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Arias, M. B., Poupin, M. J., & Lardies, M. A. (2011). Plasticity of life-cycle, physiological thermal traits and Hsp70 gene expression in an insect along the ontogeny: Effect of temperature variability. J. Therm. Biol., 36(6), 355–362.
Abstract: It is considered that extreme environmental temperature, rather than mean temperatures exert a selective pressure in ectotherms. Consequently, it is important to understand how the predicted increase in temperature variance with a higher frequency of extreme events in climate change is likely to impact on organisms. Thermal tolerance traits (i.e. chill-coma, recovery time, Hsp70 expression) are directly linked with performance in ectotherms and have consequences in life-history traits. We examined the effects of temperature variability on thermal tolerance and life-history traits through ontogeny of an insect with a complex life-cycle: the yellow mealworm beetle Tenebrio molitor. We established two common gardens with 100 recently ovoposited eggs each. Larvae were reared from hatching to adult on either a variable (mean=18 degrees C and a variance of 6.8 degrees C) or constant (18 +/- 1 degrees C) thermal environment. Development rate and growth rate were similar between thermal environments. Results indicate that larvae reared in a variable environment are more cold-tolerant than larvae of a constant environment. Interestingly, these results are reversed in the adult stage, outlining an inter-stage physiological cost. Gene expression pattern of an Hsp70 gene was well correlated with larval thermotolerance to cold in the variable environment but higher gene expression in adults is not correlated with individual's thermotolerance. We conclude that chill-coma, recovery time and Hsp70 gene expression are plastic in response to a thermal environment but also change significantly their responses depending on the ontogenetic stage, implying that the response of adult individuals is linked to early stages of the life-cycle. (C) 2011 Elsevier Ltd. All rights reserved,
Osores, S. J. A., Ruz, G. A., Opitz, T., & Lardies, M. A. (2018). Discovering divergence in the thermal physiology of intertidal crabs along latitudinal gradients using an integrated approach with machine learning. J. Therm. Biol., 78, 140–150.
Abstract: In intertidal marine crustaceans, phenotypic variation in physiological and life-history traits is pervasive along latitudinal dines. However, organisms have complex phenotypes, and their traits do not vary independently but rather interact differentially between them, effect that is caused by genetic and/or environmental forces. We evaluated the geographic variation in phenotypic integration of three marine crab species that inhabit different vertical thermal microhabitats of the intertidal zone. We studied seven populations of each species along a latitudinal gradient that spans more than 3000 km of the Chilean coast. Specifically we measured nine physiological traits that are highly related to thermal physiology. Of the nine traits, we selected four that contributed significantly to the observed geographical variation among populations; this variation was then evaluated using mixed linear models and an integrative approach employing machine learning. The results indicate that patterns of physiological variation depend on species vertical microhabitat, which may be subject to chronic or acute environmental variation. The species that inhabit the high- intertidal sites (i.e., exposed to chronic variation) better tolerated thermal stress compared with populations that inhabit the lower intertidal. While those in the low-intertidal only face conditions of acute thermal variation, using to a greater extent the plasticity to face these events. Our main results reflect that (1) species that inhabit the high-intertidal maintain a greater integration between their physiological traits and present lower plasticity than those that inhabit the low-intertidal. (2) Inverse relationship that exists between phenotypic plasticity and phenotypic integration of the physiological traits identified, which could help optimize energy resources. In general, the study of multiple physiological traits provides a more accurate picture of how the thermal traits of organisms vary along temperature gradients especially when exposed to conditions close to tolerance limits.