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Selwyn JD, Johnson JE, Downey-Wall AM, Bynum AM, Hamner RM, Hogan JD, Bird CE.2017. Estimating the number of lionfish (Pterois volitans) that colonized the Atlantic Ocean. PeerJ Preprints5:e3033v1https://doi.org/10.7287/peerj.preprints.3033v1
The invasion of the western Atlantic Ocean by the Indo-Pacific red lionfish (Pterois volitans) has had devastating consequences for marine ecosystems. Estimating the number of colonizing lionfish can be useful in identifying the introduction pathway and can inform policy decisions aimed at preventing similar invasions. It is well-established that at least ten lionfish were initially introduced. However, that estimate has not faced statistical scrutiny and is based solely on the number of haplotypes in the maternally-inherited mitochondrial control region observed in samples from the western Atlantic Ocean. To rigorously estimate the number of lionfish introduced, we used a forward-time, Wright-Fisher, population genetic model of the mitochondrial control region in concert with a demographic life-history model to simulate the invasion. The colonization of the western North Atlantic and subsequent spread to the Caribbean and Gulf of Mexico were modeled as single introductions of 1-800 females, which should conservatively estimate the most likely number of colonizing lionfish relative to a model with multiple introductions. Assuming a balanced sex ratio and no Allee effects, the simulations indicate that the Atlantic population was most likely founded by 118 (54-514, 95% HPD) lionfish from the Indo-Pacific, the Caribbean by 84 (22-328, 95% HPD) lionfish from the Atlantic, and the Gulf of Mexico by at least 114 (no upper bound on 95% HPD) lionfish from the Caribbean. Considering the additional possibilities that (1) multiple Indo-Pacific populations colonized the Atlantic and (2) Allee effects (e.g. 50% reduction in fecundity) plagued the colonists, the most likely number of lionfish increased to 180 (88-416, 95% HPD). These results, in combination with all other published data, support the hypothesis that lionfish were introduced to the Atlantic via the aquarium trade, rather than shipping. The most parsimonious introduction pathway is a single release of lionfish in one location, but it seems likely that a combination of smaller and larger releases from a variety of aquarium trade stakeholders occurred near Miami, Florida. Efforts to prevent future invasions via the aquarium trade should focus on the education of stakeholders and the prohibition of release, with adequate rewards for compliance and penalties for violations.
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Two R code files are included the first: "model_functions.R" contains the code used to run the model as described here. The second "run_lionfish_colonizations.R" initializes the relevant data collected from the literature as described in the manuscript and runs the model for different source and destination populations.
This file contains mtDNA sequence data from the control region of Pterois volitans in the FASTA file format. Samples were obtained from Indonesia, the western North Atlantic, Caribbean, and Gulf of Mexico via GenBank ( Freshwater et al., 2009; Betancur-R. et al., 2011; Toledo-Hernández et al., 2014; Butterfield et al., 2015; Johnson et al., 2016).
This file contains mtDNA sequence data from the control region of Pterois volitans in the Arelquin file format. Samples were obtained from Indonesia, the western North Atlantic, Caribbean, and Gulf of Mexico via GenBank ( Freshwater et al., 2009; Betancur-R. et al., 2011; Toledo-Hernández et al., 2014; Butterfield et al., 2015; Johnson et al., 2016).