Temperature effects on life-history trade-offs, germline maintenance and mutation rate under simulated climate warming

Abstract

Mutation has a fundamental influence over evolutionary processes, but how evolutionary processes shape mutation rate remains less clear. In asexual unicellular organism, increased mutation rates have been observed in stressful environments and the reigning paradigm ascribes this increase to selection for evolvability. However, this explanation does not apply in sexually reproducing species, where little is known about how the environment affects mutation rate. Here we challenged experimental lines of seed beetle, evolved at ancestral temperature or under simulated climate warming, to repair induced mutations at ancestral and stressful temperature. Results show that temperature stress causes individuals to pass on a greater mutation load to their grand-offspring. This suggests that stress-induced mutation rates, in unicellular and multicellular organisms alike, can result from compromised germline DNA repair in low condition individuals. Moreover, lines adapted to simulated climate warming had evolved increased longevity at the cost of reproduction, and this allocation decision improved germline repair. These results suggest that mutation rates can be modulated by resource allocation trade-offs encompassing life-history traits and the germline and have important implications for rates of adaptation and extinction as well as our understanding of genetic diversity in multicellular organisms.

Experimentally reduced insulin/IGF-1 signaling in adulthood extends lifespan of parents and improves Darwinian fitness of their offspring

“…The trade-off between offspring number and offspring quality is a well-known concept in life-history evolution (Stearns 1992) but is rarely considered in biogerontological research (reviewed in Maklakov and Immler 2016). Germline maintenance is costly (Sniegowski et al 2000;Agrawal and Wang 2008;Maklakov and Immler 2016;Berger et al 2017), and increased investment into somatic maintenance can, in theory, result in increased mutation rate and reduced fitness of progeny.…”

Sexual selection and the evolution of male and female cognition: A test using experimental evolution in seed beetles*

“…Adults typically die 7–14 days after emergence in the absence of food or water (e.g., Berger et al. ). All experiments have been carried out within national regulations and laws.…”

Multigenerational downregulation of insulin/IGF-1 signalling in adulthood improves lineage survival, reproduction, and fitness inC. eleganssupporting the developmental theory of ageing

“…These results are in line with the hypothesis that a gradual decline in selection gradients with advancing age after reproductive maturity results in suboptimal gene expression in adulthood contributing to somatic deterioration 2,22-27 . However, it has been proposed that reduced germline maintenance can be a hidden cost of increased lifespan 18 . Germline maintenance, the repair and surveillance of genomic and proteomic integrity in germline stem cells and gametes, is energetically expensive 18,28 and germline signalling plays a key role in resource allocation to somatic maintenance 18,28,29,30 . Germline ablation results in increased somatic maintenance and lifespan in Drosophila melanogaster fruitflies 31 and 4 Caenorhabditis elegans nematodes [32][33][34][35][36] , although lifespan extension in C. elegans requires an intact somatic gonad 32 .…”