Patterns of Genetic Similarity Between Larrea divaricata of North and South America

摘要: Seeds of Larrea divaricata were collected from four Argentina and 34 United States sites, certain morphological, anatomical, physiological, cytological characteristics the fruit seedlings grown seed in a uniform environment noted. The three warm deserts which occurs exhibit an east-west cline increasing aridity, with Argentinian climate being overall most similar to Chihuahuan. Mitotic chromosome counts made root tips in- dicated that different race exists each deserts. Of some 16 other showed significant desert differences, 15 exhibited clines States. plants 'Chihuahuan plants. It is difficult say whether strong pattern genetic divergence indicates adaptation divergent environments, path historic plant migration, or both. A hypothesis was developed present disjunct range originated by Chihuahuan types evolving common trans- tropic prototype later became extinct. hypoth- esized have been minor element early Madro-Tertiary flora.