Competition and Adaptations in Upper-Ordivician Brchiopods (Draft 2)
This article submitted by Morio, Steve; Harden, Tim; Gianfagna, Karen. [e-mail: Moriose@miavx1.muohio.edu ] on 10/13/97.
This study of Upper-Ordovician brachiopods as observed in the Richmodian stage of the Cincinnatian series in southeast Indiana is expected to uncover patterns of adaptations within particular species of brachiopods. Through observing these patterns of adaptation within the target species and comparing the adaptations of the species to one another evidence as to the nature of inter- and intra- species competition should be evident. In addition, the abundance of the brachiopod phylum in the Upper-Ordovician suggests great success and even dominance for the brachiopods in the environment of the Upper-Ordovician. Therefore, the adaptations seen in the brachiopods could be used as proxy climate data for the corresponding time frame.
The sampling will be conducted in the southeast of Indiana in the vicinity of Lake Brookville. The sample area lies entirerly within the Cincinnatian series and the Richmodian stage. The formations smapled will be the Arnheim, Waynesville, Liberty, and Whitewater formations. Fossil availability may further limit the study to the Waynesville and Liberty formations. Most, if not all of the sampling will be conducted along the roadcut on Indiana State Highway 1. Some sampling may be conducted at the Brookville Lake Causeway roadcut, especially for Dalmenella meeki in the Waynesville formation.
The method of sampling will be fairly simple and possibly not too terribly time consuming. The primary tools involved will be a tape measure, rock hammer, hand lens, rope, and a caliper. Using the rope and the tape measure we will mark off a one meter wide column in each formation. Then, treating the base of the Arnheim formation (or the Liberty formation in the event that the study is further limited) as ground zero we will measure of one meter vertically within the marked column and collect all the brachiopods contained within this one square meter area. This process will be repeated for the entire column, thereby sampling the entire Richmodian stage. If one such column sampling doesn’t prove to be sufficient, the entire process will be repeated. Once we have gathered all of our specimens (making sure to keep track of where each sample came from of course) we will take the calipers to the brachiopods gathering information about their size and the changes in size throughout time and space. The measurements we will be concerned with will be width and length, although some species may even offer significant thickness measurements. Once these measurements have been taken the data set can then be entered into a spreadsheet and manipulated and evaluated to reveal the desired patterns. Specific patterns of interest will be the relative abundance of the different target species and how this relationship changes over time. These changes will be indicative primarily of inter-species competition. Also of interest will be the changes in size within the target species which will be indicative of intra-species adaptation to both competition and climatic change.
The target species referred to above will be determined by the samples collected. This study will be concerned only with the most abundant brachiopod species. Therefore, the final data set will be comprised of a limited number of brachiopod species which can be tentatively identified based on preliminary sampling and research. All of the species involved in this study will be of the class Articulata. The dominant orders will be Orthida, Strophomenida, and perhaps Rhynchonellida. The majority of specimens will most likely be of the order Orthida incuding such species as Plaesiomys subquadrata, Hebertella occidentalis, Platystrophia clarksvillensis and Dalmenella meeki. From the order Strophomenida will come the species of Strophomena planumbona and Rafinesquina ponderosa. Finally, from the order Rhynchonellida, the species Lepidocyclus perlamellosus may prove to be significant to this study.
As is mentioned above, the conclusions of this study will be concerned with the changes in relative abundance and size of the target species listed above. Changes in the relative abundance of the different species over time and space will be considered to be indicative of the competition within species and between species. Changes in size within species will be indicative of adaptations within the given species resulting form both inter- and intra-species competition as well as climatic changes. In short, the adaptations evidenced by the samples will provide insight into the ecology of the Upper-Ordovician in the Cincinnatian series and the climatic changes that occurred over time.
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