Biology subjects

Walczynska, A.

Publications and source records attributed to Walczynska, A..

4 recordsLinked to original sources

bioRxiv2020

Body size variability across habitats in the Brachionus plicatilis cryptic species complex

The body size response to temperature is one of the most recognizable but still poorly understood ecological phenomena. Other covarying environmental factors are frequently invoked as either affecting the strength of that response or even driving this pattern. We tested the body size response in five species representing the Brachionus plicatilis cryptic species complex, inhabiting 10 brackish ponds with different environmental characteristics. Principal Component Analysis selected salinity and the oxygen concentration as the most important factors, while temperature and pH were less influential. Path analysis showed a positive interclonal effect of pH on body size. At the interspecific level, the size response was species and factor dependent. Under the lack of a thermos-oxygenic relationship, the expected negative response of size to temperature disappeared, but a positive response of size to oxygen remained. Our results confirm the driving role of oxygen in determining the size-to-temperature patterns observed in the field.

ecology↗

bioRxiv2020

Clonal thermal preferences affect the strength of the temperature-size rule

Genetically similar organisms act as a powerful study system for the subtle differences in various aspects of life histories. The issue of trade-offs among traits is of special interest. We used six parthenogenetic rotifer clones previously exposed to different thermal laboratory conditions. Interclonal differences in female body size were examined in common garden conditions. We estimated the population growth rate and strength of the size-to-temperature response across four thermal regimes. We tested hypotheses on the existence of the relationships between (i) thermal acclimation and species body size, (ii) thermal specialization and fitness and (iii) thermal specialization and strength of the temperature-size rule. Positive verification of (i) would make it justifiable to refer the other investigated traits to thermal preference and, further, to thermal specialization. Addressing the issues (ii) and (iii) is our pioneering contribution to the question on the strength of size-to-temperature response as differing across life strategies. We hypothesized that this plastic response may be affected by the level of thermal specialization and that this pattern may be traded off with the temperature-dependent potential for population growth rate. Additionally, we investigated the differences in reproductive strategy (number of eggs laid by a female and female lifetime duration) in one temperature assumed optimal, which acts as an important supplement to the general clonal life strategy. We confirmed that the thermal acclimation of a clone is related to body size, with clones acclimated to higher temperatures being smaller. We also found that warm-acclimated clones have a narrower thermal range (= are more specialized), and that the temperature-size rule is stronger in rotifers acclimated to intermediate thermal conditions than in specialists. Our results contribute into the issue of trade-offs between generalist and specialist strategies, in the context of plastic body size respone to different temperatures.

ecology↗

bioRxiv2020

Aerobic scope does matter in temperature-size rule, but only under optimal conditions

We united the theoretical predictions on the factors responsible for the occurrence and evolutionary significance of the temperature-size rule. We tested the causal connection among them assuming that (i) the temperature-size rule is the response to temperature-dependent oxygenic conditions, (ii) body size decrease is a consequence of cell shrinkage in response to exposure to hypoxia, (iii) this response enables to keep the wide scope for aerobic performance, and (iv) it prevents the decrease in fitness. We conducted our tests on three clones of the rotifer Lecane inermis with different thermal preferences. These clones were exposed to three experimental regimes: mild hypoxia, severe hypoxia driven by a too high temperature, and severe hypoxia driven by an inadequate oxygen concentration. The results showed that our causative reasoning was generally correct, but only under mildly hypoxic conditions. In more stressful environments, rotifers had clone- and condition-specific responses, which in fact were equally successful in terms of the levels of fitness. Our results join for the first time all factors connecting the cause and effect in the temperature-size rule. They indicate the importance of the conditions under which it should be tested. The most important messages from this study were that (i) a decrease in the body size was one of but not the only option for preventing fitness reduction under hypoxia, and (ii) such a response to higher temperature enabled the maintenance of wide aerobic scope in clone-specific, thermally optimal conditions.

ecology↗

bioRxiv2020

Should I shrink or should I flow? - body size adjustment to thermo-oxygenic niche

Organisms adjust their size according to temperature and supposedly also respond to its negative covariate, oxygen. To what extent is size a response to temperature or oxygen? We analyzed the thermo-oxygenic niche for the community of 188 rotifer species. Evolution toward ranges of thermal tolerance occurred separately from evolution toward their optima. Body size was adjusted to both temperature and oxygen, but the cues for body size response differed; size was either driven by optimal temperatures or by the oxygen tolerance range. Animals are clearly separated into generalists or specialists, and their evolutionary body size adjustment is realized through differential responses to environmental factors. Oxygen is as important as temperature in the evolution of body size and ecological niche preference. An important conclusion from this study is that oxygen deprivation following global warming seems to be as problematic for the studied organisms as the temperature increase itself.

evolutionary biology↗