In situ genetic conservation of a naturally restricted and commercially widespread species, Pinus radiata

Abstract

Unlike many other forest tree species of commercial significance, the domestication of Pinus radiata (Monterey pine) has occurred largely outside its native range in coastal California and Mexico. The extant native forest is represented by only five disjunct populations: three along the central coast of California and two on Mexican islands off the coast of Baja California. The remaining native forest is dwarfed in comparison with the area in plantation culture—over 4 million ha—largely in Chile, New Zealand, Australia, and Spain. The biological attributes of Monterey pine most relevant to genetic conservation challenges and strategies are its population structure (few, coastal, or insular populations that are highly differentiated genetically and ecologically); an evolutionary history that suggests considerable population movement, expansion, and local extirpations and founding events in response to climatic triggers; an evolutionary relationship with fire disturbance; and semi-serotinous cones that are held tightly on trees, often for years. Mirroring the high degree of population differentiation, threats to overall longevity and genetic diversity vary considerably in intensity and expression from one population to another. With a large proportion of the current habitat in private ownership, and continuing loss and fragmentation of native forest, the most critical conservation action is land purchase to protect remaining forests from degradation or conversion to other uses. Complementary, recent, and effective conservation measures include conservation easements on privately held Monterey pine forests, the public education and (regulatory) monitoring activities of environmental nongovernmental organizations, nonpolitical educational fora for habitat owners and managers, and international collaborations that bring the commercial interest in the species into the sphere of conservation of native gene pools.