JANSEN, STEVEN1*, PIETER BAAS2, and ERIK SMETS1. 1Laboratory of Plant Systematics, Institute of Botany and Microbiology, K.U.Leuven, Kasteelpark Arenberg 31, B-3001 Leuven, Belgium; 2Nationaal Herbarium Nederland, Universiteit Leiden branch, P.O. Box 9514, 2300 RA Leiden, The Netherlands. - Vestured pits: a wood anatomical character with strong phylogenetic signals at high taxonomic levels.
Based on original observations and a critical literature survey,
vestured pits are found in approximately 48 families according to the
APG-system, including 14 families in which vestures were not recorded
previously. Constancy in the presence or absence of vestured pits
throughout the secondary xylem of a given specimen is generally
supported. However, in some taxa that frequently show vestigial
vestures, the occurrence is restricted to particular areas within the
limits of a single wood sample. Phylogenetic hypotheses based on DNA
sequences are frequently supported by the presence or absence of
vestured pits in eudicots. The character is found to be relatively
widespread at the base of the eurosids I (Zygophyllaceae, Fabales,
very few Rosales, Malpighiales), eurosids II (Myrtales, Malvales,
Brassicales), and euasterids I (Gentianales, Lamiales, Solanales), but
the feature probably has been lost or originated independently in
several more derived branches of these clades. Representatives from
euasterids II always show nonvestured pits. Vestured pits characterise
the orders Myrtales and Gentianales sensu APG. Other taxa that
consistently show vestured pits include Malpighiaceae, Polygonaceae,
Brassicaceae, and most Fabaceae. While numerous parallel origins
undoubtedly underlie the occurrence of vestured pits, there are at
least few instances where vestured pits most likely have been lost
during evolution. Our results put major doubt on the earlier suggested
homology of vestures and warts. Possible functions of both structures
remain speculative or unclear.
Key words: eudicots, phylogeny, scanning electron microscopy, vestured pits, warts, wood anatomy