高山极端环境下的繁殖策略:刺芒龙胆的可塑性花寿命及蝇类传粉

Reproductive strategies in alpine extreme environments: the plastic flower longevity and fly pollination in Gentiana aristata

关键词:  刺芒龙胆, 龙胆属, 传粉生物学, 繁育系统, 高山环境

Key words:  Gentiana aristata, Gentiana, pollination biology, breeding system, alpine environment

摘要:

刺芒龙胆(Gentiana aristata)作为龙胆属典型高山植物,是解析物种对极端环境适应机制、开发特色药用活性成分及选育耐寒观赏新种质的理想研究材料。为揭示刺芒龙胆的传粉生物学特征及其对高山极端环境的繁殖适应策略,该研究采用野外观测与控制实验相结合的方法,系统探究其开花动态、花粉活力、柱头可授性、花粉/胚珠比(P / O)、繁育系统及传粉昆虫组成等繁殖特征。结果表明:(1)刺芒龙胆具有雌雄异位和不完全雌雄异熟现象,单花花期为(5.97±0.19)d,在隔离昆虫条件下,花期显著延长至(16.13±0.78)d,表现出对高山多变传粉环境的一种适应策略。(2)刺芒龙胆的花粉活力与柱头可授性均可维持约4 d,其中花粉活力在开花第2天达到峰值,柱头可授性则在柱头完全开放后第2天达到最高水平。(3)繁育系统结果表明,不去雄套袋存在结实,推测该结果主要由花冠暂时性闭合引发的自动自交以及蓟马(Thripidae spp.)和蚂蚁(Formica spp.)等小型昆虫的协助自交所致; 去雄后自然传粉和不去雄套袋的坐果率和结籽率较低且无显著性差异,表明自交和异交的结实能力相似,但均低于自然传粉。(4)刺芒龙胆的传粉昆虫以灰地种蝇(Delia platura)为优势类群,其访花次数占总访花次数的55.17%,访花频率为(0.24±0.04)times·flower^-1·h^-1,其余传粉昆虫包括多种蝇类和甲虫等。综上认为,刺芒龙胆花寿命可塑性强,具有异交与自交并存的混合交配方式,其主要传粉者为数量丰富、访花频率较高的蝇类,上述特征是该物种适应高山传粉环境不确定性的关键繁殖策略。该研究结果为刺芒龙胆种质资源保护与药用开发提供了关键理论支撑。

Abstract:

Gentiana aristata, a typical alpine species of the Gentiana genus, serves as an ideal research material for analyzing species adaptation mechanisms to extreme environments, developing distinctive medicinal bioactive compounds, and breeding cold-resistant ornamental germplasm. To uncover the pollination biology characteristics of G. aristata and its reproductive adaptation strategies to alpine extreme environments, this study employed a combination of field observations and controlled experiments to systematically investigate its reproductive traits, including flowering dynamics, pollen viability, stigma receptivity, pollen/ovule ratio(P/O), breeding system, and composition of pollinating insects. The results were as follows:(1)G. aristata exhibited herkogamy and incomplete dichogamy. The longevity of individual flower of G. aristata was(5.97±0.19)d, which significantly extended to(16.13±0.78)d under insect-excluded conditions, representing an adaptive strategy to the variable pollination environment in alpine regions.(2)Both pollen viability and stigma receptivity of G. aristata were maintained for approximately 4 d, with pollen viability peaking on the second day after anthesis and stigma receptivity reaching its maximum on the second day after the stigma fully opened.(3)The results of breeding system showed the fruit setting in bagging without emasculation flowers was primarily attributed to autonomous selfing via temporary corolla closure and assisted selfing by small insects like thrips(Thripidae spp.)and ants(Formica spp.). The fruit setting rates and seed setting rates were low and showed no significant difference between those flowers under natural pollination after emasculation and bagging without emasculation, indicating that both selfing and outcrossing have similar reproductive success, but both were lower than that under natural pollination.(4)The main pollinator of Gentiana aristata was Delia platura, which accounted for 55.17% of all flower visits, with a visit frequency of(0.24±0.04)times·flower^-1·h^-1. In addition to D. platura, other pollinators included various flies and beetles. In summary, Gentiana aristata exhibits high plasticity in flower longevity and possesses a mixed mating system combining selfing and outcrossing. Its main pollinators are abundant flies that show relatively high floral visitation frequency. These traits collectively represent a key reproductive strategy for adapting to the unpredictability of alpine pollination environments. The findings provide critical theoretical support for the conservation of G. aristata germplasm resources and its medicinal development.