Introduction and Hypotheses

           Human-initiated movements of flora and fauna all over the globe have had drastic impacts on natural ecosystems when the non-native organisms were released into the wild (Sharma, Raghubanshi, and Singh, 2005). The exotic species may out-compete and eventually eliminate native species in newly recruited areas. These invasive species usually have characteristics that facilitate the species’ establishment in the new environment. Such characteristics include abundant seed or gamete production, rapid growth rates, no natural predators, and tolerances to abiotic factors found in the new environment (Sharma et al., 2005). Another factor that may influence the success of invasive species is called the “novel weapons hypothesis” (Callaway and Aschehoug, 2000). This hypothesis proposes that exotic species have an advantage over native species due to possession of “new weapons,” such as allelopathic chemicals, against which native species have no current defense (Orr, Rudgers, and Clay, 2005).

            Many exotic plant species have been brought to Florida with the intention of beautifying the landscape or removing excess water from the land (Jones and Doren, 1997). Some of these species have become extremely problematic, causing Florida to invest large amounts of funding in removal and control (Cuda, Ferriter, Manrique, and Medal, 2006). One species that now presents a huge problem in Florida is Schinus terebinthifolius (Brazilian pepper). This plant is native to South America and was introduced to Florida for ornamental use in the 1800s (Williams, Overholt, Cuda, and Hughes, 2005). Schinus terebinthifolius is found as scattered individuals in its native habitat and co-exists with other plants in native areas, but when S. terebinthifolius invades areas in Florida, it typically forms monocultures (Cuda et al., 2006). This species has been so successful, in part, because it possesses all of the characteristics of successful invasive species, including rapid recovery following physical damage, tolerance for a wide range of environmental conditions, fast growth rates, and profuse seed production (Jones and Doren, 1997; Cuda et al., 2006).

           Schinus terebinthifolius is an evergreen, woody perennial with a multiple-stemmed trunk that is capable of reaching heights of seven meters (Jones and Doren, 1997). This dioecious plant generates small flowers on branched inflorescences, usually between August and October in Florida (Cuda et al., 2006). Schinus terebinthifolius flowers are pollinated by insects and the seeds are dispersed by birds and small mammals or by water movement in estuaries (e.g., Rejmanek and Richardson, 1996; Jones and Doren, 1997; Mielke, Furtado de Almeida, Gomes, Mangabeira, and Da Costa Silva, 2005; Morgan and Overholt, 2005; Donnelly, Green, and Walters, 2008). It produces clusters of small red fruits on female trees annually between November and February and these fruits can stay on plants for up to eight months (Cuda et al., 2006). Observations have shown that these seed clusters have more than 100 individual fruits per stalk.

           As a close relative to poisonwood, poison oak, and poison ivy, Schinus terebinthifolius cannegatively affect its surrounding environment byproducing noxious secondary compounds in its fruits (Inderjit and Callaway, 2003; Morgan and Overholt, 2005). When secondary chemicals produced by an organism negatively affect other species, this chemical defense is called allelopathy (Orr et al., 2005). Other well known species that evince allelopathic properties include the black walnut tree (Juglans nigra), tobacco (Nicotiana rustica), and rice (Oryza sativa) (Rivenshield, 2005). Previous studies have shown high densities of crushed S. terebinthifolius seeds at high salinities reduced survival and growth rates of the black mangrove Avicennia germinans and the red mangrove Rhizophora mangle (Donnelly et a l., 2008). Based on the results of Donnelly et al. (2008), we decided to test fruit density variation on survival of estuarine invertebrates.

            Because S. terebinthifolius has become a problem along the Indian River Lagoon, specifically Mosquito Lagoon (Donnelly et al., 2008), we chose this as our collection site for our field-collected organisms. The only species used in the research that was not collected in Mosquito Lagoon was the brine shrimp Artemia salina, which is commonly used as a model organism in aquatic biological assays for toxicity because it is inexpensive and easy to obtain in large quantities. Hence, we ran our trials three times with A. salina to look for potential variation among trials. To minimize impact on Mosquito Lagoon, all wild-collected organisms were only used in one trial.
In our research, we investigated the impact of S. terebinthifolius on the viability of mobile invertebrate species. Specifically, we asked if S. terebinthifolius fruits were lethal to a variety of mobile invertebrates that are commonly found in Mosquito Lagoon. Our null hypothesis was that S. terebinthifolius would not have an effect on the survival of the test organisms. Our alternative hypotheses were that S. terebinthifolius would have a significant negative impact on organism survival, that percent survivals would decrease as the quantity of fruits increased, and that crushed fruits would result in lower percent survivals than whole fruits.

           In our research, we investigated the impact of S. terebinthifolius on the viability of mobile invertebrate species. Specifically, we asked if S. terebinthifolius fruits were lethal to a variety of mobile invertebrates that are commonly found in Mosquito Lagoon. Our null hypothesis was that S. terebinthifolius would not have an effect on the survival of the test organisms. Our alternative hypotheses were that S. terebinthifolius would have a significant negative impact on organism survival, that percent survivals would decrease as the quantity of fruits increased, and that crushed fruits would result in lower percent survivals than whole fruits.

Methods