Asymmetric energetic costs in reciprocal-cross hybrids between carnivorous mice (Onychomys).
Aerobic respiration is a fundamental physiological trait dependent on coordinated interactions between gene products of the mitochondrial and nuclear genomes. Mitonuclear mismatch in interspecific hybrids may contribute to reproductive isolation by inducing reduced viability (or even complete inviability) due to increased metabolic costs. However, few studies have tested for effects of mitonuclear mismatch on respiration at the whole-organism level. We explored how hybridization affects metabolic rate in closely related species of grasshopper mice (genus Onychomys) to better understand the role of metabolic costs in reproductive isolation. We measured metabolic rate across a range of temperatures to calculate basal metabolic rate (BMR) and cold-induced metabolic rate (MRc) in O. leucogaster, O. torridus and O. arenicola, and in reciprocal F1hybrids between the latter two species. Within the genus, we found a negative correlation between mass-specific BMR and body mass. Although O. arenicola was smaller than O. torridus, hybrids from both directions of the cross resembled O. arenicola in body mass. In contrast, hybrid BMR was strongly influenced by the direction of the cross: reciprocal F1hybrids were different from each other but indistinguishable from the maternal species. In addition, MRcwas not significantly different between hybrids and either parental species. These patterns indicate that metabolic costs are not increased in Onychomys F1hybrids and, while exposure of incompatibilities in F2hybrids cannot be ruled out, suggest that mitonuclear mismatch does not act as a primary barrier to gene flow. Maternal matching of BMR is suggestive of a strong effect of mitochondrial genotype on metabolism in hybrids. Together, our findings provide insight into the metabolic consequences of hybridization, a topic that is understudied in mammals.
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
J Ryan
JR
Shipley
Department of Integrative Biology, Oklahoma State University, Stillwater, OK 74078, USA.
Polly
P
Campbell
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
Jeremy B
JB
Searle
Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA bret.pasch@nau.edu.|Bioacoustics Research Program, Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA.|Macaulay Library, Cornell Lab of Ornithology, Cornell University, Ithaca, NY 14850, USA.|Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA.
Bret
0000-0001-9168-6770
B
Pasch
D000818:Animals; D003411:Arvicolinae / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D001481:Basal Metabolism / Q000235:genetics / Q000502:physiology*; D002678:Chimera / Q000235:genetics / Q000378:metabolism; D003080:Cold Temperature; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D010085:Oxidative Phosphorylation
F1 hybrid; Interspecific hybrids; Metabolic rate; Mitonuclear mismatch; OXPHOS; Reproductive isolation