Taxon-specific variability of leaf traits in three long-ranging fossil-species of the Paleogene and Neogene: Responses to climate?

Abstract

Data of climate-sensitive leaf traits, which are usually collected and analyzed for entire fossil leaf assemblages, also include intraspecific responses to environmental conditions. Intraspecific correlations between climate and leaf traits represent plastic responses on the individual level as well as plasticity caused by genetic differences between disjunct populations of a species. Plasticity is taxon-specific, as documented by various studies on extant plants. Data on plasticity in fossil plants are, however, rare. In this study, the plasticity of climate-sensitive leaf traits of three long-ranging species, each covering an extended time interval from the late middle Eocene to the late Oligocene or to even the early Miocene, were tracked by using material from 16 sites located in Austria, Czech Republic and Germany. Selected taxa are Daphnogene cinnamomifolia, Eotrigonobalanus furcinervis and Platanus neptuni. Leaf size-related data (lamina size, length, width) as well as leaf shape-related data (centroid, length-to-width ratio and two parameters for “roundness”) were considered. All three considered fossilspecies show various site-specific and significant differences for leaf size-related traits as well as for leaf shape-related traits. Data from allochthonous marine deposits show the highest plasticity, probably due to the accumulation of heterogeneous plant material from different growing sites. For the Oligocene and Miocene, the results are mostly consistent with palaeo-temperature data. This is particularly the case for “roundness” data, confirming the suitability of this trait as an indicator for climate. The high variability of various traits found for the Eocene is, however, difficult to attribute to temperature alone. Rather, the considerable variability of Eocene trait data may be explained by environmental instability during climate transition, such as changing precipitation patterns. ROTH-NEBELSICK ET AL.: TAXON-SPECIFIC VARIABILITY 2 Anita Roth-Nebelsick. State Museum of Natural History, Rosenstein 1, 70191 Stuttgart, Germany. anita.rothnebelsick@smns-bw.de Michaela Grein. Übersee-Museum Bremen, Bahnhofsplatz 13, 28195 Bremen, Germany. m.grein@uebersee-museum.de Christopher Traiser. Department of Geoscience, University of Tübingen, Schnarrenbergstr. 94-96, 72076 Tübingen, Germany. christopher.traiser@uni-tuebingen.de Lutz Kunzmann. Senckenberg Natural History Collections Dresden, Königsbrücker Landstr. 159, 01109 Dresden, Germany. lutz.kunzmann@senckenberg.de Jiří Kvaček. National Museum Prague, Václavské náměsti 68, 115 79 Prague 1, Czech Republic. jiri.kvacek@nm.cz Janina Wypich. State Museum of Natural History, Rosenstein 1, 70191 Stuttgart, Germany; Janina.wypich@smns-bw.de Johanna Kovar-Eder. State Museum of Natural History, Rosenstein 1, 70191 Stuttgart, Germany. johanna.eder@smns-bw.de