Palm stem anatomy and computer‐aided identification: The Coryphoideae (Arecaceae)

Abstract

Some tribes are easy to identify (Borasseae, Cryosophileae, Phoeniceae, Caryoteae); others are rather heterogeneous and more difficult to define (Chuniophoeniceae, Trachycarpeae). Caryoteae presents some unique states of the Arecoideae.

Stem anatomy in the spiny american palm Bactris (Arecaceae-Bactridinae)

“…We have shown (figure 2) that these internal lacunae originate initially as intercellular spaces that become widened by transverse cell expansion, followed by collapse of vertical plates of cells so that there is a longitudinal space extension. This can appear superficially in TS as if the ground tissue is occupied by very wide cells (figure 4 n) and this has so been described by Thomas (2011) and Thomas and De Franceschi (2013) who did not examine longitudinal sections. The feature may be diagnostic for Bactris, and is most striking in wider stems but does not occur in all species.…”

“…Several typologies for the anatomy of the palm stem exist, as summarized extensively by Thomas (2011) and Thomas and De Franceschi (2013). They emphasize two distinct forms; first those with a relatively uniform distribution of vascular bundles within the ground tissue of the central cylinder (their Type A) and those in which the central bundles of the central cylinder have a much more diffuse distribution of vascular bundles, with a fairly abrupt transition from the dense congested peripheral vascular bundles via a sub-peripheral region to the center (their type B).…”

“…The overall result, which has been extensively documented in a number of palms by Rich (1987), has mechanical consequences because the base of the stem increases in stiffness with age, an obvious adaptive feature in terms of conservation of biomass over the life span of a trunk. The contrast between the two types defined by Thomas (2011Thomas ( , 2013 has some phylogenetic relevance because type A stems seem more prevalent in the early diverging clades of Calamoideae and Coryphoideae, whereas type B is expressed most extensively in the Arecoideae to which the Bactridinae belong (Dransfield et al 2008). Such stem developmental features thus seem to run in parallel with the changes in lamina anatomy extensively documented in Tomlinson et al (2011).…”

“…Consequently our paper provides a sign-post for any student of palm anatomy and particularly for the paleobotanists confronted with systematic identification of fossil palms. The identification problem is not wholly unsurmountable as indicated by Thomas (2011) and Thomas and De Franceschi (2013), who produced results of value at higher taxonomic levels.…”

“…As a consequence of these difficulties the identity of fossil palms in terms of extant species is rendered difficult. An overview of this problem is provided in Thomas (2011) and Thomas and De Franceschi (2013) with some suggestions for a resolution. However, our limited knowledge of the systematic usefulness of anatomical characters in the stem of existing palms hinders any understanding of the changes that may have occurred in stem histology as palms evolved.…”