University of Windsor

About: University of Windsor is a education organization based out in Windsor, Ontario, Canada. It is known for research contribution in the topics: Population & Argumentation theory. The organization has 10654 authors who have published 22307 publications receiving 435906 citations. The organization is also known as: UWindsor & Assumption University of Windsor.

Polyphyletic origins of asexuality in daphnia pulex. ii. mitochondrial-dna variation.

Abstract: Allozyme studies of the cladoceran Daphnia pulex have shown that most populations reproduce by obligate parthenogenesis, although some cyclically parthenogenetic populations remain throughout the southern portion of its range. Clonal diversity within the obligate parthenogens is extremely high and has been attributed to the polyphyletic origin of asexuality. Specifically, it has been proposed that the clonal diversity in the obligate parthenogens was generated via the spread of a sex-limited meiosis suppressor through populations of a cyclically parthenogenetic ancestor. In this study, analysis of polymorphism of restriction-endonuclease sites in the mitochondrial genome, in conjunction with allozyme analysis, was used to determine whether obligate parthenogenesis has a monophyletic or polyphyletic origin in D. pulex. An allozyme survey of 77 populations from Ontario and Michigan was first conducted to determine breeding systems and levels of clonal diversity (Hebert et al., 1989). Mitochondrial-DNA variation was then surveyed in one isolate of each clone from each population reproducing by obligate parthenogenesis and in 2-4 isolates from each population reproducing by cyclic parthenogenesis. Seventeen restriction enzymes were used in this analysis. Thirty-five mitochondrial genotypes were found among the 36 obligate clones (as identified by allozyme analysis), while 17 mitochondrial genotypes were identified among 40 cyclic isolates from 14 populations. Five mitochondrial genotypes were found in both groups. Parsimony and phenetic-clustering methods were used to construct trees showing the genetic relationship among mitochondrial genotypes. The results clearly show that obligate parthenogenesis had a polyphyletic origin in this species. The close relationship between cyclic and obligate parthenogens in the Great Lakes region suggests that many obligate clones have recently been derived from cyclic populations and that the generation of clones is still occurring in this area. Patterns of clonal diversity based on the joint consideration of allozyme and mitochondrial-DNA data are discussed.

Is Bone Mineral Composition Disrupted by Organochlorines in East Greenland Polar Bears (Ursus Maritimus)

Abstract: We analyzed bone mineral density (BMD) in skulls of polar bears (Ursus maritimus) (n = 139) from East Greenland sampled during 1892–2002. Our primary goal was to detect possible changes in bone mineral content (osteopenia) due to elevated exposure to organochlorine [polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane (DDT) and its metabolites, chlordanes (CHLs), dieldrin, hexacyclohexanes, hexachlorobenzene] and polybrominated diphenyl ether (PBDE) compounds. To ensure that the BMD value in skull represented the mineral status of the skeletal system in general, we compared BMD values in femur and three lumbar vertebrae with skull in a subsample. We detected highly significant correlations between BMD in skull and femur (r = 0.99; p < 0.001; n = 13) and skull and vertebrae (r = 0.97; p < 0.001; n = 8). BMD in skulls sampled in the supposed pre-organochlorine/PBDE period (1892–1932) was significantly higher than that in skulls sampled in the supposed pollution period (1966–2002) for subadult females, subadult males, and adult males (all, p < 0.05) but not adult females (p = 0.94). We found a negative correlation between organochlorines and skull BMD for the sum of PCBs (∑PCB; p < 0.04) and ∑CHL (p < 0.03) in subadults and for dieldrin (p < 0.002) and ∑DDT (p < 0.02) in adult males; indications for ∑PBDE in subadults were also found (p = 0.06). In conclusion, the strong correlative relationships suggest that disruption of the bone mineral composition in East Greenland polar bears may have been caused by organochlorine exposure.

Reassessment of Species Invasions Concepts: The Great Lakes Basin as a Model

Abstract: The Laurentian Great Lakes have an extensive history of species introductions, many of which occurred as a result of ballast water discharge by trans-oceanic ships. Most nonindigenous species (NIS) of animals and protozoans that established in the Great Lakes since 1985 are native to the Black, Azov and Caspian Seas or other regions of Eurasia. Analysis of vector strength from global port regions indicates that these NIS, which include amphipods, crustacean zooplankton, mussels and fishes, have been transported principally along dominant shipping routes from native or introduced habitats in northern and western Europe to the Great Lakes. A large group of additional taxa, many of which have extensive invasion histories, is available for transfer to the Great Lakes from key European ports. Thus, joint consideration of invasion corridors and the NIS species established in key donor ports provides an indication of taxa that may colonize the Great Lakes in future. Recent studies indicate that risk assessment may be extended even further for inland lakes subject to NIS invasion from the Great Lakes in cases where invasion vectors can be identified and quantified. Identification of invasion corridors and quantification of vector pathways, using lakes as model systems, provide a promising opportunity for the evolution of invasion biology from a largely descriptive science into a more predictive and quantitative discipline.

Active and non-active porosity in concrete Part I: Experimental evidence

Abstract: The findings of an experimental study are described, documenting and quantifying the influence of concrete porosity on its mechanical properties in saturated and dry states Concrete porosity consists of capillary and entrained air, and described respectively as active and non-active, depending on its influence on mechanical properties with changing moisture state It was found that the active (capillary) porosity influence on mechanical properties is more pronounced with decreasing moisture The influence of non-active (entrained-air) porosity on concrete mechanical properties is invariant of moisture state