Bidirectional introgression between loblolly pine (Pinus taeda L.) and shortleaf pine (P. echinata Mill.) has increased since the 1950s (2011)Stewart, J. F., Tauer, C. G., & Nelson, C. D. (2011). Bidirectional introgression between loblolly pine (Pinus taeda L.) and shortleaf pine (P. echinata Mill.) has increased since the 1950s. Tree Genetics & Genomes, 8(4), 725-735. Retrieved from https://link.springer.com/article/10.1007/s11295-011-0459-2 Hybridization between loblolly pine and shortleaf pine has been shown in sympatric and allopatric portions of the species native ranges. In this study, we used 25 microsatellite markers to determine the hybrid status of 165 and 151 loblolly pine and shortleaf pine trees sampled across their ranges, respectively, and to estimate population differentiation within these species. Estimated differentiation (ΦPT) for these current-day samples was significantly higher in both species—0.115 in loblolly pine and 0.146 in shortleaf pine—than for trees planted from seed collected from the same locations in the 1950s. These increases are likely due to anthropogenic causes such as habitat fragmentation. In addition, the proportion of hybrids rose dramatically in both species: 27.3% hybrids in loblolly pine populations and 46.7% hybrids in shortleaf pine populations compared to rates of 4.5% and 3.3%, respectively, in the 1950s populations. Our results suggest that shortleaf pine and remnant naturally regenerated loblolly pine are at risk https://link.springer.com/article/10.1007/s11295-011-0459-2
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