o_19ko2dt161ng2j4e1tgnoqv1s45a.pdf

LEE et al (2007)
Even if the habitat remains untouched, all populations face some risk of decline through exposure
to the vagaries of natural temporal and spatial variations, such as environmental and demographic
variations. Hence, monitoring of population size should also be conducted at appropriate intervals
to detect any drastic reduction so that timely management prescriptions can be provided to
ensure their health.
At five-year intervals, the populations should be enumerated to determine its size distribution,
mortality, recruitment, population growth and other demographic variables. The information
generated helps to understand the mechanisms that influence population behavior and can be
used to predict population trends. In addition, genetic assessment should also be conducted to
determine population bottlenecks and inbreeding depression. The 8-ha study plot is already
available for Sungai Pinang and this should be included in the core area. A similar study plot
shall be established in Pangkor Selatan, Segari Melintang, Lumut and Teluk Muroh. Although
monitoring is an expensive process in terms of time and resources, it is the only way to ensure
that S. lumutensis is conserved effectively.
A management plan for the conservation areas must be developed to regulate human intervention
in a manner that ensures the population viability of the target species is maintained or enhanced
(Maxted et al. 1997a). Given the large amount of genetic diversity detected presently,
S. lumutensis should have enough genetic resources necessary for short-term ecological
adaptation and for long-term evolutionary change. However, all the populations exhibited high
positive values of fixation index, an indication of homozygote excess, which might indicate
depression due to inbreeding. In Sungai Pinang, the inbreeding depression can be either due to
high selfing rate or biparental mating. Inbreeding causes the loss of heterozygosity with no
change in allele frequencies, because continuous selfing and mating between relatives will
purge the deleterious recessive alleles and expose them as homozygotes to the environment
(Oostermeijer et al. 2003). It is generally agreed that inbreeding is associated with increased
seed abortion, low germination rates, high seedling mortality, and poor growth and flowering
of the offspring (Dudash & Carr 1998). Thus, if a population consists of less than 60 reproductive
individuals, the priority should be to enlarge the population size to minimize inbreeding
depression due to small population size. If a population consists of a few hundred reproductive
individuals, thinning is required to reduce the degree of spatial genetic structure and thus
minimize the inbreeding depression due to biparental mating.
The direct estimation of gene flow showed that its pollen flow is not extensive, which might
indicate that its pollen do not cross large forest openings. Because the five populations were
isolated from each other due to geographical barrier or fragmentation, if the populations are
allowed to exist in small population sizes for a long period of time, it is expected that the loss
of genetic variation by drift cannot be compensated for by immigration of seeds or pollens
from other populations. This leads to genetic erosion and increased genetic differentiation among
populations. Consequently, low levels of genetic diversity might reduce evolutionary potential
and increase the probability of population extinction. The most effective way to counter genetic
risks is to allow for migration, i.e., the exchange of pollen and seeds with neighbors. The idea
of habitat corridors initially developed for animal conservation (Simberloff & Cox 1987) might
be an option, and provided resources are available, this approach may be applied to bridge the
Sungai Pinang population with that in the Pangkor Selatan, and Teluk Muroh population with
the Lumut population.
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