Systematic Implications of Chloroplast Dna Variation in the Subtribe Microseridinae (Asteraceae: Lactuceae)

Abstract

Phylogenetic relationships among six of the seven currently recognized genera of the subtribe Microseridinae were examined using comparative restriction site mapping of the chloroplast genome. Complete cleavage maps of 17 enzymes were constructed for 35 of the 46 species in the subtribe and six representative outgroup species from four other subtribes of the Lactuceae. A total of 373 restriction site mutations was detected, 180 of which were phylogenetically informative. The chloroplast DNA mutations were used to generate phylogenetic trees using Dollo, Wagner, and weighted parsimony, and the resulting monophyletic groups were evaluated by the bootstrap method. The results indicate that the Microseridinae is paraphyletic because Stephanomeria is nested within the six core genera of the subtribe. Five of the genera of the Microseridinae are monophyletic, whereas Microseris is paraphyletic because one of its species, M. lindleyi, is more closely related to Agoseris and Nothocalais. The distant relationship of M. lindleyi to the rest of the species of Microseris is enigmatic, especially in view of its known involvement in the origin of two allotetraploid species, M. decipiens and M. heterocarpa. The taxonomic implications of these results lead to a revised classification of Microseris in which the genus Uropappus is revived to accommodate M. lindleyi, and a new genus, Stebbinsoseris, is described to include the allotetraploids. The cpDNA phylogeny is used to evaluate the patterns of character evolution within the Microseridinae, as well as to test previous hypotheses that differences in generation time result in unequal rates of chloroplast DNA evolution.

Molecular evidence for an extinct parent of the tetraploid species Microseris acuminata and M. campestris (Asteraceae, Lactuceae)

“…On the basis of this study and previous studies (Chambers 1955;Wallace & Jansen 1990;Jansen et al 1991;Van Houten et al 1993;Wallace & Jansen 1995;Roelofs & Bachmann 1997) we now propose a nearly completely resolved phylogenetic relationship among all annual Microseris species, including tetraploids derived through reticulation (Fig. 5).…”

“…Wendel et al (1995) observed interlocus homogenization of ITS sequences in Gossypium alloploids and suggested mitotic and meiotic unequal crossing over between repeats from different chromosomes. Gossypium rDNA arrays are located on telomeric and subtelomeric chromosomal loci, which may allow sporadic pairing and exchange between homologous rDNA loci without deleterious cytogenetic effects.On the basis of this study and previous studies (Chambers 1955;Wallace & Jansen 1990;Jansen et al 1991;Van Houten et al 1993;Wallace & Jansen 1995;Roelofs & Bachmann 1997) we now propose a nearly completely resolved phylogenetic relationship among all annual Microseris species, including tetraploids derived through reticulation (Fig. 5).…”

“…Microseris species, outgroup Uropappus lindleyi and the hybrid genus Stebbinsoseris as proposed by Chambers (1955;Jansen et al 1991 agarose gels and blotted on to Qiabrane plus membranes. DNA digested with HinfI (four base-pair recognition site) was separated on 6% polyacrylamide sequence gels and electroblotted using the methodology described by Van Houten et al (1993).…”

“…2 Two Californian annual tetraploids have to be treated as intergeneric hybrids, after their common paternal parent, Uropappus lindleyi, was removed from Microseris (Jansen et al 1991). They are Stebbinsoseris heterocarpa (from M. douglasii) and S. decipiens (from M. bigelovii) (Chambers 1955).…”

Chloroplast DNA Restriction Site Variation and Phylogenetic Relationships in the Genus Thlaspi sensu lato (Brassicaceae)

“…High levels of sequence divergence between the major clades of Thlaspi suggest: 1) these lineages may have experienced a long evolutionary history comparable to genera in other families; 2) the rates of cpDNA evolution in Thlaspi may be faster than in other genera of tribe Lepidieae, a situation now being assessed. Several previous restriction site studies have reported unequal rates of cpDNA evolution from different lineages (Doyle et al 1990;Jansen et al 1991;Kim et al 1992), whereas studies in other taxa do not reject a cpDNA evolutionary clock (Crawford et al 1991;Rieseberg et al 1991;Sytsma and Gottlieb 1986).…”