ABSTRACT A FLORISTIC STUDY OF A FORMER LAND BRIDGE IN THE BAHAMA ARCHIPELAGO by Mark Leo Daniels A floristic study of plant communities was conducted on the islands of Eleuthera, Little San Salvador, and Cat Island. The objectives of this analysis were to explore the species composition and distribution of dry forest communities among the three study sites, and to propose new classification types to facilitate plant conservation in The Bahamas, as outlined by the International Classification of Ecological Communities for Caribbean vegetation types. Unconstrained ordination, cluster analysis and indicator species analysis indicated two dominant forest types across the three study sites: the Coccothrinax argentata-Reynosia septentironalis and Coccoloba diversifolia-Bursera simaruba Alliances. Nested within these forest types were 8 species associations: Coccothrinax argentata– Reynosia septentrionalis – Pithecellobium keyense association; Zanthoxylum flavum – Jacquinia keyensis – Casasia clusiifolia association; Acacia choriophylla - Pithcellobium keyense - Guapira discolor association; Coccoloba diversifolia- Sideroxylon americanum-Pseudophoenix sargentii association; Maytenus buxifolia- Sideroxylon salicifolium association; Exothea paniculata-Tabebuia bahamensis- Metopium toxiferum association; Guaiacum sanctum association; Eugenia foetida- Exostema caribeaum-Bourreria succulenta association. A FLORISTIC STUDY OF A FORMER LAND BRIDGE IN THE BAHAMA ARCHIPELAGO A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science by Mark Leo Daniels Miami University Oxford, Ohio 2016 Advisor: Dr. Michael A. Vincent Reader: Dr. James Hickey Reader: Dr. Richard C. Moore ©2016 Mark Leo Daniels This Thesis titled A FLORISTIC STUDY OF A FORMER LAND BRIDGE IN THE BAHAMA ARCHIPELAGO by Mark Leo Daniels has been approved for publication by The College of Arts and Science and Department of Biology ____________________________________________________ Michael A. Vincent ______________________________________________________ R. James Hickey _______________________________________________________ Richard C. Moore Table of Contents Page List of Tables……………………………………………………………………………..iv List of Figures……………………………………………………………………………..v Acknowledgements…………………………………………………………………….…vi Introduction………………………………………………………………………………..1 Methods……………………………………………………………………………………7 Study Sites………………………………………………………………………...7 Data Collection…………………………………………………………………....9 Data Analysis…………………………………………………………………….12 Results……………………………………………………………………………………13 Island Summary Statistics………………………….…………………………….13 Ordination, Clustering and Indicator Species Analysis – Tree Layer………...…17 Ordination, Clustering and Indicator Species Analysis – Shrub Layer………….26 Discussion………………………………………………………………………………..27 Clustering Patterns……………………………………………………………….27 Taxon Distribution……………………………………………………………….29 Rare and Endemic Species……………………………………………………….32 Classification of Caribbean Plant Communities…………………………………33 Community Classifications and Island Vegetation Maps.……………………….36 Implications for Plant Conservation in the Bahama Archipelago….………………...….41 Literature Cited…………………………………………………………………………..44 iii List of Tables Table Page 1. Summary statistics of plot data……………………………………………………...14 2. Pearson correlation coefficient values………………………………………………25 3.Taxa distribution across study sties………………………………………………….30 iv List of Figures Figure Page 1. Map of The Bahama Archipelago…………………………………………………...….2 2. Map of study sites on Eleuthera, Little San Salvador and Cat Island…………………..7 3. Map of plot locations on Eleuthera……………………………………………………10 4. Map of plot locations on Little San Salvador…………………………………………11 5. Map of plot locations on Cat Island…………………………………………………...11 6. Schematic diagram of plot layout……………………………………………………..12 7. Boxplot diagrams of density, basal area and species richness by study site…………..16 8. Unconstrained ordination diagram with NMDS of tree plots………………………....17 9. Constrained ordination diagram with CCA of tree plots…………………………...…18 10. Ward’s cluster dendrogram of tree layer Groups 1 and 2…………………..………..19 11. Boxplot diagram of elevation and distance from coastline for Groups 1 and 2……..20 12. Boxplot diagram of basal area and species richness for Groups 1 and 2…………….20 13. Ward’s cluster dendrogram of tree layer subgroups 1-7……….…………...………..21 14. Unconstrained ordination diagram with NMDS of tree subgroups 1-7………...…....21 15. Scatterplot diagrams of dependent versus independent variables……………………23 16. Unconstrained ordination diagram with NMDS of shrub groups 1 and 2 with environmental vectors………………………………………………………………..23 17. Unconstrained ordination diagram with NMDS of tree plots by island………...…...24 18. Unconstrained ordination diagram with NMDS of shrub plots by island…………...25 19. Species accumulation curves for plots at study sites………………………………...26 20. Undescribed species of Cynanchum sp. from Little San Salvador…………………..31 21. Bahamian endemic species Thouinia discolor and Waltheria bahamensis………….33 22. Vegetation map of plant communities at Eleuthera study site……….………………37 23. Vegetation map of plant communities at Little San Salvador study site………….....39 24. Vegetation map of plant communities at Cat Island study site………………………41 v Acknowledgements I would like to thank my advisor Dr. Michael A. Vincent for his guidance and support throughout this process. My co-advisors Dr. R. James Hickey and Dr. Richard C. Moore were instrumental in providing constructive critique and instilling confidence in my abilities. Thanks to Dr. Janet Franklin and Dr. Julie Ripplinger for graciously providing their expertise in statistical analyses of dry forest communities in the Caribbean. Your assistance was central to the successful completion of this project and I am forever grateful. I want to acknowledge the management and staff of The Bahamas National Trust and The Leon Levy Native Plant Preserve. Dr. Ethan Freid, Eric Carey and Falon Cartwright were essential to the execution of my fieldwork, thank you for providing resources and logistical support for me while in The Bahamas. Thank you to the management and staff of Half Moon Cay for facilitating access to Little San Salvador and accommodating me during my field work on island. Sincere gratitude goes to Shelby White and The Leon Levy Foundation for their moral and financial support in my pursuit of an advanced degree. Thank for you inspiring me to take on such a great challenge. vi INTRODUCTION Island floras have the reputation as being living laboratories engaged in natural experiments of evolution. The West Indies or Caribbean Archipelago divides the Atlantic Ocean from The Caribbean Sea, and is made up of three smaller island chains: the Bahama Archipelago, the Greater Antilles, and the Lesser Antilles. The flora of the region, comprising 231 families, 1447 indigenous genera and ca. 10, 948 species of plants (Acevedo-Rodriguez & Strong 2011), is strongly influenced by continental Central and South America. Endemism is relatively high; 13.2% of the genera and 72% of species are endemic to the West Indies (Acevedo-Rodriguez & Strong 2011). The historical biogeography of this region is complex due to the differing ages of the islands, tectonic movements, and sea level changes that have occurred throughout the millennia. The islands of the Caribbean vary widely in degree of isolation, island size and shape, landscape, geology, climate, and moisture patterns, resulting in a diversity of habitats and microclimates that support endemic species. The Caribbean is designated as one of the 35 global hotspots for conservation, characterized by high levels of endemics and having lost more than 70% of their natural habitats (Mittermeier et al. 2011). The Caribbean Island Hotspot contributes high biodiversity from a relatively small land area, earning its global conservation priority status. The islands of the Bahama Archipelago, The Bahamas, are emergent peaks of the limestone-capped Bahamas Platform, spanning 1,400 km between the southeast coast of Florida and the northeast coast of Cuba. Territorially, the archipelago consists of the island nations of The Bahamas and The Turks and Caicos Islands (Figure 1). The island land mass of the Bahama Archipelago covers 13,880 km2, and is made up of approximately 35 islands, hundreds of cays and thousands of exposed, vegetated rocks. The flora of The Bahamas comprises 136 families, 654 genera and 1351 species of vascular plants (Acevedo- Rodriguez and Strong 2011). The most speciose families are Poaceae (144) and Fabaceae (128), and the most speciose genus is Euphorbia (30) (Acevedo-Rodriguez and Strong 2011). Endemic plant species of The Bahamas had previously been numbered at 114 (Correll and Correll 1982). However, a recent review of endemism in the flora has decreased the number of endemics to 89 species within 54 genera and 29 families (Freid et al. 2014). The endemics make up approximately 6% of the total flora, and the most 1 endemic rich families represented in the archipelago are the Rubiaceae (14), Euphorbiaceae (11) and Asteraceae (9). Biogeographical analyses of endemic species distribution throughout the Bahama archipelago has resolved a clustering of endemic species into northern (35 species), central (38 species) and southern (59 species) island groupings. Fifty endemic species are restricted to one (31) or two (19) island groupings, and are a high priority for native plant conservation efforts