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Climate and pH Predict the Potential Range of the Invasive Apple Snail (Pomacea insularum) in the Southeastern United States

Aberystwyth University, United Kingdom
PLoS ONE (Impact Factor: 3.53). 02/2013; 8(2):e56812. DOI: 10.1371/journal.pone.0056812
Source: PubMed

ABSTRACT Predicting the potential range of invasive species is essential for risk assessment, monitoring, and management, and it can also inform us about a species' overall potential invasiveness. However, modeling the distribution of invasive species that have not reached their equilibrium distribution can be problematic for many predictive approaches. We apply the modeling approach of maximum entropy (MaxEnt) that is effective with incomplete, presence-only datasets to predict the distribution of the invasive island apple snail, . This freshwater snail is native to South America and has been spreading in the USA over the last decade from its initial introductions in Texas and Florida. It has now been documented throughout eight southeastern states. The snail's extensive consumption of aquatic vegetation and ability to accumulate and transmit algal toxins through the food web heighten concerns about its spread. Our model shows that under current climate conditions the snail should remain mostly confined to the coastal plain of the southeastern USA where it is limited by minimum temperature in the coldest month and precipitation in the warmest quarter. Furthermore, low pH waters (pH <5.5) are detrimental to the snail's survival and persistence. Of particular note are low-pH blackwater swamps, especially Okefenokee Swamp in southern Georgia (with a pH below 4 in many areas), which are predicted to preclude the snail's establishment even though many of these areas are well matched climatically. Our results elucidate the factors that affect the regional distribution of , while simultaneously presenting a spatial basis for the prediction of its future spread. Furthermore, the model for this species exemplifies that combining climatic and habitat variables is a powerful way to model distributions of invasive species.

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Available from: James Byers, Jul 08, 2015
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    • "Nonindigenous Pomacea are abundant in many of Florida's aquatic ecosystems and are spreading throughout the southeastern US (Byers et al. 2013). The goal of this study was to evaluate the effectiveness of hand removal to manage Channeled Apple Snail in a small urban pond. "
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    ABSTRACT: Introduced apple snails (Ampullariidae: Pomacea) have been responsible for crop and habitat damage in freshwater systems around the world. Two Pomacea species known to damage aquatic vegetation, P. maculata (Island Apple Snail) and P. canaliculata (Channeled Apple Snail), have been introduced into Florida. This investigation was conducted to evalu-ate efficacy of a hand-removal program for the management of nonindigenous Pomacea in a small (1.62 ha), relatively isolated urban pond. We removed snails and egg masses from the pond by hand at pre-determined time intervals during May 2008–June 2011. We made a to-tal of 107 collections; 21,343 snails and 20,244 egg masses were removed during the study period with >90% of both removed during the first year (20,961 and 18,934, respectively). Snail densities were reduced in the wadeable near-shore habitat from 1–3/m 2 to <0.001/m 2 . The total cost of the project (salary, supplies, travel) was $10,475. At the time of the final collection in year 3, we observed no snails and removed only two egg masses. Four follow-up assessments September 2011–May 2012 indicated that the hand-removal program was successful and snails had been nearly eradicated from the site. Occasional connections with a population occupying an adjacent drainage ditch could result in a future re-colonization of the pond. Compared with chemical methods, control was achieved with lower monetary cost and less ecological risk. Further evaluations of this method will be necessary to apply it or use it in larger connected ecosystems.
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    • "First, as is typical for almost all large-scale climate models for aquatic species, air temperature was used in place of water temperature in both the logistic regression and the MaxEnt models. Air temperatures typically track water temperatures well, and similar approaches have been successfully used to model aquatic species including freshwater diatoms, snails, salamanders and trout (Kumar et al., 2009; Milanovich et al., 2010; Wenger et al., 2011; Blank & Blaustein, 2012; Byers et al., 2013). There will be some discrepancies between air temperature and water temperature, and these differences will probably be greater for large bodies of water, systems with large amounts of groundwater inputs and hot springs. "
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