Systematic significance of the cupule/nut complex in living and fossil Fagus

Living species of Fagus can be clearly distinguished by using the morpholog y of the cupule/nut complex, although most of the morphological characteris tics display a high degree of parallelism. Therefore, a complete set of inf ormative characters is necessary to accurately identify living species. Clu ster analysis of modern taxa results in two well-separated species groups. However, these groups do not always reflect phylogenetic relationships but include taxa that merely share characteristics of no phylogenetic significa nce. Character evolution in Fagus cupules appears to go from medium-sized c upules with scalelike appendages, short peduncles, and unwinged nuts that a re clearly longer than the cupule valves to either very small or very large cupules with short to very long and slender peduncles, spinelike appendage s, and nuts that are as long as the cupule valves. Investigations of modern cupules demonstrate that several diagnostic characters are easily lost dur ing water transportation. Such cupules show patterns of degradation very si milar to those also found in fossil taxa and on which fossil species have b een based. The three European Tertiary fossil species based on cupule/nut c haracteristics (Fagus deucalionis Unger, Fagus decurrens Reid & Reid, and F agus microcarpa Miki emend. Uemura) are not clearly distinguishable but are connected by morphoclines. Accordingly, we propose to treat them as one fo rm-species F. deucalionis Unger emend. Denk et Meller. Fagus deucalionis al so appears to be conspecific with cupules of the Central Asiatic fossil spe cies Fagus antipofii Heer and very similar to the western North American fo ssil species Fagus pacifica Chaney. All these taxa are "modern" in appearan ce, displaying spinelike cupule appendages and conspicuously winged nuts. T hey resemble the modern East Asiatic Fagus crenata Blume (Japan), Fagus lon gipetiolata Seemen (China), Fagus tientaiensis T. N. Liou (China), and part ly Fagus hayatae Palibin (China mainland, Taiwan), Fagus grandifolia (North America, Mexico), and Fagus sylvatica L. (Europe, southwestern Asia). Prev iously noted specific similarities between European Oligocene cupule/nut ta xa and the modern F. grandifolia Ehrh., and European Pliocene cupule/nut ta xa and the modern Japanese F. crenata, cannot be confirmed.