紫翅猪毛菜、钠猪毛菜不同个体大小繁殖分配差异及随海拔的变化

以新疆准噶尔盆地藜科猪毛菜属植物紫翅猪毛菜(Salsola affinis C.A.Mey)、钠猪毛菜(Salsola nitraria Pall)为研究对象,用繁殖分配比例的方法对比分析了两种猪毛菜不同海拔同一种群内不同个体大小繁殖分配的特点,并用异速生长模型分析了不同海拔繁殖生物量与营养生物量之间分配与个体大小的依赖关系。结果发现:1)不同海拔繁殖生物量(R)与营养生物量(V)呈不同程度的异速生长。紫翅猪毛菜随海拔的升高R-V的异速生长斜率显著升高,截距随海拔的升高没有显著增加;而钠猪毛菜的斜率随海拔升高显著降低,截距则显著升高。2)紫翅猪毛菜在较低海拔个体大小与繁殖分配呈负相关,在较高海拔呈正相关;钠猪毛菜在较低海拔个体大小与繁殖分配呈正相关,在较高海拔呈负相关;两种猪毛菜繁殖分配的适应对策相反。3)将同一种群个体大小分成大、中、小3种类型,多重比较发现紫翅猪毛菜在较低海拔,中小个体的繁殖分配显著高于大个体的繁殖分配;在较高海拔,大个体的繁殖分配显著高于中小个体的繁殖分配。钠猪毛菜在较低海拔,大个体的繁殖分配显著高于中、小个体的繁殖分配;在较高海拔,小个体的繁殖分配显著高于大、中个体的繁殖分配。综合分析认为:两个物种随海拔变化产生不同的繁殖分配策略,除遗传效应外,环境和个体大小对钠猪毛菜繁殖分配的变化均产生重要影响,而紫翅猪毛菜繁殖分配的变化主要由海拔差异导致。由于微生境对同一种群的个体大小产生影响,进而产生不同的繁殖分配模式,所以在干旱区更应重视个体大小对繁殖分配的影响。

Influence of altitude and difference of different-sized individuals on reproductive allocation in Salsola affinis C. A. Mey. and Salsola nitraria Pall.

In this study, we focused on two plant species in the genus Salsola (Chenopodiaceae), Salsola affinis C. A. Mey. and Salsola nitraria Pall., which are distributed in the Junggar Basin, Sinkiang, northwest China. We compared the characteristic of within-population reproductive allocation of different-sized plants (large, medium, and small) of S. affinis and S. nitraria at different altitudes using the ratios (the percentage of total biomass in reproductive biomass). In addition, we analyzed the relationship between reproductive biomass (R) and vegetative biomass (V) and the size-dependent allocation at different altitudes using a classical allometric model. We obtained the following results. (1) There were different levels of allometry between the R and V at different altitudes. The allometric slope (exponent) of the R-V relationship increased significantly with increasing altitude for S. affinis; however, there was a significant negative relationship for S. nitraria. We also found a significant positive relationship between the intercept of the regression of log R on log V and elevation for S. nitraria, although the relationship was not significant among populations of S. affinis. (2) There was a negative correlation at lower altitude and a positive correlation at higher altitude for the relationship between individual size and reproductive allocation in S. affinis. Conversely, there was a positive correlation at lower altitude and a negative correlation at higher altitude for the relationship between individual size and reproductive allocation in S. nitraria. This indicates that these Salsola species exhibit contrasting adaptation strategies. (3) Plants within the same population of S. affinis and S. nitraria were divided into three size classes, large, medium, and small. Multiple comparisons showed that, at lower altitudes, the reproductive allocation of small and medium-sized individuals of S. affinis was significantly higher than that of large individuals, but that at higher altitudes, the reproductive allocation of large individuals was significantly higher. In contrast, the reproductive allocation of large individuals of S. nitraria was significantly higher than that of medium-sized and small individuals at lower altitudes, whereas the reproductive allocation of small individuals was significantly higher than that of medium-sized and large individuals at higher altitudes. Comprehensive analysis suggests that two Salsola species adopt different reproductive allocation strategies concomitant with a change in elevation. In addition to the genetic effect, the environment and individual size had significant influences on the variation in reproductive allocation of S. nitraria, whereas individual size in S. affinis had no significant influence on the variation in reproductive allocation with altitude. The microenvironment of the arid Junggar Basin region also had an impact on individual plant size in the same population, and produced different reproductive allocation patterns. We therefore suggest that more attention should be paid to the impact of individual size on reproductive allocation in arid areas.