Herbarium records identify the role of long‐distance spread in the spatial distribution of alien plants in New Zealand

Aim To use herbarium records to characterize important correlates of spatial spread, areal occupancy and clustering of 100 alien plant species of conservation concern in the North and South Islands of New Zealand. Location New Zealand. Methods Using herbarium data of 6294 records representing 100 alien plant species, we assessed spatial heterogeneity in the distribution of alien species by examining the role of major urban areas as sources of sampling bias. A novel method to account for spatial biases in sampling effort was developed and applied to two simple distance metrics: nearest‐ and furthest‐neighbour spread rate. The relative importance of these two distance metrics in determining the range, areal extent and dispersion of alien species across both the North and South Islands of New Zealand was also assessed. Results The spatial distribution of herbarium records was highly clustered with a significant bias towards the more populated regions. Once sampling bias was taken into account, there was no indication that species were found closer to these urban centres than might be expected based on sampling effort. The nearest‐neighbour spread rates were usually 1–5 km yr^?1 and correlated positively with the furthest‐neighbour spread rates that were an order of magnitude higher. Range and area increased and clustering decreased with higher spread rates and longer recording time span. The spread rates divided species into five groups that were clearly distinguishable in terms of the extent of their distribution and the degree of clustering. Species occurring on both islands did not exhibit similar spread rates or spatial patterns. Main conclusions The nearest‐ and furthest‐neighbour spread rates from herbarium records can explain the area and pattern of alien plant distributions and improve the understanding of the dynamics of their spread. Five groups emerge from the spread rates in relation to a null model. Fast‐spreading plants had the widest, least clustered distribution, which suggests widespread chronic problems; slow‐spreading plants had localized, but dense, clustered distributions, indicating acutely problematic weeds. These patterns appear robust and may be useful in predicting the future patterns of spread and in planning long‐term management strategies in New Zealand.     

Fine-grain pattern in Southern Cape plateau forests

Abstract. Regeneration levels, size class distributions and a nearest neighbour technique were used to describe apreliminary dynamics frameworkfortheplateauforests. Taken over a large area, most of the canopy dominants have a negative exponential distribution of stems > 10 cm dbh per size class. In small (0.04 ha) plots, if present as more than one stem, most species are present as both canopy (> 25 cm dbh) and understorey (10–15 cm dbh) individuals. The canopy dominants maintain their rank in the bank of advance regeneration (> 5 cm height < 10 cm dbh). However, relative numbers of all regeneration of most canopy individuals are not strongly correlated with canopy closure or local abundance of conspecific adults. The mean area of nearest neighbour polygons of canopy individuals around saplings of the more common species are small. In conclusion, most species appearto be shade tolerant and locally persistent conferring a fine grain on this forest. We support recent questioning of universality of the gaps/non gaps paradigm.     

The Influence of Matrix Size on Statistical Properties of Co-Occurrence and Limiting Similarity Null Models

Null models exploring species co-occurrence and trait-based limiting similarity are increasingly used to explore the influence of competition on community assembly; however, assessments of common models have not thoroughly explored the influence of variation in matrix size on error rates, in spite of the fact that studies have explored community matrices that vary considerably in size. To determine how smaller matrices, which are of greatest concern, perform statistically, we generated biologically realistic presence-absence matrices ranging in size from 3–50 species and sites, as well as associated trait matrices. We examined co-occurrence tests using the C-Score statistic and independent swap algorithm. For trait-based limiting similarity null models, we used the mean nearest neighbour trait distance (NN) and the standard deviation of nearest neighbour distances (SDNN) as test statistics, and considered two common randomization algorithms: abundance independent trait shuffling (AITS), and abundance weighted trait shuffling (AWTS). Matrices as small as three × three resulted in acceptable type I error rates (p < 0.05) for both the co-occurrence and trait-based limiting similarity null models when exclusive p-values were used. The commonly used inclusive p-value (≤ or ≥, as opposed to exclusive p-values; < or >) was associated with increased type I error rates, particularly for matrices with fewer than eight species. Type I error rates increased for limiting similarity tests using the AWTS randomization scheme when community matrices contained more than 35 sites; a similar randomization used in null models of phylogenetic dispersion has previously been viewed as robust. Notwithstanding other potential deficiencies related to the use of small matrices to represent communities, the application of both classes of null model should be restricted to matrices with 10 or more species to avoid the possibility of type II errors. Additionally, researchers should restrict the use of the AWTS randomization to matrices with fewer than 35 sites to avoid type I errors when testing for trait-based limiting similarity. The AITS randomization scheme performed better in terms of type I error rates, and therefore may be more appropriate when considering systems for which traits are not clustered by abundance.     

Species abundance patterns of plants in Swedish semi-natural pastures

This investigation is based on a species inventory m semi-natural pastures, remnants of an "old" traditional landscape, in Sweden The aim was to examine relationships between species richness and pasture area, neighbour pasture area, distance to nearest pasture, pasture heterogeneity and fertilization Species occurrences were also investigated individually for the same parameters Pasture area, neighbour pasture area and distance to nearest pasture were not found to influence species richness Habitat heterogeneity and indications that pastures had been influenced by fertilization were however associated with both species richness and species occurrences Heterogeneity had only positive effects whereas the effects of fertilization were only negative Species regional abundance pattern tended to be bimodal, as predicted by the core-satellite hypothesis No correlation between abundance and plant height, or seed size was found, as would have been expected if competitive dominance effects determined species regional abundance There was a close to significant tendency that pasture area was positively associated with occurrences of species with features favouring a high seed dispersal capacity We suggest that the previous history of pasture distribution and management may be of vital importance for present day species abundance pattern, even though this remains obscure in the recent landscape     

广西常绿阔叶林的聚类分析

本文用聚类分析法对取自广西不同地区的30个常绿阔叶林的样地资料进行了分类。样地间相似性的计算采用了Bray—Curtis距离和Euclidian距离公式。聚合策略是用最近邻体法、最远邻体法,中线法、形心法、组平均法、可变组平均法、可变法以及平方和增量法等八种聚合方法。结果证明,用聚类法所划分的类型与按优势种划分的类型既有相似之点,又有不同之处。但是聚类分析法可以对样地进行更为仔细的分离,即不但可把取自不同地区而优势种相同的归为一类,有时还可把它们划分开来;同时也会把优势种不同而地区相同的样地归并到一起。这反映了与地区的纬度、海拔等生境条件相联系的区系组成的变化。根据聚类分析结果把25个样地划分出7种类型,并在其中5类中找出了它的标志种,此外还对8种聚类法和等级划分阈值进行了讨论。     

海南岛吊罗山山地雨林物种多样性

在海南岛吊罗山热带山地雨林设置两５０００ｍ＾２的样地,分别从物种多样性指数,种－多度曲线,空间格局多样性,时间格局多样性,组成格局多样性对其进行了研究。结果表明海南岛吊罗山山地雨林物种多样性指数Ｓｈａｎｎｏｎ－Ｗｅａｖｅｒ和Ｓｉｍｐｓｏｎ指数分别为４．１９５和０．０２１,均匀度为０．８８０和２．９６２。     

Nearest-neighbour interactions in species-rich shrublands: the roles of abundance, spatial patterns and resources

We explored pairwise nearest‐neighbour interactions in four species‐rich shrubland plant communities, asking the question: how often is an individual of species j the nearest‐neighbour of species i? In the observed data and null models, less than 35% of the maximum possible number of nearest‐neighbour species pairs was present, and at three of the four sites the number of observed nearest‐neighbour pairs were significantly less than those occurring in simulated null communities. Many of the missing pairs included woody shrubs whose absence might be interpreted as evidence of site‐specific competition between larger growth forms for soil resources or space. Less than 5% of the pairs of species that occurred did so at frequencies different from that expected under random mixing, and many of these pairs were conspecific. Of the heterospecific pairs whose frequency differed significantly from random mixing there was a weak bias towards pairs occurring at higher rather than lower frequencies than expected. There was no evidence for asymmetry (interaction of species j with species i but not the reverse) in the frequency of species pairs. Nearest‐neighbour relationships are species‐specific rather than between plant functional types. The four sites form a soil nutrient and water availability gradient, and, according to the stress gradient hypothesis, positive species interactions should be most prevalent at the most stressful sites. However, we found the opposite: the site with the highest availability of resources had both proportionally the most heterospecific pairs, and the most conspecific and heterospecific species pairs with frequencies departing significantly from that expected under random mixing.     

Eukaryotic community distribution and its relationship to water physicochemical parameters in an extreme acidic environment, Rio Tinto (southwestern Spain)

The correlation between water physicochemical parameters and eukaryotic benthic composition was examined in Río Tinto. Principal component analysis showed a high inverse relationship between pH and most of the heavy metals analyzed as well as Dunaliella sp., while Chlamydomonas sp. abundance was positively related. Zn, Cu, and Ni clustered together and showed a strong inverse correlation with the diversity coefficient and most of the species analyzed. These eukaryotic communities seem to be more influenced by the presence of heavy metals than by the pH.     

A DNA barcode library for Germany′s mayflies,stoneflies and caddisflies (Ephemeroptera,Plecoptera and Trichoptera)

Mayflies, stoneflies and caddisflies (Ephemeroptera, Plecoptera and Trichoptera) are prominent representatives of aquatic macroinvertebrates, commonly used as indicator organisms for water quality and ecosystem assessments. However, unambiguous morphological identification of EPT species, especially their immature life stages, is a challenging, yet fundamental task. A comprehensive DNA barcode library based upon taxonomically well‐curated specimens is needed to overcome the problematic identification. Once available, this library will support the implementation of fast, cost‐efficient and reliable DNA‐based identifications and assessments of ecological status. This study represents a major step towards a DNA barcode reference library as it covers for two‐thirds of Germany's EPT species including 2,613 individuals belonging to 363 identified species. As such, it provides coverage for 38 of 44 families (86%) and practically all major bioindicator species. DNA barcode compliant sequences (≥500 bp) were recovered from 98.74% of the analysed specimens. Whereas most species (325, i.e., 89.53%) were unambiguously assigned to a single Barcode Index Number (BIN) by its COI sequence, 38 species (18 Ephemeroptera, nine Plecoptera and 11 Trichoptera) were assigned to a total of 89 BINs. Most of these additional BINs formed nearest neighbour clusters, reflecting the discrimination of geographical subclades of a currently recognized species. BIN sharing was uncommon, involving only two species pairs of Ephemeroptera. Interestingly, both maximum pairwise and nearest neighbour distances were substantially higher for Ephemeroptera compared to Plecoptera and Trichoptera, possibly indicating older speciation events, stronger positive selection or faster rate of molecular evolution.     

Abundance-variance and abundance-occupancy relationships in a marine host-parasite system: the importance of taxonomy and ecology of transmission

Abundance-occupancy and abundance-variance relationships are two of the most general macroecological patterns capturing essential fundamentals of the structuring of species distributions and are widely documented for free-living animal and plant species populations at different spatial scales. However, empirical data for parasites have been gathered using appropriate sampling designs only recently. We performed analyses across species of the variation in infection parameters and patterns of aggregation of the most widespread parasites in the marine sparid fish Boops boops across seven localities of two marine biogeographical regions, the North East Atlantic and the Mediterranean. We used a large dataset of multiple population samples replicated over time for 20 parasite species and carried out assessments both intraspecifically and interspecifically, across taxonomic and ecological groupings. This taxonomically diverse complex of species representing five major metazoan higher taxa with differing transmission ecologies allowed us to assess the effect of taxonomic and ecological determinants on the abundance-occupancy and abundance-variance relationships in the model marine host-parasite system. The results revealed that: (i) a power function, relating spatial variance to mean abundance, represents a suitable model for the spatial distribution of the species; (ii) prevalence, abundance and the degree of spatial heterogeneity are true species characteristics and differ consistently between higher level taxonomic groupings; (iii) infection parameters and abundance-variance relationship are dependent on host specificity and regional distribution patterns of the parasites; and (iv) the observed infection parameters agree well with predictions from the epidemiological negative binomial abundance-occupancy model built on parameters of Taylor's power law both within and across species.     

Yellow crazy ant (<Emphasis Type="Italic">Anoplolepis gracilipes</Emphasis>) invasions within undisturbed mainland Australian habitats: no support for biotic resistance hypothesis

Ants are highly successful invaders, especially on islands, yet undisturbed mainland environments often do not contain invasive ants, and this observation is largely attributed to biotic resistance. An exception is the incursion of Yellow crazy ant Anoplolepis gracilipes within northeast Arnhem Land. The existence of A. gracilipes within this landscape’s intact environments containing highly competitive ant communities indicates that biotic resistance is not a terminally inhibitory factor mediating this ant’s distribution at the regional scale. We test whether biotic resistance may still operate at a more local scale by assessing whether ecological impacts are proportional to habitat suitability for A. gracilipes, as well as to the competitiveness of the invaded ant community. The abundance and species richness of native ants were consistently greater in uninfested than infested plots but the magnitude of the impacts did not differ between habitats. The abundance and ordinal richness of other macro-invertebrates were consistently lower in infested plots in all habitats. A significant negative relationship was found for native ant abundance and A. gracilipes abundance. No relationships were found between A. gracilipes abundance and any measure of other macro-invertebrates. The relative contribution of small ants (<2.5 mm) to total abundance and relative species richness was always greater in infested sites coinciding with a reduction of the contribution of the larger size classes. Differences in the relative abundance of ant functional groups between infested and uninfested sites reflected impacts according to ant size classes and ecology. The widespread scale of these incursions and non-differential level of impacts among the habitats, irrespective of native ant community competitiveness and abiotic suitability to A. gracilipes, does not support the biotic resistance hypothesis.     

Eukaryotic Community Distribution and Its Relationship to Water Physicochemical Parameters in an Extreme Acidic Environment, Río Tinto (Southwestern Spain)

The correlation between water physicochemical parameters and eukaryotic benthic composition was examined in Río Tinto. Principal component analysis showed a high inverse relationship between pH and most of the heavy metals analyzed as well as Dunaliella sp., while Chlamydomonas sp. abundance was positively related. Zn, Cu, and Ni clustered together and showed a strong inverse correlation with the diversity coefficient and most of the species analyzed. These eukaryotic communities seem to be more influenced by the presence of heavy metals than by the pH.     

How do weeds differ in their response to the timing of tillage? A study of 61 species across the northeastern United States

Previous research has demonstrated that the season in which soil is tilled (spring versus fall) can strongly influence weed community assembly and subsequent species composition and abundance in annual cropping systems. Despite this understanding, it is unknown whether finer‐scale, within‐season variation in the timing of tillage has similar impacts on weed community assembly. We conducted an experiment on four research farms across the northeastern USA to test the effects of tillage timing on weed emergence periodicity. Soil was tilled at 12 different times that were 2 weeks apart from 29 April to 30 September (the entire growing season) and the composition and abundance of the weed seedlings that emerged was measured 6 weeks later. Weed species clustered into three tillage timing groups at the two New York locations and clustered into five tillage timing groups at the New Hampshire and Maine locations. Individual species associated with each window of tillage time varied by location. No single trait or combination of traits were consistently associated with species‐by‐tillage time groupings across locations; however, within each location several traits were associated with particular groups of species, including: (a) seed length, (b) seed weight, (c) cotyledon type, (d) life span, (e) ploidy level and (f) photosynthetic pathway. These results suggest that fine‐scale variation in the timing of tillage can lead to predictable changes in the species composition and trait distribution of weed communities in annually tilled agroecosystems.     

Use of a rank correlation coefficient for comparing mutational spectra]

It is suggest to use the Kendall's rank correlation coefficient tau for the analysis of correlation between mutation spectra. The results of computer simulations and analysis of real spectra showed that the approach can be recommended for the analysis of mutation spectra.     

Changes in the abundance and diversity of coastal wetland fauna from the open water/macrophyte edge towards shore

Great Lakes coastal wetlands are widely recognized as areas of concentrated biodiversity and productivity, but the factors that influence diversity and productivity within these systems are largely unknown. Several recent studies have suggested that the abundance and diversity of flora and fauna in coastal wetlands may be related to distance from the open water/macrophyte edge. We examined this possibility for three faunal groups inhabiting a coastal wetland in Saginaw Bay, Lake Huron. We sampled crustacean zooplankton and benthic macro-invertebrates at five distances from open water in the summer 1994, and fish at three distances from open water in 1994 and 1995. We found significant spatial trends in the total abundance and diversity of zooplankton and fish, as well as the diversity of benthic macro-invertebrates. Zooplankton abundance and taxa richness were highest at intermediate distances from open water in a transition zone between the well-mixed bayward portion of the wetland, and the non-circulating nearshore area. Benthic macro-invertebrate taxa richness increased linearly with distance from open water. In contrast, fish abundance and species richness declined linearly and substantially (abundance by 78%, species richness by 40%) with distance from open water. Of the 40 taxa examined in this study, 21 had significant horizontal trends in abundance. This led to notable differences in community composition throughout the wetland. Our results suggest that distance from open water may be a primary determinant of the spatial distributions of numerous organismal groups inhabiting this coastal wetland. Several possible reasons for these distributions are discussed.     

The phylogenetic properties of native‐ and exotic‐dominated plant communities

Phylogenetic properties of communities (phylogenetic diversity and phylogenetic structure) allow for the characterisation of phylogenetic patterns and provide the information necessary to infer mechanisms of species assembly. Because humans have introduced exotic species and modified the physical conditions of landscapes, the phylogenetic properties of communities should change according to the proportion of natives to exotics hosted by sites and to the strength of the conditions that act as habitat filters in human‐disturbed habitats. To assess the effects of the introduction of exotic plant species, we characterized the phylogenetic properties of 67 plant communities with different degrees of exotic species dominance in a region of central Chile with a Mediterranean climate. Five indices were used to estimate the phylogenetic properties. The Faith index (FPD), the mean pairwise distance (MPD) and the mean nearest neighbour distance (MNND) were used to estimate phylogenetic diversity, and the nearest relative index (NRI) and the nearest taxon index (NTI) were used as estimators of the phylogenetic structure (the phylogenetic distribution of taxa in a community) of species assemblages. We observed greater phylogenetic diversity of natives versus exotic plants despite the fact that natives accounted for a fewer number of taxa among the studied communities. Second, assemblages exhibited a phylogenetically clustered structure, which is attributable to an over‐representation of some families of exotic flora (Asteraceae, Brassicaceae, Fabaceae, Papaveraceae, Poaceae) and suggests habitat filtering processes that could have acted by selecting species with traits that permit adaptation to the harsh conditions of human‐disturbed sites.     

The three-dimensional structure of schools in the minnow, Phoxinus phoxinus (L.)

A photographic technique is described for determining the three-dimensional position of fish schooling in front of a mirror in a flow tank. School structure is discussed in terms of the distance, horizontal bearing, and elevation of nearest neighbours. Nearest neighbour distances were measured snout-to-snout. A technique of analysis is described which considers the probability distribution of nearest neighbours in space. At speeds of flow 0 to 0·125 metres per second it was possible to show that Phoxinus, a facultative schooler, tended to maintain a school structure as previously reported for obligate schooling species. The structure was present only in a dynamic statistical sense and not in the sense of a rigid crystal lattice. Minnows maintained themselves at approximately 0·9 of their body length from each other under normal conditions and the bearings of neighbour fish suggested an attempt to maintain an optimum packing at this distance. At high speeds of flow the school structure tended to break up as fish sought areas of refuge from the current. All minnow schools were ellipsoidal in shape. The strategic and tactical methods by which schooling fish derive anti-predator advantage are discussed in relation to the school structure.     

Pyrolysis gas-liquid chromatography applied to a study of variation in Arthroderma tuberculatum

Replicates of whole colonies of four species of closely related dermatophytes were analyzed by pyrolysis gas-liquid chromatography (PGLC). The four species included fifteen strains of Arthroderma tuberculatum, and two strains each of A. benhamiae, Nannizzia gypsea and N. incurvata.Individual/peaks on different pyrograms were identified as homologous with the aid of internal markers by the superimposition of pyrograms. The peak height data extracted from the pyrograms of the fungal samples were analyzed to compute average similarities between pairs of pyrograms. The average was calculated with each peak weighted equally, and log weighted for its information content. The results of the cluster analyses of proximities were generally similar.Most, but not all, replicates of each strain were similar enough to be clustered together. Some strains belonging to the same species were also similar enough to be grouped in one cluster. Other strains of a single species varied sufficiently to be put in separate clusters. The nearest neighbour to each OTU (pyrogram) was always a replicate of the same strain.     

长江口东滩湿地芦苇生境大型底栖无脊椎动物群落结构的月动态

2015年5月至2016年4月对长江口东滩湿地芦苇生境的大型底栖无脊椎动物群落结构进行监测,分析了该生境下底栖动物群落物种组成和多样性的月变化.结果表明: 芦苇株高和盖度均在3—8月逐渐增大,9月后逐渐降低;芦苇密度和地上生物量(干质量)均在7月达到最大值.调查期间,共发现大型无脊椎底栖动物20种(包括2种鉴定到属,2种鉴定到科).其中,腹足纲种类最多,有11种(包括1种鉴定到属);软甲纲有5种;昆虫纲和多毛纲均只有2种.以緋拟沼螺、堇拟沼螺和尖锥似蟹守螺等为主要优势种.从生活型来看,底上附着型种类数最多(11种),其次为穴居型(5种)和底内型(4种).大型底栖动物密度和生物量存在明显的季节或月变化,夏季(8月)出现全年最高值.Margalef物种丰富度指数(D)和Shannon指数(H)月份间差异显著,Pielou均匀度指数(J)月份间差异不显著(除11月).大型底栖动物群落在42%相似性水平上划分为3个群聚.从非度量多维标序(nMDS)排序图可知,5月、10—11月与其他月份差异较大.水温、芦苇地下生物量和盐度等环境因子对于底栖动物密度变化具有一定影响,但未达到显著水平(P>0.05).受人类活动的持续影响,长江口东滩湿地芦苇生境底栖动物群落物种多样性有所下降,芦苇生境价值急需重视.     

Using soundscape recordings to estimate bird species abundance, richness, and composition

ABSTRACT Point counts are the most frequently used technique for sampling bird populations and communities, but have well‐known limitations such as inter‐ and intraobserver errors and limited availability of expert field observers. The use of acoustic recordings to survey birds offers solutions to these limitations. We designed a Soundscape Recording System (SRS) that combines a four‐channel, discrete microphone system with a quadraphonic playback system for surveying bird communities. We compared the effectiveness of SRS and point counts for estimating species abundance, richness, and composition of riparian breeding birds in California by comparing data collected simultaneously using both methods. We used the temporal‐removal method to estimate individual bird detection probabilities and species abundances using the program MARK. Akaike's Information Criterion provided strong evidence that detection probabilities differed between the two survey methods and among the 10 most common species. The probability of detecting birds was higher when listening to SRS recordings in the laboratory than during the field survey. Additionally, SRS data demonstrated a better fit to the temporal‐removal model assumptions and yielded more reliable estimates of detection probability and abundance than point‐count data. Our results demonstrate how the perceptual constraints of observers can affect temporal detection patterns during point counts and thus influence abundance estimates derived from time‐of‐detection approaches. We used a closed‐population capture–recapture approach to calculate jackknife estimates of species richness and average species detection probabilities for SRS and point counts using the program CAPTURE. SRS and point counts had similar species richness and detection probabilities. However, the methods differed in the composition of species detected based on Jaccard's similarity index. Most individuals (83%) detected during point counts vocalized at least once during the survey period and were available for detection using a purely acoustic technique, such as SRS. SRS provides an effective method for surveying bird communities, particularly when most species are detected by sound. SRS can eliminate or minimize observer biases, produce permanent records of surveys, and resolve problems associated with the limited availability of expert field observers.