Contrasting ecotypic differentiation for growth and survival in Pinus canariensis
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We tested genetic and environmental effects and their interaction on the behaviour of 21 provenances of Pinus canariensis Chr.Sm. Ex DC from the Canary Islands and three seed sources from Israel at seven study sites covering a wide range of ecological conditions. Survival and growth traits (height, diameter and polycyclism) and their relationship with environmental parameters were assessed to evaluate their adaptive value and establish patterns of variation of the species inside and outside its natural distribution area. The results showed a high level of ecotypic differentiation for survival. As a general pattern, seed sources from favourable environments exhibited lower survival rates at dry sites than those from harsh environments (r=-0.76, P<0.05, between survival and site index at the seed source). By contrast, growth traits presented a high phenotypic plasticity, scarce differentiation among seed sources and a negligible genotype x environment interaction. With few exceptions, local provenances from the Canary Islands did not stand out for survival or growth when compared with the rest at each trial site, whereas local seed sources from Israel were among the best growing and survived better at the experimental sites in this country. Therefore, the possibility of a locally adapted land race in Israel is discussed. We also discuss the low geographic differentiation for growth in the Canary Islands pine in the light of the current knowledge of the species' life history and the potential use of this species in reforestation programs in semi-arid environments.
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