are threatened or not. This study provides a baseline assessment from which trends in the status of plant biodiversity can be measured and periodically reassessed.     

The habitats exploited and the species trapped in a Caribbean island trap fishery

We visually observed fish traps in situ to identify the habitats exploited by the U.S. Virgin Islands fishery and to document species composition and abundance in traps by habitat. Fishers set more traps in algal plains than in any other habitat around St. John. Coral reefs, traditionally targeted by fishers, accounted for only 16 % of traps. Traps in algal plain contained the highest number of fishes per trap and the greatest numbers of preferred food species. Traps on coral reefs contained the most species, 41 of the 59 taxa observed in the study. Acanthurus coeruleus was the most abundant species and Acanthuridae the most abundant family observed in traps. Piscivore numbers were low and few serranids were observed. Traps in algal plain contained the most fishes as a result of: ecological changes such as shifts in habitat use, mobility of species and degradation of nearshore habitat (fishery independent); and, catchability of fishes and long-term heavy fishing pressure (fishery dependent). The low number of serranids per trap, dominance of the piscivore guild by a small benthic predator, Epinephelus guttatus, and dominance of trap contents overall by a small, fast-growing species of a lower trophic guild, Acanthurus coeruleus, all point to years of intense fishing pressure.     

Monkeys in the Middle: Parasite Transmission through the Social Network of a Wild Primate

In wildlife populations, group-living is thought to increase the probability of parasite transmission because contact rates increase at high host densities. Physical contact, such as social grooming, is an important component of group structure, but it can also increase the risk of exposure to infection for individuals because it provides a mechanism for transmission of potentially pathogenic organisms. Living in groups can also create variation in susceptibility to infection among individuals because circulating levels of immunosuppressive hormones like glucocorticoids often depend on an individual’s position within the group’s social structure. Yet, little is known about the relative roles of socially mediated exposure versus susceptibility in parasite transmission among free-living animal groups. To address this issue, we investigate the relationship between host dominance hierarchy and nematode parasite transmission among females in a wild group of Japanese macaques (Macaca fuscata yakui). We use social network analysis to describe each individual female’s position within the grooming network in relation to dominance rank and relative levels of infection. Our results suggest that the number of directly-transmitted parasite species infecting each female, and the relative amount of transmission stages that one of these species sheds in faeces, both increase with dominance rank. Female centrality within the network, which shows positive associations with dominance hierarchy, is also positively associated with infection by certain parasite species, suggesting that the measured rank-bias in transmission may reflect variation in exposure rather than susceptibility. This is supported by the lack of a clear relationship between rank and faecal cortisol, as an indicator of stress, in a subset of these females. Thus, socially mediated exposure appears to be important for direct transmission of nematode parasites, lending support to the idea that a classical fitness trade-off inherent to living in groups can exist.     

Alterations in zooplankton community structure after selenium-induced replacement of a fish community: a natural whole-lake experiment

Most of the fish species in Belews Lake, a cooling reservoir in the Piedmont area of North Carolina (USA), were eliminated in 1976–77 because of selenium poisoning. Zooplankton samples collected in 1974–75, prior to the fish kill, when the lake's fauna included a regionally-typical assemblage of piscivores and planktivores at a density of 14000 ha^–1, were compared to those collected in 1984–86, when the piscine community was dominated by three planktivorous fish (Notropis lutrensis, Pimephales promelas and Gambusia affinis) at a density of 28000 ha^–1. Zooplankton diversity was similar in 1984–86 compared to that in 1974–75. However, densities of the predominant cladocerans (Bosmina longirostris, Pseudosida bidentata, Ceriodaphnia pulchella, Holopedium amazonicum, Daphnia parvula, D. ambigua) and copepods (Diacyclops thomasi, Mesocyclops edax, Tropocyclops prasinus, Skistodiaptomus pallidus, S. reighardi) declined, though the magnitude of the reduction was greatest for the cladocerans and S. reighardi. Densities of copepod nauplii and rotifers also decreased markedly. No colonizations or extinctions of crustacean species occurred between 1975 and 1986. Thus, while crustacean species richness (n = 18 species) remained the same, the relative proportions of individual species changed dramatically, most notably among the Cladocera. The observed changes in crustacean species densities and dominance are attributed to the replacement of the regionally-typical fish fauna by one consisting primarily of planktivores.     

不同生境中杉阔混交林物种多样性特征初步研究

根据生境因子应用主分量分析和动态聚类方法进行生境的划分,在此基础上分析不同生境中杉阔混交林群落数量特征。结果表明：不同生境中植物群落的主要优势种组成不一,其重要值也不同。不同生境中植物群落乔木层的物种数目、物种多样性、群落均匀度均有较大差异。海拔对不同生境中植物群落乔木层的物种数目、物种多样性和群落均匀度有很大影响,坡向则对个体总数和种类的影响较大。海拔和坡向对不同生境中植物群落乔木层生态优势度则无明显影响,应该重视不同生境中杉阔混交林多样性的保护。     

Population, habitat and genetic correlates of mycorrhizal specialization in the 'cheating' orchids corallorhiza maculata and C. mertensiana

Unlike photosynthetic plants, several distantly related nonphotosynthetic plants are highly specialized toward their mycorrhizal fungi. It is unknown whether this specialization varies geographically or is influenced by the environment. We have investigated these questions in the nonphotosynthetic orchids Corallorhiza maculata and C. mertensiana by amplifying fungal internal transcribed spacer (ITS) fragments from widespread mycorrhiza samples and then discriminating putative fungal species using ITS restriction fragment length polymorphisms (RFLPs). Three fungal species were found across 27 plants representing seven populations of C. mertensiana; 20 species were found across 104 plants and 21 populations of C. maculata. All fungi belonged to the Russulaceae, an ectomycorrhizal family. Partitioning of Simpson's diversity showed that 48% of the variance in occurrences of fungal species coincided with population boundaries in C. mertensiana, vs. 68% in C. maculata. This differentiation coincided with geography but not habitat in C. mertensiana. In contrast, likelihood ratio tests showed strong associations between fungal occurrence and both habitat and phenotype in C. maculata. For example, C. maculata populations growing under oaks had no fungi in common with nearby populations growing under conifers, and those above 2000 m had no fungi in common with those below 2000 m. However, plant genetic differentiation may underlie some of these patterns. C. mertensiana and C. maculata never shared fungal species, even when growing intermixed at the same site, demonstrating genetic control that was independent of habitat. Similarly, intermixed normal and pale-coloured variants of C. maculata had no fungal species in common. These results demonstrate fine-scale genetic influences and geographical mosaicism in a mycorrhizal interaction.     

基于结构方程模型分析荒漠啮齿动物优势种对不同放牧干扰的响应

放牧被认为是草地生态系统的主要干扰之一。许多研究表明,放牧影响了啮齿动物的个体条件、繁殖、种群动态、群落组成及群落多样性等多个方面。由于受传统统计学方法的限制,这些研究只是单独的对放牧作用进行假设检验,而没有将多个假设放在同一个框架内进行验证。2006—2011年,采用标志重捕法对内蒙古阿拉善荒漠区不同放牧生境中啮齿动物优势种的数量进行研究并使用结构方程建模的方法将可能影响荒漠啮齿动物优势种的环境因子(气候条件、土壤硬度、植物隐蔽、植物生物量等19个指标)与啮齿动物优势种种群动态结合后进行多假设检验,旨在找出不同放牧干扰下制约优势啮齿动物环境因子的发生途径。结果表明:气候条件对五趾跳鼠和三趾跳鼠有直接不利影响,隐蔽对于两足活动的五趾跳鼠有负效应,而对四足活动的子午沙鼠有正效应。植物生物量对五趾跳鼠有正效应,但对子午沙鼠有负效应。土壤硬度的增加间接的有利于五趾跳鼠,对子午沙鼠有直接的正效应。因此荒漠啮齿动物优势种种群动态是多个过程共同作用的结果,气候条件是驱动啮齿动物种群动态的根本原因,而放牧会因为改变植物隐蔽而影响啮齿动物在群落中的组成。     

Breeding ecology of the endemic Black Lark <Emphasis Type="Italic">Melanocorypha yeltoniensis</Emphasis> on natural steppe and abandoned croplands in post-Soviet Kazakhstan

Since the collapse of the Soviet Union in 1991, the abundance and distribution of many central Asian steppe birds have been affected by changes in agricultural land management, such as the abandonment of large areas of cropland and changing grazing patterns. However, the underlying population processes that drive patterns of abundance and distribution are poorly understood. We compared the population ecology of the Black Lark Melanocorypha yeltoniensis on natural steppe and abandoned cropland. Between 2009 and 2013, we used distance sampling to quantify Black Lark population density, monitored 220 nests to assess reproductive performance, and modelled habitat selection at several scales. Arthropod food availability was compared using pitfall traps. Mean population densities were three times higher on abandoned cropland compared to those in steppe, and varied with time since abandonment. Nest survival rates were significantly lower on abandoned cropland compared to steppe, probably due to higher predation pressure. Chick growth rates were also lower on abandoned cropland, despite higher insect availability in this habitat. Habitat selection was strongly influenced by grazing intensity and vegetation structure. We suggest that Black Larks are generally attracted to abandoned cropland because of its suitable vegetation structure and higher food availability. The results of a fecundity model suggested that the number of breeding attempts on abandoned cropland necessary to produce the same number of fledglings as one nesting attempt in steppe habitat was 2.04 in 2011 and 3.62 in 2013. However, a phenological analysis revealed that there were only two peaks in first egg dates, making more than two re-nesting attempts per year unlikely. Therefore, abandoned cropland could, at least in some years, be an ecological trap for the species. Our results illustrate that the effects of land-use change on animal populations should not only be assessed using species densities, but also incorporate detailed demographic analyses. If current densities in steppe habitat corresponded to maximum carrying capacity, overall population densities of Black Larks are likely to decline in the near future as availability of abandoned cropland as nesting habitat is currently decreasing.     

小兴安岭凉水自然保护区蝶类多样性

2012—2013年选取原始阔叶红松林、人工林、天然次生林和灌丛草甸4种典型植被生境,对小兴安岭凉水自然保护区的蝶类进行了系统研究。共捕获蝶类1438头,分属7科47属76种,4种植被生境中蝶类群落优势类群均为蛱蝶科,不同生境蝶类群落相似性与生境植被类型密切相关。计算分析了4种植被生境中蝶类多样性指数、物种丰富度、优势度指数、均匀度指数和种-多度关系,结果表明:3种森林生境蝶类多样性大于灌丛草甸,原始阔叶红松林蝶类具有最高的多样性指数、较高的物种丰富度、均匀度指数以及最低的优势度指数,种-多度分布为对数正态分布,说明环境质量优越,最适合蝶类生存和繁衍;灌丛草甸蝶类的多样性指数、物种丰富度和均匀度指数均为最低,而优势度指数最高,种-多度分布为对数级数分布,反映植物群落结构较单一,适合各种蝶类生存和繁衍的资源不足;天然次生林蝶类多样性指数、物种丰富度高于人工林,均匀度小于人工林,但前者种-多度分布为对数级数模型,后者为对数正态模型,说明在封山育林状态下,对森林植被组成进行适当合理的干扰,有利于森林的健康发展