Distance and Environment
A basic Mantel test of geographic and genetic distance was strongly
significant (r = 0.56, P < 0.001) based on 999
permutations. Pooled across sites, pairwise Fstfor NTA, COH, and CHR equal 0.16, 0.18, and 0.19, which even under
simplistic models (Wright 1931; Slatkin 1993) suggests 1.04–1.35
migrants per generation between the three major lineages (see Mills and
Allendorf 1996). Examination of linearized Fstagainst geographic distance reveals an apparently strong linear
relationship <50km, which levels off to ~0
after 100km (Fig. 4). This is driven by strong within-lineage IBD for
the geographically restricted, montane Cohutta and Nantahala lineages
and little to no between-lineage relationship or within the Piedmont
lineage. These results were corroborated by the GDM, which dropped
elevation, BIO9, and BIO13 based on a ~0 sum of
coefficients, and only estimated geographic distance as significant
(P= 0.04) with a similar exponential plateau after
~50–100km (Fig. 3–4). These findings mirror the
overall low impact of most climatic variables in the SDM and suggest a
relatively minimal role for IBE in geographic genetic diversification
for any measured predictors. The overall model was significant atP< 0.0001 and explained 52% deviance, an ordinary
amount within the expected range of several past studies (see Mokany et
al. 2022).