Spectral Sagebrush
Additional Funding Sources
The project described was supported by NSF Award No. OIA-1757324 from the NSF Idaho EPSCoR Program and the National Science Foundation. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NSF.
Abstract
Big Sagebrush (Artemisia tridentate) is a keystone species that dominates much of the semi-arid climate ecosystems of the western United States. Currently, three subspecies are widely accepted, which occupy distinct ecological niches and differ genetically and chemically. Mountain Big Sagebrush (A. t. vaseyana) prefers more moisture and is bound to higher elevation. It produces a large amount of coumarins, for herbivory and UV-protection, resulting in higher overall UV fluorescence. Basin Big Sagebrush (A. t. tridentata) prefers deep and well drained soils and exhibits no UV fluorescence, while Wyoming Big Sagebrush (A. t. wyomingensis) prefers, dry, rocky cold deserts and high elevation plateaus and exhibits varying UV fluorescence. Hybrids between subspecies have been reported in transition zones where multiple subspecies co-occur. Here, we sampled a transect between previously identified and genetically confirmed subspecies to test the hypothesis that (i) distinct subspecies will exhibit distinct spectral profiles and UV-fluorescence, while potential hybrids will have varying spectral profiles and intergrading UV-fluorescence. We also predict that (ii) we will detect variation in absorbance and fluorescence along the transect, but not in the distinct ecological niches. To test these hypotheses, aqueous leaf extracts were analyzed for fluorescence intensity and spectral absorbance. A random forest (RF) algorithm was trained with genetically confirmed absorbance and fluorescence data, which then allowed the validation of the transect samples. The RF revealed that a combination of both, absorbance and fluorescence, can be used to differentiate between subspecies. Additionally, absorbance at specific wavelengths (345, 350, 355,360) as well as fluorescence intensity were identified to be the most important variables for subspecies classification. While subspecies vaseyana was well classified by the RF, the absorbance difference between wyomingensis and tridentate was found to be small, which led to ambiguous results. Similarly, genetic evidence for hybridization is still lacking and more confirmed hybrid individuals are required to improve classification using spectrophotometry and RF.
Spectral Sagebrush
Big Sagebrush (Artemisia tridentate) is a keystone species that dominates much of the semi-arid climate ecosystems of the western United States. Currently, three subspecies are widely accepted, which occupy distinct ecological niches and differ genetically and chemically. Mountain Big Sagebrush (A. t. vaseyana) prefers more moisture and is bound to higher elevation. It produces a large amount of coumarins, for herbivory and UV-protection, resulting in higher overall UV fluorescence. Basin Big Sagebrush (A. t. tridentata) prefers deep and well drained soils and exhibits no UV fluorescence, while Wyoming Big Sagebrush (A. t. wyomingensis) prefers, dry, rocky cold deserts and high elevation plateaus and exhibits varying UV fluorescence. Hybrids between subspecies have been reported in transition zones where multiple subspecies co-occur. Here, we sampled a transect between previously identified and genetically confirmed subspecies to test the hypothesis that (i) distinct subspecies will exhibit distinct spectral profiles and UV-fluorescence, while potential hybrids will have varying spectral profiles and intergrading UV-fluorescence. We also predict that (ii) we will detect variation in absorbance and fluorescence along the transect, but not in the distinct ecological niches. To test these hypotheses, aqueous leaf extracts were analyzed for fluorescence intensity and spectral absorbance. A random forest (RF) algorithm was trained with genetically confirmed absorbance and fluorescence data, which then allowed the validation of the transect samples. The RF revealed that a combination of both, absorbance and fluorescence, can be used to differentiate between subspecies. Additionally, absorbance at specific wavelengths (345, 350, 355,360) as well as fluorescence intensity were identified to be the most important variables for subspecies classification. While subspecies vaseyana was well classified by the RF, the absorbance difference between wyomingensis and tridentate was found to be small, which led to ambiguous results. Similarly, genetic evidence for hybridization is still lacking and more confirmed hybrid individuals are required to improve classification using spectrophotometry and RF.