Loblolly Pine and Shortleaf Pine Hybridization Analysis Using Chromatography and Geographic Information Systems: A Case Study in East Texas

The spatial quantification of hybridization is of growing interest as southern United States pine forests come under greater influence of improved pine genetics in the face of the warmer, drier conditions from climate change. High Performance Liquid Chromatography (HPLC) and spatial interpolation using the Inverse Distance Weighted method were conducted using extracted terpenes derived from foliar tissue of shortleaf pine (Pinus echinata), loblolly pine (Pinus taeda), and putative hybrids of a sample of 24 individuals (14 overstory and 10 advanced regeneration individuals) sampled on a north to south gradient in East Texas. Chromatograms were obtained and 14 peaks representing terpene constituents were measured for peak intensity. T-Tests indicated no significant differences for peak intensity between forest strata. Two-way ANOVA tests indicated that the site variable was significant for six peaks, the species class variable was significant for five peaks, and the interaction of site and species class was significant for one peak. Tukey HSD tests indicated that the comparison of shortleaf pine to shortleaf x loblolly pine was the most consistently significant. From spatial interpolation of peak intensities, both north-south and west-east variations in chemical composition were realized. A pattern of species differentiation at the population scale and individual responses to environmental stressors is implied. Knowledge of spatial patterns of species identity and individual resiliency to environmental stressors is valuable for the sustainable management of forests in the face of rapidly changing forest genetic compositions and climatic conditions.

Keywords:Hybridization; Shortleaf pine; Loblolly pine; Climate change; Chromatography

Abbreviations:ASP: Atlanta State Park; MTSP: Mission Tejas State Park; TSP: Tyler State Park; IDW: Inverse Distance Weighted