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Biochemical, Cytogenetic and Morphological Relationships of a New Species of Machaeranthera sect. Arida (Compositae)

1978; American Society of Plant Taxonomists; Volume: 3; Issue: 2 Linguagem: Inglês

10.2307/2418314

1548-2324

Michael L. Arnold, R. C. Jackson,

Biological Control of Invasive Species

Biochemical, morphological and cytological data indicate that the taxon described in the present study, M. turneri, is a distinct species. Biochemically, M. turneri is more distinct from M. parvi/ora than the latter is from M. arizonica. Cytogenetic data show a small translocation and a paracentric inversion difference between M. turneri and M. parvoiora. There is no overlap in five morphological characteristics used to separate the new species from M. parvflora. The genus Machaeranthera has been the subject of several partial taxonomic treatments over the past 18 years. Shinners (1950, 1964) transferred certain taxa of Haplopappus section Blepharodon of Hall (1928) to the genus, and Machaeranthera was formally reconstituted by Cronquist and Keck (1964) as a taxon separate from Aster and more closely related to Haplopappus section Blepharodon. However, the latter authors maintained the yellow-rayed taxa in Haplopappus, a decision with which we generally concur because of known genetic relationships (Jackson, 1978 and unpublished) and priority of the name Haplopappus. As a result of hybridization between Psilactis arida Turner & Horne and two species of Machaeranthera, Jackson (1962) suggested the merger of the two genera. The same conclusion was reached independently by Turner and Horne (1964), who revised Machaeranthera to contain a new section Psilactis. Jackson and Johnson (1967) suggested that Machaeranthera parvif/ora A. Gray and M. arizonica Jackson & Johnson, be added to the new section. More recently, the generic boundaries of Machaeranthera have been brought into question by hybridization between Machaeranthera and species of Aster section Oxytripolium (Stucky & Jackson, 1975; Stucky, 1978), and it has been the opinion of one of us (R.C.J.) for some time that this section more properly belongs in Machaeranthera. The most recent partial taxonomic studies of Machaeranthera are those of Hartman (1976) and Turner and Hartman (1976). The latter treats species we currently regard as Haplopappus and need not be considered further here. Hartman (1976) essentially followed the concepts of Shinners with modifications based on more recent work. His studies showed that flavonoid compounds were not very useful in delimiting the genus, but they could be used for sectional groupings, and on this and morphological grounds he proposed the new section Arida which included taxa with n = 5. Our studies thus far have emphasized experimental approaches inBiological Sciences and Museum, Texas Tech University, Lubbock, TX 79409.