Biochemical and molecular genetic markers in biosystematic studies of forest trees

Abstract

Biochemical and molecular markers have proven to be powerful tools for discerning biosystematic, biogeographic, and phylogenetic relationships. Biosystematic information can be important for guiding traditional breeding programs, gene transfer, interspecific hybridization, and gene conservation. A phylogenetic framework is usually necessary, but frequently ignored, for making valid statistical tests in studies of adaptive evolution. Several studies have indicated a strong correlation between biochemical “races” and traits important to growth and adaptation, suggesting that evolutionary legacy may affect genetic architecture of fitness traits — with consequences for seed transfer, breeding strategies, and tolerance of climate change. A number of methods for phylogenetic analysis exist, but differ in their assumptions. Use of an inappropriate method — such as a method that assumes constant rates of evolution when rates in fact vary — can lead to incorrect phylogenies. Because of their complexity, phylogenetic topologies are often difficult to determine unambiguously; estimates of statistical confidence should therefore accompany phylogenetic trees if they are to be regarded as providing new knowledge, or strong confirmation, of relationships. Molecular genetic markers are more expensive than biochemical markers such as allozymes and terpenes, but they provide increased accuracy and expanded scope of biosystematic inference, and facilitate statistical analyses of phylogenetic trees.