| Long term overgrazing has led to increasingly serious grassland degradation.The rapid diffusion and spread of toxic plants in natural grassland has significantly changed the community structure of grassland.The restoration of large-scale degraded grassland is imminent.However,people’s attention to poisonous plants is more focused on prevention and control,utilization and development of secondary metabolites,etc.There is a lack of relevant research on the ecological adaptability of toxic organisms to environmental conditions and the relationship between toxic plants and other species.Stellera chamaejasme is a poisonous plant widely distributed in China.Its flowers have strong fragrance and bright color.It is an insect-borne plant that depends on seeds to reproduce offspring.S.chamaejasme has self-incompatibility and its flower volatiles play an important role in attracting a large number of flower visiting insects to complete pollen transmission and improving seed setting rate of seed plants.It is of great significance for scientific management of natural grassland and restoration of degraded grassland to further study the effects of environmental factors on the floral components and flower visiting insects of S.chamaejasme and reveal the ecological mechanism of S.chamaejasme pollination adaptability under different habitat conditions.Based on the scientific purpose of clarifying the differences of components and contents of S.chamaejasme flowers in different habitats,exploring the differences of species and diversity of flower visiting insects,and revealing the relationships between ecological factors,floral components and flower-visiting insects.In this study,the floral volatile of S.chamaejasme was taken as the starting point,and five research sites were selected: Hailar,Inner Mongolia,Guyuan,Hebei,Yajiang,Sichuan,Hongyuan,Sichuan and Nagqu,Tibet.Different habitats and different flower colors of S.chamaejasme were selected as the research objects.We measured the content of floral components,investigated the diversity of flower-visiting insects and analyzed the the correlation between atmospheric temperature,air humidity,soil moisture,floral components of S.chamaejasme and flower visiting insects.The main results and conclusions are as follows:(1)The differences of temperature,humidity and soil water content in different areas had significant effects on the floral components and content of S.chamaejasme.In Hailar and Naqu area,the relative abundance of esters methyl salicylate and benzyl acetate were49.65% and 36.12%,significantly higher than those in other sites;the relative abundance of syringaldehyde and syringol in Guyuan and Naqu were significantly higher than those in other areas,of which 45.20% were in Naqu region;In Yajiang area,alkanes are abundant only in Yajiang area,accounting for 50.20%.Compared with daytime,the relative abundance of terpenes in floral volatile at night increased significantly,up to 55.34% in Naqu area.However,the relative abundance of esters showed the opposite trend.The regression analysis of floral components and environmental factors showed that temperature and the relative abundance of esters and terpenes were significantly negatively correlated.The drought and low humidity could alleviate this inhibitory effect,and a certain range of high temperature and low humidity environment could promote the synthesis of alkanes.(2)The differences in floral composition of S.chamaejasme resulted in different pollination patterns in different areas.In Hailar area,the daytime and night time floral components were mainly methyl salicylate and lilac,which only pollinated at night.S.chamaejasme released a large amount of dodecane and tetradecane in Yajiang area during the daytime,while 3-methyl-1,3-pentanediol was the main alcohol at night,forming a pattern of pollination only during the day.The components of flowers in Guyuan and Hongyuan were similar,and benzyl acetate and terpenes were the main components in both day and night,which was a mixed pollination strategy.(3)The flower-visiting insects of S.chamaejasme were adapted to the characteristics of flower structure.The height of corolla tube in Yajiang area was significantly higher than that in Hailar area,which was consistent with the fact that S.chamaejasme mainly relied on butterflies for pollination in Yajiang area,and only depended on moths for pollination in Hailar area.In conclusion,in the process of mutual selection between the same plant and different pollinators in different habitats,obvious differentiation of flower characteristics can promote the adaptation to pollination.(4)The pollination adaptation strategy of S.chamaejasme flower visiting insects was the result of the combined effect of environmental factors and floral components.The results of PLS-SEM model showed that temperature could directly promote or inhibit flower visiting insects,and could also indirectly regulate insect diversity by affecting flower volatiles.Temperature promotes the release of alkanes and attracts a large number of different butterflies and bud flies;temperature has obvious inhibitory effects on esters and terpenes,especially benzyl acetate,syringaldehyde and syringol,which play an important role in attracting day and night insects.Overall,this study systematically expounded the diurnal and nocturnal differences in flower volatiles and flower-visiting insects in different habitats during the day and night,discussed the regulation of the main components of flower volatiles on the diversity of flower-visiting insects.This work also revealed the pollination adaptation strategy and reproductive ecological mechanism of S.chamaejasme in different habitats.It can be seen that in the long-term adaptation and evolution process of different habitats,the S.chamaejasme adapts to the flower-visiting insects by changing the floral composition,content of each component and flower structure.It gradually forms different pollination adaptation strategies to improve the ability of the wolf venom population to reproduce and expand. |
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