The Biogeography of the Caribbean Land Snail Family Annulariidae
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The Biogeography of the Caribbean Land Snail Family Annulariidae Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Nicholas David Skomrock, B.S. Graduate Program in Evolution, Ecology and Organismal Biology The Ohio State University 2014 Thesis Committee: Meg Daly, Advisor John Freudenstein G. Thomas Watters Copyright by Nicholas David Skomrock 2014 Abstract The complex nature of historical Caribbean geology confounds the understanding of biogeographic information and the reconstruction of historical biogeographic patterns. Explanations of distributions of terrestrial organisms have included over-water disperal, land dispersal and vicariance, with two main explanations being the vicariance model of Rosen (1975) and the GAARlandia hypothesis of Iturralde-Vinent and MacPhee (1999). The land snail family Annulariidae, endemic to the Caribbean, has shown similar patterns to other organisms in the region and is used to help evaluate the relative role of over water dispersal, land dispersal and vicariance. A molecular phylogeny using regions of the nuclear ribosomal 28S, mitochondrial ribosomal 16S, and the mitochondrial protein coding gene COI was reconstructed and used to assess patterns of biogeography. Ancestral ranges were reconstructed using the program RASP with the BBM and S-diva algorithms. These analyses suggest a proto-Antillean origin of the fauna with subsequent over-water dispersals, relying heavily on land or over-water dispersals as a mechanism. Little evidence was found in support of the GAARlandia hypothesis, yet it cannot be completely removed as a potential explanation. Herein, we describe the historical biogeographic patterns of the present day Annulariidae. ii Acknowledgments I would like to thank the following for help providing specimens: Paulo Albano, Kurt Auffenberg, Kevin Cummings, Glenn Duffy, Zoltan Fehér, Alejandro Fernández Velázquez, Raúl Fernández-Garcés, Steffen Frank, Alan Gettleman, Rich Goldberg, Jozef Grego, Adrienne Jochum, Homer Rhode, Emilio Rolán-Alvarez, John Slapcinsky, Jozef Šteffek, Fred Thompson, and G. Thomas Watters. I would also like to thank Meg Daly, John Freudenstein, Kelsey Fultz, Paul Larson, Jason Macrander, Abby Reft and Brandon Sinn for assistance in the lab. iii Vita June 2006 ................................................................. Harvey High School June 2010 ................................................................. B.S. Evolution and Ecology, The Ohio State University 2012 to 2013........................................................... Metro Fellow, The Ohio State University 2011 to present .................................................... Graduate Teaching Associate, Department of Evolution, Ecology and Organismal Biology, The Ohio State University Fields of Study Major Fields: Evolution, Ecology and Organismal Biology Statistics iv Table of Contents Abstract............................................................................................................................... ii Acknowledgments..............................................................................................................iii Vita..................................................................................................................................... iv Table of Contents................................................................................................................ v List of Figures................................................................................................................... vii List of Tables ...................................................................................................................viii Introduction......................................................................................................................... 1 Materials and Methods........................................................................................................ 5 Taxon and gene sampling ............................................................................................... 5 Phylogenetic analyses ..................................................................................................... 7 Ancestral Range Reconstruction..................................................................................... 8 Results............................................................................................................................... 10 Taxon and gene sampling ............................................................................................. 10 Phylogenetic analyses ................................................................................................... 15 Ancestral Area Reconstruction ..................................................................................... 20 v Discussion......................................................................................................................... 22 Origins........................................................................................................................... 22 Biogeographic Patterns ................................................................................................. 23 Temporal relationships.................................................................................................. 25 Evidence for dispersal................................................................................................... 26 Challenges and future directions................................................................................... 27 Conclusion .................................................................................................................... 28 References......................................................................................................................... 29 vi List of Figures Figure 1 Species richness and sampling coverage.............................................................. 6 Figure 2 Maximum likelihood reconstruction of the full data set .................................... 17 Figure 3 BBM Analysis on subset data set ....................................................................... 19 Figure 4 Ancestral range reconstruction using S-Diva..................................................... 21 vii List of Tables Table 1 List of taxa represented in this study. ................................................................................ 10 viii Introduction The Caribbean is a geologically complex region whose incompletely-known history confounds the interpretation of biogeographic and distributional data for the species found there (Hedges 2001, Crews and Gillespie 2010). The distributions of terrestrial organisms within this region have been explained with reference to three primary models: overwater dispersal, land dispersal and vicariance. These have been inferred to reflect possible geologic patterns but have long been debated (Hedges 2001). Historically, biogeographers described patterns of island biogeography as the result of overwater dispersal from one landmass to the other, which was supported by the subsequent decrease in diversity from island to island. Starting at the mainland, organisms transferred to the closest islands and “hopped” across to islands further away through mechanisms of wind or water. Several current studies invoke this as a primary or secondary mode to explain distributions across different taxa (e.g. Hedges 2006, Michelangeli et al. 2008). This concept was the primary explanation in the Caribbean until the idea of vicariance was applied to this region by Rosen (1975). The vicariance model of Rosen (1975) posits that there were islands that linked Central and South America, called the proto-Antilles, through which organisms were continuously distributed. The proto-Antilles separated via the subduction of the Caribbean Plate between the North and South American plates, fanning out into the 1 present-day Antilles and leading to vicariant speciation in the lineages endemic to the islands. This model predicts the origins of the terrestrial organisms in the Greater and Lesser Antilles to be Central America with radiations to the proto-Antilles, which later diverged concordantly with the separation of land masses. An alternative terrestrial route for dispersal was proposed as the GAARlandia hypothesis by Iturralde-Vinent and MacPhee (1999). The GAARlandia hypothesis proposes a recent land bridge throughout the Caribbean that facilitated the movement of land organisms from South America through the Lesser Antilles via the Aves Ridge and into the Greater Antilles with subsequent vicariance (Iturralde-Vinent and MacPhee 1999). This hypothesis suggests Caribbean fauna originated in South America, subsequently invading the Greater Antilles through the landbridge composed of the Aves Ridge. Both the vicariance and GAARlandia models hypothesize landmasses whose presence or availability for colonization have not been confirmed from geological evidence (Hedges 2001). The geologic models describing the origin of the Carribean are not always consistent, but the model with what appears to have the most support is that of Pindell and Barrett (1990) (reviewed in Graham 2003). This model describes the emergence of the Antilles as already formed submerged islands that were uplifted in a sequential pattern starting in Cuba and moving eastward across the Greater Antilles and through the Windward Islands. This suggests