Genetic assessment reveals inbreeding, possible hybridization, and low levels of genetic structure in a declining goose population

The population numbers of taiga bean goose (Anser fabalis fabalis) have halved during recent decades. Since this subspecies is hunted throughout most of its range, the decline is of management concern. Knowledge of the genetic population structure and diversity is important for guiding management and conservation efforts. Genetically unique subpopulations might be hunted to extinction if not managed separately, and any inbreeding depression or lack of genetic diversity may affect the ability to adapt to changing environments and increase extinction risk. We used microsatellite and mitochondrial DNA markers to study the genetic population structure and diversity among taiga bean geese breeding within the Central flyway management unit using non-invasively collected feathers. We found some genetic structuring with the maternally inherited mitochondrial DNA between four geographic regions (278;(ST) = 0.11-0.20) but none with the nuclear microsatellite markers (all pairwise F-ST-values = 0.002-0.005). These results could be explained by female natal philopatry and male-biased dispersal, which completely homogenizes the nuclear genome. Therefore, the population could be managed as a single unit. Genetic diversity was still at a moderate level (average H-E = 0.69) and there were no signs of past population size reductions, although significantly positive inbreeding coefficients in all sampling sites (F-IS = 0.05-0.10) and high relatedness values (r = 0.60-0.86) between some individuals could indicate inbreeding. In addition, there was evidence of either incomplete lineage sorting or introgression from the pink-footed goose (Anser brachyrhynchus). The current population is not under threat by genetic impoverishment but monitoring in the future is desirable.

Automated summary

The population of taiga bean geese has halved in recent decades, mainly due to hunting throughout their range. Understanding the genetic population structure and diversity is crucial for management and conservation efforts. Different genetic subpopulations within the species need to be managed separately to prevent extinction, and inbreeding or lack of genetic diversity could pose risks to their adaptation and survival. The study found some genetic structuring in mitochondrial DNA but not in nuclear microsatellite markers, suggesting that the population can be managed as a single unit.