4.4. The link between drought tolerance and local climate
Our results indicated a weak but statistically significant climatic
signal in relation to drought tolerance (Fig. 4). There appears to be a
trend where genotypes from wetter locations
(higher wetness index, WI) tended to be less drought tolerant than those
from drier ones (lower WI) (Fig. 4 and Appendix Fig. A. 4.). Our
findings therefore seem to agree with our expectation i.e. that
genotypes from drier areas would be more drought tolerant than genotypes
from wetter areas, though the low R2 of the
relationship indicates that the observed signal is not very strong.
These results concur with Choat et al., (2007) who observed that
differences in water availability across sites could drive intraspecific
variation among Cordia species. Studies (Bongarten and Teskey,
1986; Peuke et al. , 2002; Baquedano, Valladares and Castillo,
2008) documented that the ecotypes of Pinus taeda , Fagus
sylvatica , Quercus coccifera , had adaptive features which were
probably driven by the local climate. In our results, WI explained
approximately 5% of the variation in drought tolerance in
RGRA across genotypes and further analysis preferably
over a wider climate range as well as WI data obtained from higher
resolution weather data are needed to verify the consistency of this
trend. Next, other factors may affect drought tolerance such as soil
hydraulic properties and local topology. Finally, drought tolerance as
determined in our study experiment may not fully reflect drought stress
in the field (see next section).