History of Sessile Organisms

The creation of assumes to determine contractable relatedness and inbreeding in organisms has shed considerable light on the class of familial diversity seen in clonal organisms. Sackville Hamilton et al. (19) present an overview of the bread and butter history and community biology of clonal organisms, proposing a model to describe different strategies in relation to r and K-selection. A more recent work by Orive (17) further relates population size to genetic relatedness, and provides a model which focuses on the sentence at which two alleles last shared a commonalty ancestor to describe their relationship in more informative, genetic terms. In support of such models, the last decade has seen the number of genetic markers and reproducible techniques of DNA fingerprint. Both have contributed greatly to a clearer understanding of how interpretation occurs in clonal populations. just about DNA fingerprinting techniques examine the polymorphism sequences in moreover the chromosome or in the plasmids or only a star gene fragment (22). In many studies, actual variation can be revealed by amplified fragment length polymorphism (AFLP) or restriction fragment length polymorphism (RFLP) or by electrophoresis, with the use of various combinations of techniques revealing the greatest levels of systematic differences.
Many of these techniques have revealed significant levels of variation within clonal populations. This has proven especially useful in bacterial stud

1. Bifani,P.; Plikaytis, B.; Kapur, V.; Stockbauer, K.; Pan, X.; Lutfey, M.; Moghazeh, S.; Eisner, W. Origin and interstate spread of a NY City multi-drug resistant Mycobacterium tuberculosis clone family. JAMA. 275(6):452- 7; 1996 (Feb.).
The freshwater snail (Potampyrgus antipodarum) occurs naturally as co-existing populations of sexual and clonal subpopulations. An examination of a single wild population of these snails (7), showed that triploid parthenogenetic forms co-existed with the sexual forms across three different home ground zones, with the clonal forms displaying high diversity (165 genotypes among 605 snails).

The frequency of triploid clonals change magnitude with increasing lake depth, with a proportionately greater number of clone individuals showing marked habitat specificity.
ies. Gray and Herwig (8) successfully extracted microbic DNA from marine sediments, yielding high molecular clog DNA for amplification and analysis. In studies of clonal pathogens where clonal individuation may be critical to the creation of successful vaccine, fingerprinting techniques have made significant contributions. In the case of the clonal pathogen Borrelia burgdorferi, which causes Lyme borreliosis in man, an examination of genetic trees of plasmid sequences taken from 15 isolates, no evidence was seen for genetic exchange between chromosomal genes and clones rarely exchanged plasmids between themselves. This indicated that of the clones examined, all were so extremely divergent that vaccines developed to combat one would be highly unlikely to effectively immunize against any of the others, with serious implications for figure (16).
7. Fox, J.; Dybdahl, M.; Jokela, J.; Lively, C.; Genetic structure of co-existing sexual and clonal subpopulations in a freshwater snail Potampyrgus antipodarum. Ecol. 50(4):1541-1548; 1996.
19. Sackville Hamilton, N.; Schmidt, B.; Harper, J. Life- history concepts and the population biology of clonal organisms.




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