Biomedical subjects

Karl I Ugland

Publications and source records attributed to Karl I Ugland.

3 recordsLinked to original sources

PubMed2006

On plotting species abundance distributions.

1. There has been a revival of interest in species abundance distribution (SAD) models, stimulated by the claim that the log-normal distribution gave an underestimate of the observed numbers of rare species in species-rich assemblages. This led to the development of the neutral Zero Sum Multinomial distribution (ZSM) to better fit the observed data. 2. Yet plots of SADs, purportedly of the same data, showed differences in frequencies of species and of statistical fits to the ZSM and log-normal models due to the use of different binning methods. 3. We plot six different binning methods for the Barro Colorado Island (BCI) tropical tree data. The appearances of the curves are very different for the different binning methods. Consequently, the fits to different models may vary depending on the binning system used. 4. There is no agreed binning method for SAD plots. Our analysis suggests that a simple doubling of the number of individuals per species in each bin is perhaps the most practical one for illustrative purposes. Alternatively rank-abundance plots should be used. 5. For fitting and testing models exact methods have been developed and application of these does not require binning of data. Errors are introduced unnecessarily if data are binned before testing goodness-of-fit to models.

Animals↗

PubMed2006

Predicting the effects of habitat homogenization on marine biodiversity.

Seafloor habitats throughout the world's oceans are being homogenized by physical disturbance. Even though seafloor sediments are commonly considered to be simple and unstructured ecosystems, the negative impacts of habitat homogenization are widespread because resident organisms create much of their habitat's structure. We combine the insight gained from remote sensing of seafloor habitats with recently developed analytical techniques to estimate species richness and assess the potential for change with habitat homogenization. Using habitat-dependent species-area relationships we show that realistic scenarios of habitat homogenization predict biodiversity losses when biogenic habitats in soft sediments are homogenized. We develop a simple model that highlights the degree to which the reductions in the number of species and functional diversity are related to the distribution across habitats of habitat-specific and generalist species. Our results suggest that, by using habitat-dependent species-area relationships, we can better predict variation in biodiversity across seafloor landscapes and contribute to improved management and conservation.

Biodiversity↗

PubMed2002

Factors influencing activities of biotransformation enzymes, concentrations and compositional patterns of organochlorine contaminants in members of a marine food web.

The accumulation of polychlorinated biphenyls (PCBs; 34 congeners), sigmaDDT (p,p'-DDT, o,p'-DDT, p,p'-DDD, o,p'-DDD and p,p'-DDE), chlordanes (sigmaCHL; trans-chlordane, cis-chlordane, trans-nonachlor, cis-nonachlor and oxychlordane), hexachlorocyclohexanes (sigmaHCH; alpha-, beta- and gamma-isomers), hexachlorobenzene (HCB) and mirex was investigated in members of a marine food web from the Hvaler and Torbjørnskaer archipelago, south-eastern Norway. The species studied were bullrout (Myoxocephalus scorpius), cod (Gadus morhua), herring gull (Larus argentatus) and harbour seal (Phoca vitulina). Furthermore, hepatic biotransformation enzyme activities (ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-depentylase (PROD) and glutathione S-transferase (GST)) were measured in all species. The objectives of the study were to investigate factors causing intraspecies variation in activities of biotransformation enzymes, as well as in concentrations and compositional patterns of the organochlorines (OCs). High correlations between EROD and PROD activities were found in all species, suggesting a single, common catalyst, CYP1A, and render the PROD assay questionable as biomarker for CYP2B inducers in marine wildlife. Furthermore, GST activities are shown to be dependent on biological factors, such as age (in harbour seal) and sex (in bullrout). In fish, the OC concentrations vary between the sexes, likely due to differences in fat deposition strategies and possibly sex dimorphism. In seals, concentrations and compositional patterns of the OCs vary with age, owing to selective transfer from mother to pup in utero and mainly through lactation, but likely also due to age specific xenobiotic metabolising capacity.

Age Factors↗