INTRODUCTION
Biological invasions are a serious threat to the diversity of plants and animals of natural areas. An invasive exotic species is a species that is not native to the area that it is growing in now and is starting to take over that area by reproducing in great numbers. Many times, if an invasive species is not controlled, its population size will increase and it will exclude native plants and animals. An example of an invasive plant species in southern Florida is Melaleuca. In the Everglades, Melaleuca changes wetland prairies into dense forests, lowers the water table, and uses up the other plants' resources. The only way to stop invasive plant species is to pull them out, burn them, or have any interaction that stops or stunts the growth of the exotic plants. Some park rangers use herbivores from the exotic's native range to control them. This is also known as biological control.

There are several reasons why some exotic species become invasive when they arrive in new areas. One of these reasons may be that they have been "released" fropm herbivore damage when they were taken from their natural environment. In their new ranges, invasive extoics grow without their natural herbivores and pests. By eating plants, herbivores slow down the growth and reproduction of the plant. In other words, the plant would not grow as fast as it would without herbivores.

In this study, we wanted to determine whether the invasive exotic Ardisia elliptica in South Florida has any herbivore damage, and if it does whether it is less than Ardisia escallonioides , a native species. Our hypothesis was that the native Ardisia would have more leaf area removed by herbivores. Our Null hypothesis is that there will be no significant difference between the native and exotic Ardisia in leaf area removal. The alternate or research hypothesis is that there will be a significant difference in herbivory between Ardisia elliptica and Ardisia escallonioides.

METHODS
This study compared the levels of herbivory on two species of plants, the exotic Shoebutton Ardisia (Ardisia elliptica) and the native marlberry (Ardisia escallonioides ). The Shoebutton Ardisia is originally from China, India an dSoutheast Asia, and it was introduced to Florida before the 1900's for commercial use. It is invasive in Hawaii and hammocks in Mimai Dade County. Marlberry is a tropical Caribbean species found in hardwood hammocks. In South Florida, both have similar leaves, but the Marlberry leaves are more lobe shaped. The widest point of the Shoebutton leaf tends to be in the middle, while the Marlberry leaf has its widest point towards the apex. Marlberry's petiole is brown and the shoebutton has a pinkish petiole.

We sampled plants from the folowing sites: Everglades National Park (ENP), Secret Woods Nature Center(SWNC), and Matheson Hammock (MHP) in southeast Florida. At each site, 39 natives and 39 exotics were sytematically sampled both along trails and in habitats. Six leaves were randomly sampled from each plant. They were taken back to the lab for photocopying, cutting and weighing. Each set of leaves was copied on one sheet of paper. The pages were then labeled by species and assigned numbers. The sheet number was written on the back of each leaf. Those with herbivory were redrawn to recreate the shape of the leaves before herbivory. All leaves were then cut out as whole leaves and weighed. The damaged area was then cut out from the redrawn leaves and the remaining leaf area was weighed. The differences in leaf weights before and after herbivory were calculated for each study group. To determine which group had the most leaf area removed, we converted the differences in area removed using a conversoin factor of 126.66 (cm²/g). This factor was derived by dividing the weight of a sheet of paper by the area of the paper. This factor was multiplied by the paper leaf weights to obtain leaf area removed. A t-test was used to determine whether there was a significant difference across the entire study region and whether there were significant differences between the three sites.

RESULTS
We sampled from three different sites, Everglades National Park (ENP), Secret Woods Nature Center(SWNC), and Matheson Hammock (MHP). At each site, we sampled from 39 A. elliptica and 39 A. escallonioides plants, resulting in a todal of 234 Ardisia plants. Herbivore damage ranged from 0% to 25% of the total leafe area. The mean area removed across the total region for A. elliptica was 2.8, while the native's was 5.0 (Table 1; Fig. 1). A t-test of these data indicate that this is a significant difference (t=2.78, df=232, p < 0.001; Table 1). By looking at the data for each of the three sites, we can find out if the same results came out for each of the sites. At ENP, the mean area removed was 3.0 cm² (std. dev. = 4.8) for A. elliptica, and 3.3 cm² (std dev. =- 3.3) for A. escallonioides. A t-test of these data was done and showd no significant difference (t=0.32, df=76,p>0.5; Table 1). The same occurred for MJP in which the A. elliptica's mean area removed was 3.7 cm² (std dev. = 5.7), and the A. escallonioides mnean area removed 4.0cm² (std dev = 7.8). The t-test was done and also showed no significant difference (t=0.19, df=76, p > 0.5; Table 1). At SWNP, A. elliptica had a mean area removed of 1.6 cm² (std dev=3.4) and A. escallonioides had a mean area removed of 7.8 cm² (std dev=8.3). The t-test showed significant difference (t=4.32, df=76,p , 0.001; Table 1). This the significant difference in herbivory for the regional data seems to be due to a significant difference at SWNC only.

DISCUSSION
At the beginning of the experiment, we predicted that there would be more herbivore damage on the native A. escallonioides than on the exotic A. ellipotica. From the results, we were able to conclude that there was more herbivore damage on the native Ardisia than the exotic; however, this seems to be due mostly to a significant difference at Secret Woods Nature Center. This may be because SWNC is locatedc in a more temperate region where subtropical herbivores may not occur.

Herbivory is probably not an important factor in the biological invasion of A. elliptica in South Florida because in spite of some herbivory, the exotic is still invading S. Florida. For example, at ENP and MHP, the exotic has approximately that sema amount of herbivore damage as the native, but yet it is still invading those two sites. At SWNC, the exotic has a lower level of herbivoer damage than the native. If herbivore damage increased to what it is at the other two sites, it would probably not affect A. elliptica's invasiveness. Perhaps the natural herbivores of the extoic are not here to eat the plant.

Further investigations on the effects of herbivory on Ardisia should be conducted to determine whether it is a factor in causing Ardisia to be invasive. A simulated herbivory experiment could show the level of herbivory at which it woudl be a limiting factor in the spread of Ardisia. Our research group started such an experiment taht will be finished by next year's NSF Research in Ecology group.