Metabolic variation in natural populations of wild yeast

Ecological diversification depends on the extent of genetic variation and on the pattern of covariation with respect to ecological opportunities. We investigated the pattern of utilization of carbon substrates in wild populations of budding yeast Saccharomyces paradoxus. All isolates grew well on a core diet of about 10 substrates, and most were also able to grow on a much larger ancillary diet comprising most of the 190 substrates we tested. There was substantial genetic variation within each population for some substrates. We found geographical variation of substrate use at continental, regional, and local scales. Isolates from Europe and North America could be distinguished on the basis of the pattern of yield across substrates. Two geographical races at the North American sites also differed in the pattern of substrate utilization. Substrate utilization patterns were also geographically correlated at local spatial scales. Pairwise genetic correlations between substrates were predominantly positive, reflecting overall variation in metabolic performance, but there was a consistent negative correlation between categories of substrates in two cases: between the core diet and the ancillary diet, and between pentose and hexose sugars. Such negative correlations in the utilization of substrate from different categories may indicate either intrinsic physiological trade‐offs for the uptake and utilization of substrates from different categories, or the accumulation of conditionally neutral mutations. Divergence in substrate use accompanies genetic divergence at all spatial scales in S. paradoxus and may contribute to race formation and speciation

Data from: Long-term culture at elevated atmospheric CO2 fails to evoke specific adaptation in seven freshwater phytoplankton species

The concentration of CO2 in the atmosphere is expected to double by the end of the century. Experiments have shown that this will have important effects on the physiology and ecology of photosynthetic organisms, but it is still unclear if elevated CO2 will elicit an evolutionary response in primary producers that causes changes in physiological and ecological attributes. In this study, we cultured lines of seven species of freshwater phytoplankton from three major groups at current (approx. 380 ppm CO2) and predicted future conditions (1000 ppm CO2) for over 750 generations. We grew the phytoplankton under three culture regimes: nutrient-replete liquid medium, nutrient-poor liquid medium and solid agar medium. We then performed reciprocal transplant assays to test for specific adaptation to elevated CO2 in these lines. We found no evidence for evolutionary change. We conclude that the physiology of carbon utilization may be conserved in natural freshwater phytoplankton communities experiencing rising atmospheric CO2 levels, without substantial evolutionary change

The effects of elevated atmospheric CO₂ on freshwater periphyton in a temperate stream

This study examines the effects of elevated CO 2 on the benthic biology of a temperate freshwater stream. We tested the hypotheses that elevated CO 2 would increase periphyton biomass, alter elemental composition, and change community composition by increasing the frequency of algal taxa most limited by CO 2 availability. Carbon dioxide was bubbled into reservoirs of stream water, increasing the ambient pCO 2 by approximately 1100 ppm. The CO 2 -enriched water then flowed into artificial stream channels. Ceramic tiles were placed into the channels to allow for periphyton colonization. Dissolved inorganic carbon increased and pH decreased with added CO 2 . Measurements of biological parameters including periphyton biomass, algal C:N:P ratios, and community composition suggest that the periphyton were unaffected by the changes in stream water chemistry. We infer that rising atmospheric CO 2 will impact stream water chemistry but that periphyton may not be the first to respond to these changes. Impacts to alkaline freshwater streams from elevated CO 2 initially may be due to changes to terrestrial inputs that affect microbial decomposition and grazer activity, rather than through increases in periphyton carbon fixation. However, environmental characteristics of freshwater systems vary considerably, and additional studies are needed for accurate predictive modeling and monitoring of the effects of increasing atmospheric CO 2 on freshwater streams

Biological impacts of ocean acidification: a postgraduate perspective on research priorities

Research into the effects of ocean acidification (OA) on marine organisms has greatly increased during the past decade, as realization of the potential dramatic impacts has grown. Studies have revealed the multifarious responses of organisms to OA conditions, indicating a high level of intra- and interspecific variation in species’ ability to accommodate these alterations. If we are to provide policy makers with sound, scientific input regarding the expected consequences of OA, we need a broader understanding of these predicted changes. As a group of 20 multi-disciplinary postgraduate students from around the globe, with a study focus on OA, we are a strong representation of ‘next generation’ scientists in this field. In this unique cumulative paper, we review knowledge gaps in terms of assessing the biological impacts of OA, outlining directions for future research