Evolutionary importance of the relationship between cytogeography and climate: New insights on creosote bushes from North and South America.

Relationships between genome size and environmental variables suggest that DNA content might be adaptive and of evolutionary importance in plants. The genus provides an interesting system to test this hypothesis, since it shows both intra- and interspecific variation in genome size. has an amphitropical distribution in North and South American deserts, where it is most speciose.