Table 1. Summary of predictor variables used in constrained ordinations.

Data	Source	Original Resolution	Connectivity Based?	Why chosen	Ref.
Elevation	ASTER DEM1	30 m.	Yes	Hypothesized beetle dispersal limitation at high elevations.	[58]
Climatic Suitability Index (CSI)	CFS2	1000 m.	Yes	Demonstrated climatic limitations to successful reproduction.	[38], [53]
Pine Volume	CFS3	1000 m.	Yes	Beetles preferentially attack large diameter trees and high-volume stands.	[24], [39]
Geographic Dist.	Calculated	1000 m.	Yes	Null hypothesis - Isolation By Distance.	[59]
Beetle PC1& PC24	Initial PCA	NA	No	Hypothesis based on known symbiosis.	[7]
Fungus PC1& PC24	Initial PCA	NA	No	Hypothesis based on known symbiosis	[7]

¹NASA DEM data were accessed through https://wist.echo.nasa.gov/api/.

²Climate suitability data were obtained through the Canadian Forest Service (CFS).

³Yemshanov, D, McKenney, D, Pedlar, J. in review. Mapping forest composition from the Canadian National Forest Inventory and satellite landcover classification maps. Environmental Monitoring and Assessment.

⁴The first and second axes of a principal coordinates analysis using Fst (PCoA) were used in distance based redundancy analysis (dbRDA).