Page 16 -

โครงการรวบรวมและจัดทําวารสารอิเล็กทรอนิกส์ มหาวิทยาลัยเกษตรศาสตร์

14 Thai J. For. 31 (1) : 10-19 (2012)

(H = 0.2205 and I = 0.3313), C. insulari- C. porrectum in the Krabi and Phuket
e
montanum (H = 0.1639 and I = 0.2393) populations had few remnant individuals.
e
(Ho, 2006), and C. camphora (H = 0.2564 Based on the Gst value, most of the
e
and I = 0.4003) (Ju and Wang, 2008). Hamrick genetic differentiation of C. porrectum was
and Loveless (1989) found that tropical trees within a population (64.49 %) which was
tended to present high levels of genetic similar to some other species in the same
diversity which was related to their life genus using ISSR markers, such as
history and ecological characteristics such C. osmophloeum (71.63 %), C. macrostemon
as a wide geographical range, outcrossing, (57.81 %), C. insulari-montanum (50.12
and biotic dispersal. On the basis of life history %) (Ho, 2006), and C. camphora (51.19
characteristics, C. porrectum is a long-lived, %) (Ju and Wang, 2008). Besides depending
woody and perennial tree species. In addition, very much on the gene pool and geographic
the mating system can influence the levels range of the species as a whole, the situation
of genetic diversity. Outcrossing species of population differentiation was related to
commonly have considerably higher levels life history traits. In addition,the mating system
of genetic diversity than selfing species played a critical role for the population
(Hamrick and Godt, 1989). Uthairatsamee genetic structure. In outcrossing species,
(2011) concluded that C. porrectum was genetic differentiation occurred less than
‘facultative outcrossing’. The combination 20% among populations (Hogbin and Peakall,
of these life history traits should enable the 1999). Although outcrossing species generally
species to maintain a high level of genetic have lower levels of population differentiation
diversity. (Hamrick and Godt, 1989; Hogbin and Peakall,
The Songkhla and Phangnga 1999), a higher level of genetic differentiation
populations had more genetic variation, was detected among populations of some
followed by the Satun, Phatthalung, Phuket, endemic and outcrossing species such as Litsea
and Krabi populations, respectively. This result szemaois (Ci et al., 2008) and, C. porrectum.
was related to population size. Nevertheless, Based on the field observation, there were
the population size was not correlated with numerous seedlings close to their presumed
genetic diversity in the cases of the Songkhla maternal trees. This suggested that fruit dispersal
and Phangnga populations. The population of C. porrectum was mainly by gravity and
size of Songkhla was smaller than for the such limited dispersal could strongly influence
Phangnga population but it showed higher the genetic diversity within and among
genetic diversity. This is agreed with the populations. Although there was no direct
studies of many plants (Schmidt and Jensen, report on pollination in C. porrectum, it
2000; Tero et al., 2003; Kang et al., 2005). probably relied on small g eneralist insects,
The results demonstrated that the uneven based on pollination studies of other species
distribution of genetic diversity wais in Cinnamomum spp. with similar floral
substantially and apparently related to the structure and habitat (Fan et al., 2006). Pollen
habitat (Lu et al., 2006). The genetic diversity dispersal was limited in insect pollinated
at the population level of this species was plants compared to the distances travelleds
very low in the Krabi and Phuket populations by wind- dispersed pollen and this tends to
(H = 0.0699 and 0.1097, respectively). increase population differentiation (Hamrick
e
Masayuki (2003) stated that a critical factors and Loveless, 1989; Hamrick and Godt,
affecting low genetic diversity within a 1989).
population was the number of remnant The indirect estimation of the level
individuals. Based on the field survey, of gene flow of C. porrectum was moderate