Polyploidy is a key factor in the evolution of higher plants and plays an important role in the variation of plant genomes, leading to speciation in some cases. During polyploidisation, different balancing processes take place at the genomic level that can promote variation in nuclear DNA content. We estimated genome size using flow cytometry in 84 populations of 67 Artemisia species and one population of Crossostephium chinense. A total of 73 sequences of nrDNA ITS and 3'-ETS were newly generated and analysed, together with previously published sequences, to address the evolution of genome size in a phylogenetic framework. Differences in 2C values were detected among some lineages, as well as an increase of genome size heterogeneity in subgenera whose phylogenetic relationships are still unclear. We confirmed that the increase in 2C values in Artemisia polyploids was not proportional to ploidy level, but 1Cx genome size tended to decrease significantly when high ploidy levels were reached. The results lead us to hypothesise that genome size in polyploids tends to a maximum as it follows saturation behaviour, in agreement with the Michaelis-Menten model. We tested different arithmetic functions with our dataset that corroborated a non-linear relationship of genome size increase in polyploids, allowing us to suggest a theoretical upper limit for the DNA content of this genus.

Using optical and scanning electron microscopy, we completed a palynological study of the subtribe Artemisiinae (Asteraceae, Anthemideae), which we started in a previous paper. This subtribe contains different genera with a systematic position that, in many cases, has been controversial. There is a group of genera closely related to Artemisia, and another one more related to Chrysanthemum sensu lato. We confirm the existence of two pollen morphological patterns ‐ concerning exine ornamentation ‐ in the tribe Anthemideae and in the subtribe Artemisiinae as currently considered: one with long spines (Anthemis type) and the other with short spinules (Artemisia type). This feature is a good taxonomic marker, well correlated with other morphological and with molecular characters. This enables a new delimitation of the subtribe Artemisiinae, which is characterized by pollen grain ornamentation constituted by short spinules (microechinate pollen), and should be restricted to Artemisia and the closely related genera that share this trait.

Twenty‐two chromosome counts of 19 taxa (21 populations) in the tribe Anthemideae and one member (one population) of the tribe Inuleae of the family Asteraceae are reported. The Anthemideae studied belong to the subtribes Artemisiinae (14 Artemisia taxa, and one species each of the genera Dendranthema, Filifolium and Neopallasia) and Tanacetinae (one species each of the genera Lepidolopha and Tanacetopsis). From the Inuleae, we studied one Inula species.  Five  counts  are  new  reports  (including  two  at  generic  level),  six  are  not  consistent  with  previous  counts and the remainder are confirmations of very limited (one to four records) previous data. Most of populations of Anthemideae studied have the basic chromosome number x = 9, with ploidy levels ranging from 2x to 10x. Dysploidy is also present, with two x = 8 diploid taxa. The species of Inuleae studied is a diploid with x = 10, also indicating dysploidy, other members of the same genus Inula having basic numbers of x = 9 or 8. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 148, 77–85.

Molecular‐phylogenetic analyses of a large sampling of Artemisia subg. Dracunculus were carried out under Bayesian and maximum parsimony criteria to circumscribe the subgenus and explore the relationships between the species in the core of the subgenus. The Dracunculus complex was resolved into two main clades: one core clade including most of the Eurasian representatives plus a few closely related North American endemic species, and a second, small clade including A. salsoloides and A. tanaitica. Segregation of the latter two species is proposed in order to keep the subgenus monophyletic. Within the core clade, the existence of different lineages such as the A. dracunculus or A. campestris complexes, as well as the relationships of Mausolea, Neopallasia and Turaniphytum, are scrutinized. Discordances between the molecular data and previous morphological taxonomic treatments are noted. The occurrence of polyploidy in the subgenus is explored using previously published and newly generated genome size data.

This work comprises 24 reports of chromosome numbers in 24 Artemisia L. species from Asia. Ten are included in the subgenus Dracunculus Besser and the rest belong to other subgenera. Seven counts are new reports, 14 are consistent with scarce previous ones, and three contribute new ploidy levels. That carried out in A. medioxima reports the highest ploidy level ever counted for the genus (16x). There is only one species with x = 8 as the basic chromosome number. In the remaining x = 9‐based species, ploidy levels range from 2x to 16x, illustrating the great role played by polyploidy in the evolution of the genus. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153, 301–310.