Byers, J. E., W. G. McDowell, S. R. Dodd, R. S. Haynie, L. M. Pintor & S. B. Wilde, , Climate and pH predict the potential range of the invasive apple snail (Pomacea insularum) in the southeastern United States. PLoS One

Aberystwyth University, United Kingdom
PLoS ONE (Impact Factor: 3.23). 02/2013; 8(2):e56812. DOI: 10.1371/journal.pone.0056812
Source: PubMed


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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    • "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.
    Full-text · Article · Sep 2014 · Southeastern Naturalist
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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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    ABSTRACT: Two dominant drivers of species distributions are climate and habitat, both of which are changing rapidly. Understanding the relative importance of variables that can control distributions is critical, especially for invasive species that may spread rapidly and have strong effects on ecosystems.Here, we examine the relative importance of climate and habitat variables in controlling the distribution of the widespread invasive freshwater clam Corbicula fluminea, and we model its future distribution under a suite of climate scenarios using logistic regression and maximum entropy modelling (MaxEnt).Logistic regression identified climate variables as more important than habitat variables in controlling Corbicula distribution. MaxEnt modelling predicted Corbicula's range expansion westward and northward to occupy half of the contiguous United States. By 2080, Corbicula's potential range will expand 25–32%, with more than half of the continental United States being climatically suitable.Our combination of multiple approaches has revealed the importance of climate over habitat in controlling Corbicula's distribution and validates the climate-only MaxEnt model, which can readily examine the consequences of future climate projections.Given the strong influence of climate variables on Corbicula's distribution, as well as Corbicula's ability to disperse quickly and over long distances, Corbicula is poised to expand into New England and the northern Midwest of the United States. Thus, the direct effects of climate change will probably be compounded by the addition of Corbicula and its own influences on ecosystem function.
    Full-text · Article · Feb 2014 · Freshwater Biology
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    • "South American apple snails (genus Pomacea) represent a recently acknowledged, highly destructive and quickly spreading group of aquatic invaders [11,12]. With some species reaching fist size or larger (shell height and operculum width up to 55 mm), competing with native species [13], feeding on live plant tissue [14-17] and possessing high fecundity [18], apple snails can completely strip water bodies of aquatic and emergent vegetation [19]. "
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    ABSTRACT: Winning the war against invasive species requires early detection of invasions. Compared to terrestrial invaders, aquatic species often thrive undetected under water and do not garner notice until too late for early action. However, fortunately for managers, apple snails (Family Ampullariidae, Genus Pomacea) provide their own conspicuous sign of invasion in the form of vibrantly colored egg clutches. Managers can potentially use egg clutches laid in the riparian zone as a means of early detection and species identification. To facilitate such efforts, we quantified differences in characteristics (length, width, depth, mass, egg number) of field-laid clutches for the two most common invasive species of apple snail, P. canaliculata and P. maculata, in native and non-native populations. Pomacea canaliculata native and non-native populations differed noticeably only in width. Native P. maculata clutches possessed significantly greater width, mass and eggs numbers compared with native P. canaliculata. Non-native P. maculata clutches significantly exceeded all other populations in all measured characteristics. Consequently, these traits may successfully distinguish between species. Fecundity data also allowed us to develop models that accurately estimated the number of eggs per clutch for each species based on clutch dimensions. We tested one, two and three dimensional models of clutches, including rendering a clutch as either a complete ellipsoid or an ellipsoid intersected by a cylinder to represent the oviposition site. Model comparisons found the product of length and depth, with a different function for each population, best predicted egg number for both species. Comparisons of egg number to clutch volume and mass implied non-native P. canaliculata may be food limited, while non-native P. maculata appeared to produce such enormous clutches by having access to greater nutrients than the native population. With these new tools, researchers and managers can quickly identify, quantify and begin eradication of new non-native apple snail populations.
    Full-text · Article · Oct 2013 · PLoS ONE
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