Paleoclimate reconstructions using plant leaf waxes often assume that long-chain waxes (≥C26/C27) are primarily produced by terrestrial vegetation and short to mid-chain waxes (≤C24/C25) by aquatic communities. However, modern leaf wax distributions at low- and mid-latitudes are sensitive to environmental conditions, including temperature and annual precipitation amount. In this study, we assess whether terrestrial plant wax Average Chain Length (ACL) changes along a climate gradient in northern Québec and Baffin Island, Nunavut, Canada. Further, we examine whether ACL within individual species varies along the gradient, or whether changes in ACL are caused by differences in plant community along the transect. We analyzed chain length distributions from leaf wax n-alkanoic acids and n-alkanes in 70 plant samples from four lake catchments along a latitudinal temperature gradient of 0.6 to 7.2 ºC mean temperature of the Months-Above-Freezing (MAF). When comparing the entire plant communities between catchments, we find that terrestrial plants produce an increasingly greater percentage of short and mid-chain waxes moving north along the transect, as the dominant growth forms transition from trees and shrubs to liverworts and mosses. These northern communities produce a greater percentage of short to mid-chain waxes (84%) than the representative submerged aquatic mosses in the catchments (57%), challenging assumptions about the division of terrestrial and aquatic leaf wax production.

We also compare ACLs of single plant species that are found in multiple catchments to infer direct relationships between wax production and MAF. These plants display high variability in ACL change along the transect, -2.0-2.7/ºC in n-alkanoic acids and -2.7-0.8/ ºC in n-alkanes with some exhibiting no change, but we find no clear relationship to the MAF temperature gradient. Our findings suggest that the apparent trend of catchment-average ACL decreasing northward is due to different species within the catchments, rather than individual species changing their wax chain length production in response to climate. If Arctic lake sediment archives record past changes in ACL, our results suggest that these variations may be interpreted to reflect changes in plant taxa present through time, rather than due to climate-induced changes in wax production by individual plant species.