The genetic diversity within and between four natural Arbutus unedo L. populations in Portugal was
investigated using morphological characters, inter-simple sequence repeats (ISSR) and random amplified
polymorphic (RAPD) markers, for a proper conservation of this resource. The results showed a high
morphological variation between and within-populations. The dry-weight, length, width and peduncle
length of the leaves were the most discriminating characters, being responsible for 52.6% of the total variation.
The molecular analysis, based on both RAPD and ISSR, indicated moderate genetic diversity within
populations, with values of Nei’s gene diversity ranging from 0.16 to 0.39 and the Shannon’s diversity
from 0.24 to 0.57. The highest genetic diversity occurred within Braganc¸ a population. At the species level,
the genetic variation was mainly within populations (75%), suggesting a low-moderate genetic differentiation
among populations. The high level of gene flow estimated among populations (1.499) showed to
be the main reason for their low differentiation. The cluster analysis showed that only one population
formed a distinctive cluster. The remaining formed a second cluster due to their geographical approach,
which has been showed to affect significantly the genetic distances among populations. No correlation
between RAPD and ISSR markers, and between the molecular and morphological data was found. From
the conservation point of view it is proposed to combine both in- and ex situ approaches. The maintenance
of sufficient gene flow and the increase of the effective population sizes are the main in situ actions
proposed. The ex situ conservation, should involve the collection of a high number of individuals within
populations.
