landscape genetic analysis of population structure and barriers to gene flow in boreal woodland caribou (rangifer tarandus caribou)
abstract
this study examines patterns of population genetic structure and gene flow of boreal
woodland caribou (rangifer tarandus caribou), which are experiencing declining
population sizes across north america. compared to previous studies, i used fine-scale
landscape genetic analyses with intensive sampling to identify genetic subdivisions
within a single range and anthropogenic and natural drivers of genetic discontinuity. the
brightsand range of ontario is among the southernmost boreal woodland caribou
populations and contains actively managed and unmanaged forests. this range
provided a unique opportunity to examine the drivers of population subdivision using
fecal dna samples (n = 788) previously obtained from non-invasive surveys. i used 12
microsatellite markers to investigate genetic diversity, identify patterns of genetic
structure, and delineate barriers to gene flow. i found high connectivity among most
sites, with low but significant population genetic substructure (fst=0.009, p<0.001). the
mantel test identified a weak pattern of isolation by distance, and genetic clustering
algorithms failed to identify a biologically meaningful pattern of population substructure.
memgene analysis and multiple regression analysis based on univariate resistances in
circuitscape indicated that wildfires acted as a barrier to gene flow, with sites
separated by burned areas having higher genetic differentiation than expected due to
isolation by distance alone. the popgraph analysis identified genetically isolated sites
among the managed portion of the range, and circuitscape analysis showed that the
range is highly fragmented within the managed portion and contains limited connectivity
corridors, whereas the unmanaged portion had high connectivity throughout. overall,
this study suggests that boreal woodland caribou are weakly genetically differentiated
across the brightsand range, with isolation by distance and isolation by resistance
contributing to variation in allele frequencies. however, while genetic differentiation was
weak, conservation efforts will be required within the managed forest area to reduce the
loss of genetic diversity by improving landscape connectivity.