Group size, crowding, and age class composition of the threatened Sambar Rusa unicolor (Kerr, 1792) (Mammalia: Cetartiodactyla: Cervidae) in the semi-arid regions of northeastern Rajasthan, India

Grouping characteristics and population growth dynamics of Sambar were studied in Bir Jhunjhunu Conservation Reserve (BJCR) and Bairasar Johad (BJ) in Rajasthan, India from July 2018 to June 2019. Following the scan sampling method, a total of 117 sightings of Sambar (N= 488 individuals) were recorded in BJCR, and 106 in BJ (N= 389 individuals), during 24 fortnightly visits. The data revealed that besides solitary sightings of Sambar, groups ranging from 2–11 and 2–12 individuals were observed in BJCR and BJ, respectively. The overall mean group size and mean crowding of Sambar were 4.2±0.2 S.E. and 5.3 respectively in BJCR, and 3.7±0.2 S.E. and 5.0 respectively in BJ. The sex ratio was skewed towards females. The overall adult male: adult female: fawn ratio was 74.4: 100: 47.1 (N= 488 individuals) in BJCR while the ratio was 92.6: 100: 41.1 (N= 389 individuals) in BJ. As far as the social organization of Sambar is concerned, six types of herds were recorded in the present study. It is urged that sambar populations outside protected area also need simultaneous strategies for conservation attention.

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.

Spatial distribution of Brevicoryne brassicae (L.) in Cabbage in mid-hills of Himachal Pradesh, India

Investigations were carried out during two consecutive Rabi seasons of 2014 and2015 at the Experi-mental Farm of the Department of Seed Science and Technology, Dr Y S Parmar University of Horticulture and For-estry, Nauni, Solan, Himachal Pradesh, India to study the spatial distribution of Brevicoryne brassicae in cabbage. One month old cabbage seedlings were planted in the field in the month of November during both the years. Distri-bution pattern of any insect population is an important aspect as it represents the interaction between individuals of the species and their habitat. Spatial distribution is useful for designing efficient sampling programmes for population estimation and development of population models. Spatial distribution is also important to understand the bioecology of the pest and to determine the sampling protocol for that species. In the present study variance to mean ratio (s2/X),mean crowding (X*), ratio of mean crowding to mean (X*/X), ‘k’ of negative binomial, Taylor’s power equation(s2 = 0.9099X1.55 during 2014 and s2 = 2.9861X1.1949 during 2015), Iwao’s patchiness regression and optimum number of samples (Nopt) required to achieve the desired precision were calculated for different densities. Cabbage aphid, B. brassicae appeared in the fourth standard week i.e last week of January( 26.2 aphids/ plant during 2014 and 0.30 aphids/ plant during 2015) and persisted upto thirteenth standard week i.e last week of April ( 18.4 aphids/ plant during 2014 and 18.2 aphids/ plant during 2015) and followed a negative binomial distribution during both years. Optimum number of samples (Nopt) required varied with mean density as well as precision level. The present study will serve as basic information to develop a sampling plan of B. Brassicae in cabbage for its monitoring and management.

The Spatial Patterns of Lilium regale Population

Approaches like the diffusion coefficient, the Morisita index, the intensity and the mean crowding are employed in this paper to determine the spatial patterns of population distribution of L. regale. The results show: (1) The diffusion coefficient and the Morisita index of L. regale are sharply greater than 1 and the spatial pattern is the cluster; (2) The mean crowing is 59.1638 and the intensity is 2.2410 and the level of intensity is rather high.

Spatial distribution of the cottony camellia scale, Pulvinaria floccifera (Westwood) (Hemiptera: Coccidae) in the tea orchards

In the north of Iran, near the Caspian Sea, about 35,627 ha is cultivated with tea plant, Camellia sinensis (L.) Kuntze on both plain and hilly land. The cottony camellia scale, Pulvinaria floccifera (Westwood) (Hemiptera: Coccidae) is one of the most important pests of tea orchards in the north of Iran. Spatial distribution is an important item in entomoecology and needs to be studied for many pest management programs. So, weekly sampling of P. floccifera population was carried out throughout the 2008-2010 season, in the tea gardens of the Tonekabon region of the Mazandaran province of Iran. Each cut branch of tea was determined as a sample unit and after primary sampling, sample size was calculated using the equation: N = (ts/dm)2, (d = 0.15, sample size = 50). The data acquired were used to describe the spatial distribution pattern of P. floccifera by Tylor’s power law, Iwao’s mean crowding regression, Index of Dispersion (ID), and Index of Clumping (IDM). Tylor’s power law (R2 > 0.84) and Iwao’s mean crowding regression (R2 > 0.82) indicated that spatial distribution of 1st and 2nd nymphal instars is aggregated, but the distribution of 3rd instars, adults, and egg ovisacs is uniform. A result of ID and IDM showed that distribution of 1st, 2nd, and 3rd instars, adults, and egg ovisacs were aggregative each time the sampling was done.

SPATIAL HETEROGENEITY IN SIMPLE DETERMINISTIC SIR MODELS ASSESSED ECOLOGICALLY

Patchy or divided populations can be important to infectious disease transmission. We first show that Lloyd’s mean crowding index, an index of patchiness from ecology, appears as a term in simple deterministic epidemic models of the SIR type. Using these models, we demonstrate that the rate of movement between patches is crucial for epidemic dynamics. In particular, there is a relationship between epidemic final size and epidemic duration in patchy habitats: controlling inter-patch movement will reduce epidemic duration, but also final size. This suggests that a strategy of quarantining infected areas during the initial phases of a virulent epidemic might reduce epidemic duration, but leave the population vulnerable to future epidemics by inhibiting the development of herd immunity.

Population Density and Spatial Distribution Pattern of Hypera postica (Coleoptera: Curculionidae) in Ardabil, Iran

The alfalfa weevil, Hypera postica (Gyllenhal), feeds almost exclusively on alfalfa, Medicago sativa L. in most region of the world where forage crop is grown. It has been investigated the population density and spatial distribution of alfalfa weevil on alfalfa in Ardabil during 2010. Using a 0.25 m2 quadrate sample unit a reliable sample size was 65, with maximum relative variation of 15%. The relative variation (RV) of the primary sampling data was 13.6. The highest population density of the alfalfa weevil was recorded on 17th April. To estimate the spatial distribution pattern of this pest, data were analyzed through index of dispersion, Lloyd’s mean crowding, Morisita’s index and two regression models (Taylor’s Power Law and Iwao’s Patchiness Regression). Taylor’s model showed an aggregated distribution pattern for all life stages. Iwao’s patchiness regression indicated that larvae, adult and total life cycle had aggregated spatial distribution (tc < tt), while pupae of alfalfa weevil exhibited a random pattern. The index of dispersion and Lloyd’s mean crowding methods indicated an aggregated distribution for this insect. Spatial distribution parameters of this species are used to outline a sampling program as well as to estimate population density of H. postica development stages. Optimum sample sizes for estimates of larval density, at three levels of precision, are presented.

Quantitative Evaluation of the Uniformity of Abrasive Distribution Based on Image Processing

In precision machining, the uniformity degree of abrasive distribution affects significantly the surface quality. To quantitatively evaluate the uniformity of abrasive distribution, in this paper digital image processing technology was employed to segment the working face images of impregnated diamond tools; mean crowding index was used to classify the pattern of abrasive distribution; fractal dimension determined by gyration radius method was applied to characterize the bulk uniformity of abrasive distribution on face plane; the coefficient of variation of Voronoi cell areas was adopted to describe the local distribution feature of abrasive grits. The results show that mean crowding index, fractal dimension and CV of Voronoi cell areas can characterize the uniformity of abrasive distribution from different points of view, and can be used to quantitatively evaluate the uniformity of abrasive distribution.