A predictive model for freshwater bioassessment (Mondego River,Portugal)

We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model. At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207 taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality, substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model, the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and increasing the number of ellipses that define quality bands. Handling editor: K. Martens     

The biological assessment of contaminated sediments — the Detroit River example

Contaminated sediments have been found in almost all water bodies which have at some time received, or are presently receiving, waste inputs from urban and industrial sources. In the Laurentian Great Lakes, sediments are classified as contaminated from bulk chemical analysis. The chemical criteria used to evaluate these results are somewhat arbitrary and only partially consider biological impacts. The absence of adequate linkage among sediment contamination, bioavailability, effects on organisms, populations, and ultimately ecosystem health, represents a major barrier to the restoration and protection of aquatic ecosystems.An integrated strategy for the assessment and delineation of contaminated sediments is proposed which provides a comprehensive evaluation of impact, as well as a cost-effective sampling and testing program. The strategy incorporates the triad approach and is to be executed in two stages. Both stages use physical, chemical and biological information; however, the second stage requires more sampling and analyses to specify the severity and extent of the associated problems. To illustrate the type of output anticipated if the strategy is used, data assembled from the Detroit River are presented. They demonstrate that combined analysis of physical, chemical and biological data can be used to link cause and effect between sediment contaminants and benthic communities.     

Predation on snails by three species of triclad and its bearing on the distribution of Planaria torva in Britain

Dugesia polychroa, D. lugubris and Planaria torva preyed upon snails of differing morphologies and while the Dugesia spp. fed approximately in proportion to snail abundance, PL torva was more selective on Potamopyrgus jenkinsi. The incidence of feeding on four snail taxa by the Dugesia spp. was significantly correlated and differed strikingly from that of PI. torva where feeding was related to its annual life cycle. Large peaks of feeding coincided in the Dugesia spp. for the four snail types; this was attributed to snail vulnerability being increased by environmental disturbance. Comparison of feeding by Dugesia spp. in the presence and absence of PI. torva indicated that severe competition was occurring for food with PI. torva having a food refuge in P. jenkinsi. The distribution of PI. torva in Britain is largely confined to productive habitats in the Glasgow-Edinburgh and East Anglia regions. It is concluded that historical rather than ecological events have played the major part in its distribution to date. The strong association of PL torva with port areas and the canal system suggests that it is a recent introduction via the timber trade with Fennoscania.     

The structure of human mitochondrial DNA variation

Summary Restriction analysis of mitochondrial DNA (mtDNA) of 3065 humans from 62 geographic samples identified 149 haplotypes and 81 polymorphic sites. These data were used to test several aspects of the evolutionary past of the human species. A dendrogram depicting the genetic relatedness of all haplotypes shows that the native African populations have the greatest diversity and, consistent with evidence from a variety of sources, suggests an African origin for our species. The data also indicate that two individuals drawn, at random from the entire sample will differ at approximately 0.4% of their mtDNA nucleotide sites, which is somewhat higher than previous estimates. Human mtDNA also exhibits more interpopulation heterogeneity (G_ST=0.351±0.025) than does nuclear DNA (G_ST=0.12). Moreover, the virtual absence of intermediate levels of linkage disequilibrium between pairs of sites is consistent with the absence of genetic recombination and places constraints on the rate of mutation. Tests of the selective neutrality of mtDNA variation, including the Ewens-Watterson and Tajima tests, indicate a departure in the direction consistent with purifying selection, but this departure is more likely due to the rapid growth of the human population and the geographic heterogeneity of the variation. The lack of a good fit to neutrality poses problems for the estimation of times of coalescence from human mtDNA data.     

Mutations for the autosomal recessive and autosomal dominant forms of polycystic kidney disease are not allelic

Summary The autosomal dominant form of polycystic kidney disease (ADPKD) has been linked to the -globin gene locus on 16p. Linkage studies between the autosomal recessive type (ARPKD) and the 3 HVR of the -globin gene cluster showed that the ARPKD and ADPKD are not allelic.     

Collaboration in scientific research: a critical need for freshwater ecology

1. Collaboration means actively working together to achieve things which could not be done alone. This article attempts to provide an overall, unified, guiding framework for collaboration in freshwater ecology by discussing aspects of collaboration at individual and organizational levels, and addressing international linkages.
2. The essential elements of collaboration are communication and trust, and effective project management. Barriers to effective collaboration include competition, organizational cultures and organizational instabilities.
3. The success of collaboration can be measured by tangible benefits such as increased numbers of peer-reviewed publications, the production of working models and a number of intangible benefits.
4. Interactions between individuals lie at the heart of an effective collaboration; organizational arrangements should facilitate this interaction. Some governments are encouraging collaboration to increase cost efficiency and allocate accountability. This trend should continue on an international level.
5. Collaboration is a key to future research in freshwater ecology.     

Larger genetic differences within africans than between Africans and Eurasians

The worldwide pattern of single nucleotide polymorphism (SNP) variation is of great interest to human geneticists, population geneticists, and evolutionists, but remains incompletely understood. We studied the pattern in noncoding regions, because they are less affected by natural selection than are coding regions. Thus, it can reflect better the history of human evolution and can serve as a baseline for understanding the maintenance of SNPs in human populations. We sequenced 50 noncoding DNA segments each approximately 500 bp long in 10 Africans, 10 Europeans, and 10 Asians. An analysis of the data suggests that the sampling scheme is adequate for our purpose. The average nucleotide diversity (pi) for the 50 segments is only 0.061% +/- 0.010% among Asians and 0.064% +/- 0.011% among Europeans but almost twice as high (0.115% +/- 0.016%) among Africans. The African diversity estimate is even higher than that between Africans and Eurasians (0.096% +/- 0.012%). From available data for noncoding autosomal regions (total length = 47,038 bp) and X-linked regions (47,421 bp), we estimated the pi-values for autosomal regions to be 0.105, 0.070, 0.069, and 0.097% for Africans, Asians, Europeans, and between Africans and Eurasians, and the corresponding values for X-linked regions to be 0.088, 0.042, 0.053, and 0.082%. Thus, Africans differ from one another slightly more than from Eurasians, and the genetic diversity in Eurasians is largely a subset of that in Africans, supporting the out of Africa model of human evolution. Clearly, one must specify the geographic origins of the individuals sampled when studying pi or SNP density.