Genetic variation and restoration of dryland tree species

ANDREA C. PREMOLI, CINTIA P. SOUTO, SONIA TRUJILLO A., RAFAEL DEL CASTILLO, PAULA QUIROGA, THOMAS KITZBERGER, ZANELI GOMEZ OCAMPO, MARINA ARBETMAN, LUCIO R. MALIZIA, ALFREDO GRAU, RAÚL RIVERA GARCÍA, AND ADRIAN C. NEWTON

Principles and Practice of Forest Landscape Restoration. Case studies from the drylands of Latin America

International Union for the Conservation of Nature

Año: 2011; p. 205 - 228

Dry forests are currently the focus of increasing conservation and restoration efforts. This is because one billion people live in dry regions of the world that cover nearly 40% of the Earth’s surface. These regions all have in common a reliance on natural resources – including biodiversity, which is declining at a rate unprecedented in recorded history (UNDP, 2004). The objectives of the ReForLan project were to identify and promote approaches for restoration of arid and semi-arid forest ecosystems. The focus of this chapter is to assess the impact of forest loss, fragmentation, and degradation on genetic variability within socioeconomically important tree species of conservation concern, in the context of restoring functional forest landscapes. In addition, the chapter provides recommendations for restoration of dryland forest resources based on an understanding of the processes influencing genetic variation. Patterns of genetic diversity in plants are the result of current and past evolutionary processes that can be used to guide conservation efforts. Molecular markers can be of great value for investigating the effects of neutral processes such as genetic drift affecting small populations and isolation owing to barriers for gene flow. Such events tend to erode genetic variation in natural populations. Markers may evolve at distinct evolutionary rates and therefore can provide information about processes acting at different temporal scales. Mutations per generation of uniparentally inherited DNA markers such as those of the chloroplast occur at rates of about 10–9, whereas for nuclear microsatellites, mutation rates are between four and six orders of magnitude greater (Provan et al., 1999). While sequences of chloroplast DNA can be used to reconstruct historical genetic patterns, nuclear markers may elucidate the contemporary genetic structure of natural populations. Hence, the combination of the two markers gives the opportunity to understand past and present genetic patterns so as to guide conservation and restoration efforts for the long-term preservation of species. Our aim was to analyze patterns of within- and between-population genetic variation in species of conservation concern, economic importance, and/or socioeconomic relevance in three areas of Latin America. Different markers were used for genetic analyses of natural populations. These included traditional isozyme methods, and novel molecular analyses such as Single Nucleotide Polymorphism (SNP), nuclear species-specific Simple Sequence Repeats (SSRs) known as microsatellites, and DNA sequences of non-recombinant regions of the chloroplast. Whereas the latter provides a historical signal, the former three mostly reflect contemporary genetic structure.