Browsing by Author "Terblanche, J. S."

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    Critical thermal limits and their responses to acclimation in two sub-Antarctic spiders : Myro kerguelenensis and Prinerigone vagans
    (Springer-Verlag, 2008-01) Jumbam, K. R.; Terblanche, J. S.; Deere, J. A.; Somers, M. J.; Chown, Steven L.
    Despite the relative richness of spider species across the Southern Ocean islands remarkably little information is available on their biology. Here, the critical thermal limits of an indigenous (Myro kerguelenensis, Desidae) and an introduced (Prinerigone vagans, Linyphiidae) spider species from Marion Island were studied after 7-8 days acclimation to 0, 5, 10 and 15°C. Critical thermal minima (CTMin) were low in these species by comparison with other spiders and insects measured to date, and ranged from -6 to -7°C in M. kerguelenensis and from -7 to -8°C in P. vagans. In contrast, critical thermal maxima (CTMax) were similar to other insects on Marion Island (M. kerguelenensis: 35.0-35.6°C; P. vagans: 35.1-36.0°C), although significantly lower than those reported for other spider species in the literature. The magnitude of acclimation responses in CTMax was lower than those in CTMin for both species and this suggests decoupled responses to acclimation. Whilst not conclusive, the results raise several important considerations: that oxygen limitation of thermal tolerance needs to be more widely investigated in terrestrial species, that indigenous and alien species might differ in the nature and extent of their plasticity, and that upper and lower thermal tolerance limits might be decoupled in spiders as is the case in insects. © 2007 Springer-Verlag.
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    Macrophysiology : a Conceptual Reunification
    (The University of Chicago Press, 2009-09-29) Gaston, K. J.; Chown, S .L.; Calosi, P.; Bernardo, J.; Bilton, D. T.; Clarke, A.; Clusella-Trullas, S.; Ghalambor, C. K.; Konarzewski, M.; Peck, L. S.; Porter, W. P.; Portner, H. O.; Rezende, E. L.; Schulte, P. M.; Spicer, J. I.; Stillman, J. H.; Terblanche, J. S.; Van Kleunen, M.
    Widespread recognition of the importance of biological studies at large spatial and temporal scales, particularly in the face of many of the most pressing issues facing humanity, has fueled the argument that there is a need to reinvigorate such studies in physiological ecology through the establishment of a macrophysiology. Following a period when the fields of ecology and physiological ecology had been regarded as largely synonymous, studies of this kind were relatively commonplace in the first half of the twentieth century. However, such large-scale work subsequently became rather scarce as physiological studies concentrated on the biochemical and molecular mechanisms underlying the capacities and tolerances of species. In some sense, macrophysiology is thus an attempt at a conceptual reunification. In this article, we provide a conceptual framework for the continued development of macrophysiology. We subdivide this framework into three major components: the establishment of macrophysiological patterns, determining the form of those patterns (the very general ways in which they are shaped), and understanding the mechanisms that give rise to them. We suggest ways in which each of these components could be developed usefully.
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    Propagule pressure helps overcome adverse environmental conditions during population establishment
    (Elsevier, 2021) Saccaggi, D. L.; Wilson, J. R. U.; Terblanche, J. S.
    ENGLISH ABSTRACT: The establishment success of a population is a function of abiotic and biotic factors and introduction dynamics. Understanding how these factors interact has direct consequences for understanding and managing biological invasions and for applied ecology more generally. Here we use a mesocosm approach to explore how the size of founding populations and the number of introduction events interact with environmental conditions (temperature) to determine the establishment success of laboratory-reared Drosophila melanogaster. We found that temperature played the biggest role in establishment success, eclipsing the role of the other experimental factors when viewed overall. Under optimal temperature conditions propagule pressure was of negligible importance to establishment success.  At adverse temperatures, however, establishment success increased with the total founding population size. This effect was considerably stronger at the cold than at the hot extreme. Whether the population was introduced all at once or by increments (changing the number of introduction events) had a negligible global effect. However, once again, a stronger effect of increasing number of introduction events was seen at adverse temperatures, with hot and cold extremes revealing opposite effects: adding flies incrementally decreased their establishment success at the hot extreme, but increased it at the cold extreme. These differing effects at hot and cold thermal extremes implies that different establishment mechanisms are at play at either extreme. These results suggest that the effort required to prevent (or conversely, to facilitate) the establishment of populations varies with the environment in ways that can be complicated but predictable.