The Exotic Invasion of Florida
A Report on Arthropod Immigration into the Sunshine State
Florida is quite literally under siege.
Almost every month, a new exotic arthropod is detected in the state. Some turn out to be serious agricultural pests, such as Mediterranean and Oriental fruit flies, brown citrus aphid, citrus leaf miner, Asian citrus psyllid, small hive beetle, etc.
Others, such as the bromeliad weevil Metamasius callizona and the cactus moth Cactoblastis cactorum, attack native plants in natural areas.
Most simply set up housekeeping and quietly go about their business, like so many immigrants to the Sunshine State. However, even these may have profound, but unrecognized effects on the environment. We simply don't know.
A special effort has been made over the last decade and a half to keep a running list of invasive exotics that have become established in Florida, both in literature and from specimens submitted to the Division of Plant Industry for identification. Since 1986, 150 species of insects, spiders, and mites have been collected in the state and considered established. These arthropods have arrived, escaped port detection, and seem to have become established in the state. These are not interception records; these records are based on specimens found out and about, presumably for the most part representing breeding populations.
Some finds have not been counted since they clearly have not become established, like the Megasoma elephas (a large tropical scarab beetle found alive in a Miami yard) or because they are known to have been eradicated, like Medfly and Oriental fruit fly. It is likely that Florida populations of some of these species have not persisted; it is equally likely that there are many other exotics already in Florida awaiting discovery.
Most of the major orders are represented, but some orders predominate. Homoptera have contributed the largest number of species to the immigrant flood, followed by Coleoptera and, all out of proportion to the size of the order, Thysanoptera. There are non-biological factors that can affect these figures, as the advent of Thrips palmi in 1991 and Toxoptera citricida in 1995 prompted intensive survey efforts for thrips and aphids, respectively, and produced many new state and country records.
The immigrants have been from all over the world, but the great majority of the exotic species arriving on our shores are from the Neotropical region or from Asia.
Frank and McCoy (1992) published Florida's immigrant species for the two preceding decades, from 1970 to 1989, allowing a comparison of the composition and characteristics of the invasion. Although Frank and McCoy's criteria for recognizing an immigrant species are somewhat looser than those used here and they only dealt with insects, a "ball park" comparison is still possible.
Frank and McCoy listed 270 species of insects as immigrant to Florida during that 20 year period. That does not count intentionally introduced species, which are not counted.
There are differences. In these charts Frank and McCoy figures are in red and figures for the last decade are in green. The proportion of Coleoptera is roughly the same, but the proportion of Homoptera has risen dramatically, while the proportion of Lepidoptera has plummeted.
The major difference, however, has been in the origins of the immigrant fauna. From 1970 to 1989, most of Florida's invaders were from the Neotropical region. But in the last 10 years, the number of Asian immigrants has increased until they now approach the number from the Neotropics.
--- M.C. Thomas (based on a paper presented at the Entomological Collections Network meeting, December 1999, in Athens, Georgia)
Created: Aug 2000 | Updated: March 2006