When Hurricane Andrew tore through tropical hardwood forests of southern Florida in 1992, it uprooted trees, stripped off leaves, fruits, flowers, and snapped off tree limbs. Opportunities for plants to recolonize were numerous in the wake of this natural disaster. But those most successful were invasive non-natives who had already gained a foothold in the forests before the hurricane struck.
In the November issue of Ecological Applications, researchers Carol Horvitz and colleagues from the University of Miami report on research that suggests that nature preserves may not be as safe for conservation of native species as previously believed.
"We found that in the aftermath of Hurricane Andrew, non-native forest species competed with native forest species for regeneration opportunities, exhibiting the same range of ecological roles as native forest species and competing for particular kinds of regeneration opportunities," said Horvitz.
If invasive species can successfully compete with natives in areas relatively free of human disturbance, explains Horvitz, they present a threat to biodiversity conservation and may considerably alter ecosystem processes.
In the case of several non-indigenous vines, not only did they form denser "blankets" than native vines, but they also inhibited the regeneration of other natives by strangling native tree seedlings and juveniles.
Horvitz points out that Florida's invasive non-natives species exhibit invasive behavior in other regions of the world, suggesting that understanding the ecological roles of such invaders in one region may help predict invasive roles in other areas.
According to the researchers, the ecological roles of invasive, non-indigenous species in forest ecosystems are poorly understood. Some analyses have proposed that such invaders become established primarily in human-disturbed areas. In contrast to these views, Horvitz and her associates suggest that successful invasion may in fact occur in natural habitats when invaders draw upon seeds, juveniles, and other sources they have sown prior to the disturbance.
Compared with native plants, the researchers found that non-native species were very similar in seed mass, and were also recruiting from diverse sources such as banks of pre-established juveniles, dormant seeds, and resprouts from pre-established adults. That meant these non-natives were not restricted to the pioneer type of life history frequently thought to be their primary option.
Horvitz's article is part of a larger series of research presented in this issue of Ecological Applications. Entitled, "Ecological Concepts in Conservation Biology: Lessons from Southeastern U.S. Ecosystems," the series presents a collection of articles which address the applicability of ecological concepts to conservation of Southeastern ecosystems.
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