Spatial genetic structure and clonal structure of Prunus serotina during invasive spread

Prunus serotina Ehrh. (black cherry) is one of the most important invaders in the European forests, but existing studies have given limited insight into demo-genetic factors underpinning the process of species invasion. Fine-scale genetic structure (FSGS) may deliver important knowledge on genetics of invasion contributing to efficient management of the alien species. Using eight microsatellites we investigated FSGS, clonal structure and relatedness in four black cherry populations which represented different stages of the invasive spread into Scots pine forests. Three populations were in a continuous forest complex and represented the colonization (Z_1) and established stages (Z_2 and Z_3). To investigate how colonization ability of the species is modified by landscape features, we analyzed an isolated population at colonization stage located in limited forest patch located in an agricultural landscape (R). Populations from continuous forest showed low yet significant positive FSGS with Sp = 0.0068 in Z_1, 0.0054 in Z_2, and 0.0066 in Z_3, while in R spatial structure was the strongest (0.0145). Considerable relatedness noted in population R suggests a dominance of within-population mating and recruitments, low immigration rate and limited seed dispersal, all of which led to the observed strong FSGS. Also, we presume that a founder effect likely involved during colonization of isolated forest patch R led to strong FSGS. In contrary, the seed shadow overlap in the populations from continuous forest prevented strong FSGS and facilitated colonization. Despite of low level of clonality, we argue that it may efficiently support black cherry seedling bank contributing to species invasiveness.