Glacial or interglacial: Artemisia, a plant indicator with dual responses

Abstract

Vegetation is sensitive to climate changes; fossil pollen records are thus used as evidence for floral pattern changes linked with climatic shifts. Such an approach applied to West European/Mediterranean Pliocene–Pleistocene series has generated a paradigm in which abundant pollen of Artemisia (a principal constituent of steppe landscapes) is correlated with glacial episodes. Our study of an uppermost Pliocene series on Zakynthos island (Ionian sea, Eastern Mediterranean) reveals a behaviour opposite to the model mentioned above, in which Artemisia peaks are coeval with interglacial phases. This unusual occurrence of Artemisia with respect to glacial/interglacial cycles led us to consider the differences in species behaviour within the recent Artemisia genus (fossil Artemisia pollen has generally not been identified to the species level up to now). Our review of ecological conditions of some Maghrebian Artemisia species shows extremely large ranges of temperature and humidity. Palaeoclimatic interpretations based on Artemisia s.l. abundances thus require vigilance. The new evidence of Artemisia pollen peak in the Zakynthos Pliocene series has therefore major implications for our understanding of the complexity of palaeoclimatic patterns.