Genetic Basis Of Evolutionary Change Research Articles

Essay Review: Restroom Reading

Do not do what 1 have just done. Do not try to read this book straight through. Instead, put it on your bedside table and read bits and pieces for 20 min or so each day. Better still, buy a second copy and put it in the guest bedroom or the outhouse or wherever visitors retreat to sev? eral times a day when they come to stay with you. At worst, you will have fascinating discussions over the dinner table. At best, your visitors will escape your teenagers and have spent time with one of the most fascinating minds of our generation. With the death of Ernst Mayr, Edward O. Wilson has inherited the mantle of the world's most distinguished evolutionary biologist. Born in Alabama in 1929, he moved to Harvard for graduate work, staying there for 50 years as he worked up through the ranks of student, fellow, assistant professor until finally he was a university professor. He has won numerous prizes, including two Pulitzer Prizes, for Wilson is not just a great scholar but also a brilliant teacher, a terrific lecturer, and an important public voice. His career has been marked by controversy. His most important book is Sociobiology: The New Synthesis, published in 1975. (As a bibliophile and book collector I dare not tell you what I paid for a first edition, first printing. It was an order of magnitude more than I paid for Richard Lewontin's The Genetic Basis of Evolutionary Change.) After a magnificent survey of the world of animal social behavior, Wilson ended with a chapter on our own species. And all hell let loose. Perhaps expectedly the social scientists did not much like this. Insecure at the best of times, with good reason they feared a take-over by the biologists. Perhaps expectedly the philosophers did not much like this. Very few have come to terms with the fact that being the end result

Detecting natural selection on cis-regulatory DNA

Changes in transcriptional regulation play an important role in the genetic basis for evolutionary change. Here I review a growing body of literature that seeks to determine the forces governing the non-coding regulatory sequences underlying these changes. I address the challenges present in studying natural selection without the familiar structure and regularity of protein-coding sequences, but show that most tests of neutrality that have been used for coding regions are applicable to non-coding regions, albeit with some caveats. While some experimental investment is necessary to identify heritable regulatory variation, the most basic inferences about selection require very little functional information. A growing body of research on cis-regulatory variation has uncovered all the forms of selection common to coding regions, in addition to novel forms of selection. An emerging pattern seems to be the ubiquity of local adaptation and balancing selection, possibly due to the greater freedom organisms have to fine-tune gene expression without changing protein function. It is clear from multiple single locus and whole genome studies of non-coding regulatory DNA that the effects of natural selection reach far beyond the start and stop codons.

The evolution of transcriptional regulation in eukaryotes.

Gene expression is central to the genotype-phenotype relationship in all organisms, and it is an important component of the genetic basis for evolutionary change in diverse aspects of phenotype. However, the evolution of transcriptional regulation remains understudied and poorly understood. Here we review the evolutionary dynamics of promoter, or cis-regulatory, sequences and the evolutionary mechanisms that shape them. Existing evidence indicates that populations harbor extensive genetic variation in promoter sequences, that a substantial fraction of this variation has consequences for both biochemical and organismal phenotype, and that some of this functional variation is sorted by selection. As with protein-coding sequences, rates and patterns of promoter sequence evolution differ considerably among loci and among clades for reasons that are not well understood. Studying the evolution of transcriptional regulation poses empirical and conceptual challenges beyond those typically encountered in analyses of coding sequence evolution: promoter organization is much less regular than that of coding sequences, and sequences required for the transcription of each locus reside at multiple other loci in the genome. Because of the strong context-dependence of transcriptional regulation, sequence inspection alone provides limited information about promoter function. Understanding the functional consequences of sequence differences among promoters generally requires biochemical and in vivo functional assays. Despite these challenges, important insights have already been gained into the evolution of transcriptional regulation, and the pace of discovery is accelerating.

Bold yet austere

Bold yet austere

When is homology not homology?

Although genes have specific phenotypic consequences in a given species, this functional relationship can clearly change during the course of evolution. Many cases of evolutionary dissociations between homologous genes and homologous morphological features are now known. These dissociations have interesting and important implications for understanding the genetic basis for evolutionary change in morphology.

THE GENETIC BASIS OF EVOLUTION OF THE MALE COURTSHIP SOUNDS IN THE DROSOPHILA VIRILIS GROUP.

When courting, males of the Drosophila virilis group vibrate their wings and emit species-specific courtship sounds consisting of trains of polycyclic sound pulses. To analyze the genetic basis of evolutionary changes in the sounds we made an F1 diallel set of reciprocal crosses between the members of the virilis phylad of the group (two stocks of D. virilis and one of D. americana americana, D. a. texana, D. novamexicana, and D. lummei). We also crossed the D. virilis stocks with the members of the montana phylad of the same group (D. kanekoi, D. littoralis, D. borealis, D. flavomontana, D. lacicola, and D. montana) and made a backcross (D. virilis x D. littoralis) x D. virilis using a D. virilis marker stock (b; sv t tb gp; cd; pe). The sounds of the hybrids were analyzed using the following parameters: the length of a pulse train (PTL), the number of pulses in a train (PN), the interpulse interval (IPI), the length of a pulse (PL), the number of cycles in a pulse (CN), and the length of a cycle (CL). In the virilis phylad, the differences between species appeared to be determined mainly by autosomal genes in each sound trait. The heritabilities (narrow-/broad-sense) obtained from the diallel tables were the following: PTL 0.662/0.817, PN 0.651/0.841, IPI 0.193/0.546, PL 0.408/0.552, CN 0.425/0.719, and CL 0.361/0.764. The direction of dominance is for longer PTL, higher PN and CN, and shorter IPI and CL. PL shows ambidirectional dominance. In the sounds of the virilis phylad species, PTL and PL seem to be phenotypically the most important parameters, since their components (PN and IPI for PTL, CN and CL for PL) are negatively correlated. In crosses between D. virilis and D. littoralis or D. flavomontana reciprocal hybrids differed from each other in PTL, IPI, PL, and CN indicating X-chromosomal or cytoplasmic inheritance. In the backcrosses between D. virilis and D. littoralis the role of the X chromosome was ascertained to be decisive. We conclude that an X-chromosomal major change allowing variation in IPI has occurred during the separation of the two D. virilis group phylads, the long IPI allowing variation also in PL (and CN). The evolution of the sounds in the virilis phylad has probably gone towards longer and denser pulse trains, while in the montana phylad the sounds have evolved in different directions.

FEMALE DRY WEIGHT AND FEMALE CHOICE IN CHAULIOGNATHUS PENNSYLVANICUS.

JOHNSON, M. S. 1976. Allozymes and area effects in Cepaea nemoralis on the western Berkshire Downs. Heredity 36:105-121. 1979. Inheritance and geographic variation of allozymes in Cepaea nemoralis. Heredity 43: 137-141. JONES, J. S., B. H. LEITH, AND P. RAWLINGS. 1977. Polymorphism in Cepaea: a problem with too many solutions? Ann. Rev. Ecol. Syst. 8:109143. JONES, J. S., R. K. SELANDER, AND G. D. SCHNELL. 1980. Patterns of morphological and molecular polymorphism in the land snail Cepaea nemoralis. Biol. J. Linn. Soc. In press. LANGLEY, C. H. 1977. Nonrandom associations between allozymes in natural populations of Drosophila melanogaster, p. 265-273. In F. B. Christiansen and T. M. Fenchel (eds.), Measuring Selection in Natural Populations. SpringerVerlag, N.Y. LEWONTIN, R. C. 1974. The Genetic Basis of Evolutionary Change. Columbia Univ. Press, N.Y. OXFORD, G. S. 1978. The nature and distribution of food-induced esterases in helicid snails. Malacologia 17:331-339. SELANDER, R. K., M. H. SMITH, S. Y. YANG, W. E. JOHNSON, AND J. B. GENTRY. 1971. Biochemical polymorphism and systematics in the genus Peromyscus. I. Variation in the old-field mouse (Peromyscus polionotus). Stud. Genet. 6:49-90.

Reviews

Book reviewed in this article: The Genetic Basis of Evolutionary Change. By R. C. Lewontin. Lea Nouveaux pygmalions: awe confins de la génétique humaine. By Jean de Grouchy. Methods and Theories of Anthropological Genetics. Edited by M. H. Crawford and P. L. Workman. Colour Vision Deficiencies: II. Proceedings of the Second Symposium of the International Research Group on Colour Vision Deficiencies, Edinburgh 1973. Edited by G. Verriest.