Relationship between the energetic cost of burrowing and genetic variability among populations of the pocket gopher, T. bottae: does physiological fitness correlate with genetic variability?

Abstract

Many studies have reported relationships between genetic variability and fitness characters in invertebrates, but there is a paucity of such studies in mammals. Here, we use a statistically powerful paired sampling design to test whether the metabolic cost of burrowing, an important physiological trait in the pocket gopher, Thomomys bottae, correlates with genetic variability. Three pairs of pocket gopher populations were used, with each pair selected from a different subspecies and comprising one high genetic variability and one low genetic variability population. Genetic variability was measured using average allozyme heterozygosity and two measures of DNA fingerprint band sharing. In addition, the cost of burrowing for individuals from each population was determined from the oxygen consumption per gram of body mass per unit of work performed. Our results indicate that the cost of burrowing was significantly higher in populations with lower genetic variability (3-way ANCOVA, P=0.0150); mass-adjusted cost of burrowing in the low variability populations averaged 0.57+/-0.24 ml O2 g(-1) kgm(-1) and that in the high variability populations averaged 0.42+/-0.19 ml O2 g(-1) kgm(-1). The magnitude of the population differences in cost of burrowing was associated with the magnitude of difference in genetic variability. We conclude that population differences in genetic variability are reflected in physiological fitness differences for a trait that is essential to gopher survival.