Invasive Widow Spiders Perform Differently at Low Temperatures from Conspecifics from the Native Range.

Temperature challenges are one of the leading abiotic causes of success or failure of non-native species in a novel environment, and this is particularly true for low temperatures. Establishing and reproducing in a novel thermal environment can alter survival, behavior, and traits related to fitness. It has been proposed that plasticity or adaptation of thermal tolerance may allow an introduced species to thrive, or that successful invaders may be those with a thermal breadth in their native habitat that encompasses their new environment. Here, we tested these hypotheses using native and invasive populations of Australian redback spiders (Latrodectus hasselti). We measured how exposure to temperatures common to invasive and native range habitats (exposure to 15 and 25°C, respectively) affected behavioral and life-history traits and trade-offs that may underlie fitness in an invasive population detected in 1995 in Japan and a native population from Australia. We found that the critical thermal minimum (CTmin) was higher in the invasive population from Japan than in the native population, but critical thermal maximum (CTmax) did not differ between populations. Compared to the invasive population, eggs from the native population had a longer development time and lower hatching success at 15°C. Both populations performed equally well at 25°C, as measured by egg development time and hatching success. Invasive juveniles tested at 15°C were faster to explore a novel environment and bolder compared to those tested at 25°C. In comparison, the native population showed faster average exploration, with no differences in boldness or exploration at the two development or testing temperatures. Overall, L. hasselti from Japan maintained hatching success and development across a wider temperature range than the native population, indicating greater thermal breadth and higher behavioral plasticity. These results support the importance of plasticity in thermal tolerance and behavior for a successful invasion under novel environmental temperatures.

Thermal acclimation has limited effect on the thermal tolerances of summer-collected Arctic and sub-Arctic wolf spiders.

High-latitude ectotherms contend with large daily and seasonal temperature variation. Summer-collected wolf spiders (Araneae; Lycosidae) from sub-Arctic and Arctic habitats have been previously documented as having low temperature tolerance insufficient for surviving year-round in their habitat. We tested two competing hypotheses: that they would have broad thermal breadth, or that they would use plasticity to extend the range of their thermal performance. We collected Pardosa moesta and P. lapponica from the Yukon Territory, Canada, P. furcifera, P. groenlandica, and P. hyperborea from southern Greenland, and P. hyperborea from sub-Arctic Norway, and acclimated them to warm (12 or 20 °C) or cool (4 °C) conditions under constant light for one week. We measured critical thermal minimum (CTmin) or supercooling point (SCP) as a measure of lower thermal limit, and critical thermal maximum (CTmax) as a measure of upper thermal limit. We found relatively little impact of acclimation on thermal limits, and some counterintuitive responses; for example, warm acclimation decreased the SCP and/or cool acclimation increased the CTmax in several cases. Together, this meant that acclimation did not appear to modify the thermal breadth, which supports our first hypothesis, but allows us to reject the hypothesis that spiders use plasticity to fine-tune their thermal physiology, at least in the summer. We note that we still cannot explain how these spiders withstand the very cold winters, and speculate that there are acclimatisation cues or processes that we were unable to capture in our study.

Overwintering Red Velvet Mites Are Freeze Tolerant.

Although many arthropods are freeze tolerant (able to withstand internal ice), small-bodied terrestrial arthropods such as mites are thought to be constrained to freeze avoidance. We field-collected active adult red velvet mites, Allothrombium sp. (Trombidiidae), in winter in Southwestern Ontario, Canada, where temperatures drop below -20°C. These mites froze between -3.6° and -9.2°C and survived internal ice formation. All late-winter mites survived being frozen for 24 h at -9°C, and 50% survived 1 wk. The lower lethal temperature (LLT50; low temperature that kills 50% of mites) was ca. -20°C in midwinter. Hemolymph osmolality and glycerol concentration increased in midwinter, accompanied by decreased water content. Thus, this species is freeze tolerant, demonstrating that there is neither phylogenetic nor size constraint to evolving this cold tolerance strategy.

Evolution of Canadian nursing curricula: a critical retrospective analysis of power and caring.

The evolution of Canadian nursing curricula has mutually influenced and reflected nursing's historical course: nursing practice and education are inextricably linked. This paper is a critical retrospective analysis of the evolution of nursing curricula in Canada from the 20th century to the present. Falk Rafael's (1996) dialectic exploration of power and caring in nursing guides the analysis. An ordered, assimilated, and empowered curriculum development framework results. Foucault's (1980) work in the sociology of knowledge and Belenky, Clinchy, Goldberger, and Tarule's (1986) epistemological conceptualization of women's knowledge development are incorporated. The intricacies of the relationship between nursing curriculum development and Canadian history, the navigation of societal paradoxes that mutually drive and inform education and practice, and the instrumental need for nursing education research are considered. A fourth and new dialectic layer is suggested that places nursing on the inter-professional team of architects of a co-constructed emancipatory curriculum.