Index Of Patchiness Research Articles

Revealing pest patterns: A comparative spatial distribution analysis of insect threats in Kharif rice across the key agricultural regions in the Eastern India.

This study investigates the spatial distribution and aggregation patterns of major insect pests in Kharif rice fields during the 2023 growing season in Eastern India. The analysis focuses on key pests such as yellow stem borer (YSB), gall midge, green leaf hopper (GLH), and brown planthopper (BPH), as well as rice thrips, caseworm, whorl maggot, Gundhi bug, grasshopper, and leaf folder. Using statistical indices, this study aims to understand pest behavior across Standard Meteorological Weeks (SMWs) to better inform pest control strategies. The study reveals significant clustering and aggregation patterns among the pests. YSB exhibited variance-mean ratio (VMR) values between 1.14 (40th SMW) and 1.96 (31st SMW), with dispersion parameter (K) values ranging from 0.57 to 21.65, and a peak index of dispersion of 132.66 (43rd SMW). Similarly, gall midge showed VMR values from 6.19 to 10.48, whereas GLH and BPH recorded VMR ranges of 1.19 to 132.10 and 1.01 to 1.50, respectively. These spatial distribution trends were confirmed through values for Iwao's patchiness index and Taylor's power law, indicating strong pest aggregation in specific areas. The results underscore the need for region-specific integrated pest management strategies that take into account pest clustering and environmental factors influencing pest distribution. Although an S-curve pattern of infestation-showing gradual population increases, rapid peaks, and eventual decline-was observed, the primary focus remains spatial patterns, which are critical for optimizing pest management and improving rice crop sustainability in the region. © 2024 Society of Chemical Industry.

“Patchiness” in mechanical stiffness across a tumor as an early-stage marker for malignancy

Mechanical phenotyping of tumors, either at an individual cell level or tumor cell population level is gaining traction as a diagnostic tool. However, the extent of diagnostic and prognostic information that can be gained through these measurements is still unclear. In this work, we focus on the heterogeneity in mechanical properties of cells obtained from a single source such as a tissue or tumor as a potential novel biomarker. We believe that this heterogeneity is a conventionally overlooked source of information in mechanical phenotyping data. We use mechanics-based in-silico models of cell-cell interactions and cell population dynamics within 3D environments to probe how heterogeneity in cell mechanics drives tissue and tumor dynamics. Our simulations show that the initial heterogeneity in the mechanical properties of individual cells and the arrangement of these heterogenous sub-populations within the environment can dictate overall cell population dynamics and cause a shift towards the growth of malignant cell phenotypes within healthy tissue environments. The overall heterogeneity in the cellular mechanotype and their spatial distributions is quantified by a “patchiness” index, which is the ratio of the global to local heterogeneity in cell populations. We observe that there exists a threshold value of the patchiness index beyond which an overall healthy population of cells will show a steady shift towards a more malignant phenotype. Based on these results, we propose that the “patchiness” of a tumor or tissue sample, can be an early indicator for malignant transformation and cancer occurrence in benign tumors or healthy tissues. Additionally, we suggest that tissue patchiness, measured either by biochemical or biophysical markers, can become an important metric in predicting tissue health and disease likelihood just as landscape patchiness is an important metric in ecology.

Activity Patterns, Population Dynamics, and Spatial Distribution of the Stick Tea Thrips, Dendrothrips minowai, in Tea Plantations.

The stick tea thrips, D. minowai Priesner (Thysanoptera: Thripidae), is one of the most economically significant thrips pests of tea (Camellia sinensis (L.) O. Ktze.) in China. Here, we sampled D. minowai in tea plantations from 2019 to 2022 to characterize its activity patterns, population dynamics, and spatial distribution. A large proportion of D. minowai individuals were caught in traps placed at heights ranging from 5 cm below to 25 cm above the position of tender leaves at the top of the tea plant, and the greatest number of individuals were captured at a height of 10 cm from the position of tender leaves at the top of the tea plant. Thrips were most abundant from 10:00 to 16:00 h in the spring and from 06:00 to 10:00 h and from 16:00 to 20:00 h on sunny days in the summer. The spatial distribution of D. minowai females and nymphs was aggregated on leaves according to Taylor's power law (females: R2 = 0.92, b = 1.69 > 1; nymphs: R2 = 0.91, b = 2.29 > 1) and Lloyd's patchiness index (females and nymphs: C > 1, Ca > 0, I > 0, M*/m > 1). The D. minowai population was dominated by females, and male density increased in June. Adult thrips overwintered on the bottom leaves, and they were most abundant from April to June and from August to October. Our findings will aid efforts to control D. minowai populations.

Assessment of spatial distribution of Plutella xylostella on Cabbage (Brassica oleracea var. capitata)

The present investigation aimed to study the distribution pattern of larvae and pupae of diamondback moth (DMB) on cabbage (Brassica oleracea var. capitata L.). The experiment was laid out in randomized block design at the Horticulture farm, Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan during rabi 2019–20 and 2020–21. The present study was carried out to understand the pattern and behaviour of the spatial distribution of DBM in cabbage. The prevalence of DBM incidence was recorded in terms of the number of larvae and pupae per plant on ten randomly selected plants in each replication at weekly intervals. The various indices, viz. variance to mean ratio, exponent–K, patchiness index, clumping index, mean colony size, mean clump size, Iwao’s patchiness regression and Taylor’s power law were analyzed to test the dispersion behaviour of diamondback moth. The value of various indices exceeded unity in most of the weekly observations indicating clumped type of distribution of diamondback moth larvae and pupae on cabbage. Clumped distribution behaviour of DBM population can aid the understanding of the pest ecology and its management.

Intraspecific Abundance\u2013Occupancy\u2013Patchiness Relations in the Intertidal Benthic Macrofauna of a Cool-Temperate North Sea Mudflat

The macroecological variable of patchiness (Lloyd’s Ip index of patchiness, P) has recently been shown to be related inter- and intraspecifically to those of abundance (numbers m−2, A), and occupancy (% occurrence in samples, O) in lower latitude seagrass macrofaunas. For the first time in higher latitudes, intraspecific relationships between three spatial variables were investigated in the intertidal mudflat macrobenthos of the Scolt Head barrier island, southern North Sea (53° N, 01° E). Sampling was conducted between early July and late September 2009–2013 using 710-µm mesh for sample processing. Strong positive interspecific A-O and negative interspecific P-O and P-A relationships were present. Two of the most numerous and widespread assemblage components, however, occurred with effectively constant occupancy (Peringia ulvae, 100%, and Tubificoides benedii, 93%) across the whole 20-ha locality and therefore could not show intraspecific relationships of occupancy with other macroecological metrics. These two apart, only one other dominant species failed to show a significant positive intraspecific A-O relationship; no species showed significant P-A relations of any form; and only two showed the negative P-O ones that have been described elsewhere. The intraspecific A-O patterns appear to contrast with those of an earlier study at another North Sea locality (the Dutch Wadden Sea), although differences are more apparent than real, but the Scolt Head fauna showed fewer intraspecific P-O and P-A relations than those characterising similar circumstances in the two lower-latitude localities previously investigated. Neither developmental mode nor variation in local abundance appears to influence these patterns. A-O-P relations therefore seem widespread but may be subject to latitudinal modification.

Morphological variation, distribution and relationship of weedy rice (Oryza sativa L.) in Peninsular Malaysia

AbstractThe dynamic changes in agricultural practices have negatively impacted rice cultivation resulting in serious weedy rice (Oryza sativa L.) infestations. In this study, field surveys were conducted at six granaries to evaluate the abundance, spatial‐distribution patterns, and morphological characteristics of weedy rice in Peninsular Malaysia. An average of 5.28 plants/m2 weedy rice density was recorded, with coverage area that ranged from 29% to 66% and occurrence at >67% frequency. Seed morphological characteristics identified the existence of at least 18 biotypes. A total of 134 weedy rice samples were characterized morphologically, and Principle Component Analysis results showed that these samples are highly diverse and are dispersed across Peninsular Malaysia. These genetically diverse reservoir of weedy rice characteristics present opportunities of exploitation in the future, especially through rice breeding and crop improvement. Weedy rice from Kelantan and Selangor displayed unique clusters in the PCA plot which suggest higher tendencies for environmental adaptation although the influencing factors have yet to be determined. Dispersion studies based on Lloyd patchiness index revealed that more than 50% of surveyed field blocks in five states displayed uniform distribution as opposed to cluster distribution observed in the remaining field blocks. These variations in dispersion suggested that farmers in Peninsular Malaysia employed inconsistent weedy rice management practices in every granary and farm block. Observation of weedy rice infestation pattern via spatial distribution suggested that weed management requires proper coordination of control efforts among farmers to ensure the degree of infestation is maintained under a controlled level.

Distribution and Host Selection of Tropical Rat Mite, Ornithonyssus bacoti, in Yunnan Province of Southwest China.

Simple SummaryThe tropical rat mite (Ornithonyssus bacoti) is a transmission vector of rickettsia pox and a potential vector of hemorrhagic fever with renal syndrome (HFRS). This article reports the distribution and host selection of O. bacoti in Yunnan Province of Southwest China. The original data came from the investigations in 39 counties of Yunnan. The prevalence (PM), mean abundance (MA) and mean intensity (MI) were calculated to reflect the infestations of the dominant rat hosts with O. bacoti mites. The patchiness index and Taylor’s power law were used to measure the spatial distribution of the mites. A total of 4121 O. bacoti mites were identified from 15 species of small mammal hosts in 27 of the 39 investigated counties, and 99.20% of them (4088/4121) were found on rodents. The majority of total O. bacoti mites was found in the flatland landscape (91.28%) and indoor habitat (73.48%). Moreover, 51.78% and 40.09% of O. bacoti mites were identified from Rattus tanezumi and R. norvegicus, the two synanthropic rat species. The mites had some host-specificity, with a preference to two dominant hosts (R. tanezumi and R. norvegicus), and they were of aggregated distribution on R. tanezumi.(1) Background: As a species of gamasid mite, the tropical rat mite (Ornithonyssus bacoti) is a common ectoparasite on rodents and some other small mammals. Besides stinging humans to cause dermatitis, O. bacoti can be a vector of rickettsia pox and a potential vector of hemorrhagic fever with renal syndrome (HFRS). (2) Objective: The present study was conducted to understand the host selection of O. bacoti on different animal hosts and the distribution in different environmental gradients in Yunnan Province of Southwest China. (3) Methods: The original data came from the investigations in 39 counties of Yunnan, between 1990 and 2015. The animal hosts, rodents and some other small mammals were mainly trapped with mouse traps. The O. bacoti mites on the body surface of animal hosts were collected and identified in a conventional way. The constituent ratio (Cr), prevalence (PM), mean abundance (MA) and mean intensity (MI) were used to reflect infestations of animal hosts with O. bacoti mites. The patchiness index and Taylor’s power law were used to measure the spatial distribution pattern of O. bacoti mites on their hosts. (4) Results: A total of 4121 tropical rat mites (O. bacoti) were identified from 15 species and 14,739 individuals of hosts, and 99.20% of them were found on rodents. More than half of O. bacoti mites (51.78%) were identified from the Asian house rat (Rattus tanezumi), and 40.09% of the mites from the Norway rat (R. norvegicus) (p < 0.05). The infestations of R. tanezumi (PM = 7.61%, MA = 0.40 and MI = 5.31) and R. norvegicus (PM = 10.98, MA = 1.14 and MI = 10.39) with O. bacoti mites were significantly higher than those of other host species (p < 0.05). The infestations of two dominant rat hosts (R. tanezumi and R. norvegicus) with O. bacoti mites varied in different environmental gradients (latitudes, longitudes, altitudes, landscapes and habitats) and on different sexes and ages of the hosts. The prevalence of juvenile R. norvegicus rats with O. bacoti mites (PM = 12.90%) was significantly higher than that of adult rats (PM = 9.62%) (p < 0.05). The prevalence (PM = 38.46%) and mean abundance (MA = 2.28 mites/host) of R. tanezumi rats with O. bacoti mites in the high latitude were higher than those in the low latitudes (p < 0.05). The majority of the total collected 4121 O. bacoti mites was found in the flatland landscape (91.28%) and indoor habitat (73.48%) (p < 0.05). The PM (10.66%) and MA (0.49 mites/host) of R. tanezumi rats with O. bacoti mites were significantly higher in the indoor habitat than in the outdoor habitat (p < 0.05). The tropical rat mites showed an aggregated distribution pattern on their first dominant host, R. tanezumi. Conclusion: The tropical rat mite (O. bacoti) is a widely distributed species of gamasid mite in Yunnan Province, Southwest China, and its dominant hosts are two synanthropic species of rats, R. tanezumi and R. norvegicus. It is mainly distributed in the flatland landscape and indoor habitat. It has some host-specificity, with a preference to rodents, especially R. tanezumi and R. norvegicus. The O. bacoti mites are of aggregated distribution on R. tanezumi rats.

闽南渔场游泳动物优势种种群聚集特性

基于2016年4月和10月闽南渔场渔业资源的专项调查数据，运用相对性重要指数、平均拥挤度指数、聚块指数、Cassie指标、Mrisita指数等方法分析闽南渔场游泳动物优势种组成及其种群聚集特性，比较不同的季节、类群和种类及其相互间的聚集状态，探究种群聚集驱动因子，旨在发现闽南渔场游泳动物优势种种群聚集的特征、内在规律和形成机制。结果表明，闽南渔场游泳动物优势种共17种，其中鱼类6种、虾类3种、蟹类4种、头足类4种；鱼类中六指马鲅（Polydactylus se-xfilis）聚集强度最强，头足类中火枪乌贼（Loligo beka）聚集强度最强；虾类和蟹类中春季以哈氏仿对虾（Parapenaeopsis hardwickii）和拥剑梭子蟹（Portunus gladiator）的聚集强度最强，而秋季以鹰爪虾（Trachypenaeus curvirostris）和日本蟳（Charybdis japonica）的聚集强度最强；鱼类、虾类、蟹类和头足类中春季分别以二长棘犁齿鲷（Evynnis cardinali）、鹰爪虾、三疣梭子蟹（P. trituberculatus）和火枪乌贼的平均拥挤度最高，而秋季分别以带鱼（Trichiurus lepturus）、鹰爪虾、拥剑梭子蟹和杜氏枪乌贼（Loligo duvaucelii）的平均拥挤度最高；闽南渔场游泳动物优势种的平均拥挤度呈现出秋季高于春季，虾类、蟹类种群聚集强度大于鱼类、头足类的特点。;The relative importance index, mean crowding index, patchiness index, Cassie index and Mrisita index were used to analyze the composition and aggregation characteristics of the dominant species of nekton in Minnan Fishing Ground using the special investigation data of fishery resources in Minnan Fishing Ground in April and October 2016. The results showed that there were 17 dominant species of nektons in Minnan Fishing Ground, including 6 species of fish, 3 species of shrimp, 4 species of crab and 4 species of cephalopod. Polydactylus se-xfilis had the strongest aggregation intensity among fishes, and Loligo beka had the strongest aggregation intensity among cephalopods in spring and autumn. Parapenaeopsis hardwickii had the largest aggregation intensity among shrimps, and Portunus gladiator had the largest aggregation intensity among crabs in spring. Trachypenaeus curvirostris had the largest aggregation intensity among shrimps, and Charybdis japonica had the largest aggregation intensity among crabs in autumn. In spring, Evynnis cardinali, Trachypenaeus curvirostris, Portunus trituberculatus, Loligo beka had the highest mean crowding among fishes, shrimps, crabs and cephalopods, respectively. In autumn, Trichiurus lepturus, Trachypenaeus curvirostris, P. gladiator and Loligo duvaucelii had the highest mean crowding among fishes, shrimps, crabs and cephalopods, respectively. The average crowding of main dominant species of nekton in autumn was higher than that in spring, and the aggregation intensity of shrimp and crab was higher than that of fish and cephalopod in the Minnan Fishing Ground.

Temporal and spatial dynamics of ascochyta blight caused by Ascochyta fabae speg. In faba bean fields in Tunisia

Ascochyta blight of faba bean, caused by Ascochyta fabae (teleomorph: Didymella fabae) is one of the most destructive diseases of faba bean in Tunisia. Temporal and spatial development of ascochyta blight were studied and characterized during 2010–2011 and 2011–2012 in three faba bean fields located in Oued Mliz, Oued Beja and Mornag, using mathematical and geostatistical analyses. Mass Disease Index (MDI) was assessed every two weeks in each quadrat located around the central source of inoculum. Richards’ function well described disease progress in all sites except for Oued Beja in 2011–2012, the shape parameter m is significantly close to 1 placing the model in its particular form of Gompertz and confirming the polycyclic characteristic of the epidemic. Empirical analysis showed that the effect to locations on epidemic dynamics was explained by highly significant environmental effect (temperature, rain events). These differences in epidemic dynamics were confirmed by the analysis of parameters estimated by the Richards’ model (average relative disease progression rate (rw), proportional average relative disease progression rate (rwp), maximum disease progression rate at inflection point (ri), time at inflection point (ti), MDI at the inflection point (yi)). Analyzing the spatial structure dynamics of the disease using Lloyed Index of Patchiness (LIP) and the mapped disease distribution at different dates showed that LIP was estimated by an exponential functionthat decreased over time in all sites and seasons. LIP dropped below 1 (limit value for aggregated distribution) after 12, 25, 30, 36 and 48 daysat Oued Beja and Oued Mliz during both seasons and during the second season in Mornag. After these periods, the disease distribution is randomly distributed. However, according to the mapping, disease distribution was aggregated in terms of severity even at the end of the epidemics, indicating different temporal dynamics such as changes in distance from the inoculum source.

Investigating the potential of Sentinel-1 to detect varying spatial heterogeneity in pasture cover in grasslands

ABSTRACT Selective grazing by livestock may be indicative of a site’s grass species diversity and depending on the grazing intensity; this may or may not promote further diversity. However, the detection of sites with spatial heterogeneity in pasture cover as a manifestation of selective grazing has not yet been investigated using satellite remote sensing. Thus, this study was conducted to address the question; can Sentinel-1 detect spatial heterogeneity induced by livestock grazing in grassy fields? Since Synthetic Aperture Radar (SAR) imaging is noted to be sensitive to vegetation architectural arrangement, this study used Sentinel-1 C-band SAR to detect spatial heterogeneity created by selective livestock grazing. The study examined a range of semivariogram, grey-level co-occurrence matrix (GLCM), and eigenvector-eigenvalue polarimetric decomposition features. The coefficient of variation estimates of the GLCM contrast feature consistently produced the strongest correlation (R 2 = 0.71) with Lloyd’s Patchiness Index and semivariogram sill while the polarimetric scattering entropy (range estimates) produced a significant linear correlation with semivariogram sill (R 2 = 0.55, p < 0.05). Inferably, the GLCM contrast and polarimetric scattering entropy can predict spatial heterogeneity in a grazing environment. This is the first time polarimetric scattering entropy estimated from Sentinel-1 has been used for the detection of spatial heterogeneity in a grazing landscape, which makes this study different from past similar studies. Nonetheless, we recommend the testing of this parameter (polarimetric scattering entropy) with a multitemporal SAR data and encourage future studies to investigate the potential of Sentinel-1 for the detection of spatial distances between grass clumps.

Do species display characteristic intraspecific levels of patchiness in a given habitat type? The case of intertidal seagrass macrobenthos

Intertidal macrobenthic assemblages associated with monospecific stands of Zostera muelleri, Cymodocea serratula, Halodule uninervis and Halophila ovalis seagrasses are known to display uniform spatial patchiness on the Moreton Bay coast of North Stradbroke Island, Queensland, as do those in Z. capensis in the Knysna estuarine bay, South Africa. Thirty-seven historical datasets of these macrobenthic assemblages were re-analysed to assess variation of local patchiness in each of the 18 most common individual assemblage components at each of these localities in terms of three metrics: overall patchiness (Lloyd's index of patchiness), levels of unoccupancy, and variation in abundance across occupied samples (Lloyd's index of mean crowding). Within-site patchiness was not caused by a restriction of individual species to specific subareas but by variation in their local density, particularly by the extent of unoccupied ‘interstitial’ spaces within patches. Especially in the more uniform Queensland conditions, the more common species occurred relatively widely across the whole locality; individual samples from which a given species was absent never themselves formed patches, the number of such samples conforming to points on truncated normal curves of the frequency of occurrence. Of the 36 species investigated, the two most abundant and widespread both in Queensland and in South Africa displayed significant or near-significant uniformity of levels of local patchiness, whilst five showed significantly uniform mean crowding and ten significantly uniform unoccupancy. This is the first demonstration that some species may display a characteristic level of patchiness in a given habitat type.

Morisita's index of patchiness and edge effects: A response to Butturi-Gomes and Petrere (2020)

Abstract In a recent paper in Ecological Indicators, Butturi-Gomes and Petrere (2020) investigated Morisita's index of patchiness in relation to edge effects and concluded: that edge avoidance by a species drives its patchiness estimation … which might be the reason behind so many claims of population aggregation' and that 'the presence of edge avoidance leads to false claims of population aggregation, based solely on Morisita's patchiness index. One of the patchiness 'claims' that they specifically criticised was that of Barnes and Laurie (2018) for intertidal seagrass macrobenthos, Butturi-Gomes and Petrere stating that these authors: disregarded possible edges, which are indeed hard to define in marine environments, but are still of importance, particularly in seagrass substrates, as Smith et al. (2008) pointed out. What Butturi-Gomes and Petrere failed to mention, however, was (a) that Barnes and Laurie did not use Morisita's patchiness index, (b) that the index they did use was not the sole basis for their finding of patchiness, and (c) that they cited extensive previous work at their site that had investigated seagrass edge effects — indeed, rather than ignoring such edges they specifically sited their study area within a non-edge zone (sensu Smith et al., 2008). The patchiness they observed was not 'false' and it was not driven by active aggregation away from edges but most likely by the effect of predation by mobile nekton on prey densities.

Daily anchovy (Engraulis ringens) egg mortality rates in different spawning zones along the Chilean coast

The daily egg mortality (Z) of small pelagic fish can be modulated by environmental variables as well as by population derived factors such as egg production and/or dispersion and aggregation processes. The anchovy daily egg mortality rate was compared across spawning areas distributed in the North (18∘25’S-26º03’S), Central (34º30’S-37º10’S), and South (38∘S-41∘20’S) zones along the Chilean coast. Daily egg production (P0) and Z were estimated through a generalized linear model (binomial negative) from egg count data obtained in yearly Daily Egg Production Method applications (2002–2014). Co-variables included P0, the spawning area (SA), sea surface temperature (SST), phytoplankton biomass (Chl-a), alongshore wind (V) and an index of the El Niño-Southern Oscillation (ENSO) during the spawning period (August–September).Egg mortality was significantly higher in the North zone, influencing spatial differences rather than yearly effects. Egg mortality was not associated with ENSO, but correlated positively with P0, SA, SST, and V, and negatively with Chl-a. The best model explained 42.3% (P<0.01) of the egg mortality rates and included SST and Chl-a. In the South zone, the egg mortality was significantly correlated with P0 and V, which was interpreted as density-dependent effects and winds driving egg concentration processes rather than dispersion. The Lloyd’s patchiness index was computed as an index of egg aggregation by embryonic development stages (Group A: early development, Group B: middle development, and Group C: close to hatching). The spawning area was negatively correlated with the patchiness index of Groups A and B in the North zone. Overall results suggested that anchovy eggs survival would be dependent on dispersion in the North zone but concentration and retention in the South spawning area and thereafter coincident with reproductive tactics of adults in the North and South areas, respectively.

Combined synthetic and biotic indices of Posidonia oceanica to qualify the status of coastal ecosystems in the North Aegean

Abstract Mediterranean seagrass Posidonia oceanica is used as a common biological indicator in the monitoring programmes of the Water Framework Directive (WFD) due to its structural and functional features providing information about the status of coastal ecosystems. In this respect synthetic seascape ecological indices using P. oceanica: the Conservation Index (CI), the Substitution Index (SI), the Phase Shift Index (PSI) and the Patchiness Index (PI) provide supplementary data on the meadow status and on the pressures affecting the meadows besides evaluating the water quality. However, these indices have not been adopted by the European Union Water Framework Directive (WFD). This survey is, therefore focused on the qualification of the status of coastal ecosystems in the North Aegean Sea with an integrated approach based on the synthetic (the CI, the SI, the PSI and the PI) and biotic indices (Biotic Index of Posidonia and Ecosystem Based Quality Index) of P. oceanica. Measurements of several parameters are conducted in four sites (2 natural, 2 anthropized) in Gokceada (North Aegean). The preliminary results confirm the efficiency of synthetic and biotic indices to evaluate the ecosystem status in relation with anthropogenic pressures at a local extent. The mean value of the CI corresponds to a “good” status, while the value of the BiPo Index corresponds to a “moderate” and the value of the EBQI corresponds to a “poor” status for Gokceada. Maximum values of the synthetic and biotic indices are recorded in natural sites. On the contrary, minimum values are recorded in anthropized sites close to marine-based activities. In addition, an early stage of a phase shift (PSI

Seasonal Population Dynamics, Sampling Distribution, and Fixed-Precision Sequential Sampling of Spectrobates ceratoniae (Lepidoptera: Pyralidae) in Pomegranate Orchards

The carob moth, Spectrobates ceratoniae Zeller, is the most destructive pest of pomegranate groves of Iran. Seasonal population dynamics of the pest was studied in pomegranate orchards of Sirvan, Ilam province, in southwestern Iran for 2 yr (2016/2017). Sampling distribution of the pest larvae on pomegranate fruits was evaluated by Taylor's power law and Iwao's patchiness index, and a fixed-precision sequential sampling plan of the pest was developed using Green's model. The adult population peaked in June. The activity period of the larvae was observed from June to October and peaked in October. Sampling distribution of the larvae on pomegranate fruits was random. Estimated optimum sample sizes ranged from 1 to 44 and 1 to 16 fruits at precision levels of 0.25 and 0.1, respectively.

Distribution pattern and sequential sampling plan for chilli thrips, Scirtothrips dorsalis Hood (Thripidae: Thysanoptera)

Spatial distribution and sequential sampling plan for chilli thrips, Scirtothrips dorsalis Hood were analyzed through Taylor’s power law (TPL) and Iwao’s mean crowding regression (IMC) for rainy and summer seasons during 2016–17 on chilli crop. The results revealed that the mean number of thrips in the field was low (1.07 thrips/plant) at early crop growth stages (32 days after transplanting (DAT)) and increased gradually with a peak (21.53 thrips/plant) at 56 DAT. Inconsistency in the mean number of thrips with shifting variance was noticed. The variance of thrips population increased with increase in its density with the best variance (122.41) observed at 56 DAT. Samples of thrips showed variance to mean ratio (S2/X), Lloyd’s patchiness index (X*/X), as well as Morisita Index more than one, revealing clumped distribution. The data on thrips population was best fit to TPL (a = 0.184, b = 1.27, R2 = 0.66) and the IMC (α = 0.93, β = 1.14, R2 = 0.94). Larger variability in sample size vis-a-vis mean population density was also achieved at 10 and 20% precision levels. Considering TPL parameters, the decisive lines of sequential sampling for S. dorsalis was chosen at d = 13n ± 8.07√n. The sequential sampling plan will thus help in reducing the costs for an effective and efficient management of S. dorsalis on chilli.

Edge influence and population aggregation: On point and interval statistical performances of Morisita patchiness index estimators in different sampling schemes

• Edge influence alone leads to false claims of patchiness level. • The shape of sampling unit is irrelevant to estimate aggregation. • Increasing sampling effort is not robust against edge influence. • Bigger sampling units greatly outperformed small ones. • Resampling methods do not solve estimation performance issues. Usually, individuals in biological populations are spatially clumped and the measures used to quantify this pattern has caught attention from ecologists due to its many implications, from species diversity to epidemiology, landscape use and ecosystem services. The Morisita patchiness index ( I δ ) is one measure of population aggregation and has proven to be useful in quadrat sampling, although the effects of edge influence and the study site shape over the index estimation are a pending issue. Thus, in this paper we aim at evaluating the statistical performances of the moment estimator as well as the bias-corrected, non-parametric bootstrap of I δ for completely random and aggregated spatial patterns, considering the presence or absence of an edge effect in convex study sites using completely random selection of sampling units in a lattice. We used computer simulations to both creating the fragment and sampling it, whilst exerting increasing sampling efforts in lattices of different shapes (quadrats, circlets, rectangles and hexagonal) and sizes. We considered increasing levels of aggregation using both, Poisson and modified Thomas point processes of homogeneous and inhomogeneous intensities to respectively modeling the absence or presence of the edge influence. We found no substantial difference in point performance when comparing study site shapes in scenarios of no edge influence, although synergetic effects between aggregation and edge avoidance further increased bias in I δ estimation. Despite useful for obtaining confidence intervals, resampling methods yielded the same results observed for the classical estimator. In addition, we observed that sampling effort was not robust against lack of precision and accuracy and, despite prior beliefs, quadrats did not outperform circlets or rectangles; indeed, they all had essentially the same point and interval performances. Finally, the best estimation performances occurred for big sampling units of any shape when compared to small ones, thus, given an appropriate scale, one should prefer bigger quadrats whenever conducting a field study. Our results ultimately pointed out that edge avoidance by a species drives its patchiness estimation even when they are randomly distributed into the core area, which might be the reason behind for so many claims of population aggregation.

Spatial Distribution of Soybean Cyst Nematode in Research Plots.

Soybean cyst nematode (SCN; Heterodera glycines Ichinohe) is a major pathogen of soybean [Glycine max (L.) Merr.] in the United States. The spatial distribution of SCN in 10 naturally infested research sites in North Dakota was examined between 2006 and 2009. Egg densities were measured in plots and expressed as arithmetic means or grouped into classes using two categorical scales based on the effect of SCN on yield. Data were used to determine spatial distribution, egg cluster sizes, minimum plot sizes, and replications in field experiments. SCN populations varied among plots from undetected to 25,800 eggs/100 cm3 of soil, and differences between adjacent plots were as high as sixfold. Mean to median ratios and Lloyd's index of patchiness suggested an aggregated distribution in nine of the 10 sites. SCN cluster sizes varied in five of the 10 sites and optimum plot size over all sites varied depending on calculation methods. The minimum number of replications needed to detect specific differences among plots varied between field sites. Grouping data into either of the two categories generally increased the ability to detect differences between plots. The spatial distribution of SCN can be a critical factor affecting design and outcomes of field experiments.

How biophysical interactions associated with sub- and mesoscale structures and migration behavior affect planktonic larvae of the spiny lobster in the Juan Fernández Ridge: A modeling approach

The Juan Fernández Ridge (JFR) is a chain of topographical elevations in the eastern South Pacific (∼33–35°S, 76–81.5°W). Rich in endemic marine species, this ridge is frequently affected by the arrival of mesoscale eddies originating in the coastal upwelling zone off central-southern Chile. The impacts of these interactions on the structure and dynamics of the JFR pelagic system have, however, not been addressed yet. The present model-based study is focused on the coupled influence of mesoscale-submesoscale processes and biological behavior (i.e., diel vertical migration) on the horizontal distribution of planktonic larvae of the spiny lobster (Jasus frontalis) around the JFR waters. Two case studies were selected from a hydrodynamic Regional Ocean Modeling System to characterize mesoscale and submesoscale structures and an Individual-based model (IBM) to simulate diel vertical migration (DVM) and its impact on the horizontal distribution and the patchiness level. DVM behavior of these larvae has not been clearly characterized, therefore, three types of vertical mechanisms were assessed on the IBM: (1) no migration (LG), (2) a short migration (0–50 m depth, DVM1), and (3) a long migration (10–200 m depth, DVM2). The influence of physical properties (eddy kinetic energy, stretching deformation and divergence) on larval aggregation within meso and submesoscale features was quantified. The patchiness index assessed for mesoscale and submesoscale structures showed higher values in the mesoscale than in the submesoscale. However, submesoscale structures revealed a higher accumulation of particles by unit of area. Both vertical migration mechanisms produced larger patchiness indices compared to the no migration experiment. DVM2 was the one that showed by far the largest aggregation of almost all the aggregation zones. Larval concentrations were highest in the submesoscale structures; these zones were characterized by low eddy kinetic energy, negative stretching deformation, and slight convergence. Stretching deformation flow appeared to be triggered by the eddy-eddy interactions and the Robinson Island barrier effect, and it likely promotes the aggregation of the spiny lobster larvae in the Juan Fernández system. These results highlighted the importance of the coupled effect of physical (mesoscale and submesoscale oceanographic features) and biological processes (DVM) in the generation of larval patchiness and concentration of spiny lobster larvae around the JFR, which could be key for their survival and retention in those waters.

Ecology and behaviour of holoplanktonic scyphomedusae and their interactions with larval and juvenile fishes in the northern Gulf of Mexico

Abstract Pelagia noctiluca is a venomous, globally distributed holoplanktonic scyphomedusa that periodically forms aggregations in coastal environments, yet little is known about its ecology and behaviour in the northern Gulf of Mexico (nGOM). Using a high resolution plankton imaging system, we describe the patch characteristics of Pelagia medusae in relation to fine-scale biological and physical variables during two summers at shallow (∼25 m, 2016) and deeper (∼45 m, 2011) sampling areas on the nGOM shelf. At the deeper site during the day, average Pelagia medusae concentrations just underneath a surface plume of fresher water (10–25 m) ranged from 0.18 to 0.91 ind. m−3, with a Lloyd’s patchiness index of 13.87, indicating strong aggregation tendencies (peak fine-scale concentration reached 27 ind. m−3). These patches were often associated with horizontal gradients in salinity, and concentrations of several zooplankton taxa (e.g. chaetognaths, hydromedusae, siphonophores, and ctenophores) were significantly negatively correlated with Pelagia medusae abundance (p &amp;lt; 0.0001, Spearman correlations). Although larval fish abundance was not correlated with Pelagia medusae on the 1 m3 scale (19.25 m horizontal distance), larval and juvenile fishes between 0.6 and 2.0 cm aggregated underneath the bell of some Pelagia medusae during the daytime only, even within hypoxic waters. Vertical distributions collected on a diel cycle demonstrated that Pelagia medusae perform a reverse diel vertical migration constrained by low salinity near the surface. These data suggest that salinity changes drive the distribution of Pelagia medusae vertically and horizontally, and when sufficient concentrations are present, medusae are capable of exerting a top-down effect on the abundances of their zooplankton prey. For zooplankton with high visual acuity, such as larval and juvenile fishes, the relationship with Pelagia medusae may change on a diel cycle and depend on the sensory ability of potential prey.