Aminochronology of Jamaican land snails: a museum-based analysis

Matthew T. McDonald

doi:10.17918/00011189

Land snails of Jamaica represent one of the most diverse terrestrial molluscan faunas in the world, with over 500 endemic species. This dissertation examines the application of amino acid racemization (AAR) geochronology to Jamaican land snail shells from museum collections, aiming to construct high-resolution age models for time-averaged death assemblages preserved in natural habitats. These assemblages, often found in limestone crevices of karst environments, can offer valuable insights into paleoecological events over the past few centuries if they can be chronologically resolved. The first few chapters contextualize the study within historical and methodological frameworks, focusing on the foundational contributions of Glenn A. Goodfriend to amino acid geochemistry in land snails, including advances in AAR kinetics, stable isotope paleoecology, and corrections for radiocarbon reservoir effects. A review of recent global applications of snail AAR follows, highlighting innovations in calibration, protein isolation, and multi-proxy analysis that now enable improved resolution in geochronology. Original research on two endemic Jamaican species, Dentellaria sloaneana and Thelidomus aspera, follows. A museum specimen-derived calibration model was developed using specimens of known ages, which demonstrated a strong correlation between D/L values and time elapsed since collection (death). Controlled heating experiments were used to derive Arrhenius parameters, which were then used to extrapolate potential racemization rates to environmental temperatures. Additionally, the effect of long-term ethanol preservation on AAR was investigated. Shells stored in 80% ethanol exhibited modest but statistically significant increases in D/L values over time compared to their dry-stored counterparts, particularly for aspartic acid and serine. The results enforce AAR as a viable dating tool for recent Jamaican land snails, with implications for Quaternary paleoecology, biodiversity monitoring, and museum science. The study concludes by proposing a forward-looking research agenda to expand taxonomic coverage, apply AAR to a greater timescale, and utilize age models for field-collected death assemblages, thereby potentially establishing Jamaican land snails as a sensitive record of anthropogenic and natural environmental change.

Aminochronology of Jamaican land snails: a museum-based analysis

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Aminochronology of Jamaican land snails: a museum-based analysis

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