Genetic parameters for seedling growth in Pinus pseudostrobus families under different competitive environments

by Víctor Hugo Cambrón-Sandoval, Nahum M. Sánchez-Vargas, Cuauhtémoc Sáenz-Romero, J. Jesús Vargas-Hernández, María Luisa España-Boquera, Yvonne Herrerías-Diego,

New Forests, March 2013, Volume 44, Issue 2, pp 219-232

http://link.springer.com/article/10.1007/s11056-012-9312-1

Abstract

Pinus pseudostrobus Lindl. is a widely distributed species in Mexico that also occurs in Guatemala, Honduras and El Salvador and has been tested outside its natural range in Brazil, Chile, Colombia, New Zealand, South Africa and Venezuela. Due to its great potential, it is necessary to select genotypes capable of increasing its production in the shortest possible time through genetic improvement strategies, where individuals are subjected to conditions forcing them to express their growth potential in advance. The objectives of the present study were to evaluate the genetic variation among half-sib progenies and to estimate heritability (h ² ) of stem height (SH) and diameter (SD) for seedlings grown under different competitive conditions in a common garden trial. A split-plot experimental design with four replications and three competitive environments (treatments) was used: (I) low inter-family competition (0.25 × 0.12 m), (II) high inter-family competition (0.12 × 0.06 m), and (III) high intra-family competition; 13 half-sib families were assessed, carrying out monthly evaluations for 10 months. Estimated h ² at individual and family-means levels for both SH and SD varied among competitive environments. For conditions I and II, a trend towards increasing h ² with age of seedlings was shown, but for condition III, a reverse trend was observed (values close to zero). High genetic stability in SH performance was found in both I and II, and II and III, pairs of environments, as measured by the type-B genetic correlation (0.70 ≤ r _B  ≤ 1.0), but it tended to decrease after 9 months, when competition increased; genetic stability in SD was lower (0.20 ≤ r _B  ≤ 0.80) in both pairs of the environments that were sampled. It was concluded that the competition conditions used in field trials for genotype evaluation may significantly affect the variance components, estimation of genetic parameters and genotype stability.

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BIODIVERSITY SCENARIOS: PROJECTIONS OF 21st CENTURY

BIODIVERSITY SCENARIOS:
PROJECTIONS OF 21st CENTURY
CHANGE IN BIODIVERSITY AND ASSOCIATED ECOSYSTEM SERVICES

A Technical Report for the Global Biodiversity Outlook 3 / CBD Technical Series No. 50 / 2010
Secretariat of the Convention on Biological Diversity

Biodiversity_Scenarios_projections_21st_century_change

Citation: Leadley, P., Pereira, H.M., Alkemade, R., Fernandez-Manjarrés, J.F., Proença, V., Scharlemann, J.P.W., Walpole, M.J. (2010) Biodiversity Scenarios: Projections of 21st century change in biodiversity and associated ecosystem services. Secretariat of the Convention on Biological Diversity, Montreal. Technical Series no. 50, 132 pages.

Summary:

“This synthesis focuses on estimates of biodiversity change as projected for the 21st century by models or extrapolations based on experiments and observed trends. The term “biodiversity” is used in a broad sense as it is defined in the Convention on Biological Diversity to mean the abundance and distributions of and interactions between genotypes, species, communities, ecosystems and biomes. This synthesis pays particular attention to the interactions between biodiversity and ecosystem services and to critical “tipping points” that could lead to large, rapid and potentially irreversible changes. Comparisons between models are used to estimate the range of projections and to identify sources of uncertainty. Experiments and observed trends are used to check the plausibility of these projections. In addition we have identified possible actions at the local, national and international levels that can be taken to conserve biodiversity. We have called on a wide range of scientists to participate in this synthesis, with the objective to provide decision makers with messages that reflect the consensus of the scientific community and that will aid in the development of policy and management strategies that are ambitious, forward looking and proactive”.

Main Conclusions:
(a) “Projections of global change impacts on biodiversity show continuing and, in many cases, accelerating species extinctions, loss of natural habitat, and changes in the distribution and abundance of species and biomes over the 21st century”.
(b) “Thresholds, amplifying feedbacks and time-lag effects leading to “tipping points” are widespread and make the impacts of global change on biodiversity hard to predict, difficult to control once they begin, and slow and expensive to reverse once they have occurred”.
(c) “For many important cases the degradation of ecosystem services goes hand-in-hand with species extinctions, declining species abundance, or widespread shifts in species and biome distributions. However, conservation of biodiversity and of some ecosystem services, especially provisioning services, are often at odds”.
(d) “Strong action at international, national and local levels to mitigate drivers of biodiversity change and to develop adaptive management strategies could significantly reduce or reverse undesirable and dangerous biodiversity transformations if urgently, comprehensively and appropriately applied”.