巨伞钟报春繁殖策略随海拔梯度的变异

巨伞钟报春(Primula florindae)是报春花属(Primula)的一种二型花柱植物,为青藏高原地区特有种。该研究于巨伞钟报春自然种群在色季拉山的分布下限(3 100m)至上限(林线4 350m)沿海拔梯度设立5个远离人为活动干扰的样点,并选取开花物候、花部结构性状、传粉昆虫、性分配、自然结实5个繁殖表征性状,通过分析比较不同海拔梯度样点的繁殖表征性状之间的差异,明确巨伞钟报春繁殖性状对海拔变化的适应策略,并探讨未来气候变化对巨伞钟报春的分布格局可能产生的影响。研究发现:(1)巨伞钟报春始花时间最早为中海拔种群,其次是低海拔种群,最晚为高海拔种群,而且随海拔高度上升,巨伞钟报春两种表型的花寿命均显著延长;花部结构面积显著增大;访花昆虫种类减少;性分配倾向于偏雌分配,各性状对于不同海拔之间异质环境的适应可能是巨伞钟报春在各海拔繁殖策略上表现出差异的主要原因。(2)随着海拔的上升,巨伞钟报春的开花数显著减少,但虫食数与虫食率也显著降低,最终不同海拔有效座果数和结籽数均无显著差异,表明巨伞钟报春通过应对不同环境形成相应的繁殖策略,在不同海拔均能保证恒定的繁殖成功率,并维持种群的稳定。(3)气候变化将会对巨伞钟报春的分布产生深远影响,其分布下限可能发生上移,但更高海拔地区现有的砂壤环境不适于巨伞钟报春的生长,且传粉昆虫在气候变化综合作用下的时空变异尚不明确,致使其分布上限上移空间有限。研究推测,未来100年内,巨伞钟报春的分布下限可能上移至其现今分布格局的中海拔地区,造成其分布区域缩小。

Altitudinal Variations of the Reproductive Strategies of Primula florindae

Primula florindae is a typical distylous speices of Primula and an endemic species in the Qinghai Tibet Plateau. In this research, we set 5 plots of natural population from 3 100 m to the treeline (4 350 m) along the Sygera Mountains without anthropogenic interference and select flowering phenology, floral display traits, pollinators, sex allocation, and natural seed set as characters. By comparing these characters among five populations along altitudinal gradients, we make certainly the adaptive strategies of reproductive characters to altitudinal variation, and discuss the possible influences of future climate change on distribution pattern of P. florindae. We highlight three conclusions: (1) initial blooming time of P. florindae did not show a correlation with elevation: the middle elevation population bloomed the earliest and the highest population bloomed last. Nevertheless, with the increase of elevation, flower longevity and floral display area of both morphs of P. florindae increased significantly, but varieties of pollinators decreased, and both morphs tend to allocate more resources to assure female sexual function. The adaption of the traits studied to heterogeneity habitats among different elevations may lead to the variation of reproductive strategies. (2) With the increase of elevation, flower number of P. florindae significantly diminished, but both herbivory number and rate also reduced, so effective fruit number of all populations showed no distinct disparity, and there were also no significant differences in seed number, showing that by shaping corresponding reproductive strategies to different environment, P. florindae guaranteed breeding success, then stabilized population in all elevations. (3) Climate change will have profound and lasting impacts on the distribution of P. florindae, the lower altitudinal limit may shift up, but sandy soils at higher elevations are unfavorable to its growth, while the temporal spatial distribution of pollinators under climate change are still unknown. We predict the lower altitudinal limit of P. florindae will move up to middle elevation and result in a decrease in its distribution over the next 100 years.