Habitat characteristics favoring native freshwater turtles in the highly invaded urban turtle community of Miami-Dade County

Abstract

Both aquatic and terrestrial habitat characteristics impact semi-aquatic turtle abundances, community composition, and sex ratios. South Florida is the global hotspot for non-native herpetofauna, but there is limited data on the turtle assemblage in this region. With the expectation that the turtle assemblage would reflect the high diversity of non-native herpetofauna species, we sought to identify both aquatic and terrestrial habitat characteristics that would support a higher percentage of native turtles in the community. We examined the relationships between a suite of habitat variables (pond characteristics, spatial structure of aquatic habitat, surrounding uplands) and turtle abundances, species richness, and sex ratios at 17 ponds in Miami-Dade County during 2019–2021. As expected, this turtle assemblage was dominated by non-natives, with 80% of individuals derived from six non-native species. This is the highest non-native turtle diversity documented in the Americas and is only rivaled by the high diversity of non-natives in a few Eurasian studies. We found that the abundance of native turtles was positively related to chlorophyll concentration, submergent vegetation density, pond area, and (surprisingly) high density urban habitat in the surrounding uplands. Road density in the surrounding uplands was also identified as an important habitat parameter, as it negatively affected both native turtle richness and the proportion of female turtles in each pond. Tracking the trajectory of the semi-aquatic turtle assemblage in this region heavily impacted by both urbanization and biotic invasions may foreshadow future changes in urban centers around the globe.