Biomedical subjects

Jurek Kolasa

Publications and source records attributed to Jurek Kolasa.

4 recordsLinked to original sources

PubMed2006

Non-omnivorous generality promotes population stability.

Using a combination of stable isotope analysis of delta13C and delta15N and long-term census data on population abundances for meiofauna in tropical aquatic rock pools, we provide evidence that species which exhibit greater variation in delta13C, an indication of a greater range of distinct carbon sources in their diet, have more stable populations than species with lower variation in delta13C. This link between increased isotope variability and reduced population variability, however, did not hold for delta15N. This suggests that increases in population stability were due to non-omnivorous feeding on multiple carbon sources within a trophic level rather than omnivorous feeding on multiple carbon sources across trophic levels. Our findings corroborate MacArthur's original hypothesis that populations that can access a greater range of resources are more stable than those which consume a more restricted range of resources.

Animals↗

PubMed2004

Are natural microcosms useful model systems for ecology?

Several recent, high-impact ecological studies feature natural microcosms as tools for testing effects of fragmentation, metacommunity theory or links between biodiversity and ecosystem processes. These studies combine the microcosm advantages of small size, short generation times, contained structure and hierarchical spatial arrangement with advantages of field studies: natural environmental variance, 'openness' and realistic species combinations with shared evolutionary histories. This enables tests of theory pertaining to spatial and temporal dynamics, for example, the effects of neighboring communities on local diversity, or the effects of biodiversity on ecosystem function. Using examples, we comment on the position of natural microcosms in the roster of ecological research strategies and tools. We conclude that natural microcosms are as versatile as artificial microcosms, but as complex and biologically realistic as other natural systems. Research to date combined with inherent attributes of natural microcosms make them strong candidate model systems for ecology.

Journal Article↗

PubMed2003

Removing the confounding effect of habitat specialization reveals the stabilizing contribution of diversity to species variability.

Earlier studies have found that diversity, S, stabilizes the relative variability of combined biomass or abundance of species making up a community. However, the effect of S on variability of constituent species has been elusive. We hypothesize that the proportion of specialists increases with S and, because specialists are more variable, this shift in composition will mask the stabilizing effect of S on populations of species making up a community. The test uses data on variability and ecological specialization of species in 49 natural rock pool invertebrate communities. Initial analyses produced inconclusive results similar to earlier studies. However, when variability owing to species' specialization was factored out, S reduced species' abundance variability, although not in all communities. Our study explains why the stabilizing effect of diversity on populations has not been found earlier.

Adaptation, Biological↗

PubMed2003

The relative sensitivity of four benthic invertebrates to metals in spiked-sediment exposures and application to contaminated field sediment.

The relative sensitivity of four benthic invertebrates (Hyalella azteca, Chironomus riparius, Hexagenia spp., and Tubifex tubifex) was determined for Cd, Cu, and Ni in water-only and in spiked-sediment exposures. Survival (median lethal concentrations [LC50s] and the concentrations estimated to be lethal to 25% of test organisms [LC25s]), and endpoints for growth and reproduction (mean inhibitory concentrations [IC25s]) were compared. The sensitivities differed depending on the species and metal, although some trends emerged. In water-only exposures, H. azteca is the most sensitive species to cadmium and nickel, with mean LC50s of 0.013 and 3.6 mg/L, respectively; C. riparius is the most sensitive species to copper, with a mean LC50 of 0.043 mg/L. In the spiked-sediment exposures, the order in decreasing sensitivity to copper is Hyalella = Hexagenia < Chironomus < Tubifex for survival and growth/reproduction. For cadmium, the order in decreasing sensitivity is Hyalella = Chironomus < Hexagenia < Tubifex, and for nickel is Hyalella << Hexagenia < Chironomus < Tubifex. Chironomus riparius and Hexagenia spp. survival can be used to distinguish between toxicity caused by different metals. Species test responses in field-collected sediment(Collingwood Harbour, ON, Canada) were examined in an attempt to determine the causative agent of toxicity throughout, using the established species sensitivities. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Test responses in the field-collected sediment do not support causality by Cu, a suspected toxicant based on comparison of sediment chemistry with sediment quality guidelines.

Animals↗