Patterns of Genetic Variation in Tree Species and their Implications for Conservation

A.C. PREMOLI, R.F. DEL CASTILLO, A.C. NEWTON, S. BEKESSY, M. CALDIZ, C. MARTÍNEZ-ARANEDA, P. MATHIASEN, M.C. NÚÑEZ-ÁVILA, P. QUIROGA, C. SOUTO AND S. TRUJILLO-ARGUETA

Biodiversity Loss and Conservation in Fragmented Forest Landscapes

CAB International

Año: 2007; p. 120 - 157

Within-species genetic variability is essential for the maintenance of the evolutionary potentialof natural populations. Information from genetic markers can help inform the developmentof conservation strategies, including those for endemic tree species. This chapter summarizesthe results of recent research into the conservation genetics of tree species inhabiting temperateforests of southern Argentina and Chile, and montane forests of northern Argentinaand Mexico. Pronounced genetic differences were recorded between populations of all speciesstudied, reflecting their complex biogeographic and evolutionary histories. Species suchas Araucaria, Fitzroya and Pilgerodendron appear to have survived in multiple refugia duringPleistocene glaciations, indicated by marked genetic differentiation over small geographicalareas. Patterns of variation in the latter two species strongly support the suggestion of localrefugia persisting east of the Andes during the last glacial period. Montane species inhabitingsubtropical latitudes, such as Podocarpus parlatorei and Pinus chiapensis, appear to havemigrated in elevation during periods of climatic change. In each case, the result is a complexpattern of local population differentiation and adaptation, differing markedly from north temperatetree taxa characterized by large-scale postglacial migrations. Some species, includingPinus chiapensis, Pilgerodendron uviferum and Nothofagus pumilio, displayed evidence of low geneticvariation within populations, reflecting the possible occurrence of inbreeding and geneticdrift as a result of population isolation. This is despite their possession of life history attributes(such as wind pollination) that imply gene flow over long distances. Results suggest that geneflow may often be restricted, even in wind-pollinated species, in fragmented forest landscapes.However, weak effects of fragmentation were measured in the self-incompatible Embothriumcoccineum. In this species, higher pollinator activity in fragments reduces selfing, therebybuffering genetic erosion and maintaining adaptive variation. Such results highlight the difficultyof generalizing about the impacts of anthropogenic disturbance on patterns of genetic variation in tree species. These results emphasize the importance of including many populationsin conservation strategies and action plans, if the full variation within a species is to beconserved. Particular priorities for conservation include areas of high genetic diversity, whichmay coincide with putative glacial refugia, such as the coastal mountain range of Chile.