Seedling adaptation of hybrid pine Pinus densata and its parental species in the high elevation habitat.

In order to test whether P. densata was more fit in its own highelevation niche than its parental species (P. tabuliformis and P. yunnanensis) and describe their adaptative characteristics in the seedling stage，we conducted a comparative analysis of the seedling adaptative characters in three species. The results showed that most of traits in the seedling stage were significantly different among species and populations, and large amount of variance was identified among species or among populations. The survival rate and the rate of budset in October were the best indicators of amongspecies divergence. The hybrid pine P. densata appeared to be intermediate between P. tabuliformis and P. yunnanensis in most of traits in the early stage. Compared with P. yunnanensis, P. densata had higher germination rate and survival rate, which were lower than P. tabuliformis, and the budset date was 30 days later than P. tabuliformis. The hybrid pine P. densata expressed transgression in four traits of seedling height, the ratios of the red seedlings, the purple seedlings and seedlings of secondary growth, which would reflect its unique adaptation in the highelevation niche. P. tabuliformis was the highest in rates of budset and seedling survival. P. yunnanensis was lowest in seedling survival and only the twoyearold seedlings had signal of budset. P. densata had a longer growing season than P. tabuliformis, and stronger adaptation than P. yunnanensis. That could be one of the reasons about P. densata to become a hybrid in the highelvation habitat.