Figure 1.
Pomacea insularum adult (6.1 cm) and an egg mass (7.6×2.5 cm).
P. insularum has a channeled suture and often exceeds 10 cm in height and lays conspicuous large pink egg masses. Photo credits: (left)–Freshwater Gastropods of North America website; (right)–J. Morgan.
Table 1.
List of environmental variables from the BIOCLIM dataset used in the MaxEnt model.
Table 2.
Experimentally determined incipient physiological tolerance limits under laboratory conditions for adult and juvenile Pomacea insularum collected in Texas (from Ramakrishnan [31]).
Figure 2.
Present populations of the island apple snail, Pomacea insularum, and its occupiable area.
Map shows the southeastern United States. As predicted by the maximum entropy model, red represents areas with the highest climatic compatibility for the snail as determined by using an inclusion threshold that correctly classifies all sites above the minimum 10% training omission threshold. Pink represents areas determined to be suitable by using the less stringent threshold calculated by correctly classifying all known P. insularum points above the minimum training presence.
Figure 3.
The average receiver operating curve from the ten model runs showing relative specificity and sensitivity.
One standard deviation above and below the average curve is shown in blue. Area Under the Curve (AUC) is calculated from this curve.
Figure 4.
Map of predicted P. insularum distribution also showing areas with low pH values.
Acidic waters may inhibit the invasion of P. insularum. Black represents areas with a predicted pH <4, the mortality threshold determined by Ramakrishnan [31] and gray areas have a predicted pH of 4–5.5, below the hatchling mortality threshold determined by Bernatis (unpublished data). The large black area in southern Georgia is Okefenokee Swamp discussed in the text.