Document Type

Thesis

Abstract

It has been debated for many years whether or not Florida’s Plio-Pleistocene Beds record a late Pliocene extinction event or a turnover of marine communities. However, no studies have attempted to quantify the effects of differences in sampling intensity and changes in evenness and abundance on observed richness patterns within the Pinecrest Beds or Bermont Formation. Evenness is a metric of diversity that measures the relative abundance of species within a given community. In a less even community, lower sampling intensity will produce an artificially low richness level. My goal here is a preliminary study of diversity, including richness and evenness, of pre-and postextinction phases of Florida gastropod communities, within a sample-standardized framework. I collected 5-gallon bulk samples from four beds within the lower Pinecrest Beds (middle Pliocene) at SMR Aggregates Quarry in Sarasota, Florida. I analyzed each bed separately to examine differences in diversity within the lower Pinecrest that might reflect ecological or taphonomic processes. The samples were sieved at a mesh size of 5mm. All specimens were sorted, and gastropods were identified to genus level whenever possible, using literature sources. Abundance data were collected by counting gastropod apices. The total number of genera identified was 85 gastropods (>1794 individuals). I randomly re-sampled each bulk sample using a sample size of 131 individuals (the smallest sample size). Bulk samples of three beds from the Bermont Formation (Early Pleistocene) were also analyzed for comparative purposes. I then applied the following evenness indices: PIE, E(1/D), E(1-D), and E-In(D), in addition to the Shannon-Weiner and the Simpson dominance indices.

Date Awarded

2007

Department

Geology

Advisor 1

Rowan Lockwood

Advisor 2

Gregory Herbert

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