Pulse Disturbance Impacts from a Rare Freeze Event in Tampa, Florida on the Exotic Invasive Cuban Treefrog, Osteopilus Septentrionalis, and Native Treefrogs

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Hylid, MacKenzie, Occupancy, PVC, Removal, Temporal

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This study documented exotic invasive Osteopilus septentrionalis and native treefrog use of artificial refugia in Tampa, Florida, USA, spanning approximately 3 years, with sampling from 1 year before and after (August 2008–November 2011) a record low temperature of −4 °C on January 11, 2010. Six pipes were inserted into the ground along the upland ecotone of 15 cypress domes located along a gradient of urban land use. Over 1000 treefrogs observations were made, with O. septentrionalis representing > 70 % of total counts. Treefrog captures peaked in January–February 2009 and were temporally auto-correlated per site. O. septentrionalis counts declined following each freeze, and a fitted smoothing function for month indicated declines were cumulative, with a significant minimum in counts during the last freeze in February 2011. A concurrent seasonal peak in native treefrog counts led to a temporary loss of O. septentrionalis dominance from January to March 2011. Temperatures of −4 °C were sufficient to cause mortality of O. septentrionalis in PVC refugia; however, after autocorrelation was addressed no significant trend in native treefrogs was observed during the study. Multiseason occupancy models indicated probability of extinction for O. septentrionalis between freeze events did not differ significantly from native treefrogs, whereas a high probability of colonization between freeze events indicated O. septentrionalis may be resilient even to rare freezes. Trends in O. septentrionalis presence were not significant, and it was captured at 14/15 sites following the third freeze event, suggesting extirpation from freezing temperature may be unlikely for O. septentrionalis.

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Biological Invasions, v. 17, issue 7, p. 2103-2111