Introduction

Amphibian populations are imperilled and continue to decline worldwide primarily due to habitat disturbance, fragmentation, and loss (Delis et al., 1996; Ficetola et al., 2015, Semlitsch et al., 2017), exacerbated by a synergy of additional anthropomorphic stressors and disease (Collins and Storfer, 2003; Lips et al., 2005; Ficetola et al., 2015; Semlitsch et al., 2017). Amphibians have been used as possible indicators of ecological change and disturbance in other regions (Welsh and Ollivier, 1998; Bank et al., 2006; Sewell and Griffiths, 2009; Rowe and Garcia, 2013), and in south Florida with the inclusion of hylid treefrogs (Waddle, 2006; Dixon et al., 2011; Guzy et al., 2012; Everham et al., 2013; Walls et al., 2014). Due to their permeable skin and biphasic life cycle,

amphibians are vulnerable to stressors in both terrestrial and aquatic environments (Vitt et al., 1990; Welsh and Ollivier, 1998; Waddle, 2006). It is anticipated that stress responses will become apparent first in sensitive species such as these (Wake, 1991; Odum, 1992; Bank et al., 2006). Hylidae is a large, diverse family of anuran amphibians with a variety of morphological and life history characteristics among the genera (Martin and Watson, 1971). Southwest Florida is home to seven native species of hylids, which includes four treefrog species, in addition to one exotic treefrog species (Ashton and Ashton, 1988; Dodd, 2013). These treefrog species all have life cycles tied to water (Ashton and Ashton, 1988; Dodd, 2013) making them particularly vulnerable to altered hydrology (Guzy et al., 2012; Walls et al., 2014).

The Big Cypress region is a mosaic of pine forests, cypress strands, hardwood hammocks, and wet prairies in the South Florida Ecosystem, located west of the sawgrass plains, ridges, and sloughs of the Everglades (Carter et al., 1973; Duever, 2005). Human activities during the past century have negatively affected the western portion of this vast wetland system. Borrow

Herpetology Notes, volume 14: 913-922 (2021) (published online on 24 June 2021)

Spatial and temporal patterns for treefrog (Anura: Hylidae) communities in conservation areas of southwestern Florida

Melinda J. Schuman1,*, Ian A. Bartoszek1, Kathy B. Worley1, Vanessa G. Booher1, and Jeffrey R. Schmid1

1 Environmental Science Division, Conservancy of Southwest Florida, 1495 Smith Preserve Way, Naples, Florida, 34102, USA.

* Corresponding author. E-mail: melindas@conservancy.org

© 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0.

Abstract. Hylid treefrogs are dependent on the aquatic environment and may provide indications of stress and disturbance in wetland habitats. Human activities over the past century have altered the natural water flow in the Big Cypress region in southwestern Florida. These anthropogenic disturbances prompted the designation of conservation areas over much of the region as well as hydrologic restoration efforts in heavily impacted areas. Spatiotemporal patterns of treefrog species composition were analysed for restoration monitoring projects in 2005-07, 2009-11, and 2016-17. Polyvinyl chloride (PVC) pipes were deployed to collect treefrogs from representative habitat types within the reference areas of Florida Panther National Wildlife Refuge (FPNWR; n = 6 sample sites) and Fakahatchee Strand Preserve State Park (FSPSP; n = 5 sites), and restoration area of eastern Picayune Strand State Forest (PSSF; n = 8 sites). The treefrog composition for PSSF differed from those of FPNWR and FSPSP and the high abundance of the non-native Osteopilus septentrionalis (Cuban treefrog) in PSSF contributed to these spatial differences. There were temporal changes to the community composition for FPNWR and FSPSP with initial high abundances of native Hyla cinerea (green treefrog) and/or H. squirella (squirrel treefrog) and O. septentrionalis becoming more abundant over time. A negative correlation was detected for abundances of exotic and native species in FPNWR but the relationship was positive for the exotic and a native species in FSPSP. Temporal changes of treefrog compositions in the reference conservation areas bring in to question the suitability of these areas to assess restoration goals. Furthermore, the exotic species populations in all conservation areas may confound any indications of restoration success. Historical habitat loss may be less obvious today in reference conservation areas but they could still be in a state of recovery owing to the rarity of indicator species such as H. gratiosa (barking treefrog) and H. femoralis (pinewoods treefrog).

Keywords. Hylidae, Cuban treefrog, invasive species, Osteopilus septentrionalis, treefrog

Melinda J. Schuman et al.914

canals excavated for highway construction in the 1920s began to alter the natural water flow and facilitated access to the interior of Big Cypress (Klein et al., 1970). Large-scale logging of pine and cypress timber in the 1930s and 1940s, respectively, resulted in loss of these forest habitats and railways for logging operations further modified the aquatic landscape (Leighty et al., 1954; Carter et al., 1973). A substantial portion of western Big Cypress was purchased for development and a network of canals and roadways was constructed in the 1960s and 1970s as part of the Golden Gate Estates subdivision, further altering the hydrologic regime (Ramsey and Addison, 1996). Land acquisition efforts initiated in the 1970s and 1980s resulted in the designation of state and federal conservation areas over much of the Big Cypress region.

Concurrent to conservation efforts in the Big Cypress region, a number of hydrologic and ecologic studies led to the development of restoration plans for the southern portion of the Golden Gate Estates subdivision (Abbott and Nath, 1996). These plans included removing

roads and plugging canals in an effort to restore pre-drainage hydrology. The Picayune Strand Restoration Project was subsequently initiated in 2004 as part of the Comprehensive Everglades Restoration Plan (USACOE and SFWMD, 2004) and included monitoring the status of water-dependent species to assess the success of these restoration efforts. The purpose of the current study was to analyse spatiotemporal patterns of treefrog assemblages during a series of monitoring projects in southwest Florida conservation areas. The objectives were (1) to compare spatial aspects of treefrog species compositions among conservation areas and (2) to compare temporal patterns of the compositions in each area.

Materials and Methods

Study Area. The study area included the conservation areas of Fakahatchee Strand Preserve State Park (FSPSP), Florida Panther National Wildlife Refuge (FPNWR), and Picayune Strand State Forest (PSSF) in Collier County, Florida (Fig. 1). Hydrologic restoration

Figure 1. Map of southwest Florida conservation areas and sampling sites for monitoring projects identified in Table 1.

in PSSF was initiated when the eastern most canal (Prairie Canal) bordering FSPSP was plugged with non-asphalt material from adjacent roads. Construction on the upper portion of the canal was completed in 2004 and the lower portion in 2007. The next phase involved degrading roads and plugging the canal (Merritt Canal) to the west during 2009 – 2015, after which the hydrology in this area was considered to be fully restored (NRC, 2018). For the initial monitoring project, sampling locations were established in representative habitat types and designated as either restoration sites in PSSF (n = 27) or reference sites in FSPSP (n = 5) and FPNWR (n = 6; Bartoszek et al., 2007). The current study includes 8 restoration sites in eastern PSSF as well as the reference sites (Table 1).

Treefrog capture. Treefrogs were sampled using polyvinyl chloride (PVC) pipes as artificial refugia (Zacharow et al., 2003; Bartareau, 2004). Two sets of three 1 m lengths of pipe, each with different inner diameters (1.3, 2.5, and 3.8 cm), were placed randomly at each of the study sites. Three pipes were attached to tree trunks by means of a hole drilled into the pipe to hook onto a nail in the tree. Each pipe was attached approximately 2 m above ground on each tree and when

trees were not present, attached to tall grass stems. Additionally, three pipes were stuck several centimetres into the ground, for a total of six pipes at each study site. Pipes were checked every two months from August 2005 through June 2007, every two months from August 2009 through April 2011, and monthly from May 2016 through April 2017. Treefrogs were carefully extracted from the pipes and collected in mesh bags using a dowel rod plunger and a section of sponge pushed gently through each pipe. Captured treefrogs were identified to species, measured, weighed, and then released on site. Treefrogs were not uniquely marked and therefore were not identifiable as a recapture during subsequent sampling events. Furthermore, multiple species of treefrog are known to inhabit the same PVC pipe with little evidence of exclusion or avoidance (Hoffman, 2007; Elston et al., 2013).

Data analyses. Sampling data for 3 monitoring projects were designated as “Baseline” (pre-restoration sampling efforts in 2005 – 2007; Bartoszek et al., 2007), “Interim” (sampling efforts during construction in 2009 – 2011; Bartoszek et al., 2011), and “Post-restoration” (post-construction sampling efforts in 2016 – 17; Worley et al., 2017). Comparisons among the projects were confounded by differences in sampling intervals (every 2 months for Baseline and Interim vs. monthly for Post-restoration) and project duration (2 years for Baseline and Interim vs. 1 year for Post-restoration). For the former, mean abundance was calculated for sequential pairs of months (May and June, July and August, etc.) in the Post-restoration project to rescale sampling frequency as every other month. Sampling years for these projects were selected as a data treatment and designated as 2005-06 (August 2005 to June 2006) and 2006-07 (August 2006 to June 2007) for the Baseline project, 2009-10 (August 2009 to June 2010) and 2010-11 (August 2010 to April 2011) for the Interim project, and 2016-17 (May 2016 to April 2017) for the Post-restoration project.

Spatial and temporal aspects of the treefrog assemblage were examined using PRIMER v6 software (Clarke and Gorley, 2006). A zero-adjusted Bray-Curtis similarity matrix was calculated for treefrog abundances at all sampling sites using a dummy variable of 0.5, the lowest value for mean abundance in the Post-restoration study (Clarke et al., 2006). Two-way crossed analysis of similarity (ANOSIM; 999 permutations) was used to compare treefrog species composition among conservation areas, allowing for possible sampling year differences, and to compare composition among

Spatial and temporal patterns for treefrog communities in southwestern Florida 915

Conservation area Site code Habitat type Latitude Longitude

FPNWR

FP1 Cypress 26.1853 -81.3790

FP2 Prairie 26.1859 -81.3788

FP3 Pine 26.1877 -81.3779

FP4 Cypress 26.1727 -81.4500

FP5 Prairie 26.1726 -81.4495

FP6 Pine 26.1725 -81.4487

FSPSP

FS1 Cypress 25.9771 -81.3678

FS2 Prairie 25.9757 -81.3671

FS3 Pine 25.9800 -81.3634

FS4 Cypress 25.9803 -81.3930

FS5 Prairie 26.0472 -81.4414

PSSF

PS6 Pine 26.1434 -81.4693

PS11 Prairie 26.1101 -81.4968

PS12 Cypress 26.1107 -81.4764

PS13 Prairie 26.0930 -81.4612

PS18 Hardwood 26.0559 -81.4988

PS19 Cypress 26.0549 -81.4719

PS24 Cypress 26.0273 -81.4790

PS25 Prairie 26.0403 -81.4634

Table 1. Sampling sites for treefrogs in southwest Florida conservation areas (PSSF - Picayune Strand State Forest, FSPSP - Fakahatchee Strand Preserve State Park, and FPNWR - Florida Panther National Wildlife Refuge).

sampling years, allowing for possible conservation area differences. The two-way similarity percentages routine (SIMPER) was used to identify taxa contributing to any dissimilarity between conservation areas. Zero-adjusted Bray-Curtis similarity matrices were calculated for sampling sites within each conservation area and one-way ANOSIM was used to compare treefrog compositions among the sampling years of each area. A pairwise matrix of R values was generated in the event of a significant difference in the ANOSIM global test. Computations for R values are not unduly affected by the number of replicates/permutations, unlike the significance levels (P-values), and are therefore considered the best measure of differences between groups (Clarke and Warwick, 2001; Clarke and Gorley, 2006). Large values (R ≈ 1) indicate high differentiation of communities, while small values (R ≈ 0) imply little or no difference. Nonmetric multidimensional scaling (NMDS) was applied to the pairwise R value matrix to plot the relationships of treefrog composition among sampling years in each conservation area. Real Statistics Data Analysis Tools add-in (Zaiontz, 2020) for Microsoft Excel was used to calculate Spearman’s rank correlation for the abundances of treefrog species collected during the sampling events in each conservation area.

Results

Two-way crossed ANOSIM indicated that conservation area and sampling year were both significant factors for differences in treefrog community composition, and conservation area (Global R = 0.26, P = 0.001) had a greater influence on community variation than sampling year (Global R = 0.16, P = 0.001). Pairwise comparisons of conservation areas suggested the treefrog community for PSSF differed the most from FPNWR (R = 0.32, P = 0.001) and FSPSP (R = 0.26, P = 0.001); however, the low to intermediate R values implied considerable overlap in species compositions. The SIMPER analyses identified Osteopilus septentrionalis Duméril & Bibron, 1841 (Cuban treefrog) as contributing the most to differences in community composition among conservation areas owing to higher average abundance in PSSF (Table 2). Temporal patterns of community composition in each conservation area were analysed separately given these spatial differences.

There were significant differences in treefrog species composition among the sampling years in each conservation area (Table 3). The intermediate global R value for FPNWR indicated differences in treefrog composition among the sampling years in this area. The intermediate to high pairwise R values suggested species composition during both sampling years of the Baseline

Melinda J. Schuman et al.916

Treefrog taxa Average abundance by conservation area

Percent contribution to dissimilarity

Average dissimilarity

FPNWR FSPSP 77.8

Osteopilus septentrionalis 0.54 0.66 44.4

Hyla squirella 0.98 1.38 34.5

Hyla cinerea 0.67 0.24 21.1

FPNWR PSSF 82.8

Osteopilus septentrionalis 0.54 2.18 63.0

Hyla cinerea 0.67 0.12 18.5

Hyla squirella 0.98 0.03 18.5

FSPSP PSSF 82.0

Osteopilus septentrionalis 0.66 2.18 66.0

Hyla squirella 1.38 0.03 23.1

Hyla cinerea 0.24 0.12 10.9

Table 2. Results of two-way crossed SIMPER analyses of taxa contributing to the dissimilarity in treefrog composition among southwest Florida conservation areas (PSSF - Picayune Strand State Forest, FSPSP - Fakahatchee Strand Preserve State Park, and FPNWR - Florida Panther National Wildlife Refuge).

project differed from those during sampling years of other projects. Average abundances of Hyla cinerea (Schneider, 1799; green treefrog) and H. squirella Bosc, 1800 (squirrel treefrog) were highest in FPNWR during the Baseline sampling years, while abundance of O. septentrionalis increased during Interim and Post-restoration sampling years (Table 4).

Despite their significance, the very low global R values (< 0.15; Table 3) for FSPSP and PSSF indicate the treefrog species compositions were strongly overlapping among sampling years in these conservation areas. The respective pairwise R values between sampling years were also low but suggested the compositions for FSPSP during both Baseline sampling years differed the most from that of the Post-restoration sampling year and the composition for PSSF during 2006-07 of the Baseline project differed the most from the sampling years of the other monitoring projects. Average abundances of H. squirella were highest in FSPSP during the Baseline sampling years but decreased substantially by the first year of the Interim project, while O. septentrionalis had the second highest abundance during Baseline years and the highest during the first year of the Interim project and the Post-restoration sampling year (Table 4).

Osteopilus septentrionalis was the dominant species in PSSF for all sampling years but the average abundance during 2006-07 was 1.5 – 2.5 times greater than that of the other years.

The NMDS ordination of pairwise R values illustrated the temporal patterns of treefrog compositions in each conservation area (Fig. 2). Both FPNWR and FSPSP had trajectories indicating species compositions differed during sampling years of the sequential monitoring projects, whereas the trajectory for PSSF indicated compositions for 2005-06 of the Baseline project and 2016-17 of the Post-restoration project were more similar to each other than those of the other sampling years.

There was a significant positive correlation for the

FPNWR Global R = 0.38, P = 0.001

2005-06 2006-07 2009-10 2010-11

2006-07 0.09 -

2009-10 0.33 0.59 -

2010-11 0.34 0.65 0.01 -

2016-17 0.60 0.81 0.10 0.22

FSPSP Global R = 0.12, P = 0.001

2005-06 2006-07 2009-10 2010-11

2006-07 -0.01 -

2009-10 0.04 0.01 -

2010-11 0.09 0.19 0.14 -

2016-17 0.20 0.27 0.16 0.10

PSSF Global R = 0.09, P = 0.001

2005-06 2006-07 2009-10 2010-11

2006-07 0.06 -

2009-10 0.10 0.17 -

2010-11 0.08 0.17 -0.01 -

2016-17 0.02 0.17 0.07 0.06

Table 3. Results of one-way ANOSIM tests of treefrog species composition in southwest Florida conservation areas (FPNWR - Florida Panther National Wildlife Refuge, FSPSP - Fakahatchee Strand Preserve State Park, and PSSF - Picayune Strand State Forest) during sampling years of monitoring projects (2005-06 and 2006-07 for Baseline, 2009-10 and 2010-11 for Interim, and 2016-17 for Post-restoration).

Figure 2. NMDS ordination of pairwise R values for comparisons of treefrog communities during the sampling years of monitoring projects in southwest Florida conservation areas (FPNWR - Florida Panther National Wildlife Refuge, FSPSP - Fakahatchee Strand Preserve State Park, and PSSF - Picayune Strand State Forest).

Spatial and temporal patterns for treefrog communities in southwestern Florida 917

ranked abundances of H. cinerea and H. squirella in FPNWR, and both species had significant negative correlations with the ranked abundances of O. septentrionalis (Table 5). Conversely, there was a significant positive correlation for ranked abundances of H. squirella and O. septentrionalis in FSPSP owing to decreased abundance of both species over time at three of the five sampling sites. There were no significant correlations between treefrog species in PSSF.

Discussion

Conservation areas in southwest Florida exhibited significant spatial differences in treefrog species composition. The relatively high abundance of the non-native O. septentrionalis at Picayune Strand State Forest (PSSF) restoration sites differentiated the treefrog community in this conservation area from those of the surrounding Florida Panther National Wildlife Refuge (FPNWR) and Fakahatchee Strand Preserve State Park (FSPSP) reference areas. Waddle et al. (2010)

Table 4. Average abundances of hylid species collected in southwest Florida conservation areas during the sampling years of each monitoring project.

Melinda J. Schuman et al.918

Conservation areas and sampling years for monitoring projects

Hyla cinerea

Hyla squirella

Osteopilus septentrionalis

Florida Panther National Wildlife Refuge

Baseline

2005-06 1.81 1.31 0.04

2006-07 1.06 3.25 0.08

Interim

2009-10 0.28 0.11 0.72

2010-11 0.10 0.07 0.40

Post-restoration

2016-17 0 0 1.43

Fakahatchee Strand Preserve State Park

Baseline

2005-06 0.50 2.60 0.72

2006-07 0.33 2.17 1.07

Interim

2009-10 0.47 0.53 1.17

2010-11 0.32 0.16 0.16

Post-restoration

2016-17 0.03 0.02 0.48

Picayune Strand State Forest

Baseline

2005-06 0.03 0 2.48

2006-07 0.02 0 4.06

Interim

2009-10 0.08 0.02 1.69

2010-11 0.10 0.10 1.65

Post-restoration

2016-17 0.01 0.01 1.61

detailed the geographic pattern of co-occurrence for O. septentrionalis with either H. cinerea or H. squirella in the study area and suggested O. septentrionalis had expanded eastward from the urban areas of Naples owing to a strong spatial gradient in their occurrence. Although relative abundances were not provided, O. septentrionalis appeared prevalent in PSSF as well as FPNWR. The latter observation and timing of their study has implications for the temporal pattern of treefrog composition in this conservation area.

There was a community shift at FPNWR reference sites from a high abundance of H. cinerea and H. squirella during the Baseline project to decreased abundance of these native species and an increase in O. septentrionalis during the Interim and Post-restoration projects. The decline in native treefrogs may be attributable to the increase in numbers of O. septentrionalis. This non-native species can negatively impact native hylids through predation and competition for food with both adult and tadpole stages (Wilson and Porras, 1983; Meshaka, 2001; Wyatt and Forys, 2004; Smith, 2005; Knight et al., 2009; Rice et al., 2011). Furthermore, studies have noted native species do not attempt to avoid O. septentrionalis, increasing

their risk to predation (Meshaka, 2001; Hoffman, 2007; Elston et al., 2013). Waddle et al. (2010) concluded that H. cinerea and H. squirella were less likely to occur at sites occupied by O. septentrionalis. Meshaka (2001) noted a negative correlation between O. septentrionalis and both H. cinerea and H. squirella, while others have noted negative correlations between H. squirella and O. septentrionalis (Bartareau, 2004; Campbell et al., 2010; Rice et al., 2011). The negative correlations in abundance observed in the current study suggests displacement of native species could be occurring at the sites within FPNWR.

Hyla squirella was the most abundant species and O. septentrionalis the second most abundant species at FSPSP reference sites during the Baseline project. All treefrog abundances, both native and exotic, declined in FSPSP during subsequent surveys in the Interim and Post-construction projects. Similar to FPNWR, there was an overall decline in native species abundance in FSPSP. However, reduced abundance of native and exotic species in both FSPSP and FPNWR was observed during the second year of the Interim project that may have been associated with a freeze event in December 2010. Dead and emaciated O. septentrionalis were noted in pipe arrays following multiple days of unseasonably cold temperatures (Bartoszek et al., 2011). Haggerty and Crisman (2015) demonstrated that a temperature of -4°C could be lethal to O. septentrionalis, though rare freeze events in southern Florida would not likely result in extirpation or produce lasting population effects. Nonetheless, the multi-day freeze event may have allowed for a temporary shift toward relatively higher abundance of H. cinerea in FSPSP and lower abundance of O. septentrionalis during the second half of the Interim project (Table 4). As indicated, O. septentrionalis was the most abundant species during Post-restoration project but their abundance was still relatively lower than previous sampling years.

The dominance of O. septentrionalis and low abundance of native species at PSSF restoration sites may have been the consequence of the severely altered hydrology in this conservation area and the life history requirements of each hylid species. Meshaka (2001) concluded that O. septentrionalis thrive in disturbed natural areas of south Florida owing to the instabilities in these areas mimicking the effects of recurrent natural disturbances in this species native range. Furthermore, long breeding season, short larval phase, and high fecundity (Meshaka, 2001; Johnson, 2017) may collectively contribute to the species success

Spatial and temporal patterns for treefrog communities in southwestern Florida 919

Table 5. Spearman rank correlations of treefrog abundance in each southwest Florida conservation area.

Hyla cinerea

Hyla squirella

Florida Panther National Wildlife Refuge

Hyla squirella

0.32 (< 0.001) -

Osteopilus septentrionalis

-0.28 (< 0.001)

-0.28 (< 0.001)

Fakahatchee Strand Preserve State Park

Hyla squirella

0.05 (0.54) -

Osteopilus septentrionalis

0.10 (0.23)

0.26 (0.001)

Picayune Strand State Forest

Hyla squirella

-0.03 (0.63) -

Osteopilus septentrionalis

0.03 (0.67)

-0.07 (0.30)

in colonizing disturbed areas with altered hydrology. Conversely, native treefrogs are dependent on the health and stability of the wetlands and are frequently used as biological indicators of hydrologic change within these habitats (Dixon et al., 2011; Walls et al., 2014). Loss or damage of wetland habitat, especially when the hydrology is impaired, can negatively affect native treefrog population levels (Guzy et al., 2012; Everham et al., 2013). Waddle (2006) concluded that H. cinerea would be suitable indicators of these changes because their populations respond rapidly to the aquatic conditions of their habitat. Unfortunately, the relatively high abundance of O. septentrionalis may confound the ability of native treefrogs to respond to hydrologic restoration in PSSF and management actions involving the removal of this invasive species would be too costly (Rice et al., 2011).

Interestingly, H. femoralis Daudin, 1800 (pinewoods treefrog), and H. gratiosa (LeConte, 1856; barking treefrog), were not caught during any of the sampling periods reported herein. Both species have been successfully captured in other regions of Florida using PVC pipes (Boughton et al., 2000; Campbell et al., 2010) and both species have been identified in western PSSF through call monitoring (Walls et al., 2014) and in FSPSP during more recent pipe sampling (Clark, 2020). The absence of these species in the current study potentially exposes the limitation of using a single method of sampling to monitor taxa and highlights the need for adaptability with methods. Although these species are indicators of wetland integrity, they are typically excluded from disturbed or degraded habitat (Delis et al., 1996; Guzy et al., 2012), and are rare in PSSF (Walls et al., 2014). Historically, large-scale logging resulted in habitat loss and hydrologic alterations in all the conservation areas of the current study. These disturbances may not have extirpated treefrog populations, however the ‘extinction debt’ created by the habitat degradation and fragmentation (Semlitsch et al., 2017) could have been a major challenge for the recovery of these rare hylid species. Wilson and Porras (1983) first noted the decline of both H. gratiosa and H. femoralis throughout south Florida given the increased urban and agricultural development and it is plausible that these species are in a state of recovery along with that of their habitats in conservation areas.

A fundamental concept in restoration ecology is the selection of reference locations for evaluating the success of restoration efforts (White and Walker, 1997). Understanding relevant ecological, spatial and temporal

factors, along with knowledge of contemporary and historic data, for both the restoration and reference locations is vital for choosing a suitable reference location (White and Walker, 1997; Durbecq et al., 2020) and for assessment of results (Griffith and McManus, 2020). Improvement in wildlife communities was expected to occur concurrently with the restoration efforts in PSSF (USACOE and SFWMD, 2004) but the trajectory for hylid species composition indicated no temporal change with the treefrog community. The domination of the non-native O. septentrionalis in the restoration area may preclude any meaningful results from the monitoring studies. In contrast, reference areas exhibited similar trajectories indicating temporal variation in species composition. Both reference areas displayed reduced abundance of native hylid species over time, whereas abundance of non-native O. septentrionalis increased in FPNWR and was variable in FSPSP. Collectively, these changes had an impact on their applicability as reference for restoration success. Amphibian communities naturally fluctuate over time (Pechmann et al., 1991) and the perceived changes to the hylid aggregations during intermittent, short-term (i.e., 1-2 years) monitoring projects may result in misinterpretation owing to these continuous fluctuations (Pechmann et al., 1991; Sewell and Griffiths, 2009). Understanding the underlying causes of these shifts along with the breadth of the exotic species invasion in these conservation areas will be key to the adaptive management of restoration efforts.

Acknowledgments. The monitoring projects reported herein were supported by the South Florida Water Management District (SFWMD), Florida Division of Forestry (FDOF), United States Fish and Wildlife Service (USFWS), and the Florida Department of Environmental Protection (FDEP). We thank personnel at Florida Panther National Wildlife Refuge, Picayune Strand State Forest, and Fakahatchee Strand Preserve State Park for permission to work on these lands and assistance with accessing sites. We thank the following for their assistance in data collection in the field: David Addison, Lindsay Addison, Glenn Buckner, David & Connor Ceilley, Ilma Dancourt, Leif Johnson, Brian Kelly, Heather Pace, David Shindle, Clinton Porter Smith, and Bethany Edmonds-Storm. Omar Rojas-Padilla and an anonymous reviewer provided helpful comments on an earlier version of the manuscript.

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Accepted by Omar Rojas-Padilla

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