IMPACT OF FOREST FRAGMENTATION AND DEGRADATION ON PATTERNS OF GENETIC VARIATION AND ITS IMPLICATION FOR FOREST RESTORATION.

A.C. PREMOLI, C.P. SOUTO, S. TRUJILLO A., R.F. DEL CASTILLO, P. QUIROGA, T. KITZBERGER, Z. GOMEZ OCAMPO, M. ARBETMAN, L. MALIZIA, A. GRAU, R.R. GARCÍA, AND A.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: 2010;

Dry forests are currently the focus of conservation and restoration efforts. This is because one-billion people live in dry regions of the world that cover nearly 40 per cent of the Earth´s surface, which in turn have all in common a reliance on natural resources – including biodiversity, which is declining at a rate unprecedented in recorded history (Massood 2004). The objectives of the Reforlan project were to identify and promote approaches for the sustainable management, conservation, and restoration of arid and semi-arid forest ecosystems. In particular, the focus of this chapter is to assess the impact of forest loss, fragmentation, and degradation on genetic variability within socio-economically important tree species of conservation concern and to provide recommendations for restoration of dryland forest resources based on the understanding of processes influencing genetic variation. Patterns of genetic diversity in plants are the result of current and past evolutionary processes which can be used to guide conservation efforts. Molecular markers can greatly contribute to investigate the effects of neutral processes such as genetic drift affecting small populations and isolation due to barriers for gene flow which tend to erode genetic variation in natural populations. Markers may evolve at distinct evolutionary rates and therefore can inform of 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 is 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 current genetic structure of natural populations. Hence, the combination of the two gives the opportunity to understand the past and the present so to guide conservation and restoration efforts for the long term preservation of species. The objective is to analyze patterns of within- and between-population variation in species of either conservation concern, economic importance, and socio-economic relevance in three areas of Latinamerica. Disctinct technics 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) or microsatellites, and DNA sequences of non-recombinant regions of the chloroplast. Whereas the later provides a historical signal, the former three mostly inform on current genetic structure. Genetic patterns were analyzed in three geographic areas: northern and southern Argentina and Oaxaca Mexico. In each of these study areas the following species were studied: three Cedrela species saltensis, lilloi, and balansae from seasonally dry subtropical forests of northern Argentina, Malacomeles denticulata from arid and perturbed soils in central state of Oaxaca, México, and the dominant tree Austrocedrus chilensis (hereafter Austrocedrus) of the forest-steppe ecotone of the Patagonian Andes.