Chromosome Numbers in Veroniceae (Plantaginaceae): Review and Several New Counts¹

Abstract

Chromosomal evolution in Veronica L. and related genera (Wulfenia Jacq., Wulfeniopsis D. Y. Hong, Paederota L., Lagotis Gaertn., Picrorhiza Royle ex Benth., and Veronicastrum Heist. ex Fabr.; Veroniceae, Plantaginaceae; formerly Scrophulariaceae) is presented. To this end, we conducted an extensive literature survey of more than 400 publications covering ca. 300 out of 500 species in the tribe. We also report 44 new chromosome counts. Chromosome numbers of Veronica hispidula Boiss. & Huet. (2n = 18, 36) and V. reuteriana Boiss. (2n = 28, 42) are reported for the first time, and both species exhibit intraspecific ploidy level variation. Other new counts confirm chromosome numbers reported previously. The evolution of chromosome numbers in Veroniceae is discussed in light of recent results from DNA-based phylogenetic analyses. Most of the subgenera of Veronica exhibit only one single basic number, i.e., x = 6, 7, 8, 9, 12, 17, or 20/21. In this genus, the putative ancestral base number of 9 has been reduced several times to 8 and 7, respectively (aneuploidy/dysploidy), often associated with transition to annual life history. In contrast, no unambiguous increase of chromosome base number has been inferred. A table that includes all species of Veroniceae and, if known, their chromosome number and full sectional and subsectional classification in Veronica is provided. For this purpose, three new combinations have been introduced (Veronica sect. Acinifolia (Römpp) Albach, Veronica sect. Glandulosae (Römpp) Albach, and Veronica subsect. Cochlidiosperma (Rchb.) Albach).