Home  About us  Contact
 

Geographical Groups (geographical + groups)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

The role of environment in shaping the genetic diversity of the subalpine mosquito, Aedes rusticus (Diptera, Culicidae)

MOLECULAR ECOLOGY, Issue 7 2003
J. P. David
Abstract The relative involvement of larval dietary tolerance to the leaf-litter toxic polyphenols in shaping population genetic structure of the subalpine mosquito Aedes rusticus was examined. This was compared with other parameters such as geographical range, type of vegetation surrounding the breeding site, and occurrence of annual larvicidal treatments. Population genetic structure was analysed at 10 presumed neutral polymorphic isoenzyme loci. Toxicological comparisons involved standard bioassays performed on larvae fed on toxic decomposed leaf litter. Significant overall genetic differentiation was observed among the 22 studied populations and within the five defined geographical groups. Analysis of molecular variance revealed an absence of relation between genetic and environmental parameters, genetic variance being essentially found within populations. This suggested that the larval dietary tolerance to the toxic leaf litter and the other studied parameters poorly influence population genetic structure. The local adaptation of subalpine mosquito populations to the surrounding vegetation thus appears as a labile trait. Such a dynamic adaptation is also suggested by the correlation between geographical and toxicological distances and the correlation between dietary tolerance to the leaf-litter toxic polyphenols and annual larvicidal treatments. [source]

Marginalization, Facilitation, and the Production of Unequal Risk: The 2006,Paso del Norte,Floods

ANTIPODE, Issue 2 2010
Timothy W. Collins
Abstract:, Drawing upon insights from the field of urban political ecology, this article extends the critical hazards concept of,marginalization,by incorporating a relational focus on,facilitation. Facilitation connotes the institutionally mediated process that enables powerful geographical groups of people to minimize negative environmental externalities and appropriate positive environmental externalities in particular places, with unjust socioenvironmental consequences. The article demonstrates the utility of a marginalization/facilitation frame for understanding the production of unequal risk based on a case study of the 2006 El Paso (USA)-Ciudad Juárez (Mexico) flood disaster. The case study reveals how uneven developments have produced complex sociospatial patterns of exposure to flood hazards and how processes of facilitation and marginalization have created socially disparate flood-prone landscapes characterized by unequal risks. The paper concludes by outlining how the frame presented helps clarify understanding of the production of unequal risk. [source]

Investigating South American biogeographic history using patterns of skull shape variation on Cerdocyon thous (Mammalia: Canidae)

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009
FABIO DE A. MACHADO
Patterns of geographic variation of the canid Cerdocyon thous have historically been obscured by its remarkable intraspecific morphological variability. The observed distribution is highly associated with phytophysiognomy, a feature considered highly dynamic along geological time. In the present study, we tested whether vegetation distribution during the Holocene Glacial Maximum of South America (HGM) explains the patterns of morphological variation within Cerdocyon thous. The species was divided in groups according to paleohabitats that could support their presence during the HGM, and then tested for differences in skull morphometrics. The results obtained demonstrate that the climatic changes during the HGM influenced the population structure of this species, resulting in the establishment of geographical groups with different degrees of morphological cohesion. Higher morphological cohesion found in the Northern group might be explained by the marked discontinuity between its geographical range and the rest of the species'distribution. The Eastern and Southern morphological divergence is less striking and, although this could be related to past vegetation distribution, the disappearance of those barriers leads to a population structure that could be slowly breaking down. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 77,84. [source]

Phenetic analysis of the Mexican midland pinyon pines, Pinus cembroides and Pinus johannis

BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2000
A. ROMERO
This account presents an analysis of allopatric, sympatric and juxtaposed populations of the pinyon pines, Pinus cembroides Zucc. and P. johannis M.-F. Robert, based on phenetic analysis of morphological data, and draws on a comparison and differentiation of P. culminicola Andresen & Beaman. A qualitative and quantitative database for populations has been assembled and used for a cluster and ordination analysis using NTSYS. It was found that individual populations of the taxa were distinguishable. The emergence of morphological intermediate populations between P. cembroides and P. johannis was confirmed. The pattern of variation inP. johannis was found to be discrete, showing three geographical groups. The phenetic similarity betweenP. johannis from Zacatecas and P. johannis from San Luis Potosi and Queretaro was lower than that of P. johannis from Zacatecas and P. culminicola from Nuevo Leon. The following traits distinguish P. cembroides and the other two species: colour and fertility of seeds; cone shape; colour and width of needles; physiognomy; seed dimensions. This last trait can be used to distinguish three subgroups of pines with white endosperm in the northern, central and southern regions of the Mexican highlands. [source]