Population genetics of loblolly pine (Pinus taeda L.) and shortleaf pine (Pinus echinata Mill.) hybridization and introgression

Abstract

Scope and Method of Study: Molecular markers, population genetics, ecological genetics, hybridization, introgression, conservation

Findings and Conclusions: Results derived from loblolly pine and shortleaf pine cultivated from seeds collected from throughout their ranges in the 1950s shows that these two species have been forming natural hybrids for some time, and microsatellite results show how much introgression could be found in stands of these two species. However, these results are in some conflict with amplified fragment length polymorphism data acquired from the same data set. Both species have low ΦPT, which is expected from wind-pollinated forest trees. Results from loblolly pine and shortleaf pine collected from naturally regenerating stands of today indicate that the rate of hybridization has increased in the last 50 years and that ΦPT is increasing in both species. These results indicate that one or both of these species are at risk of extinction by introgression. However, there has been no significant change in the degree of introgression in the shortleaf pine stands of the Caney Creek Wilderness Area, and ΦPT is normal for the populations found there, despite these stands living so close to cultivated loblolly pine plantations.