Norwati Muhammad

Genetic Diversity and Outcrossing Rate between Undisturbed and Selectively Logged Forests of Shorea curtisii (Dipterocarpaceae) Using Microsatellite DNA Analysis

To evaluate the effect of flowering tree density on genetic variation in a dominant tree species, genetic diversities and outcrossing rates of Shorea curtisii (Dipterocarpaceae) were compared between undisturbed and selectively logged forests using microsatellite markers. The mean heterozygosity and the effective number of alleles per locus in the selectively logged plot were not significantly different from those of the undisturbed plot. However, the average number of alleles derived from the pollen donor was significantly lower in the selectively logged forests, indicating the possibility of a loss of genetic variation in future generations. The average outcrossing rate for 11 trees in an undisturbed plot was 96.3%, which was similar to other reports from dipterocarp species based on isozyme analysis. However, the outcrossing rate in the selectively logged plot was 52.2% for five trees, which was significantly lower than that in the undisturbed plot. This decline of outcrossing rate in the selectively logged plot may result from the much lower density of conspecific flowering trees, and the high rate of selfing may result in inbreeding depression and/or a decrease in genetic variation of this forest in future generations.

Selfing and inbreeding depression in seeds and seedlings of Neobalanocarpus heimii (Dipterocarpaceae).

We evaluated the degree of selfing and inbreeding depression at the seed and seedling stages of a threatened tropical canopy tree, Neobalanocarpus heimii, using microsatellite markers. Selection resulted in an overall decrease in the level of surviving selfed progeny from seeds to established seedlings, indicating inbreeding depression during seedling establishment. Mean seed mass of selfed progeny was lower than that of outcrossed progeny. Since the smaller seeds suffered a fitness disadvantage at germination in N. heimii, the reduced seed mass of selfed progeny would be one of the determinants of the observed inbreeding depression during seedling establishment. High selfing rates in some mother trees could be attributed to low local densities of reproductive individuals, thus maintenance of a sufficiently high density of mature N. heimii should facilitate regeneration and conservation of the species.

MICROSATELLITE ANALYSIS OF THE BREEDING SYSTEM AND SEED DISPERSAL IN SHOREA LEPROSULA (DIPTEROCARPACEAE)

To understand the breeding system and seed dispersal in Shorea leprosula (Dipterocarpaceae) in Peninsular Malaysia, a microsatellite analysis was conducted of embryos of immature and mature fruits fallen in litter traps under the crowns of five trees. Outcrossed and selfed progeny mothered by the trees and those dispersed from other trees were distinguished by genotypes of three polymorphic microsatellite loci. The mean outcrossing rate of mature fruit embryos in S. leprosula pollinated by thrips (0.91) was not lower than those previously reported from Shorea species pollinated by bees, even though thrips seem to be less efficient pollinators than bees. Although four of the five trees showed high and stable outcrossing rates during fruit maturation, the outcrossing rate increased in one tree with highly selfed embryos of immature fruits. These results suggest that inbreeding depression during fruit maturation as well as self‐incompatibility reduce the proportion of inbred embryos. The proportion of fruits dispersed from neighbor trees in fruits trapped under a tree crown had a mean value of 0.20 and was lowest under the tree with highly selfed embryos of immature fruits. This low fraction of dispersed fruits under this tree suggests long distances from this tree to reproductive neighbors, which may reduce cross pollination.

Paternity analysis-based inference of pollen dispersal patterns, male fecundity variation, and influence of flowering tree density and general flowering magnitude in two dipterocarp species

BACKGROUND AND AIMS Knowledge of pollen dispersal patterns and variation of fecundity is essential to understanding plant evolutionary processes and to formulating strategies to conserve forest genetic resources. Nevertheless, the pollen dispersal pattern of dipterocarp, main canopy tree species in palaeo-tropical forest remains unclear, and flowering intensity variation in the field suggests heterogeneity of fecundity. METHODS Pollen dispersal patterns and male fecundity variation of Shorea leprosula and Shorea parvifolia ssp. parvifolia on Peninsular Malaysian were investigated during two general flowering seasons (2001 and 2002), using a neighbourhood model modified by including terms accounting for variation in male fecundity among individual trees to express heterogeneity in flowering. KEY RESULTS The pollen dispersal patterns of the two dipterocarp species were affected by differences in conspecific tree flowering density, and reductions in conspecific tree flowering density led to an increased selfing rate. Active pollen dispersal and a larger number of effective paternal parents were observed for both species in the season of greater magnitude of general flowering (2002). CONCLUSIONS The magnitude of general flowering, male fecundity variation, and distance between pollen donors and mother trees should be taken into account when attempting to predict the effects of management practices on the self-fertilization and genetic structure of key tree species in tropical forest, and also the sustainability of possible management strategies, especially selective logging regimes.

Molecular database for classifying Shorea species (Dipterocarpaceae) and techniques for checking the legitimacy of timber and wood products.

The extent of tropical forest has been declining, due to over-exploitation and illegal logging activities. Large quantities of unlawfully extracted timber and other wood products have been exported, mainly to developed countries. As part of the export monitoring effort, we have developed methods for extracting and analyzing DNA from wood products, such as veneers and sawn timbers made from dipterocarps, in order to identify the species from which they originated. We have also developed a chloroplast DNA database for classifying Shorea species, which are both ecologically and commercially important canopy tree species in the forests of Southeast Asia. We are able to determine the candidate species of wood samples, based on DNA sequences and anatomical data. The methods for analyzing DNA from dipterocarp wood products may have strong deterrent effects on international trade of illegitimate dipterocarp products. However, the method for analyzing DNA from wood is not perfect for all wood products and need for more improvement, especially for plywood sample. Consequently, there may be benefits for the conservation of tropical forests in Southeast Asia.

Nuclear and chloroplast DNA phylogeography reveals Pleistocene divergence and subsequent secondary contact of two genetic lineages of the tropical rainforest tree species Shorea leprosula (Dipterocarpaceae) in South‐East Asia

Tropical rainforests in South‐East Asia have been affected by climatic fluctuations during past glacial eras. To examine how the accompanying changes in land areas and temperature have affected the genetic properties of rainforest trees in the region, we investigated the phylogeographic patterns of a widespread dipterocarp species, Shorea leprosula. Two types of DNA markers were used: expressed sequence tag‐based simple sequence repeats and chloroplast DNA (cpDNA) sequence variations. Both sets of markers revealed clear genetic differentiation between populations in Borneo and those in the Malay Peninsula and Sumatra (Malay/Sumatra). However, in the south‐western part of Borneo, genetic admixture of the lineages was observed in the two marker types. Coalescent simulation based on cpDNA sequence variation suggested that the two lineages arose 0.28–0.09 million years before present and that following their divergence migration from Malay/Sumatra to Borneo strongly exceeded migration in the opposite direction. We conclude that the genetic structure of S. leprosula was largely formed during the middle Pleistocene and was subsequently modified by eastward migration across the subaerially exposed Sunda Shelf.

Impact of logging on genetic diversity in humid tropical forests.

Sustained management of natural forests depends on their ability to regenerate. Successful regeneration of forests accompanied by conservation of genetic diversity of its species is important for both short-term adaptation to environmental change and long-term impact on species and communities (Templeton 1995).

Can Tiny Thrips Provide Sufficient Pollination Service During a General Flowering Period in Tropical Rainforest

One of the most crucial and interesting topics in tropical rainforest research is the pollination systems adapted to mast species, which flower massively at multiyear intervals. Highly fecund flower thrips are the primary pollinators and can respond rapidly to such an abrupt increase of flowers. Because thrips are minute and rather weak flyers, however, it had remained unclear to what extent they could contribute to cross-pollination of mast species growing at low population densities. However, microsatellite DNA analyses of single pollen grains adhering to pollinators, combined with the direct observation of flower visitors with the aid of canopy observation systems, revealed the pollination efficiency of flower thrips during the masting period. In this study of Shorea acuminata, the principal flower visitors were flower thrips, accounting for more than 60% of the collected insects during the flowering time. The thrips visitation pattern was clearly synchronous with the flowering phenology of S. acuminata. However, the genetic analysis of pollen grains suggested geitonogamous self-pollination by flower thrips. Thus, flower thrips made a small contribution to the outcrossing of S. acuminata, although their high visitation frequency on S. acuminata synchronous with the flowering phenology of the trees brought about vast production of self-pollinated seeds. On the other hand, the greater genetic diversity of seeds than that of their adherent pollen load implied the existence of other pollinators that provide sufficient pollination service for S. acuminata. In this study, lygaeid and plant bugs (Hemiptera) were collected frequently (12.2%), placing them third after flower and stipule thrips. Lygaeid bugs typified by big-eyed bugs (Geocoris and Piocoris) are known to prey on thrips, and their visitations to S. acuminata trees increased with increasing numbers of flower thrips. Thus, it was considered that outbreaks of flower thrips may attract the visitation of lygaeid bugs to flowering S. acuminata trees as edible resources during the general flowering period, and such an ecological food chain would provide high levels of genetic diversity of seeds and promote sufficient pollination service for S. acuminata.

PCR-RFLP analysis of mitochondrial DNA cytochrome b gene among Haruan (Channa striatus) in Malaysia.

Haruan (Channa striatus) is in great demand in the Malaysian domestic fish market. In the present study, mtDNA cyt b was used to investigate genetic variation of C. striatus among populations in Peninsular Malaysia. The overall population of C. striatus demonstrated a high level of haplotype diversity (h) and a low-to-moderate level of nucleotide diversity (π). Analysis of molecular variance (AMOVA) results showed a significantly different genetic differentiation among 6 populations (F(ST)=0.37566, P=0.01). Gene flow (Nm) was high and ranged from 0.32469 to infinity (∞). No significant relationship between genetic distance and geographic distance was detected. A UPGMA tree based on the distance matrix of net interpopulation nucleotide divergence (d(A)) and haplotype network of mtDNA cyt b revealed that C. striatus is divided into 2 major clades. The neutrality and mismatch distribution tests for all populations suggested that C. striatus in the study areas had undergone population expansion. The estimated time of population expansion in the mtDNA cyt b of C. striatus populations occurred 0.72-6.19 million years ago. Genetic diversity of mtDNA cyt b and population structure among Haruan populations in Peninsular Malaysia will be useful in fisheries management for standardization for Good Agriculture Practices (GAP) in fish-farming technology, as well as providing the basis for Good Manufacturing Practices (GMP).

Non-Density Dependent Pollen Dispersal of Shorea maxwelliana (Dipterocarpaceae) Revealed by a Bayesian Mating Model Based on Paternity Analysis in Two Synchronized Flowering Seasons

Pollinator syndrome is one of the most important determinants regulating pollen dispersal in tropical tree species. It has been widely accepted that the reproduction of tropical forest species, especially dipterocarps that rely on insects with weak flight for their pollination, is positively density-dependent. However differences in pollinator syndrome should affect pollen dispersal patterns and, consequently, influence genetic diversity via the mating process. We examined the pollen dispersal pattern and mating system of Shorea maxwelliana, the flowers of which are larger than those of Shorea species belonging to section Mutica which are thought to be pollinated by thrips (weak flyers). A Bayesian mating model based on the paternity of seeds collected from mother trees during sporadic and mass flowering events revealed that the estimated pollen dispersal kernel and average pollen dispersal distance were similar for both flowering events. This evidence suggests that the putative pollinators – small beetles and weevils – effectively contribute to pollen dispersal and help to maintain a high outcrossing rate even during sporadic flowering events. However, the reduction in pollen donors during a sporadic event results in a reduction in effective pollen donors, which should lead to lower genetic diversity in the next generation derived from seeds produced during such an event. Although sporadic flowering has been considered less effective for outcrossing in Shorea species that depend on thrips for their pollination, effective pollen dispersal by the small beetles and weevils ensures outcrossing during periods of low flowering tree density, as occurs in a sporadic flowering event.