Genetic diversity-seeing the forest through the trees

Abstract

Forest trees, populations, races, species, and taxonomic groups above the species level display rich variation in biochemical markers. The variation stems from inherited modifications that trace back in time, through converging ancestries, towards common progenitors. Past movements of continents, mountain building events, and climate changes isolated forest populations one from another and provided critical challenges to the lineages that survived to the present day. A wealth of molecular variants in forest trees characterize these widely-distributed, large, long-lived, outbreeding, organisms. Forest trees have an abundance of rare variants and over one third of all the alleles (different forms of one gene) occur only rarely (< 2% frequency) in a few trees of a species sample. Those rare alleles may either represent new variation or persistent forms of genes that have low adaptive value under present conditions. From another perspective, however, the largest share of genetic variation in forest trees is due to the presence of multiple alleles found at intermediate frequencies for only a small percentage of all the genes, and those alleles are commonly widespread throughout species areas. These common alleles may mark genes that track historical events in lineages or mark genes with adaptive significance in present populations. Evidence from enzyme studies supports the conclusion that highly comparable functional genes are common to different forest taxa. Future research will be toward understanding the phenotypic expression of particular genes and revealing the relative importance of genetic variants to adaptation and growth.

Citation

Conkle, M. Thompson. 1992. Genetic diversity–seeing the forest through the trees. New Forests 6: p. 5-22