Adaptive cellular evolution or cellular system drift in hares

Abstract

Adaptations occur at many levels, for example, from DNA sequence of regulatory elements and cellular homeostatic systems to organismal physiology and behaviour (Mayr, 1997). Established adaptations are maintained by purifying and stabilizing selection. Students of animal diversity tend to focus on higher order traits, anatomy, physiology, organismal function and interactions. The core cellular and metabolic systems of metazoans evolved early in their history and are assumed to be rather similar between groups. The housekeeping functions and core metabolic functions of cells are generally considered relatively static, especially among closely related species. The extent to which evolution shapes core cellular metabolism and physiology in animals is largely unexplored. Ecological opportunities or strong positive selection can alter basal metabolic rate, activity levels and life‐history traits (e.g., life span, age of maturity, offspring number) and potentially lead to divergence in core cellular and metabolic trait systems (Norin & Metcalfe, 2019; Speakman, 2005). Furthermore, systems under stabilizing selection can also change. Developmental systems of related species may produce the same phenotype or structure, but experience drift that can alter connections and even lead to turnover of cogs in the system (True & Haag, 2001). Are the cellular functions of animals highly constrained, subject to cellular system drift or affected by positive selection? This was tackled by a new study by Kateryna Gaertner and colleagues in a From the Cover manuscript in this issue of Molecular Ecology (Gaertner et al., 2022), using fibroblasts from the closely related but ecologically distinct brown and mountain hares.

Editorial 2024

“…show differences in gene expression patterns between the two hare species, which affect fundamental cellular processes including cell growth, respiration, and metabolism, providing clear evidence that speciation can have significant impacts on cellular‐level functions. Moreover, as Palsson and Steele (2023) note in their accompanying perspective, ‘This study suggests immortalized fibroblasts have utility for ecological and evolutionary research, to explore divergence in cellular and metabolic traits and the cellular basis of organismal physiology’.…”

Empirical evidence for metabolic drift in plant and algal lipid biosynthesis pathways

“…In particular, they proposed that the melting temperature is under selection and the underlying mechanisms of thermostability could vary without impacting the associated phenotype. Other cellular processes involving proteins could be impacted by these drifts ( Palsson and Steele, 2023 ). A major one is the metabolism with enzymes catalyzing biochemical reactions.…”