Effects of fish on reptile and amphibian community assemblages in wetlands of variable permanence

74 Pages·2014·2.3 MB·English

by  Joshua Holbrook

EFFECTS OF FISH ON REPTILE AND AMPHIBIAN COMMUNITY
ASSEMBLAGES IN WETLANDS OF VARIABLE PERMANENCE
by
Joshua David Holbrook

A Thesis Submitted to the Faculty of
the Charles E. Schmidt College of Science
In Partial Fulfillment of the Requirements for the Degree of
Master of Science

Florida Atlantic University
Boca Raton, FL
August 2014

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Copyright 2014 Joshua David Holbrook

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ACKNOWLEDGEMENTS
Nathan Dorn provided invaluable insight, edits and advice throughout this
research as did committee members Brian Benscoter and Dale Gawlik. Staff at Jonathan
Dickinson State Park provided great amounts of logistical support, especially Rob
Rossmanith and Scott Tedford. The Home Depot in Lake Park, FL donated trapmaking
supplies, and Tom Chesnes and Palm Beach Atlantic University lent ~100 traps.
Numerous people assisted with note taking in the field, including students from Dr.
Dianne Owen’s Ecology classes, Hans van der Heiden and Rich Jones. Dianne Owen also
assisted with GIS logistics. Ashley Romnosky and Amanda Berman were extremely
helpful during fieldwork. The author’s parents, David and Ruth Holbrook provided, as
always, encouragement and support; and finally, the author’s wife Rebekah Holbrook
provided note-taking assistance, helpful remarks on the manuscript, prayers, patience and
sanity.
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ABSTRACT
Author: Joshua David Holbrook
Title: Effects of Fish in Wetlands of Variable Permanence on Reptile and
Amphibian Community Assemblage

Institution: Florida Atlantic University
Thesis Advisor: Dr. Nathan Dorn
Degree: Master of Science
Year: 2014

Many herpetofaunal species are imperiled, and the causes of this are often a
synergy of multiple factors. In wetlands specifically, two of the possible determinants of
species occurrence and faunal community assemblage are fish presence and wetland
permanence, which are not always correlated. Twenty wetlands were sampled in
Jonathan Dickinson State Park, Florida, USA to observe how wetland herpetofaunal
communities vary with fish, wetland permanence and other environmental factors.
Herpetofaunal communities with and without fish were significantly different from one
another and differences between herpetofaunal communities were primarily due to the
contribution of four species of frogs, two generalist ranids and two specialist hylids.
Wetland permanence had no observable effect on community structure. Fishless wetlands
were significantly more species-rich and possessed higher numbers of individuals even
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for species that occurred in both fishless and fish wetlands, regardless of their
permanence. These findings have implications for wetlands restoration and herpetofaunal
conservation.
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EFFECTS OF FISH IN WETLANDS OF VARIABLE PERMANENCE ON REPTILE
AND AMPHIBIAN COMMUNITY ASSEMBLAGE
List of Tables..……………..……………………………………………………………viii
List of Figures…………………………...………………………………………………..ix
Introduction………………………………...……………………………………………...1
Materials and Methods…………………………….………………………………………6
Study Area…………………...……………………………………………………6
Habitat Variables…………….……………………………………………………8
Sampling Protocol…………………………………………………………………9
Statistical Analysis……………………………………………..………………...10
Results……………………………………………………………………...…………….12
Discussion.…………………….…………………………………………….…………...15
Fish or permanence?..............................................................................................15
Effects of fish on aquatic herpetofauna………………………………………….17
Ecological and management ramifications of fish absence……………………...19
Conclusion……………………………………………………………………………….22
Appendices……………………………………………………………………………….32
References………………………………………………………………………………..55

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TABLES
Table 1. Habitat variables for 20 wetlands sampled at Jonathan Dickinson
State Park (JDSP), Martin Co., FL, USA.............................................................22
Table 2. Categorization of wetlands at JDSP by combinations of variables of
fish presence and wetland permanence, with numbers of wetlands
falling into each category.....................................................................................23
Table 3. Species list, total captures, number of wetlands occupied and percent
occurrence in fish-inhabited (n=11) and fishless (n=9) wetlands during
sampling 1 June – 20 November, 2013 at Jonathan Dickinson State
Park, FL, USA......................................................................................................24

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FIGURES
Figure 1. Map of Jonathan Dickinson State Park, Florida, USA, with wetland
sites.....................................................................................................................21
Figure 2. Reptile and amphibian community composition of 20 wetlands in JDSP
by NMDS ordination of Bray-Curtis values.......................................................25
Figure 3. Mean catch per unit effort (± standard error) of the top ten most
abundant reptiles and amphibians for fishless and fish-inhabited
wetlands in JDSP...............................................................................................26
Figure 4. Rarefied Species richness in 20 wetlands at Jonathan Dickinson State
Park, Florida USA..............................................................................................27

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1. Introduction
Reptiles and amphibians offer numerous ecosystem services including biomass
production (Burton and Likens 1975, Madsen and Shine 1996), trophic dynamics (Beard
et al. 2002, Flecker et al. 1999), as well as economic and sustenance benefits to humans
(Norman 1987). However, on a global scale, many herpetofaunal populations are
imperiled and declining (Gibbons et al 2000, Houlahan et al 2000, Sala et al 2001) these
declines are often attributed to a combination of largely-anthropogenic factors, including
habitat modification (Gardner et al 2007, Sala et al. 2001), introduction and proliferation
of non-native invasive species (Phillips et al 2003, Kats and Ferrer 2003, Ryan et al.
2014) as well as disease, which has been especially adverse to amphibian populations in
recent years (Daszak et al 1999, Sleeman 2013).
Aquatic herpetofaunal populations may face similar threats as reptiles and
amphibians as a whole, but may also succumb to threats especially common to freshwater
systems. Threats to aquatic habitats are of particular concern to amphibians, the majority
of which must utilize water bodies as breeding habitat. These threats may include:
eutrophication, which may remove natural ecological mechanisms for disease control
(Johnson and Chase 2004), wetland loss via development or shortened hydroperiods
(Semlitsch 2000, Ryan et al. 2014) or fish introductions, that is, large generalist predators
which are otherwise poor overland dispersers (Bradford 1989, Ryan et al. 2014).
Wetland permanence can impose significant restrictions on species presence and

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