EVOLUTION OF CARBON ISOTOPIC COMPOSITION OF DEVONIAN AND EARLY CARBONIFEROUS PLANTS

This project focuses on eight representative fossil plant genera of Devonian and Early Carboniferous time period (410- 320 Ma): Archaeopteris, Drepanophycus, Genselia, Leclercquia, Pertica, Psilophyton, Rhacophyton and Tetraxylopteris, which were collected from multiple localities mainly in the Appalachian Basin. Stable carbon isotopic composition (δ¹³C) of fossil plants show considerable variation in δ¹³C values, ranging from -20‰ to -30‰. At some localities, several different genera have been found from the same outcrop, which will allow evaluation of differences, e.g. water-use efficiency (WUE) and genetic variation, among different fossil plant taxa in a single ecosystem. Since environmental parameters would have been similar, differences in the carbon isotopic composition of different taxa are likely to have been caused by genome characteristics of different plant lineages, and so would the values of WUE. Several taxa are long-ranging, which will allow assessment of secular variation in WUE under changeable climate conditions, within individual lineages of early land plants. It is also possible to compare the same plant taxon from different geographic sites from the same geologic time period, which could supply ecological information from different habitats.