Inbreeding effects on standard metabolic rate investigated at cold, benign and hot temperatures in Drosophila melanogaster.
Inbreeding increases homozygosity, which is known to affect the mean and variance of fitness components such as growth, fecundity and mortality rate. Across inbred lines inbreeding depression is typically observed and the variance between lines is increased in inbred compared to outbred lines. It has been suggested that damage incurred from increased homozygosity entails energetic cost associated with cellular repair. However, little is known about the effects of inbreeding on standard metabolic rate. Using stop-flow respirometry we performed repeated measurements of metabolic rate in replicated lines of inbred and outbred Drosophila melanogaster at stressful low, benign and stressful high temperatures. The lowest measurements of metabolic rate in our study are always associated with the low activity period of the diurnal cycle and these measurements therefore serve as good estimates of standard metabolic rate. Due to the potentially added costs of genetic stress in inbred lines we hypothesized that inbred individuals have increased metabolic rate compared to outbred controls and that this is more pronounced at stressful temperatures due to synergistic inbreeding by environment interactions. Contrary to our hypothesis we found no significant difference in metabolic rate between inbred and outbred lines and no interaction between inbreeding and temperature. Inbreeding however effected the variance; the variance in metabolic rate was higher between the inbred lines compared to the outbred control lines with some inbred lines having very high or low standard metabolic rate. Thus genetic drift and not inbreeding per se seem to explain variation in metabolic rate in populations of different size.
Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark; Department of Molecular Biology and Genetics, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark. Electronic address: palle.jensen@agrsci.dk.
Palle
P
Jensen
Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Johannes
J
Overgaard
Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Volker
V
Loeschcke
Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Mads Fristrup
MF
Schou
Department of Bioscience, Aarhus University, Ny Munkegade 116, DK-8000 Aarhus C, Denmark.
Hans
H
Malte
Department of Biotechnology, Chemistry and Environmental Engineering, Section of Biology and Environmental Science, Aalborg University, Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark.
Torsten Nygaard
TN
Kristensen
D000818:Animals; D003080:Cold Temperature; D004331:Drosophila melanogaster / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006358:Hot Temperature; D007178:Inbreeding; D007700:Kinetics; D008297:Male
Genetic stress; Inbreeding by environment interaction; Inbreeding depression; Locomotor activity; Thermal stress