Environmental Associations (environmental + association)

Distribution by Scientific Domains

Selected Abstracts

Modeling the genetic and environmental association between peer group deviance and cannabis use in male twins

ADDICTION, Issue 3 2009
Nathan A. Gillespie
ABSTRACT Background Peer group deviance (PGD) is linked strongly to liability to drug use, including cannabis. Our aim was to model the genetic and environmental association, including direction of causation, between PGD and cannabis use (CU). Method Results were based on 1736 to 1765 adult males from the Mid-Atlantic Twin Registry with complete CU and PGD data measured retrospectively at three time-intervals between 15 and 25 years using a life-history calendar. Results At all ages, multivariate modeling showed that familial aggregation in PGD was explained by a combination of additive genetic and shared environmental effects. Moreover, the significant PGD,CU association was best explained by a CU,PGD causal model in which large portions of the additive genetic (50,78%) and shared environmental variance (25,73%) in PGD were explained by CU. Conclusions Until recently PGD was assumed to be an environmental, upstream risk factor for CU. Our data are not consistent with this hypothesis. Rather, they suggest that the liability to affiliate with deviant peers is explained more clearly by a combination of genetic and environmental factors that are indexed by CU which sits as a ,risk indicator' in the causal pathway between genetic and environmental risks and the expression of PGD. This is consistent with a process of social selection by which the genetic and environmental risks in CU largely drive the propensity to affiliate with deviant peers. [source]

Type and spatial structure of distribution data and the perceived determinants of geographical gradients in ecology: the species richness of African birds

GLOBAL ECOLOGY, Issue 5 2007
Jana M. McPherson
ABSTRACT Aim, Studies exploring the determinants of geographical gradients in the occurrence of species or their traits obtain data by: (1) overlaying species range maps; (2) mapping survey-based species counts; or (3) superimposing models of individual species' distributions. These data types have different spatial characteristics. We investigated whether these differences influence conclusions regarding postulated determinants of species richness patterns. Location, Our study examined terrestrial bird diversity patterns in 13 nations of southern and eastern Africa, spanning temperate to tropical climates. Methods, Four species richness maps were compiled based on range maps, field-derived bird atlas data, logistic and autologistic distribution models. Ordinary and spatial regression models served to examine how well each of five hypotheses predicted patterns in each map. These hypotheses propose productivity, temperature, the heat,water balance, habitat heterogeneity and climatic stability as the predominant determinants of species richness. Results, The four richness maps portrayed broadly similar geographical patterns but, due to the nature of underlying data types, exhibited marked differences in spatial autocorrelation structure. These differences in spatial structure emerged as important in determining which hypothesis appeared most capable of explaining each map's patterns. This was true even when regressions accounted for spurious effects of spatial autocorrelation. Each richness map, therefore, identified a different hypothesis as the most likely cause of broad-scale gradients in species diversity. Main conclusions, Because the ,true' spatial structure of species richness patterns remains elusive, firm conclusions regarding their underlying environmental drivers remain difficult. More broadly, our findings suggest that care should be taken to interpret putative determinants of large-scale ecological gradients in light of the type and spatial characteristics of the underlying data. Indeed, closer scrutiny of these underlying data , here the distributions of individual species , and their environmental associations may offer important insights into the ultimate causes of observed broad-scale patterns. [source]

Self-injurious behaviour in Cornelia de Lange syndrome: 2. association with environmental events

J. Sloneem
Abstract Background Self-injurious behaviour is commonly seen in Cornelia de Lange syndrome (CdLS). However, there has been limited research into the aetiology of self-injury in CdLS and whether environmental factors influence the behaviour. Methods We observed the self-injury of 27 individuals with CdLS and 17 participants who did not have CdLS matched for age, gender, level of intellectual disability and mobility. Descriptive analyses were used to determine the extent to which environmental events were associated with self-injury. Results Lag sequential analysis of the association between self-injurious behaviour and environmental events revealed no differences between the two groups in terms of either the number or degree of environmental associations. Conclusions The results suggest that the associations between the environment and self-injury in CdLS do not differ from those seen in the broader population of people with intellectual disability. By implication the social reinforcement hypothesis is equally applicable to both groups. [source]

Structure and environmental relationships of insectivorous bat assemblages in tropical Australian savannas

Abstract Patterns in the composition of assemblages of microbat species sampled during the late dry season (the ,build-up') in north Australian savannas were assessed against a range of environmental factors as well as four a priori defined habitat types (riparian, escarpments, coastal and woodlands). Distinct species assemblages were most strongly associated with topographic and climatic variables. There were also limited associations with vegetation structure, fire and local roost potential but no associations with insects or water availability. Total species diversity at sample sites was associated with distance to rivers and rainfall. In general, species assemblages were not clearly defined and the number of significant environmental associations was relatively few. We compare these associations with those reported for bat assemblages elsewhere in Australia. [source]