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Copyright of Acta Zoologica Lilloana is the property of Fundacion Miguel Lillo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Parasites are typically concentrated on a few host individuals, and identifying the mechanisms underlying aggregated distribution can facilitate a more targeted control of parasites. We investigated the infestation patterns of hard ticks and chigger mites on two rodent species, the striped field mouse, Apodemus agrarius, and the lesser ricefield rat, Rattus losea, in Taiwan. We also explored abiotic and biotic factors that were important in explaining variation in the abundance of ticks and chiggers on rodent hosts. Ticks were more aggregated than chiggers on both rodent species. Factors important for the variation in parasitic loads, especially biotic factors, largely differed between ticks and chiggers. Variation partitioning analyses revealed that a larger proportion of variation in chiggers than in ticks can be explained, especially by abiotic factors. If, as proposed, the higher number of parasites in males is due to a larger range area or immunity being suppressed by testosterone, when A. agrarius males host more ticks, they are expected to also host more chiggers, given that chiggers adopt a similar host finding approach to that of ticks. Instead, the similar abundance of chiggers in male and female A. agrarius implies that a large home range or suppressed immunity does not predispose males to inevitably host more parasites. More variations were explained by abiotic than biotic factors, suggesting that controlling practices are more likely to be successful by focusing on factors related to the environment instead of host traits. Our study indicated that the extent of parasitism is rarely determined by a sole factor, but is an outcome of complex interactions among animal physiology, animal behavior, characteristics of parasites, and the environments. [ABSTRACT FROM AUTHOR]

Cedrela odorata L. was introduced as a possible forest restauration species in classified forests at Côte d'Ivoire. Because of its demonstrated invasive behavior in other tropical forests, this study aimed to assess the impact of Cedrela odorata on the regeneration of spontaneous plant species in tree plantations. On the base of Cedrela odorata larger tree densities, two types of forest plantation were considered: Type I (240 stems/ha) and Type II (176 stems/ha). In these plantations, plots with 0.25 ha were chosen to locate each tree with dbh = 2.5 cm, in an orthonormal reference. The tree density, the basal area, the species richness, the Shannon diversity index and the rank-abundance curves were determined considering smaller and larger trees. The horizontal spatial arrangement and Ripley's K function were performed to understand the spatial relationship between Cedrela odorata smaller trees and those of spontaneous species. The results shown lower spontaneous plant species richness (15-20 species) and diversity (1.15 - 1.43); the dominance of Cedrela odorata smaller trees (43.02 - 62.95 % of all stems). The Cedrela odorata smaller trees and those of other species have dependent spatial distributions; expressed by a spatial repulsion between the two groups up to a distance of 18 m in the most densified forest plantation. This repulsion was related to an aggregated distribution of Cedrela odorata smaller trees in plantation with higher tree density. The study suggests a 170-stems/ha (or lower) of Cedrela odorata planting density for biodiversity establishment improvement outcomes in forest plantations. [ABSTRACT FROM AUTHOR]

Cedrela odorata L. was introduced as a possible forest restauration species in classified forests at Côte d’Ivoire. Because of its demonstrated invasive behavior in other tropical forests, this study aimed to assess the impact of Cedrela odorata on the regeneration of spontaneous plant species in tree plantations. On the base of Cedrela odorata larger tree densities, two types of forest plantation were considered: Type I (240 stems/ha) and Type II (176 stems/ha). In these plantations, plots with 0.25 ha were chosen to locate each tree with dbh ≥ 2.5 cm, in an orthonormal reference. The tree density, the basal area, the species richness, the Shannon diversity index and the rank-abundance curves were determined considering smaller and larger trees. The horizontal spatial arrangement and Ripley’s K function were performed to understand the spatial relationship between Cedrela odorata smaller trees and those of spontaneous species. The results shown lower spontaneous plant species richness (15-20 species) and diversity (1.15 - 1.43); the dominance of Cedrela odorata smaller trees (43.02 – 62.95 % of all stems). The Cedrela odorata smaller trees and those of other species have dependent spatial distributions; expressed by a spatial repulsion between the two groups up to a distance of 18 m in the most densified forest plantation. This repulsion was related to an aggregated distribution of Cedrela odorata smaller trees in plantation with higher tree density. The study suggests a 170-stems/ha (or lower) of Cedrela odorata planting density for biodiversity establishment improvement outcomes in forest plantations.

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Entomology is the property of Chinese Journal of Applied Entomology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The importance of intraspecific trait variability (ITV) to the spatial distribution of individual species is unclear. We hypothesized that intraspecific trait dispersions underlying niche processes deviate more from null model expectations, by reducing their spread (range and variance), kurtosis, and standard deviation of near-neighbor distance, for species with aggregated than those with random distributions. The link between species’ spatial distributions and ITV patterns was examined using an individual tree-based trait data set, in which specific leaf area, mean leaf area, leaf dry matter content, and diameter at breast height were measured for 18,773 stems of 45 species in a 4.84 ha mapped subtropical forest plot in China. The nearest-neighbor distance analysis showed that, of 45 species, 14 species were distributed in random and 31 species were distributed in aggregation, while no species was distributed in uniform in the plot. The dispersions of all studied traits in species with an aggregated distribution on average deviated more strongly from the null expectation than those in species with a random distribution and that the extent of deviation was negatively associated with the degree of spatial randomness across species. Our results indicate that niche processes are primarily responsible for the spatial structure of species with aggregated distributions, while stochastic processes drive those with random distributions. Our results highlight the fundamental role of ITV in shaping spatial patterns of co-existing species. [ABSTRACT FROM AUTHOR]

Aim Understanding the relative contribution of different species interactions in shaping community assembly has been a pivotal aim in community ecology. Biotic interactions are acknowledged to be important at local scales, although their signal is assumed to weaken over longer distances. We examine the relationship between positive, neutral and negative pairwise bird abundance distributions and the phylogenetic and functional distance between these pairs after first controlling for habitat associations. Location France and Finland. Time period 1984 to 2011 (Finland), 2001 to 2012 (France). Major Taxa studied Birds. Methods We used results from French and Finnish land bird monitoring programmes, from which we created three independent datasets (French forests, French farmlands and Finnish forests). Separately for the three datasets, we fitted linear mixed-effects models for pairwise abundance values across years per point count station to infer the association between all common species pairs, while controlling for geographical distribution and habitat associations, and saved pairwise regression coefficients for further analyses. We used a null model approach to infer whether the observed associations (effect sizes) differ from random. Finally, using quantile regression, we analysed the relationships between functional dissimilarity/phylogenetic distance and effect sizes. Results Our results show both negative and positive species interactions, although negative interactions were twice as common as positive interactions. Closely related species were more likely to show strong associations, both negative and positive, than more distant species across broad spatial scales. For functional dissimilarity, the results varied across datasets. Main conclusions Our results emphasize the potential of functional and phylogenetic proximity in generating both negative and positive species associations, which can produce pervasive patterns from local to geographical scales. Future assembly studies should refrain from strict dichotomies, such as compensatory dynamics versus environmental forcing, and instead consider the possibility of positive interactions. [ABSTRACT FROM AUTHOR]

O objetivo do presente trabalho é identificar e descrever o padrão dedistribuição espacial de Hymenaea courbaril L. (Fabaceae) e os fatores condicionantes em um fragmento florestal, denominado Mata do Açude, município de Jataí Estado de Goiás. O procedimento adotado para coleta dos dados espaciais foi o método da distância conhecidocomo T – Square, utilizado para duas classes de tamanho: jovens e adultos, com circunferência de caule inferior e superior a 15 cm, respectivamente. Os fatores condicionantes analisados foram o padrão espacial de deposição das sementes e as características do substrato (solo e serrapilheira). A estrutura espacial da população foi identificada pelo teste de Hines (ht), a qual apresentou distribuição agregada, tanto para indivíduos adultos (ht = 1,47, p < 0,005) quanto juvenis (ht = 1,88, p < 0,005) e um maior número de sementes em torno de 4 m da planta-mãe. As condições edáficas não se diferenciaram entre os pontos amostrados, ao contrário da serrapilheira que apresentou diferenças significativas para umidade relativa e matéria seca. Os dados sugerem que o recrutamento e, consequentemente, a distribuição espacial dos jatobás na Mata do Açude é fortemente estruturada pelo padrão de deposição das sementes e pelas características do substrato, principalmente aquelas atribuídas à serrapilheira. The objective of this study was to identify and describe the pattern of spatial distribution of Hymenaea courbaril L. (Fabaceae) and its structuring factors in the Mata do Açude forest fragment in Jataí Municipality, Goiás state. We used two individual size classes: juveniles and adult, with stalk circumference smaller and bigger than 15 cm, respectively. The population spatial data were sampled by the ‘T-Square’ distance method and the structuring factors analyzed were the spatial deposition pattern of seeds and substrate conditions (soil and litter). The Hines statistical test (ht) was used to detect the population spatial pattern. The tree population presented aggregated spatial structure, for both adults (ht = 1.47, p < 0.005) and juveniles (ht = 1.88, p < 0.005), with greater seed density at four meters from the plant. The soil conditions were not different among sampled points. On the other hand, the litter conditionspresented significant differences for moisture and dried organic matter. These data suggested that the recruitment and spatial distribution of H. courbaril in the Mata do Açude is strongly structured by the seed deposition pattern and litter conditions.

O presente estudo teve por objetivo comparar os resultados de distribuição espacial obtidos entre os métodos clássicos e os métodos que estimam a variância entre parcelas. Foram analisadas duas espécies, Vernonia aurea e Duguetia furfuracea. Foram utilizados a Distribuição de Poisson (padrão aleatório), a Distribuição Binomial Negativa (padrão agregado) e os métodos BQV, TTLQV e PQV (variância entre parcelas), bem como a razão variância:média (I), coeficiente de Green (Ig) e o índice de dispersão de Morisita (Im). Ambas metodologias detectaram padrão de distribuição espacial agregado para as populações analisadas, com resultados similares quanto ao nível de agregação, além de complementação das informações, em diferentes escalas, entre os métodos clássicos e de variância entre parcelas. Desse modo, recomenda-se a utilização desses métodos estatísticos em estudos de estrutura espacial, uma vez que os testes são robustos e complementares e os dados são de fácil coleta em campo.This study aims to compare the results of spatial structure obtained between the classic and quadrat variance methods. Two species were analised, Vernonia aurea and Duguetia furfuracea. The Poisson distribution (random pattern), the Negative Binomial distribution (aggregate pattern), the BQV, TTLQV and PQV methods, the ratiovariance: mean (I), the Green coefficient (Ig) and the Morisita’s index of dispersion (Im) were used to detect the populations spatial pattern. An aggregated spatial pattern distribution was detected through both methodologies, with similar results as for the aggregation level and the complementation of the information in different scales between classic and quadrat variance methods. Thus, the utilization of these statistic methods in studies of the spatialstructure is recommended, given that tests are robust and complementary and field data samples are easy to collect.

Nas restingas, devido aos microhábitats favoráveis, como as moitas, não ocorrerem de forma homogênea, mas em manchas, e devido à elevada taxa de reprodução vegetativa em bromélias, testa-se a hipótese de que o padrão de distribuição espacial das bromélias em uma restinga seria agregado. Utiliza-se como área para o teste de hipótese a restinga do Parque Nacional da Restinga de Jurubatiba. Analisa-se o padrão de distribuição espacial de cada espécie encontrada através do índice de dispersão de Morisita (Id). Encontra-se 10 espécies de bromélias, com 10179 indivíduos em 0,98 ha amostrados. Na área estudada, nove espécies possuíram um padrão de distribuição agregado (Id > 1). Sugerimos que o padrão de distribuição agregado de bromélias em restinga pode ser explicado pela taxa de reprodução vegetativa, distribuição de condições abióticas favoráveis e substratos disponíveis nas moitas, as quais ocorrem em manchas na restinga estudada, favorecendo a ocorrência de bromélias.In "restingas", because favorable microhábitats have patchy distribution, and due to the high vegetative reproduction rate in bromeliads, we tested the hypothesis that the pattern of spatial distribution of bromeliads in a "restinga" habitat would be aggregated. We used the "restinga" of the Parque Nacional da Restinga de Jurubatiba as our hypothesis test area. We analyzed the spatial distribution pattern of each studied species using Morisita dispersion Index (Id). We found 10 bromeliad species, with 10179 individuals in the 0,98 ha sampled. In the study area, nine species had an aggregated distribution pattern (Id > 1). We suggest that the aggregated distribution pattern of bromeliads may be explained by the rate of vegetative reproduction, distribution of the favorable abiotic conditions and availability substrates in clumps, which occur in patches in the study area, favoring the bromeliads occurrence.

The Yunnan red-backed vole Eothenomys miletus (Rodentia: Cricetidae) is an endemic rodent species and reservoir host of zoonoses in southwest China. Based on a large host sample (2463 voles collected from 39 localities between 2001 and 2013), a general analysis of four categories of ectoparasite (fleas, sucking lice, chigger mites and gamasid mites) on E. miletus across its entire range of distribution was made. This analysis identified a total of 71 895 ectoparasites belonging to 320 species (30 species of flea, 9 of sucking louse, 106 of gamasid mite and 175 of chigger mite) with a high prevalence (87%), mean abundance (29.19) and mean intensity (33.69). Of the 18 vector species of zoonoses found on E. miletus, the flea Ctenophthalmus quadratus (Siphonaptera: Hystrichopsyllidae) and chigger mite Leptotrombidium scutellare (Trombidiformes: Trombiculidae) were the dominant species; these are the main vectors of zoonoses in China. All of the dominant parasite species showed an aggregated distribution pattern. Male voles harboured more species of parasite than females. Chigger mites represented the most abundant species group on voles and their prevalence was positively correlated with mean abundance ( r = 0.73; P < 0.05). As a single rodent species, E. miletus has a high potential to harbour abundant ectoparasites with high species diversity and high rates of infestation. The sex of the vole affects ectoparasite infestation. [ABSTRACT FROM AUTHOR]

Diraceus melacanthus has become a key pest of maize in Brazil, primarily during the early vegetative growth stages. This study examined the spatial distribution of D. melacanthus in maize and developed a sequential sampling plan for monitoring the pest in maize at the vegetative stage. The samples were collected from six fields of 1250 m2 each in the second crop seasons of 2012 and 2013. The sampling unit consisted of five randomly chosen plants per plot, which were visually examined for D. melacanthus on a weekly basis, totaling 250 plants evaluated per field on each sampling date. To construct the sampling plan, an economic threshold of 0.8 stink bugs per sample unit (five plants) was adopted. According to the indices of dispersion and by fitting the frequency data to mathematical distributions, the spatial distribution of D. melacanthus in maize is aggregated. From the obtained data, two decision lines were generated, one of which, S1 = 3.5683 + 0.5702 N, recommends taking control action, whereas the other, S0 = −3.5683 + 0.5702 N, suggests that no control action is needed. The sequential sampling plan indicated an expected maximum number of 26 sampling units (∼130 plants) to determine whether to control the pest with prefixed precision level of 95%. This sampling plan may help the decision-making for the control of D. melacanthus in maize, contributing for a sustainable management of this herbivore to increase farmers' profit. • D. melacanthus has shown an aggregated distribution in maize fields. • A sampling plan was built for decision-making in fields with susceptible hybrids. • Ninety-five plants should be inspected when the stink bug reaches the control level. • A maximum number of 130 plants should be inspected to determine whether to control. [ABSTRACT FROM AUTHOR]

Fish and wildlife often exhibit an aggregated distribution pattern, whereas local abundance changes constantly due to movement. Estimating population density or size and survey detectability (i.e. gear efficiency in a fishery) for such elusive species is technically challenging. We extend abundance and detectability (N-mixture) methods to deal with this difficult situation, particularly for application to fish populations where gear efficiency is almost never equal to one. The method involves a mixture of statistical models (negative binomial, Poisson, and binomial functions) at two spatial scales: between-cell and within-cell. The innovation in this approach is to use more than one fishing gear with different efficiencies to simultaneously catch (sample) the same population in each cell at the same time-step. We carried out computer simulations on a range of scenarios and estimated the relevant parameters using a Bayesian technique. We then applied the method to a demersal fish species, tiger flathead, to demonstrate its utility. Simulation results indicated that the models can disentangle the confounding parameters in gear efficiency and abundance, and the accuracy generally increases as sample size increases. A joint negative binomial–Poisson model using multiple gears gives the best fit to tiger flathead catch data, while a single gear yields unrealistic results. This cross-sampling method can evaluate gear efficiency cost effectively using existing fishery catch data or survey data. More importantly, it provides a means for estimating gear efficiency for gear types (e.g. gillnets, traps, hook and line, etc.) that are extremely difficult to study using field experiments. [ABSTRACT FROM AUTHOR]

The vertical and horizontal distributions of Pseudorobitis gibbus adults on Lagerstroemia indica were analyzed by using the aggregation indices and geostatistics. The results from aggregation index methods indicated that its vertical distribution was an aggregated distribution, and the aggregation average (λ) was above two, showing that the aggregation resulted from its bionomics and behaviors, not from the environmental factors. The results of geostatistic analysis showed that the best fitting models for the five different sampling data in June 4, June 16, June 29, July 25 and August 22 were Gaussian, Gaussian, Linear, Gaussian and Linear models, respectively, but random models in July 12 and August 7. It was concluded that the horizontal distribution of the pest was aggregated on the whole, and there existed a spatial correlation ranging from 1. 68 to 9. 79 m on the different dates. [ABSTRACT FROM AUTHOR]

Whether bacterial drug-resistance is drug-induced or results from rapid propagation of random spontaneous mutations in the flora prior to exposure, remains a long-term key issue concerned and debated in both genetics and medicinal fields. In a pioneering study, Luria and Delbrück exposed E. coli to T1 phage, to investigate whether the number of resistant colonies followed the Poisson distribution. They deduced that the development of resistant colonies is independent of phage presence. Similar results have since been obtained on solid medium containing antibacterial agents. Luria and Delbrück's conclusions were long considered a gold standard for analyzing drug resistance mutations. More recently, the concept of adaptive mutation has triggered controversy over this approach. Microbiological observation shows that, following exposure to drugs of various concentrations, drug-resistant cells emerge and multiply depending on the time course, and show a process function, inconsistent with the definition of Poisson distribution (which assumes not only that resistance is independent of drug quantity but follows no specific time course). At the same time, since cells tend to aggregate after division rather than separating, colonies growing on drug plates arise from the multiplication of resistant bacteria cells of various initial population sizes. Thus, statistical analysis based on equivalence of initial populations will yield erroneous results. In this paper, 310 data from the Luria-Delbrück fluctuation experiment were reanalyzed from this perspective. In most cases, a high-end abnormal value, resulting from the non-synchronous variation of the two above-mentioned time variables, was observed. Therefore, the mean value cannot be regarded as an unbiased expectation estimate. The ratio between mean value and variance was similarly incomparable, because two different sampling methods were used. In fact, the Luria-Delbrück data appear to follow an aggregated, rather than Poisson distribution. In summary, the statistical analysis of Luria and Delbrück is insufficient to describe rules of resistant mutant development and multiplication. Correction of this historical misunderstanding will enable new insight into bacterial resistance mechanisms. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum: Biological Sciences is the property of Universidade Estadual de Maringa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the marine environment, aggregated distribution in the genus Crepidula is a very common phenomenon. Works from Pechenik''s group suggested that this is the result of gregarious settlement of larvae in response to cues associated with conspecific adults. In this study, we investigated the existence of larval metamorphic cues associated with adults of C. onyx, a slipper limpet introduced to Hong Kong from the U.S. in the 1970s, through a series of laboratory bioassays. The results showed that derived cues in adult C. onyx were waterborne and the waterborne cues were not derived from bacteria associated with the shell and soft body of the adult Crepidula. The natural biofilm also induced the larval metamorphosis of C. onyx. The cues from the biofilm were associated with the surface of the biofilm and were not waterborne. The aggregated distribution in nature of adult C. onyx may result from a selective larval settlement process. On a small scale in the water column near the conspecific adults, larvae of C. onyx initially detect the waterborne conspecific cues, which then lead to positive downward swimming or passive sinking. This activity increases the chances for larvae to make contact with the biofilm and to be exposed into the higher concentration of waterborne conspecific cues. This may eventually lead to the enhanced larval settlement pattern on or near the conspecific adults. [Copyright &y& Elsevier]

The aim of this investigation was to clarify whether pheromone traps could provide a reliable tool for early detection of a S. littoralis adult population and for indicating infestation by its larvae in the field. The aggregated pattern of distribution of adults is indicated by the fit of data to Taylor's Power Law or to the negative binomial distribution. However, the relatively high k values obtained indicate that S. littoralis adults are only slightly aggregated and sometimes almost randomly distributed. Trap position in the field and number of traps per area unit affected size of catches in both female-baited and synthetic-pheromone-baited traps. No relationship between size of catches and temperature, wind velocity or moon phase was detected. Variations in size of catches among traps was not affected much by the baited females. Pheromone traps proved to be a reliable tool for estimating fluctuations in population density and for indicating adult peaks. However, no correlation between male catches and infestation by larvae in the experimental plots was found. Pheromone traps may serve only as a warning device indicating the possibility of potential attack due to an increase in adult population level. Mercury vapor light traps were inferior to pheromone traps in detecting changes in S. littoralis population densities. Synthetic pheromone ('Litlure') was somewhat less efficient in attracting males than virgin females; however, it is suitable for detecting fluctuations in the S. littoralis adult population. [ABSTRACT FROM AUTHOR]

O objetivo deste estudo foi verificar o padrão espacial e a estrutura populacional de cinco espécies arbóreas em um fragmento de cerrado sentido restrito no município de Jataí, sudoeste goiano. Foram demarcadas 50 parcelas de 10 × 10 m (100 m²) e amostrados todos os indivíduos dentro de cada parcela. Para detectar o padrão espacial da população, foram utilizadas as distribuições teóricas de Poisson e Binomial Negativa e dois índices de dispersão: a razão variância/média (I) e o coeficiente de Green (Ig). A estrutura diamétrica foi verificada pela distribuição de frequências de seis classes de tamanho. As espécies apresentaram distribuição espacial agregada, com os indivíduos menores espacialmente disjuntos dos maiores, com exceção de Qualea grandiflora Mart., e distribuição diamétrica em forma de "J-invertido", embora que com algumas peculiaridades. Isso sugere diferenças no padrão estrutural das cinco populações estudadas e, consequentemente, nos processos de estruturação e dinâmica de cada espécie.

Former authors claimed that, due to parasites' aggregated distribution, small samples underestimate the true population mean abundance. Here we show that this claim is false or true, depending on what is meant by 'underestimate' or, mathematically speaking, how we define 'bias'. The 'how often' and 'on average' views lead to different conclusions because sample mean abundance itself exhibits an aggregated distribution: most often it falls slightly below the true population mean, while sometimes greatly exceeds it. Since the several small negative deviations are compensated by a few greater positive ones, the average of sample means approximates the true population mean.