In this thesis I examined factors limiting population success of apple snails (Pomacea spp.) in Florida wetlands. First, I examined effects of summertime hydropattern in replicated wetlands on reproduction and juvenile growth. Annual reproductive effort of Florida apple snails (Pomacea paludosa) and the invasive apple snail P. maculata under was not affected by deeper water in the summer. When juvenile P. paludosa were forced to grow in reportedly favorable and relatively deeper summertime depths survival was high between treatments and growth was unaffected. In the other chapter I examined interactions between the two snails with a series of observations and experiments. I examined historical data on the assemblages and found that P. paludosa were locally extinguished in one of the wetlands within six years of invasion by P. maculata. Two field experiments gave conflicting results about the importance of interspecific inhibition of P. paludosa by the invasive snail, but in either case resource reduction could not be demonstrated. Lab exposure to P. maculata chemical cues strongly inhibited P. paludosa growth, although P. paludosa did not behaviorally avoid mucus of P. maculata. In mesocosms Pomacea paludosa growth was reduced with increasing exposure to adult P. maculata waterborne cues, and the results suggest that contact with mucus at a low exposure may even have a greater inhibiting effect. This interspecific direct chemical growth inhibition was novel for gastropods, but could be more generally important, and its potential impacts to P. paludosa populations should be explored further. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

Invasive species are detrimental to native biotas worldwide. Recently, Florida was invaded by a freshwater snail (Pomacea canaliculata) native to Argentina. This snail is a serious pest of rice crops in Asia, but little is known about its interactions within Florida ecosystems. Possible competitive exclusion of the native congener (P. paludosa) is a concern because it is the almost exclusive prey of the federally endangered Everglades snail kite (Rostrhamus sociabilis). My research consisted of three parts. First, to identify possible methods to control P. canaliculata in the egg stage, I experimentally evaluated the effects of photoperiod, substrate availability, and food type and availability on hatching success and hatchling survival. None of these factors significantly affected hatching or survival, suggesting that P. canaliculata could invade many water bodies. Second, I used a randomized block design to assess the separate and combined effects of population density and food availability on growth and spawning of P. canaliculata. Food availability but not density significantly affected growth; snails fed less food grew less, but neither factor affected spawning. Third, I used a replacement series design to assess competition between P. canaliculata and P. paludosa under food limitation. For both species, snails fed less grew significantly less, and snails exposed to greater congener densities spawned less than when exposed to conspecifics only. While my results predict that P. paludosa should exclude P. canaliculata, previous literature and current invasions suggest that the exotic snail may co-exist with its North American congener.