Rejection of the beneficial acclimation hypothesis (BAH) for short term heat acclimation in Drosophila nepalensis
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ORIGINAL PAPER
Rejection of the beneficial acclimation hypothesis (BAH) for short term heat acclimation in Drosophila nepalensis Seema Ramniwas1 · Girish Kumar2 · Divya Singh1 Received: 4 April 2020 / Accepted: 8 August 2020 © Springer Nature Switzerland AG 2020
Abstract Beneficial acclimation hypothesis (BAH) is the phenotypic plasticity in response to changing environments which enables organisms to enhance their fitness. In recent years, however, BAH has received vigorous criticism and is still debatable. In this study, we tested thermal hardiness phenotypes (melanization, chill coma recovery, heat knockdown and percentage survival) on adult and pre-adult stages of Drosophila nepalensis, reared in different thermal environments (14, 17, 21 and 25 °C) to check whether increasing natural surrounding temperature and acclimation limit towards environmental change is detrimental or beneficial. Results showed that rearing D. nepalensis at higher temperatures (21 and 25 °C) reduces its melanization and cold hardiness but improves heat knockdown times. When temperature was raised to 26.2 °C (0.6 °C above the upper thermal maxima), to determine the short-term acclimation effects, survival and fitness of adults diminished approximately 1.5 to 2 folds. These results suggest that D. nepalensis has long-term developmental acclimation to both heat and cold which would be extremely beneficial as temperatures and climates alter in the region due to global warming. However, a lack of short-term heat acclimation suggests that rapid shifts in thermal extreme could be detrimental to D. nepalensis. Keywords Climate change · Drosophila nepalensis · Beneficial acclimation hypothesis · Stress resistance · Fitness · Himalayas
Introduction The ability of a single genotype to exhibit different phenotypes under varied environmental conditions is referred to as phenotypic plasticity. It is a ubiquitous feature of organisms which allows to adapt and survive in changing environments. Nevertheless, phenotypic plasticity not always facilitates selection for adaptive genotype (e.g., Chevin et al. 2010; Lande 2009; Price et al. 2003; Schlichting and Pigliucci 1998; Via et al. 1995; West-Eberhard 2003). For species that live in a temperate zone, seasonal changes are common and cyclical. Cold seasons alternate with warmer seasons; * Seema Ramniwas [email protected] * Divya Singh [email protected] 1
University Center for Research and Development, Chandigarh University, Gharuan, Mohali 140413, India
Genomics and Bioinformatics Cluster, Department of Biology, University of Central Florida, 4110 Libra Drive, Orlando, FL 32816, USA
2
and rainy periods may alternate with drier times. The rate at which temperatures change during seasonal transitions could determine whether an organism can gain from acclimation or not (Nilsson-Örtman and Johansson 2017). Hardening and acclimation in insects are the result of stressful environmental conditions experienced across developmental stages although evidence for this remains weak. Hence,
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