PLAYING GOD OR GARDENING?
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PAST, PRESENT ... AND FUTURE? CONSERVATION PRACTICE AND THE CONSERVATION GENETICS OF PLANT POPULATIONS. Q.O.N. KAY As new, effective and rapid molecular techniques for the determination of patterns of genetic variation have been introduced during the past 20-25 years, the remarkable diversity of genetic situations in plant populations, both within and between species, has become increasingly clear. The real situations, revealed by isozyme and DNA analysis, often prove to differ from those that would in the past have been predicted from knowledge of the apparent breeding system and population structure of the species. Such divergence from classical expectation appears to be particularly frequent in rare and declining species, which are usually those of greatest immediate conservation concern. Knowledge of these genetic structures and patterns of genetic variation is centrally important for plant conservation. Sources of genetic data What sources of genetic data are available for conservation programmes? They are:Classical, primarily morphological taxonomic data. Although taxonomic distinctions are usually based on genetic differences, these differences may sometimes be extremely small and the distinctions dependent upon subjective judgement or opinion. In many cases, however, classical taxonomic judgements are a good guide to genetic relationships; fortunately so, because these judgements are the normal basis on which species, subspecies etc. are recognised for conservation purposes. Classical studies of ecotypic variation, from Turesson (or earlier) onwards. These are usually based on the demonstration of genetically based variation by comparative cultivation, for example in Succisa pratensis (Devil’s-bit Scabious). When available, these studies are extremely useful as indications of the pattern and degree of geographic and ecotypic genetic variation in a species. This variation is usually adaptive and thus subject to natural selection. Classical genecological studies of visible or easily detected polymorphisms For example leaf-pattern, flower colour, cyanogenesis, perhaps also metal tolerance and self-incompatibility alleles. These studies are indicative of breeding systems and likely levels of variation, and sometimes significant for conservation purposes (SI allele polymorphisms especially so) but in general are of limited scope, and only available for a few species (e.g. Trifolium repens (White Clover) , Lotus corniculatus (Common Bird’s-foot Trefoil) and Papaver rhoeas (Common Poppy)). Studies of molecular variation and polymorphism; isozyme analysis, various DNA techniques from RAPD analysis to direct DNA sequencing. These new techniques have proved to be enormously valuable and informative, although each technique has its strengths and weaknesses. For use in conservation work, a technique should ideally be fast and cheap, widely
Trans. Suffolk Nat. Soc. 37 (2001)