Darwin’s Naturalization Hypothesis states that non-native species which are more related to native species are less likely to thrive in the same community, whereas the preadaptation hypothesis posits the inverse relationship. Our aim was to test Darwin's naturalization hypothesis using a phylogenetic framework by examining seven woody perennial plant communities along an east coast transect. We plant community data from National Ecological Observatory Network (NEON) and collected DNA sequences data for members of the community, focusing on three gene regions: rbcL, matK, and ITS.The USDA PLANTS database was used to determine native status of each species. We performed phylogenetic and community diversity analyses of communities with native and non-native plants to address three questions: (1) Are non-native species more closely related to native species? (2) Does plant community diversity influence the number of non-native species in a community? (3) Is there a higher proportion of non-native species at lower latitudes?
We found a trend of non-native species being more closely related to native species when there is a high proportion of non-native species in a community and non-native species being more distantly related to native species when there is a low proportion of non-native species in an observed community. We also found that when there is a high proportion of non-native species in a community, diversity indices are lower and that the proportion of non-native species tends to increase with latitude. Our study helps elucidate why some non-native species are able to establish themselves in a new community while others cannot. The existing community structure likely plays a significant role in determining if an invader can establish itself in a new community.