INVASIVE POTENTIAL OF THE AQUATIC MACROPHYTE CRYPTOCORYNE BECKETTII ...

114 Pages·2013·2.02 MB·English

INVASIVE POTENTIAL OF THE AQUATIC MACROPHYTE
CRYPTOCORYNE BECKETTII

DISSERTATION

Presented to the Graduate Council of
Texas State University-San Marcos
in Partial Fulfillment
of the Requirements

for the Degree

Doctor of PHILOSOPHY

by

Florence M. Oxley, B.S., M.S.

San Marcos, Texas
August 2013
INVASIVE POTENTIAL OF THE AQUATIC MACROPHYTE
CRYPTOCORYNE BECKETTII

Committee Members Approved:

Paula S. Williamson, Chair

Mara Alexander

Tina M. Cade

Kathryn Kennedy

Thomas R. Simpson

Floyd W. Weckerly

Approved:

J. Michael Willoughby
Dean of the Graduate College
COPYRIGHT

by

Florence M. Oxley

2013
FAIR USE AND AUTHOR’S PERMISSION STATEMENT

Fair Use

This work is protected by the Copyright Laws of the United States (Public Law 94-553),
section 107). Consistent with fair use as defined in the Copyright Laws, brief quotations
from this material are allowed with proper acknowledgment. Use of this material for
financial gain without the author’s express written permission is not allowed.

Duplication Permission

As the copyright holder of this work I, Florence M. Oxley, authorize duplication of this
work, in whole or in part, for educational or scholarly purposes only.
ACKNOWLEDGEMENTS

I thank the members of my committee for their support, guidance, patience and
good humor through a long process. Butch Weckerly for opening the doors to statistical
analysis and giving me an important tool I will use throughout my professional career;
Tina Cade for introducing me to a new way of looking at the world. I look forward to
working with you in the future to learn how people perceive nature and the natural world;
Kathryn Kennedy who was everything a committee member should be and more; Randy
Simpson, who jumped in in the middle and was helpful throughout the process. Paula
Williamson, my chair, who is my teacher, mentor, advocate, and, above all, my friend.
I would also like to thank the staff of the graduate college who took me under
their wings and made each visit a pleasure; my mother, Juliette McDougall, who put her
money where her mouth is and made sure I didn’t have to “sweat the small stuff.” And,
last, but never least, Bill Oxley who believed in me even when I didn’t believe in myself.
This manuscript was submitted on June 16, 2013.

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TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS .................................................................................................v
LIST OF TABLES ............................................................................................................ vii
LIST OF FIGURES ......................................................................................................... viii
ABSTRACT ....................................................................................................................... ix
CHAPTER
I. INTRODUCTION ......................................................................................................1
II. POTENTIAL OF CRYPTOCORYNE BECKETTII TO BECOME A
WIDESPREAD INVASIVE PLANT ................................................................18

III. PUBLIC PERCEPTIONS AND ATTITUDES TOWARDS INVASIVE
SPECIES AND INVASIVE SPECIES MANAGEMENT IN THE SAN
MARCOS RIVER, SAN MARCOS, TEXAS ..................................................43

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LIST OF TABLES
Table Page
2.1 Measurements of vegetative growth (mean ± standard error) in different
temperature treatments ...........................................................................................32

2.2 Measurements of vegetative growth (mean ± standard error) in different
light treatments.......................................................................................................33

2.3 Measurements of vegetative growth (mean ± standard error) in different
rhizome segment size classes .................................................................................34

3.1 Results of a one-way analysis of variance comparison of individual
statements showing significant differences among different ethnic
groups in the study of public perceptions of nonnative invasive species ..............86

3.2 Results of a one-way analysis of variance comparison of individual
statements showing significant differences among different age categories
in the study of public perceptions of nonnative invasive species .........................88

3.3 Results of a one-way analysis of variance comparison of individual
statements showing significant differences among different education
levels in the study of public perceptions of nonnative invasive species ................93

3.4 Results of a one-way analysis of variance comparison of individual
statements showing significant differences among different employment
categories in the study of public perceptions of nonnative invasive species .........97

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LIST OF FIGURES
Figure Page
1.1. Photograph of Cryptocoryne beckettii .......................................................................11
2.1 Experimental growth chamber ....................................................................................35
2.2 Light treatment design viewed from above ................................................................36
2.3 Photograph of Cryptocoryne beckettii plantlet showing shoot system and
adventitious roots ...................................................................................................37

2.4 Mean biomass (g) of plantlets produced by rhizome segments of varying
sizes under different temperature treatments .........................................................38

2.5 Mean shoot system height (cm) of plantlets produced by rhizome segments
of varying sizes under different light intensities ...................................................39

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ABSTRACT

INVASIVE POTENTIAL OF THE AQUATIC MACROPHYTE
CRYPTOCORYNE BECKETTII

by

Florence M. Oxley, B.S., M.S.

Texas State University-San Marcos
August 2013

SUPERVISING PROFESSOR: PAULA S. WILLIAMSON
Invasive species are a major threat to global biodiversity, resulting in a need to
understand characteristics that cause a species to be invasive and increasing pressure to
control or eradicate invasive species in order to mitigate their impacts. Cryptocoryne
beckettii, native to Sri Lanka, has been introduced to the U.S. and is known to occur in
freshwater ecosystems in Florida and Texas. Cryptocoryne beckettii, a relatively new
introduction, is listed as invasive by the USDA. New introductions should be carefully
studied to determine their potential to invade habitats, and, should they prove to be
invasive, determine whether or not the public will support management efforts. My study
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objectives were to: 1) determine ability of C. beckettii to reproduce asexually; 2)
determine environmental factors influencing vegetative growth in C. beckettii; 3)
determine community awareness, perceptions, and attitudes towards invasive species and
their control in the San Marcos River; and, 4) determine effectiveness of dredging to
control C. beckettii in the San Marcos River. I found that C. beckettii is capable of
vegetative reproduction, with 24-34% of rhizome segments producing plantlets over a 12-
week period. While significantly more plantlets were produced at a cooler temperature,
plantlets were also produced at both moderate and warm temperatures demonstrating
tolerance for a range of temperatures. To assess public awareness of invasive species, I
administered a survey instrument and found that the public’s overall awareness of
invasives in the San Marcos River was moderate. There was a high level of support for
control and eradication programs, mainly among men. Proposed management methods
influenced levels of support and projects involving chemical controls or animal death
were least supported.

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