The Community Context Of Relationships Between Flowering Traits,Nectar Characteristics And Their Effects On Pollination In An Alpine Meadow

Plant-pollinator interaction plays a vital role in maintaining the biodiversity of terrestrial ecosystems.The flower characteristics,such as flower shape,size,color,smell,etc.,were used to attract pollinators,and at the same time nectar and other rewards were produced,which are essential nutrients for pollinators.The different pollinating groups have different nectar nutritional requirements,so they have certain selectivity to plants.These interactions may lead to an adaptive relationship between plants and pollinators.The aim of our study was to explore the relationship between plants and pollinators in the community in combination with the nectar and other floral characteristics.Three study sections were set:1)To explore whether there are phylogenetic limits to the differences in floral traits,phylogenetic signals were tested for 11 floral traits and two nectar traits.The results showed that there were no phylogenetic signals of sugar concentration,phenology,flower opening direction,nectar feeding difficulty and autonomous and self-pollinating.While there were significant phylogenetic signals of nectar volume,sexual system,dichogamy,stigma-anther distance,floral display area,corolla type and inflorescence type.These traits showed high variability at the community level.2)To explore the responses of floral traits to nectar characteristics,redundancy Analysis were used to determine the main "honest signal" in response to nectar characteristics.The results showed that there is no correlation between nectar volume and nectar concentration.The difficulty of nectar obtaining has a significant explanatory for the nectar volume.The Honesty signal would help the pollinator group to judge the nectar reward of the target plant.3)Through redundancy analysis and stepwise regression analysis,the effects of flowering traits and nectar characteristics on visiting preference and visiting frequency of pollinators were investigated.The results of redundancy analysis showed that bumblebees preferred to visit plants with racemes or spikes,flower openings spreading horizontally or at an Angle of 135-180°.The visiting proportion of bumblebees increased with the increase of flower tube length.Diptera prefer to visit plants with erect plants and flower heads.Other bees mainly visited cymes with flower orientations ranging from 90-135°,and other bees also visited the proportion increased with the increase of nectar volume,nectar concentration and flower display area.Apis may not have specific visit preference and belong to generalized pollinators.The stepwise regression results showed that there was a significant positive correlation between visiting frequency and nectar volume,indicating that the higher the floral reward,the more attractive the pollinators were.There was a significant negative correlation between the frequency of floral visits and the length of floral tubes.With the increase of floral tube length,the frequency of floral visits of plant species decreased.It is speculated that this may be because the length of the flower tube is related to the matching rate of the pollinating group.The longer the flower tube is,the longer the tongued of the pollinating group is,and the number of long-tongued pollinators in the community is less than that of short-tongued pollinators.This may explain to some extent the lower visiting frequency of long-tubed flowers.Based on the above research results,we can clarify the specific relationship between the composition of plant pollinators in the community though the floral traits and nectar characteristics.And a clearer scientific understanding of how nectar affects the relationship between plants and pollinators in the community would be obtain.