Genetic conservation of Parashorea malaanonan (M. Blanco) Merr. in Mt. Makiling, Laguna, Philippines

April 28, 2006 by

Portia Gamboa-Lapitan

College of Forestry and Natural Resources, University of the Philippines Los Banos

Tel. 063-49-5363572, E-mail: portialapitan@yahoo.com

and

Jung Oh Hyun

College of Agriculture and Life Sciences, Seoul National University, Korea

E-mail: hyunjung@snu.ac.kr



Abstract


The genetic diversity of P. malaanonan was previously assessed from isozyme analysis of 61 individuals spread in two elevational sites within Mt. Makiling Forest Reserve (MFR) to identify conservation strategies for the population in this forest. The genetic diversity as indicated by observed heterozygosity (Ho) was found to be directly proportional to the species’ outcrossing rate. Comparison of F values of the adult (-0.200 to –0.068) and filial population (0.010) revealed that selection in favour of heterozygotes occurred in the population. The number of seedlings surviving from a given crop decreased through time. Considering this information, the most appropriate and cost-effective conservation strategy for the species is the immediate in situ conservation of P. malaanonan in the MFR. P. malaanonan’s resources in the area are well protected and are accessible therefore interventions for enhanced reproductive efficiency and effective conservation of the species is technically possible and economically feasible. The recommended interventions are: 1) “rescue” of randomly selected seedlings to increase survival of progenies and increase further the level of diversity in the area, 2) active management for enhanced seed production and reproductive success of selected mother trees and their use as seed sources for enrichment planting in the reserve and for future plantation establishment in other areas, and 3) protection from Swietenia macrophylla, which is reported to have become an invasive species in Mt. Makiling.


Keywords: genetic diversity, outcrossing rate, in situ conservation, Parashorea malaanonan, Mt. Makiling



Introduction



In the global market, Philippine dipterocarps are well known by their international trade name, Philippine mahogany. This group of tree species has played an important role as the primary export commodity and dollar earner of the Philippines for a long time. Of these, Parashorea malaanonan belongs to the timber group of Light Red Philippine Mahogany. The volume of log export for this species, however, had dramatically plunged during the last decade (Forestry Statistics, FMB, 1997) because of decline in supply.


P. malaanonan is not only economically-important it is also ecologically significant in that it provides shelter and support to other organisms. It commonly grows together with palms, vines, shrubs and other tree species. It is distributed from the north to the south of the Philippines (Newman et al. 1996). The study of Tsumura et al. (1996) on the phylogeny of dipterocarps indicated that Parashorea is a very close relative of the more common Shorea.


P. malaanonan is now threatened by unabated exploitation endangering not only this species but also the other associated species. Although there have been efforts to reverse the adverse effect of massive destruction of forest ecosystems as a result of excessive forest harvesting, very little attention and studies have been directed on the basic science of conservation of forest species as a whole, and much more so on remaining populations of species like Parashorea.


In Mt. Makiling, Laguna, Philippines, a natural population of P. malaanonan spread from the Makiling Botanic Gardens (200 m asl) to the area beyond the Mudspring with an elevation of about 400-450 m asl. The forest has been declared a forest reserve and the population of P. malaanonanhere is probably the only remaining intact population of such species in the country.


Basic information about the genetic diversity, mating system and regeneration of P. malaanonan were determined lately by the authors for use in crafting strategies for conservation and sustainable management of the species. Very recently an analysis of inbreeding coefficient of progenies, maternal and adults of the population in Mt. Makiling and its implications to the conservation of P. malaanonan was undertaken. The monitoring of the growth and survival of regenerants in Mt. Makiling is a continuous activity that provides necessary information for updating the conservation strategy for the population of P. malaanonanin the forest reserve.



Materials and methods



In this study, the results of the population genetic analysis conducted in 2004 on 61 trees of P. malaanonan randomly selected in elevations of 250 – 450 m asl in Mt. Makiling. (Lapitan et al. 2005) were evaluated with the results of a related study on the mating system of P. malaanonan (Lapitan and Hyun 2005), and the regeneration of the species in the study site to identify conservation strategies for the population in this forest. Wright’s FIS was calculated from these data to determine the genetic differences between the samples which can be grouped into two adult populations owing to the different elevation of the area from where they were located. The inbreeding coefficient of the progenies, Fe, of the mating system study was also computed and compared with the parental F value. The formulae used are:…

Sources: 8th Round-Table Conference on Dipterocarps

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