Recently, invasion ecology has looked to the molecular techniques of landscape genetics to understand how small populations of non-natives transition to larger naturalized populations. Newly colonized invasive species typically have low genetic diversity due to the founder effect. Some invasive species overcome this limitation by increasing genetic diversity through admixture of conspecifics from different populations. Viburnum dilatatum and Viburnum sieboldii are non-native, ornamental species that escaped cultivation and expanded their range within the last 30 years in the New York metropolitan area, central New Jersey, and the greater Philadelphia area. While both are successful invaders little is known about the genetic structure among naturalized populations. Previous work demonstrated differences in dispersal: V. sieboldii has a higher probability for long distance seed dispersal by fall migratory birds whereas V. dilatatum is dispersed locally by resident birds in the winter. We hypothesize that V. sieboldii will have relatively higher gene flow between different populations of conspecifics than V. dilatatum due to the differences in bird-enhanced dispersal, assuming no hybridization occurs between the two species. To test this hypothesis, a subsample of 16 individuals per species, representative of the naturalized populations in New York City, central New Jersey and Philadelphia were sent to SNPsaurus for single nucleotide polymorphism (SNPs) discovery. SNPs were used to compare genetic diversity of conspecifics across populations, as well as to understand how populations are changing over time.
Results/Conclusions
There were 3814 SNPs used for analysis of V. dilatatum and V. sieboldii. Surprisingly, we found low Fst values for both species, indicating individuals within species and between populations are freely interbreeding despite observed differences in dispersal between the species. This suggest that while migratory birds are likely responsible for seed dispersal between populations of V. sieboldii, resident birds may have large enough ranges to disperse seeds between populations of V. dilatatum. The Tajima’s D values suggests that V. dilatatum has overcome the founder effect and the population is expanding while V. sieboldii is still in a genetic bottleneck despite similar invasion timelines. This disparity between the two species can largely be attributed to the differences in generation time. V. dilatatum has a shorter generation time and therefore higher rates of molecular change than V. sieboldii which would allow V. dilatatum to overcome the founder effect more quickly. To ensure that our preliminary understanding of the populations genetic structure holds true the sample size should be expanded in future analyses.