Genetic assessment reveals inbreeding, possible hybridization and low
levels of genetic structure in a declining goose population
Abstract
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
the 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 (ɸST = 0.11-0.20) but none
with the nuclear microsatellite markers (all pairwise
FST-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 HE = 0.69) and there were
no signs of past population size reductions, although significantly
positive inbreeding coefficients in all sampling sites
(FIS = 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 (A.
brachyrhynchus). The current population is not under threat by genetic
impoverishment but monitoring in the future is desirable.