Effects of inbreeding on fitness in the North Atlantic right whale (Eubalaena glacialis)

Abstract

Offspring that are a product of inbreeding often have reduced fitness, known as inbreeding depression. Though our understanding of the impacts of inbreeding depression in wild populations is in its infancy, it is thought that the effects of inbreeding depression are much stronger in the wild than previously suspected. This is due to the cost of inbreeding being higher in wild populations than in captive. The North Atlantic right whale (Eubalaena glacialis) is one of the most endangered large whale species and has shown little signs of recovery over the past 70 years. This lack of recovery is due, at least in part, to a reproductive rate that is three-times lower than their known potential. North Atlantic right whales also have extremely low levels of genetic diversity. This project was conducted to assess the degree to which inbreeding could explain the variation seen in the fitness of individuals of this species. Demographic and genetic data measured at 35 microsatellites, made available to us from the North Atlantic Right Whale Consortium, were used to calculate measures of both fitness and inbreeding for individual right whales from 1990-2016. Fitness was measured through the use of the de-lifing method, and the inbreeding coefficient quantified was the internal relatedness calculation. Measures of fitness in survival showed small amounts of variation between years with most individuals surviving. Mean values of fecundity each year showed greater amounts of variation and overall lower levels of fitness. Results from linear regression analyses showed that inbreeding explains little of the variation in both survival and fecundity for this species. This study has provided quantified measures of fitness for each right whale. Further studies should be completed using genomic data to continue examining the potential impacts of inbreeding on fitness in the North Atlantic right whale.