Patterns of Genetic Similarity Between Larrea divaricata of North and South America
Barbour MG. 1969. Patterns of Genetic Similarity Between Larrea divaricata of North and South America. The American Midland Naturalist. 81(1):54-67
Seeds of Larrea divaricata were collected from four Argentina and 34 United States sites, and certain morphological, anatomical, physiological, and cytological characteristics of the fruit and of seedlings grown from seed in a uniform environment were noted. The three warm deserts of the United States in which Larrea occurs exhibit an east-west cline of increasing aridity, with the Argentinian climate being overall most similar to the Chihuahuan. Mitotic chromosome counts made from root tips of seedlings indicated that a different chromosome race exists in each of the three United States deserts. Of some 16 other characteristics which showed significant desert differences, 15 exhibited east-west clines in the United States. Argentinian plants were overall most similar to Chihuahuan plants. It is difficult to say whether the strong east-west pattern of genetic divergence indicates adaptation to divergent environments, path of historic plant migration, or both. A hypothesis was developed that the present disjunct range of Larrea divaricata originated by Larrea of the Chihuahuan and Argentinian types evolving from a common transtropic prototype which later became extinct. The prototype was hypothesized to have been a minor element of the early Madro-Tertiary flora.
- Type
- Journal Article
- Authors
- Barbour, Michael
- Units
- SODN
- Keywords
- Botany (Morphology Anatomy Embryology Genetics), Botany (Plant Distribution), Botany (Systematic Floras Plant Lists), Genetic, Larrea, North America, South America