Paper No. 332-6
Presentation Time: 2:45 PM
FUNCTIONAL SPACE OCCUPATION AFTER THE PERMO-TRIASSIC MASS EXTINCTION: A STUDY OF THE EARLY TRIASSIC VIRGIN LIMESTONE MEMBER (MOENKOPI FORMATION)
DINEEN, Ashley A.1, FRAISER, Margaret L.2 and ROOPNARINE, Peter D.1, (1)Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, CA 94118, (2)Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave, Milwaukee, WI 53201, adineen@calacademy.org
The Permo-Triassic mass extinction (PTME), the most devastating loss of life in recorded Earth history, permanently altered the taxonomic and ecologic structure of marine communities. Recovery or restructuring in the aftermath must have consisted of changes to taxonomic diversity and ecosystem function, but less attention has been paid to non-taxonomic measures of community structure and functioning. This is of utmost importance, as the range and number of organismal functions present in a community has been shown to be more important to ecosystem stability and functioning than that of taxonomic diversity, especially during intervals of high biotic and abiotic stress such as that of the Early Triassic. Functional diversity metrics have emerged as useful tools to quantify individual organismal traits independent of taxonomy, allowing us to assess levels of ecosystem functioning. Here we quantify the functional diversity (i.e., richness, evenness, divergence) of the Spathian Virgin Limestone Member (Moenkopi Formation) at Lost Cabin Springs in southern Nevada. We then compare these results to that of the Virgin Limestone from the Beaver Dam Mountains and Hurricane Cliffs localities of Utah in order to determine the influence of paleogeography and environment on restructuring.
Results indicate that taxonomic and functional richness were decoupled; high taxonomic diversity did not equate to comparatively high functional diversity. Both communities also demonstrated low functional evenness, with numerical dominance by one functional group resulting in an uneven packing of functional ecospace. Furthermore, while new Triassic taxa co-occupied the same functional space as holdovers from the Permian, the density of their distributions differed in that holdover individuals are rare where Triassic individuals are common. This shift in functional emphasis suggests that the extreme reorganizational nature of the PTME had significant and potentially permanent effects on the intrinsic structure of ecosystems well into the Early Triassic.
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