Gene Flow and Adaptation in Lonicera japonica

Little is known about the genetic and adaptive dynamics of biological invasions. Here I use Japanese honeysuckle (Lonicera japonica), a horticultural vine invading North America, to assess population genetic processes and adaptive change in an invasion. Lonicera japonica plants from 17 populations in the core of the invaded range (100-150 years old) and 14 populations in the range margin (65 years old or younger) were compared to determine genetic structure at multiple scales, whether divergent evolution has occurred during invasion, and the potential for populations from these sources to invade novel areas. There was little genetic structure in L. japonica's invaded range. Genetic variation was distributed over short spatial scales, with most variation accounted for within populations and within patches in populations, but not between core and margin regions. Four genetic groups were identified, suggesting multiple introductions, and admixture is ongoing, with 170f samples of mixed origin. Genetic diversity did not affect patch-level reproduction, but increasing local conspecific cover resulted in more fruit production, indicating the presence of Allee effects. These findings show that human dispersal of invaders can lead to high levels of local genetic variation, which may increase population growth rates and spread in this self-incompatible species. Adaptive evolution was found within L. japonica's invaded range. After three years growth in core and margin gardens, margin plants had 36 0reater biomass and 30 0reater survival than core plants, regardless of planting location or genetic group. Margin plants also were larger and had 54 0reater survival after two years in gardens iii beyond the range edge. Size influenced survival, suggesting that margin plants had higher survival because they grew more rapidly. Across latitudes, winter mortality increased with increasing latitude, and core plants had 39 0gher winter mortality than margin plants. Increased performance of margin plants indicates that range expansion has selected for plants with greater ability to establish and this reinforces selection by short growing seasons for rapid growth rates at the margin. In total, evolution in margin populations suggests that adaptations promoting colonization can drive invasions and increase the likelihood of further spread, especially as global temperatures increase.

Note: Abstract extracted from PDF text