Multi-Locus Adaptation
The RDA using 7 environmental variables identified 77 SNPs significantly
correlated with 4 of them (Fig. 5): months > 10 degrees C
(37 loci), BIO4 – Temperature Seasonality (26), PET of the warmest
quarter (12), and BIO18 – Precipitation of the Warmest Quarter (2). The
phenotypic analysis estimated 30 significant associations with 9
variables: ON and FL (6 each); TW and TO (4); and SVL, IC, HL, ED, and
CW (2). These primarily reflect body size, head shape, and limb length.
Of the significant loci, 18 are shared between the environmental and
phenotypic predictors, with 12 related to months > 10
degrees C and limb length or head shape. Of those remaining, 2 SNPs are
related to PET of the Wettest Quarter and tail width, and 4 are related
to Temperature Seasonality and head shape. Consequently, we conclude
that there is a limited but non-zero degree of adaptive genetic
differentiation with respect to ecomorphology along axes of temperature,
precipitation, and phenotypic robustness. Given the lack of a suitable
reference genome, we cannot pinpoint the physical location of these
sites.