Herpetofaunal community change in multiple habitats after fifteen years in a southwest Florida preserve, USA.

John R Cassani,Deborah Hanson,Brenda Brooks,Joseph Bozzo,Edwin M Everham,David W Ceilley,Dean A Croshaw,Jacob Lawrence Kerby

doi:10.1371/journal.pone.0125845

Abstract

Herpetofaunal declines have been documented globally, and southern Florida, USA, is an especially vulnerable region because of high impacts from hydrological perturbations and nonindigenous species. To assess the extent of recent change in herpetofauna community composition, we established a baseline inventory during 1995-97 at a managed preserve in a habitat rich area of southwest Florida, and repeated our sampling methods fifteen years later (2010-11). Nine drift fence arrays were placed in four habitat types: mesic flatwood, mesic hammock, depression marsh, and wet prairie. Trapping occurred daily for one week during 7-8 sampling runs in each period (57 and 49 total sampling days, respectively). Species richness was maintained in mesic hammock habitats but varied in the others. Catch rates of several native species (Anaxyrus terrestris, Lithobates grylio, Anolis carolinensis, Nerodia fasciata) declined significantly. Other native species (Lithobates sphenocephalus, Siren lacertian, and Notophthalmus viridescens piaropicola) that were abundant in 1995-97 declined by greater than 50%. Catch rate of only two species (the nonindigenous Anolis sagrei and the native Diadophis punctatus) increased significantly. Hierarchical cluster analysis indicated similarity within habitat types but significant dissimilarity between sampling periods, confirming shifts in community composition. Analysis of individual species’ contributions to overall similarity across habitats shows a shift from dominance of native species in the 1990s to increased importance of nonindigenous species in 2010-11. Although natural population fluctuations may have influenced differences between the two sampling periods, our results suggest considerable recent change in the structure and composition of this southwest Florida herpetofaunal community. The causes are unknown, but hydrological shifts and ecological impacts of nonindigenous species may have contributed.

Highlights

Global herpetofauna declines, especially among amphibians, have been well documented at various spatial scales and in diverse habitat types [1,2,3,4,5,6,7,8]
The Similarity Percentage Test (SIMPER) analysis indicated a mean among-habitat similarity in 1995–97 of 59.38% with more than 50% of that similarity driven by five species (Table 3): L. sphenocephalus (15.10%), L. grylio (12.03%), Gastrophryne carolinensis (11.09%), Acris gryllus (9.63%) and the nonindigenous E. planirostris (9.05%)
Nonindigenous species increased in importance after a relatively short period between sampling rounds (15 years) and several native species

Summary

Introduction

Especially among amphibians, have been well documented at various spatial scales and in diverse habitat types [1,2,3,4,5,6,7,8]. Current amphibian declines and extinctions greatly exceed background rates, and as many as one third of amphibian species have been affected severely [9,10]. This trend has prompted the recognition of an amphibian decline crisis in the context of maintaining community biodiversity [4]. Declines of reptile populations around the world have been documented, with increased calls for monitoring and vigilance [2, 8, 10]. Gardner et al [12] and Dodd and Smith [13] suggested that habitat change is the primary cause of population decline of reptiles and amphibians worldwide, additional factors may contribute. Complex synergistic effects among multiple causes have the potential to impact amphibian populations [14]

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Conclusion