The study of past historical events that have led to ecological changes is a recurrent topic in many disciplines. Given that many of these events have left a large and long-lasting evolutionary imprint on the extant population genetic structure of species, phylogeographic studies on modern taxa have been largely used to infer the impacts of these events and to complement previous paleoecological and paleobotanical surveys. In spite of the geographical and geological complexity of North America, converging patterns can be observed when comparing the available genetic data for forest trees. Such patterns include the co-location of genetic discontinuities among species and their coincidence with mountain ranges (e.g., the Appalachians, the Rocky Mountains, the Sierra Nevada, or the Transverse Volcanic Belt) and with previously inferred glacial refugia. Using examples drawn from the available literature, we illustrate such shared features and present the contrasting phylogeographic patterns observed among the...

Inferring the past from the present phylogeographic structure of North American forest trees : seeing the forest for the genes

Trees are key ecosystem engineers. Many analyses of the genetic diversity of forest trees over substantial parts of their distributional ranges are appearing. These studies are of relevance for forest and landscape management, the inventory of botanical genetic resources and the conservation biology of rare, endemic, relictual, and endangered tree species. This review focuses on (i) recent investigations of the influence of human disturbances, (ii) comparative analyses of closely related and hybridizing species, (iii) reconstructions of refugia and of the spread of tree populations during the postglacial, (iv) studies of both range-wide and range-edge genetic patterns, and (v) assessments of the role of tree genetic diversity in the face of future climate warming. There is a need to include more tropical and austral trees in genetic analyses, as most studies have dealt with the relatively species-poor Palaearctic and Nearctic regions. Further studies are also needed on the role of tree genetic diversity in variations in phenology, resistance to insect defoliators and fungal pathogens, reactions to increased CO2 and ozone concentrations, growth, mortality rates and other traits. Most macroecological and scaling patterns of species richness still need to be studied for genetic diversity. Open research questions in this rapidly evolving field involve invasion biology, island biogeography, and urban ecology. There is a need for more knowledge transfer from the many studies of tree genetic diversity to the day-to-day management of trees and forests.

Geographical genetics and the conservation of forest trees

The report details the IUCN conservation status of 762 tree species and also includes information on current and potential uses of each species, in the hope that this will help promote sustainable resource management and conservation in the future. Various parts of trees found in the forest are used to make products as diverse as baseball bats, toothpaste, clothing dyes and hammocks and several species have edible parts or medicinal properties. Some species are also important culturally, with one being used during the important Dia de Muertos folk festival.

The Red List of Mexican Cloud Forest Trees

Tree species have been the focus of increasing interest regarding the so-called conservation-through-use approach, which aims to achieve conservation by increas- ing the value of wild resources to local communities. Although tree species display many characteristics that increase their potential for sustainable use, the approach is rarely successful in practice. The reasons for this are examined with reference to case studies, considering five conditions needed for success: (1) sustainable harvesting, (2) no interaction between threats, (3) successful commer- cialization, (4) economic benefits received by producers, and (5) use of financial income to support conservation action. Case studies illustrate that even when the first four of these conditions are met, trade in forest products often provides insufficient financial returns to protect the forest against other threats. This highlights the importance of understanding the interactions between threats for conser- vation-through-use to be achieved, an issue illustrated by a conceptual model. Recommendations are presented in- dicating how the conservation of tree species through sus- tainable use may be achieved in practice. Critically, financial rewards of sustainable use need to be large enough to support practical conservation action, which is required to counter the many threats to which tree species are exposed.

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Conservation of tree species through sustainable use: how can it be achieved in practice?

In recent years, the land area under agriculture has declined as also has the rate of growth in agricultural productivity while the demand for food continues to escalate. The world population now stands at 7 billion and is expected to reach 9 billion in 2045. A broad range of agricultural genetic diversity needs to be available and utilized in order to feed this growing population. Climate change is an added threat to biodiversity that will significantly impact genetic resources for food and agriculture (GRFA) and food production. There is no simple, all-encompassing solution to the challenges of increasing productivity while conserving genetic diversity. Sustainable management of GRFA requires a multipronged approach, and as outlined in the paper, biotechnologies can provide powerful tools for the management of GRFA. These tools vary in complexity from those that are relatively simple to those that are more sophisticated. Further, advances in biotechnologies are occurring at a rapid pace and provide novel opportunities for more effective and efficient management of GRFA. Biotechnology applications must be integrated with ongoing conventional breeding and development programs in order to succeed. Additionally, the generation, adaptation, and adoption of biotechnologies require a consistent level of financial and human resources and appropriate policies need to be in place. These issues were also recognized by Member States at the FAO international technical conference on Agricultural Biotechnologies for Developing Countries (ABDC-10), which took place in March 2010 in Mexico. At the end of the conference, the Member States reached a number of key conclusions, agreeing, inter alia, that developing countries should significantly increase sustained investments in capacity building and the development and use of biotechnologies to maintain the natural resource base; that effective and enabling national biotechnology policies and science-based regulatory frameworks can facilitate the development and appropriate use of biotechnologies in developing countries; and that FAO and other relevant international organizations and donors should significantly increase their efforts to support the strengthening of national capacities in the development and appropriate use of pro-poor agricultural biotechnologies.

Biotechnologies for the management of genetic resources for food and agriculture

Fagus grandifolia var. mexicana(Fagaceae) is a Mexican endemic tree, currently threatened with extinction. In order to assess the level and structure of genetic variation in four remaining populations, leaf samples were analysed using random amplified polymorphic DNA (RAPD) and cpDNA PCR-RFLP markers. A sample of the more widespread congener, F. grandifoliavar. grandifolia from the USA was also analysed for comparison. Thirty-three polymorphic RAPD bands were produced using 18 10-mer primers. AMOVA of RAPD data indicated significant (P < 0.002) population differentiation, with 15.6% of variation recorded between Mexican populations. PCR-RFLP analysis enabled three cpDNA haplotypes to be identified, denoted types A, B, and C. Types A and B were each restricted to an individual Mexican population, whereas Type C was fixed for two Mexican populations, and the population from the USA. Within-population genetic variation, quantified as percentage polymorphic bands, Shannon's Diversity Index and Nei's gene diversity measure, was found to be lower in Mexican populations than in that from the USA, and was positively related to population size. These results suggest that an unexpectedly high degree of genetic variation exists within Mexican beech, and this variation should be considered in developing the conservation strategy that is urgently required if extinction of this taxon is to be prevented.

Ashley Robertson

Papers

Conservation Genetics of Mexican Beech, Fagus grandifolia var . mexicana