Hybridization Leads to Loss of Genetic Integrity in Shortleaf Pine: Unexpected Consequences of Pine Management and Fire Suppression
Hybridization between shortleaf pine and loblolly pine is causing loss of genetic integrity (the tendency of a population to maintain its genotypes over generations) in shortleaf pine, a species already exhibiting dramatic declines due to land-use changes. Recent findings indicate hybridization has increased in shortleaf pine stands from 3% during the 1950s to 45% for present-day natural regeneration. This drastic increase in hybridization is likely because of increased and wide-spread planting of loblolly pine and reduced selection pressure against loblolly pine and hybrids caused by fire suppression. Because shortleaf pine is more fire and drought tolerant than loblolly pine, loss of genetic integrity of shortleaf pine may reduce the resiliency and adaptability of southeastern conifer forests in the face of climate change and other stressors. Loblolly pine may also be at risk, with hybrids increasing in natural stands of loblolly pine from 4% in the 1950s to 27% at present.