Preferential Associations of Invasive Lantana camara (Verbenaceae) in a Seasonally Dry Hawaiian Woodland

Lantana camara L. is known to be one of the world's worst invasive species, yet in Hawai'i, where it has been present for decades, little is known about factors influencing its establishment. This study examines influence of tree composition and disturbance, including fire and disturbance corridors, on its spread at the edge of its current distribution. We assessed whether lantana spreads in association with particular plants, disturbances, or environmental features within protected areas. Using 100 m(2) plots, we measured vegetation cover, soil depth, evidence of pig disturbance, and presence of fallen trees in 105 plots (84 randomly generated and 21 selected for presence of lantana) across submontane woodland in Hawai'i Volcanoes National Park on Hawai'i Island. We found that lantana was more common than expected in association with the native nitrogen-fixing tree Sophora chrysophylla, and less common than expected near the exotic nitrogen-fixing tree Morella faya. Fire also strongly predicted its occurrence, as did proximity to roads: it was absent from all unburned plots, and in burned areas it was more common within 200 m of roads. Thus, three factors facilitated invasion by lantana: fire, roads, and presence of a native nitrogen-fixing tree.