Stephen F. Austin State University SFA ScholarWorks Electronic Theses and Dissertations 8-2018 Delineating Metrics of Diversity for a Snake Community in a Rare Ecosystem Zachary John Marcou [email protected] Follow this and additional works at: https://scholarworks.sfasu.edu/etds Part of the Other Ecology and Evolutionary Biology Commons Tell us how this article helped you. Repository Citation Marcou, Zachary John, "Delineating Metrics of Diversity for a Snake Community in a Rare Ecosystem" (2018). Electronic Theses and Dissertations. 200. https://scholarworks.sfasu.edu/etds/200 This Thesis is brought to you for free and open access by SFA ScholarWorks. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of SFA ScholarWorks. For more information, please contact [email protected]. Delineating Metrics of Diversity for a Snake Community in a Rare Ecosystem Creative Commons License This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License. This thesis is available at SFA ScholarWorks: https://scholarworks.sfasu.edu/etds/200 DELINEATING METRICS OF DIVERSITY FOR A SNAKE COMMUNITY IN A RARE ECOSYSTEM By ZACHARY JOHN MARCOU, Bachelor of Science Presented to the Faculty of the Graduate School of Stephen F. Austin State University In Partial Fulfillment Of the Requirements For the Degree of Master of Science STEPHEN F. AUSTIN STATE UNIVERSITY August, 2018 DELINEATING METRICS OF DIVERSITY FOR A SNAKE COMMUNITY IN A RARE ECOSYSTEM By ZACHARY JOHN MARCOU, Bachelor of Science APPROVED: ____________________________________________ Stephen J. Mullin, Ph.D., Thesis Director ____________________________________________ Matthew A. Kwiatkowski, Ph.D., Committee Member ____________________________________________ D. Brent Burt, Ph.D., Committee Member ____________________________________________ Daniel Saenz, Ph.D., Committee Member ____________________________________________ Josephine Taylor, Ph.D., Committee Member ____________________________________ Pauline M. Sampson, Ph.D. Dean of Research and Graduate Studies ABSTRACT Snakes are among the least understood vertebrate groups despite their considerable diversity. A diverse community of snakes in an ecosystem can indicate a complex habitat structure that is capable of supporting a robust assemblage of other biota. I used remote photography arrays (RPA) to quantify metrics of diversity for the snake community occurring in a ~7,000–ha tract of contiguous Longleaf Pine (Pinus palustris) Savanna within the Angelina National Forest (ANF; Angelina and Jasper Cos., TX), over the course of two consecutive snake activity seasons. I quantified the snake species richness, Shannon diversity, and Shannon equitability for the snake community in ANF. I performed several statistical analyses to identify the factors (both habitat and temporal variables) that most influenced the assemblage of snake species detected in ANF. In total, RPA detected 1,094 snakes representing 19 species and four families. An additional five species were documented during field survey efforts. Habitat parameters that typically correlate well with metrics of snake diversity were weak predictors at my study site, and temporal variables that might be reliable for predicting snake activity patterns were similarly poor. The ecological roles of individual species of snakes and the structuring of the snake community in ANF remain unclear. Nevertheless, the 24 species of snakes that I detected at ANF, several of which were poorly documented during previous sampling iv efforts at the same site, represent a diverse community within a relatively homogeneous habitat. v ACKNOWLEDGMENTS There are several individuals who played integral roles in the undertaking and completion of this project. It has been an honor working with you. I would like to thank all the people from Stephen F. Austin State University, the USDA Forest Service Southern Research Station, and the USDA Forest Service Zavalla Ranger Station for their pedagogical, financial, and logistical support throughout this project. Most importantly, I would like to thank my family. To my parents, Ken and Mona, for their steadfast support of my endeavors—I am eternally grateful for everything you have done for me throughout my life, and especially after I left Massachusetts. To my eldest brother, Jordan, for generously offering your financial support in my time need. To “the middle brother”, Kyle, for motivating me to work hard with your unconventional practices. Last of all, to my cats, Bynx and Bynx Jr., thank you for teaching me patience and compassion in all aspects of my life. vi TABLE OF CONTENTS Abstract iv Acknowledgments vi List of Abbreviations viii List of Figures x List of Tables xiii Introduction 1 Methods 12 Results 27 Discussion 60 References 75 Appendices 101 Vita 109 vii LIST OF ABBREVIATIONS Abbreviation Definition Information Formula ANF Angelina National Forest study site n/a RPA Remote Photography Array(s) sampling apparatuses; sampling localities n/a S Species Richness metric of species diversity; number of species raw count present H Shannon Diversity index of species diversity −Σ(Pi(lnPi)) Hmax Maximum Diversity index of species diversity ln(S) EH Shannon Equitability index of species diversity H/Hmax J Jaccard Similarity coefficient of the percent similarity of pairwise (|RPAx∩RPAy|÷|RPAx∪RPAy|)×(100) comparisons of Shannon diversity: see methods BA; ba basal area estimate of area occupied by tree stems at breast m2/ha height % soil exposed soil percent of ground covered by bare soil n/a soil (%) % herb herbaceous plants percent of ground covered by herbaceous plants n/a herb (%) % debris woody debris percent of ground covered by fine, or coarse woody n/a debris (%) debris % grass grasses & forbs percent of ground covered by grasses and/or forbs n/a grass (%) % deciduous deciduous plants percent of ground covered by small, deciduous plants n/a deciduous (%) viii % litter leaf litter percent of ground covered by leaf litter n/a litter (%) % closure canopy closure percent of sky obscured by tree canopy n/a closure (%) foliage understory foliage density modified index of understory foliage density ((ln2/D)) × (0.317397)) foliage (KRPA) time (h) time of day 24–hour clock n/a temperature dry bulb ambient temperature degrees Celsius n/a (°C) Season sampling season periods during which data was being collected n/a year ix LIST OF FIGURES 1. Schematic view of a remote photography array deployed in the Angelina National Forest (Angelina and Jasper counties, Texas) from February 2016–October 2017. Wildlife game cameras (black box with arrow) photographed the 1–m2 area represented by the gray square every 30 sec, capturing images of snakes that were guided to that point by navigating along the fences (broad shaded arrows). 24 2. Loading plot from a principal components analysis of 10 habitat variables measured at 20 remote photography arrays (RPA) in May–June 2016 in the Angelina National Forest (ANF; Angelina and Jasper counties, Texas). Principal component one (PC1) expresses 28.5% of the variation, and PC2 expresses 19.6% of the variation among the habitat structure at each locality. The habitat variables (hollow diamonds) are plotted as vectors about their association with each PC, and the degree of association (vector length). 39 3. Score plot from a principal components analysis of 10 habitat variables measured at 20 remote photography arrays (RPA) in May–June 2016 in the Angelina National Forest (ANF; Angelina and Jasper counties, Texas). Principal component one PC1 expresses 28.5% of the variation, and PC2 expresses 19.6% of the variation among the habitat structure at each locality. Plotted are all 20 RPA (numerically labeled diamonds) in ANF plotted against two PCs for habitat parameters. See Appendices I and II for a geographic representation and coordinates of the location of each RPA. 40 4. Fitted bivariate linear regressions (solid lines) displaying snake species richness (S) as a function of four separate habitat parameters (x-axes). Clockwise from upper left: principal components one and two (each derived from 10 habitat parameters measured in May–June 2016; PC1, PC2), the top predictor in 2016 (debris [%]), and the top predictor in both 2016 and 2017 (basal area [m2/ha]) among 20 remote photography arrays (numerically labelled diamonds) in the Angelina National Forest (Angelina and Jasper counties, Texas) from February 2016–December 2016 (y-axes = S 2016), or from February 2016–October 2017 (y-axis = S). Dashed lines represent 95% confidence of fit. 41 5. Fitted bivariate linear regressions (solid lines) displaying snake species diversity (H) as a function of four separate habitat parameters (x-axes). Clockwise from upper x left: principal components one and two (each derived from 10 habitat parameters measured in May–June 2016; PC1, PC2), the top predictor in 2016 (debris [%]), and the top predictor in both 2016 and 2017 (basal area [m2/ha]) among 20 remote photography arrays (numerically labelled diamonds) in the Angelina National Forest (Angelina and Jasper counties, Texas) from February 2016–December 2016 (y-axes = H 2016), or from February 2016–October 2017 (y-axis = H). Dashed lines represent 95% confidence of fit. 42 6. Fitted bivariate linear regressions (solid lines) displaying snake species equitability (EH) as a function of four separate habitat parameters (x-axes). Clockwise from upper left: principal components one and two (each derived