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).