Genetic systems in the south-west flora: implications for conservation strategies for Australian plant species

Abstract

Is genetic diversity a reliable indicator of evolutionary capability? A comparative study of genetic systems in Australian native plants, particularly from south-west Australia, suggests the primitive condition to be recombinationally capable with low allelic diversity. Diversity has accumulated in some nursery lineages in association with lethal equivalent polymorphisms. This generated an elevated evolutionary capability which allowed escape from the benign nursery into the demanding arid playground. Lethal equivalent polymorphisms also generate a high genetic load which drives genetic system evolution towards the minimisation of that load. Many of the devices which reduce the genetic load, including chiasma localisation at meiosis and reduced chromosome numbers, are impedimenta to recombination and they must reduce evolutionary capability. Thus, to correctly interpret the levels and patterns of genetic diversity within an Australian plant population system we need to know how its genetic system operates and how much it is recombinationally impeded. It may be true that in many Australian plant population systems, the more genetic diversity we see, the less evolutionary potential there is. Conservation strategies based on a misunderstanding of the relevance of genetic diversity in population systems may be quite disastrous.