Importation dynamics as proxies for propagule pressure are necessary but not sufficient to explain establishment success in non-native herpetofauna

Abstract

Florida is a major entry point for global wildlife trade, creating a high risk of introducing non-native reptiles and amphibians. Using Law Enforcement Management Information System records of reptiles and amphibians imported into Florida from 1999 to 2018, we examined temporal trends in live imports, particularly for legally regulated species, and assessed whether import volumes were associated with establishment probability using a probabilistic model. During the study period, 12.74 million reptiles (1,162 species) and 4.59 million amphibians (350 species) entered through the three main Florida ports. Annual imports decreased significantly over time (Reptiles: 32,731 individuals per year; Amphibians: 10,155 individuals per year), particularly among regulated species, with the reductions occurring gradually. Logistic regression models revealed a strong positive relationship between import numbers and establishment success; for reptiles, import numbers explained 26.4% of the variation in establishment outcomes, while for amphibians, import numbers explained 8.26% of the variation, values expected given that establishment is influenced by multiple unmeasured biological and environmental factors beyond propagule pressure. For reptiles, establishment probability reached 10% at 6,000 imported individuals, 25% at 46,000, and 50% at 369,000. Amphibians did not exceed the establishment‐probability thresholds. Using updated bibliographic sources, a total of 61 reptiles and five amphibians have been reported as being established in Florida. However, our models predict that around 99 reptiles (95% CI: 71.06–147.32) and 6 amphibians (95% CI: 5.41–9.15) could be established in the state based on import volumes alone. Our findings highlight the relevance of integrating predictive modeling, law enforcement data, and decision-making to conduct risk assessments to guide prevention, control, and vigilance efforts. Although the observed patterns are not causal and explain only part of the variation, they provide a basis for identifying broad trends and guiding future research and monitoring efforts.