The distribution and divergence during evolution of families of repetitive DNA sequences inLathyrus species

Abstract

Evolution and divergence among, species within the genusLathyrus have involved an approximately fivefold increase in the amounts of nuclear DNA. Most species inLathyrus are diploids with the same chromosome number, 2n=14. Significant changes in the amounts of repetitive sequences have accounted for much of the evolutionary DNA variation between species. Seven diploidLathyrus species with a twofold variation in nuclear DNA amounts between them were investigated. Using higher derivative analysis of the thermal denaturation profiles of the reassociated repetitive DNA, the reiteration frequency and divergence of repetitive families were compared. Much variation in the reiteration frequency was observed within and between species. In species with larger 2C DNA amounts repetitive families had on average greater amounts of DNA. Despite the massive differences in DNA amounts, six species were consistently similar in the number of repetitive families in their genomes, and they showed a similar pattern in base sequence divergence. In terms of base sequence relationships the repetitive families appeared to be heterogeneous. The evolutionary significance is discussed.