油松伊云南松人工杂种与亲本种在高山松生境下的苗期指标对比分析
Comparison analysis of seedling traits for hybrids between Pinus tabuliformisⅹP. yunnanensis and its parental species in P. densata habitat site.
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摘要: 在油松与云南松人工杂交并获得杂种的基础上,采用多杂交组合杂种、亲本种和高山松种子在高山松最适宜 生境下(西藏林芝)进行了田间对比试验,并通过苗期的适应性指标和生长指标来论证高山松及其亲本种间生态分 化及杂种高海拔特殊生境适应性的来源。结果表明:1)多数适应性指标上,油松伊云南松杂种苗木与高山松表现 相似;2)油松伊云南松不同杂交组合苗木间的适应性指标有一定幅度变异,一些群体有更高的封顶率和保存率;3) 油松苗木的适应性指标最高,云南松最低,高山松适应性指标介于两者间;4)高山松生长指标最高,油松生长指标 最低;5)与亲本不同,高山松与杂种苗木在第2 年均有二次生长现象,且比率相似;6)最好杂交组合苗木生长与高 山松相似,高山松与人工杂种苗木在高海拔生境下表现了突出的适应性与生长综合优势,具有在该生境条件下优 于亲本种的发展潜力。以上结果表明,在特定条件下种间杂种具有一定的生态适应性优势,生态选择在高山松高 海拔特殊生境下进化成种的过程中起到了关键作用。Abstract: Pinus densata had been suggested by genetic analyses to be a homoploid hybrid pine originated from natural hybridization between P. tabuliformis and P. yunnanensis. The alpine habitat of P. densata is distributed in southeastern Tibet between 2 700 and 4 200 m above sea level, exceeding that of its two parental species. To understand the ecological differentiations among these pines and investigate the mechanisms involved in hybrid adaptation to diverged niche, lines of artificial hybrid were built up and field comparison incorporating the natural hybrid pine, parental pines and the artificial pines, was applied in a typical habitat of the natural hybrid pine (Linzhi, Tibet). Ten traits of seedling validity and six traits of seedling growth were examined. Our results suggested that:1) the artificial hybrids (P. tabuliformisⅹP. yunnanensis) and P. densata displayed similar characteristics on most traits for seedling validity; 2) the artificial lines of hybrids were divergent in the traits by their origin, and some of them exhibited higher rates of bud-set and survival; 3) seedlings of P. tabuliformis had the highest validity,seedlings displayed highest performance in growth traits, while P. tabuliformis displayed the lowest; 5) in contrast to the parents, the phenomenon of diauxic growth in the second year was found in both the seedlings of P. densata and the artificial hybrids in similar percentage; 6) a line of artificial hybrid resembled the natural hybrid in most of the traits examined. Both the seedlings of natural and artificial hybrids exhibited superiority in both validity and growth under the habitat of high elevation, implying more developmental potential than their parental species in the alpine habitat. This study provides evidences for ecological speciation of P. densata via hybridization of P. tabuliformis and P. yunnanensis, and highlights the important role of ecological selection in the colonization of the Tibetan Plateau for hybrid pine. P. yunnanensis had the lowest, and P. densata was intermediated to its parents; 4) natural hybrid
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