Plant Color Diversity Under The Vision Of Visiting Insects In Yulong Snow Mountain, Northwest Yunnan

Flower color is one of the most important floral traits mediating the plant-pollinator interaction.Compared with floral scent,which is hard to track and hard to target the signal due to its volatility,floral color is generally the final and key cue for pollinators to locate a flower.Flower colors of angiosperms show extremely high diversity in the vision of human beings However,pollinating animals,especially pollinating insects' visual systems are different with ours and also vary among different insect taxa.There,this project is aimed to explore floral UV-pattern,which under the wavelength that human are not sensitive to but most of insects(bees)are sensitive to it.China is one of countries in the world with highest plant diversity,the Mountain of Southwest China a mega-biodiversity hotspots all over the world.In this region,it harbors the richest apline plant species.However,in China,the floral color studies are still rare.Our study will fill the gaps of floral color study in China,will allow us for a better understanding of floral color in extremely environments on the Mountains of Southwest China.Therefore,in this project,we used a newly developed technique,false-color photography to take photos for alpine and subalpine plant flowers on Yulong Snow Mountain of Northwest Yunnan following an elevation gradient from 2700m to 4200m.We then analyzed the UV photos and investigate the floral UV-pattern.We further analyzed the elevation distribution of floral UV-pattern among taxa,explored whether there were new floral UV-pattern types at such extreme environments;and also checked if the ultraviolet color was an adaptative strategy for flowers living in high altitudes with stronger UV radiation.In total,we took false color photographs for 326 species,and processed and analyzed their floral color pattern,we found that 32%of the total species(n = 103)have floral UV-pattern,but we did not found out a significant trends of elevation change of the proportion of UV pattern;we discovered a new type of floral UV-pattern nectar mimicry;furthermore,flowers among different species showed uv-reflecting and uv-absorbing of their petals adaxially and abaxially differed,which might be an adaptive strategy to against UV harm to pollen grains.1.Floral UV-pattern diversity and its altitudinal distributionIn total,we took and analyzed UV photos for 326 species on Yulong Snow Mountain along six 6 altitudes(2700-4200m).We defined floral UV-pattern as follow:floral parts within one flower showing significant difference of UV-reflecting and UV-absorbing.Following this definition,we classified floral UV-pattern as three types:bull's eye,nectar mimicry t and others type(which it shows difference of a flower's UV-reflecting and UV-absorbing but obviously not belonging to the previous two types).There were 32%of species(103)comprised floral UV-pattern.We found out these three types of floral UV-pattern among species showed no any distribution tendency and more likely randomly distributed in different locations.Therefore our results does not support the hypothesis that the floral UV-pattern were more common in the habitats in the higher altitudes with increased UV radiation.2.The new type of floral UV-pattern:nectar mimicryA new type of mimicry phenomenon:nectar mimicry,was discovered by false-color photography using our database collected in Yulong Snow Mountain.We found tiny structures within flowers show striking distinction of incident light reflection and absorption between the glossy area and the adjacent non-glossy area,for example,the staminodes tips in parnassia and the protuberance of petals in Saxifraga spp.This reflection is as how real nectar droplets reflect the light that caused by mirror-angle,thus it can be categorized as a new mimicry phenomenon and it does not vary for humans even with different color hue.The RGB value show significant difference in UV,green and blue wavelength,which under each wavelength the RGB value of the glossy area is much more higher than the adajcent non-glossy area,and most significantly higher in UV.Even though the structure with this phenomenon which caused by mirror-angle is very tiny,previous studies had proved that the insects(bees and flies)can recognize these nanometer-structures,so this mimicry should be a kind of nectary guide and attracts insect pollinators to target the location of nectar.3.Whether the ultraviolet color of petals adaxial side and abaxial side has the protection function for pollensFloral UV-pattern presents different UV-reflection and UV-absorption in a flower indicating where the UV-absorbing pigments mainly located in the flower.These UV-absorbing pigments have already been proved that they can decrease the harm efficiently from the UV radiation.Therefore we investigated whether the adaxial side and the abaxial side of petals reflect and absorb the UV differently and if it has the function for protecting pollens.We investigated 43 species and took UV photos for the adaxial side and abaxial side of petals to see if they reflect and absorb UV differently.Then we extracted the UV-reflectance data from those UV photos for quantitatively analysis.We found that the different UV-reflection and UV-absorption of petals adaxial side and abaxial side caused the different color of flowers upper side and lower side.The UV-reflection and UV-absorption of petals adaxial side and abaxial side distinct significantly,and the abaxial side of flower bud absorb the UV may protect the pollens from the UV radiation.