云南松、思茅松和卡西亚松天然种群间的针叶表型变异

Needle phenotype variation among natural populations of Pinus yunnanensis, P. kesiya var. langbianensis and P. kesiya

研究近缘种复合体的针叶表型变异及其地理分布格局,有助于从生理生态机制上理解针叶树种的地理变异、种群动态以及对区域气候的响应。云南松(Pinus yunnanensis)、思茅松(P.kesiya var.langbianensis)和卡西亚松(P.kesiya)是一个跨越了东南亚热带和亚热带地区的近缘种复合体,具有典型的地理替代分布特征,拥有丰富的表型变异和遗传变异。该研究在3种松树分布区采集了31个代表种群,每个种群选择10个样木,测量了针叶长度、气孔密度、气孔保卫细胞长度和宽度、木质增厚层长度和宽度、气孔腔长度和宽度等共8个性状。采用巢式方差分析计算性状在树种间和种群间的差异,通过主成分分析和聚类分析揭示针叶性状的种群变异结构;分析针叶性状随纬度的变化规律,运用多元线性回归模型来确定影响针叶性状变异的主要环境因子。结果表明:(1)针叶性状在种群间的变异系数为12.01%-34.08%,气孔保卫细胞长度、木质增厚层长度和宽度、针叶长度和气孔密度的表型分化系数较高;(2)云南松和卡西亚松在大多数性状上存在显著差异,思茅松介于二者之间,聚类分析结果表明3种松树针叶性状的种群变异结构与其地理区域分布一致;(3)针叶长度和气孔密度与纬度正相关,气孔腔长度和宽度与纬度负相关;(4)影响针叶性状变化的关键环境因子是最干季平均气温、降水量季节性变异系数、平均气温日较差、最湿月降水量和最干月降水量。3种松树针叶性状具有丰富的种间和种群间变异,呈现显著的纬度梯度变异趋势,反映了其对环境长期适应的结果。热带亚热带松树针叶性状变异及其对环境因子的响应可为造林育种的地理种源选择提供科学依据。

Aims Investigating the needle phenotypic variation and its geographical distribution pattern of related species complexes will aid in understanding conifer geographic variation,population dynamics,and physiological and ecological responses to geographical climates.Here we focus on the Pinus kesiya,P.yunnanensis,and the hybrid species P.kesiyavar.langbianensis,which are primarily distributed across tropical and subtropical Southeast Asia,exhibiting abundant climate and genetic variation.Methods We selected thirty-one representative populations covering the distribution areas of three pine species,and sampled ten individuals from each population.Eight traits were measured,including needle length,stomatal density,stomatal guard cell length,stomatal guard cell width,woody thickening layer length,woody thickening layer width,stomatal cavity length,and stomatal cavity width.Variation between species and populations was assessed using a nested variance analysis.Principal components analysis was applied to evaluate the underlying dimensionality of the needle variation.Clustering analysis among populations was performed using the Ward method to infer the population structure.Pearson’s correlation coefficient between latitude and needle characters was assessed.Finally,a multiple linear regression model was used to identify the main environmental factors influencing needle trait variation.Important findings The variation coefficients of the eight needle traits ranged from 12.01%to 34.08%across populations.The phenotypic differentiation coefficient was higher for stomata guard cell length,woody thickening layer length and width,needle length,and stomatal density.Most morphological needle characteristics were significantly different between P.yunnanensis and P.kesiya,while P.kesiyavar.langbianensis showed intermediate values between the two parental pines.Hierarchical clustering analysis showed that the variation pattern of needle traits was related to geographical region.Needle length and stomatal density were positively correlated with latitude,while the stomatal cavity length and width were negatively correlated with latitude.The key environmental factors affecting the needle traits of the three pine species were mean temperature during the driest quarter,precipitation seasonality,mean diurnal range,precipitation during wettest month,and precipitation during the driest month.The needle traits of the three pine species displayed high interspecific and interpopulation variation.The significant latitudinal gradient trend in needle trait variation indicates long-term evolutionary adaptation to the environment.The response of needle character variation to environmental factors can provide essential insights for geographical provenance selection in afforestation breeding.