New species of Picea A. Dietrich (Pinaceae) from the middle Eocene of Axel Heiberg Island, Arctic Canada

Abstract

The discovery of several hundred fertile and vegetative remains of three new species of Picea A. Dietrich (P. sverdrupii, P. nansenii, P. palustris) from the middle Eocene (45 Myr) sediments of the Buchanan Lake Formation on eastern Axel Heiberg Island, Canadian High Arctic provides a basis for re-assessment of the fossil record of the genus and evaluation of the morphological variability in this taxon. The identification and classification of extantPicea is based on a whole-tree concept that in turn is based on the importance of one or more of the following features: cross-sectional shape of the leaves; degree of pubescence of the twigs; arrangement of the stomata on the leaves; colour of the leaves and new growth shoots; length and shape of the cones; shape and degree of pubescence of the buds; and cone-scale morphology. However, the degree of intraspecific variability of these characters is poorly understood and has contributed a great deal towards our general inability to interpret reliably the evolutionary history and phylogenetic relationships within the genus. Examination of the bracts of the Axel Heiberg spruces and all extant species of Picea indicates that bract morphology is distinctive for each species and useful for species circumscription. These data allow the genus to be divided into two broad morphological groups that are in general agreement with topologies based on molecular data.