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Phylogenetic Relationships Among Lactuca (Asteraceae) Species and Related Genera Based on ITS-1 DNA Sequences
Wim J. M. Koopman, Eli Guetta, Clemens C. M. van de Wiel, Ben Vosman and Ronald G. van den Berg
American Journal of Botany
Vol. 85, No. 11 (Nov., 1998), pp. 1517-1530
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2446479
Page Count: 14
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Internal transcribed spacer (ITS-l) sequences from 97 accessions representing 23 species of Lactuca and related genera were determined and used to evaluate species relationships of Lactuca sensu lato (s.1.). The ITS-1 phylogenies, calculated using PAUP and PHYLIP, correspond better to the classification of Ferskova than to other classifications evaluated, although the inclusion of sect Lactuca subsect. Cyanicae is not supported. Therefore, exclusion of subsect Cyanicae from Lactuca sensu Ferakova is proposed. The amended genus contains the entire gene pool (sensu Harlan and De Wet) of cultivated lettuce (Lactuca satire). The position of the species in the amended classification corresponds to their position in the lettuce gene pool. In the ITS-1 phylogenies, a clade with L. sativa, L. serriola, L. dregeana, L. altaica, and L. aculeata represents the primary gene pool. L. virosa and L. saligna, branching off closest to this clade, encompass the secondary gene pool L. virosa is possibly of hybrid origin. The primary and secondary gene pool species are classified in sect. Lactuca subsect. Lactuca. The species L. quercina, L. viminea, L. sibirica, and L. tatarica, branching off next, represent the tertiary gene pool. They are classified in Lactuca sect. Lactucopsis, sect Phaenixopus, and sect Mulgedium, respectively, L. perennis and L. tenerrima, classified in sect. Lactuca subsect. Cyanicae, form clades with species from related genera and are not part of the lettuce gene pool.
American Journal of Botany © 1998 Botanical Society of America, Inc.