The persistence of invasive populations of kudzu near the northern periphery of its range in New York City determined from historical data1,2

Abstract

In 1989, Edward Frankel recorded the distribution of Pueraria montana var. lobata (kudzu) in and around New York City, motivated by the concern that kudzu was extending its range northward from the southeastern USA, where it is an aggressive invasive species. Understanding species persistence is important in determining the dynamics of the distribution of invasive species as they spread, particularly since harsh environmental conditions at the periphery of a species range might result in frequent extinctions. Long-term species persistence data are difficult to obtain; the Frankel (1989) data thus represent a valuable contribution to documenting population persistence. In this study, we were able to identify unambiguously 22 of Frankel's original 34 sites of kudzu in the New York City metropolitan area. After more than 20 yr, we found only 32% of kudzu populations persisted in and around New York City. In contrast, we used herbarium records to identify 19 sites in Georgia and South Carolina where P. montana var. lobata was documented to occur in the same approximate time period as Frankel's data, and found that 95% of these populations persisted. Even accounting for the difference between urban and rural sites, populations of P. montana var. lobata go extinct more often near the periphery of the range than at the core of the invasion.