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Range Restriction (range + restriction)
Selected AbstractsAggression in imported fire ants: an explanation for shifts in their spatial distributions in Southern United States?ECOLOGICAL ENTOMOLOGY, Issue 4 2009HENRY Y. FADAMIRO Abstract 1.,The imported fire ants, Solenopsis invicta Buren (red), S. richteri Forel (black), and their hybrids (S. invicta × S. richteri) are sympatric congeners with overlapping but shifting spatial distributions in northern Alabama and Mississippi, United States. 2.,The abilities of workers of the three ant forms (or species) to recognise non-nestmate conspecifics and heterospecifics were compared in separate aggression bioassays using three group sizes of competitor numbers (battles): 1-1, 5-1, and 5-5 resident,intruder battles. 3.,Workers of all three forms showed significant aggression toward non-nestmate conspecifics and heterospecifics. The results of the intra-specific aggression bioassays showed that S. invicta had the lowest aggression threshold, whereas S. richteri was the least aggressive. Survival rates 1 day after intra-specific encounters were higher for S. richteri than for S. invicta or hybrids, consistent with its lower aggressiveness. 4.,In inter-specific interactions, S. invicta workers showed the greatest aggression and were more aggressive towards S. richteri than to hybrids. Furthermore, survival 1 day after inter-specific encounters was highest for S. invicta workers, whether they were the intruders or residents. The hybrid form was intermediate between both parental forms in aggression and post-aggression survival. 5.,The live 1-1 and 5-5 battles produced similar and consistent results, but differences were amplified in the 5-5 battles, suggesting an effect of group size on aggression. These results may explain the observed shifts in the spatial distributions of the three forms and range restriction of S. richteri in southern United States. [source] On Making Progress in Communication ScienceHUMAN COMMUNICATION RESEARCH, Issue 4 2002Franklin J. Boster This essay advances practices for designing, analyzing, and reporting communication research. The arguments presented center around improving researchers' abilities to cumulate results across studies, but also apply to improving the utility of the individual study. Practices advocated include: (a) sophistication, falsification, and replication as important criteria for evaluating research design; (b) diminishing the importance of the null hypothesis statistical significance test, employing confidence intervals, and correcting correlations for both measurement error and range restriction when analyzing data; and (c) including both descriptive statistics and measures of the strength of bivariate relationships when reporting results. [source] Patterns in diversity of anurans along an elevational gradient in the Western Ghats, South IndiaJOURNAL OF BIOGEOGRAPHY, Issue 5 2007Rohit Naniwadekar Abstract Aim, To examine patterns in anuran species richness along an elevation gradient and identify factors that govern anuran species richness on a tropical elevational gradient. Location, Sampling for anurans was carried out in Kalakad Mundanthurai Tiger Reserve (KMTR) in the southern Western Ghats, India. Methods, Night-time sampling for anuran species richness was carried out from 20 November 2004 to 20 April 2005, during the north-east monsoon and dry seasons, using transects (50 × 2 m) and visual encounter surveys along the streams. The entire gradient was classified into thirteen 100-m elevation zones. Sampling at the alpha (single drainage basin) level was carried out in the Chinnapul River drainage basin (40,1260 m a.s.l.) and at the gamma (landscape) level in four drainage basins. Additionally, published records were used to arrive at an empirical species richness (S) for the entire landscape. Mid-Domain Null software was used to test for the possible influence of geometric constraints on anuran species at both the alpha and gamma levels. The influence of area under each elevation zone on empirical S was tested. The pattern in anuran species richness along the elevational gradient was investigated using: (1) species boundaries in each elevation zone and their habitat correlates, (2) abiotic factors as predictor variables, (3) mean snout vent lengths of anurans, and (4) correlation between the matrices of distance in the elevation zones based on microhabitat parameters and species composition. Cluster analysis on species presence,absence in the elevation zones was used to categorize the entire gradient into high, middle and low elevations. In these three elevation categories, pattern in composition of species was examined for endemism in Western Ghats,Sri Lanka biodiversity hotspot, uniqueness to an elevation zone, adaptations of adults and modes of breeding. Results, Species richness at the alpha level increased linearly with elevation, while at the gamma level there were three peaks. Maximum species richness was observed at the highest elevation (1200 m) at both the alpha and the gamma levels. The observed patterns differed significantly from mid-domain null predictions. The multi-modal pattern in species richness was a consequence of overlapping species range boundaries. Soil temperature was the best single measure in explaining the majority of variation in species richness at the alpha level (r2 = 0.846, P < 0.01). However, soil moisture was the best predictor when both the alpha and the gamma sites were pooled (r2 = 0.774, P < 0.01). Anuran body size decreased with an increase in elevation. The highest proportions of endemic and unique species were found at high elevations (> 700 m). The proportion of arboreal anurans increased from low to high elevation. Anurans exhibiting direct development were predominantly found at high elevations. Main conclusions, Geometric constraints did not influence anuran species richness along the elevational gradient. Overlapping range boundaries influenced species richness at the gamma level. Abiotic factors such as soil temperature and moisture influenced anuran species richness in the mountain range. The ,Massenerhebung effect' could be responsible for range restriction and endemism of anurans, differences in guilds and mode of reproduction. These findings highlight the importance of cloud forests for endemic anurans. [source] Methods for Generating Longitudinally Correlated Binary DataINTERNATIONAL STATISTICAL REVIEW, Issue 1 2008Patrick J. Farrell Summary The analysis of longitudinally correlated binary data has attracted considerable attention of late. Since the estimation of parameters in models for such data is based on asymptotic theory, it is necessary to investigate the small-sample properties of estimators by simulation. In this paper, we review the mechanisms that have been proposed for generating longitudinally correlated binary data. We compare and contrast these models with regard to various features, including computational efficiency, flexibility and the range restrictions that they impose on the longitudinal association parameters. Some extensions to the data generation mechanism originally suggested by Kanter (1975) are proposed. Résumé L'analyse des données longitudinales corrélées fait récemment l'objet d'un grand intérêt. Comme l'estimation des paramètres des modèles pour de telles données est souvent basée sur des études asymptotiques, il est nécessaire de procéder à des simulations pour explorer les propriétés des estimateurs en petits échantillonages. Dans ce papier, nous présentons une revue des méthodes qui ont été proposées pour générer des données binaires longitudinales corrélées. Nous les comparons sous différents aspects, notamment en termes d'efficience, flexibilité, et des restrictions qu'elles peuvent avoir sur les paramètres dits d'association longitudinale. Quelques extensions, de la méthode suggérée par Kanter (1975) pour générer de telles données, sont aussi proposées. [source] The Impact of Hunting on the Mammalian Fauna of Tropical Asian ForestsBIOTROPICA, Issue 3 2007Richard T. Corlett ABSTRACT People have hunted mammals in tropical Asian forests for at least 40,000 yr. This period has seen one confirmed global extinction (the giant pangolin, Manis palaeojavanica) and range restrictions for several large mammals, but there is no strong evidence for unsustainable hunting pressure until the last 2000,3000 yr, when elephants, rhinoceroses, and several other species were progressively eliminated from the large parts of their ranges. Regional declines in most species have occurred largely within the last 50 yr. Recent subsistence hunting has typically focused on pigs and deer (hunted with dogs and spears or with snares), monkeys and other arboreal mammals (often caught with blowpipes), and porcupines and other rodents (smoked or dug out of burrows). Over the last 50 yr, the importance of hunting for subsistence has been increasingly outweighed by hunting for the market. The hunted biomass is dominated by the same species as before, sold mostly for local consumption, but numerous additional species are targeted for the colossal regional trade in wild animals and their parts for food, medicines, raw materials, and pets. Many populations of mammalian dispersers of large seeds and understory browsers have been depleted or eliminated, while seed predators have had a more variable fate. Most of this hunting is now illegal, but the law enforcement is generally weak. However, examples of successful enforcement show that hunting impacts can be greatly reduced where there is sufficient political will. Ending the trade in wild animals and their parts should have the highest regional conservation priority. [source] | |||||||||||||