Why did a prehistoric community of snails in Hawaii go extinct?

Methods

Summary

Our study site, Ka'ena Point State Park, contains the shells of three Hawaiian land snail families: one species from the family Endodontidae, one species from the family Helicinidae, and multiple species from the family Amastridae. We have collected shells from each of these families, and are in the process of taxonomically identifying these shells to the species level.

We plan to isotopically analyze 20 shells total: four shells from Amastra sp., four shells from Endodonta sp., four shells from Pleuropoma laciniosa (our Helicinid), and four shells from Leptachatina spp.

Our shells will be cleaned and prepared for isotopic analysis in our lab at Hawaii Pacific University. Full protocols for preparing the shells for shipping can be found under our Protocols listing. After preparation, shells will be shipped to outside facilities for isotope analysis.

Graphical trends in the data will be analyzed, and corresponding trends in vegetation, temperature, and precipitation will be estimated. 

With all this data, we will be able to determine how the climate at Ka'ena Point State Park changed over the studied time period.

Pre Analysis Plan

Our shells will undergo isotopic analysis at outside facilities. Once we receive the data back from these facilities, we will analyze the data and their corresponding environmental trends. 

Graphical analysis will be performed to better visualize the data, and their corresponding environmental parameters. 

Based on our preliminary data, we anticipate that the data will show a rise in both d13C values and d18O values as we move towards the modern day. A rise in d13C values would indicate that the environment was becoming hotter and drier over time, leading to the loss of vegetation adapted to cooler conditions and a rise in vegetation adapted to hotter conditions. Similar to d13C, a rise in d18O values could indicate that rainfall was becoming more scarce at the site; it could also indicate that the ambient temperature at the site was becoming hotter.