Pairwise relatedness patterns of beluga whales (Delphinapterus leucas) in the St. Lawrence River population

Abstract

The St. Lawrence River beluga whale (Delphinapterus leucas) population is geographically and reproductively isolated from other beluga populations. This small population is also endangered, therefore learning the population dynamics and social structure of the St. Lawrence belugas is of great interest for not only biological reasons, but also for establishing conservation strategies. The main goal of this study was to uncover the genetic structure and final-scale relatedness patterns of the St. Lawrence River beluga population, and in particular to establish if the population follows a matrilineal social structure, similar to other cetaceans such as sperm whales and orcas. These queries are addressed by genotyping DNA of beluga whales in the St. Lawrence at 22 microsatellite loci. These genotypes were used to estimate pairwise relatedness of all individuals. Network analyses were then conducted on these data to assess clustering patterns within the population, as well as to assess the patterns of genetic connectivity among individuals. The population shows significant signs of clustering, with females being more clustered than males, and males having higher connectivity than females. These findings suggest that the St. Lawrence River beluga population does follow a matrilineal social structure since females cluster with other females based on close genetic relatedness, and males act as conduits of gene flow between these maternal clusters. Future studies will combine these network data with field observation to identify how genetic clusters reflect habitat use patterns and differential exposure to anthropogenic disturbances in the area.