Biology subjects

Ghosh, S. M.

Publications and source records attributed to Ghosh, S. M..

4 recordsLinked to original sources

bioRxiv2026

Scaling Across Environments: Temperature and nutrition independently shape the genetics of size plasticity and morphological scaling

Across animals, variation in adult body size is accompanied by coordinated variation in the size of individual morphological traits. However, the same morphological trait can scale differently with body size depending on what drives the size variation. In Drosophila melanogaster, for example, wing size scales differently with body size when size varies because of developmental nutrition versus developmental temperature. Whether the genetic basis of size plasticity and scaling is shared across different environmental regulators of size remains unclear, but is central to predicting how selection acts on the developmental mechanisms that regulate trait size, plasticity and morphological scaling. Using ~200 isogenic D. melanogaster lineages, we measured wing and leg size across nutritional and thermal treatments. For each lineage, we estimated nutritional and thermal plasticity for both traits, as well as the wing-leg individual-level scaling relationship, or ILSR, generated by each environmental source of size variation. We found extensive genetic variation in both thermal and nutritional plasticity for wings and legs, and in the slope of the ILSR between them. However, a lineages thermal plasticity was genetically uncorrelated with its nutritional plasticity for either trait, and we detected no genetic correlation between the slopes of thermal and nutritional wing-leg ILSRs. We also found no genetic correlation in the slope of nutritional wing-leg ILSRs across temperatures. Thus, the slope of a lineages nutritional ILSR at 17{degrees}C was not predictive of its slope at 25{degrees}C of 28{degrees}C. Nevertheless, the overall pattern of nutritional ILSRs was conserved across temperatures. These results suggest that the genetic architecture of size plasticity and scaling depends on the environmental source of size variation. Consequently, the evolutionary response of scaling to selection in heterogeneous environments may not be predictable from genetic variation measured in any single environment.

genetics↗

bioRxiv2024

Thermal Plasticity of Stage Specific Development Time in Drosophila melanogaster under Shifting Temperatures

We examined how thermal shifts influence development time and adult body size in Drosophila melanogaster. Individual flies were exposed to alternating temperatures of 25{degrees}C (optimal) and 17{degrees}C (cold), with shifts introduced at key developmental transitions: larval hatching and pupariation. We found while larval-stage temperature is the biggest determinant of thermal plasticity of development time and adult size, the egg-stage temperature also influences the pace of development and growth throughout pre-adult duration. The effect of low-to-high and high-to-low temperature shifts on development and growth may not be symmetric. When eggs are reared at 25{degrees}C and then shifted to 17{degrees}C, larval and pupal durations undergo reduction compared to constant 17{degrees}C, but it produces slightly larger adults. A higher egg-stage temperature thus seem to exert a carryover effect that accelerates subsequent development and growth when later stages experience colder temperatures. Surprisingly, flies whose egg stage is exposed to 17{degrees}C followed by a shift to 25{degrees}C also have reduced larval duration and larger size, relative to those developing at constant 25{degrees}C. We speculate this could be either because 17{degrees}C to 25{degrees}C represents a low-to-high temperature shift or a sub-optimal-to-optimal thermal shift that results in metabolic and/or hormonal changes accelerating differentiation and growth. While pupal duration is sensitive to current and to some extent prior thermal environments, it does not contribute substantially to thermal plasticity of size. Development time is longer in males than in females, and this difference seems to start from larval stage while the pupal duration plays a bigger role in creating this sex-specific difference. Overall, employing individual fly rearing, this study helped to unravel the effect of thermal shifts on growth and development in D. melanogaster with great precision.

evolutionary biology↗

bioRxiv2023

Long-term cold adaptation leads to increased thermal plasticity of male body size and thermal canalization of fecundity in populations of Drosophila melanogaster: an experimental evolution study

From laboratory populations of Drosophila melanogaster maintained at 25{degrees}C for many decades, new populations were derived and maintained at 17{degrees}C for over 60 generations. Fitness traits such as body size and fecundity of the cold and warm selected populations were quantified at both 17{degrees}C and 25{degrees}C. Flies from both selection regimes had similar body weight when grown at 25{degrees}C, but 17{degrees}C selected males had greater dry weight and less relative water content than 25{degrees}C selected males, when grown at 17{degrees}C. Cold selected males thus evolved greater thermal plasticity of body weight and density compared to controls. Fecundity data showed, 25{degrees}C selected females laid less eggs at 17{degrees}C compared to 25{degrees}C treatment, but 17{degrees}C selected females did not show significant difference in fecundity between 25{degrees}C and 17{degrees}C. Cold evolved flies thus showed thermal canalization of fecundity, possibly buffering the repressing effect of cold. Whether or not (i) greater body mass and density of cold evolved males, and (b) unrepressed fecundity of cold evolved females, both observed when reared at cold, are causally related, remain to be investigated. The study thus shows thermal selection can lead to evolution of greater thermal plasticity in a trait, while result in thermal canalization of another.

evolutionary biology↗

bioRxiv2019

Does Long-Term Selection for Development Time Result in Canalization: A Test Using Drosophila melanogaster

Canalization denotes the robustness of a trait against genetic or environmental perturbation. Plasticity, in contrast indicates the environmental sensitivity of a trait. Stabilizing selection is thought to increase canalization of a trait, whereas directional selection is often thought to lead to decanalization. However, the relationship between selection, canalization and plasticity remains largely unclear. Experimental evolution is a powerful approach for addressing fundamental questions in evolution. Here, we ask whether long-term directional selection for reduced pre-adult development time in Drosophila melanogaster results in the evolution of increased canalization for development time, the trait under primary selection. We additionally investigate whether pre-adult survivorship, a trait only secondarily under selection in this experimental regime, also evolves to become canalized. We examine canalization both in terms of stability of population means and of within population variability across two environmental axes. We used four large outbred populations of D. melanogaster selected for rapid pre-adult development and early reproduction for 295 generations, and four corresponding ancestral control populations that were not under conscious selection for development time or early reproduction. The selected populations had evolved 25% reduction in both development time and pre-adult survivorship at the time of this study. We studied development time and pre-adult survivorship of the selected populations and controls across various combinations ofrearing temperature and larval density. Development time in the selected populations had become more canalized than controls with regard to density, but not temperature. Canalization of development time across density appears to have evolved due to evolutionary changes in the lifehistory and physiology of the selected populations. Pre-adult survivorship, only a secondary correlate of fitness in the selected populations, did not show any clear trend in terms of canalization with regard to either density or temperature, and, overall variation in the trait was greater compared to development time within and across environments. Whether long-term directional selection canalizes or not, therefore, appears to be dependent in a complex way on specific interactions of trait, selection regime and environmental factor in the context of the ecology and physiology of the popualtions under study.

evolutionary biology↗