Variations In The Ultraviolet Floral Patterns And Pollinator Preference Among Selected Non-Invasive And Invasive Plants Of Tamil Nadu, India

Fossil evidence shows that pollinator-mediated plant reproduction evolved [~]140 million years ago and bee facilitated pollination evolved [~]70 million years ago. Human vision is limited to the visible color range of 400 to 750 nanometres, whereas most pollinators can perceive the ultraviolet (UV) range in addition to visible colors. Bees have been reported to have highest spectral sensitivity in the ultraviolet spectrum. The main objectives of the study were (1) to assess the prevalence of ultraviolet floral patterns, (2) to analyse floral patterns in relation to plant-pollinator interaction among invasive and non-invasive plants, and (3) to test for intraspecific floral pattern variations among plants with different flower color morphs. A study was conducted on 188 plant species (80 invasive and 108 non-invasive) from parts of Western and Eastern Ghats region of Tamil Nadu, India. The flowers of the studied plant species were imaged in ultraviolet (320-380 nm) and visible spectrums. The mode of pollination for the selected species were documented and confirmed with existing literature. The intraspecific variations in the floral patterns among flower color polymorphic plant species (N=10) were documented in ultraviolet and visible spectrums. Among the studied plant species, around 58% had discernible floral patterns when observed in the UV spectrum, whereas the rest were observed to completely absorb or reflect UV radiation. Whereas 46% of the studied plants exhibited no pattern in the visible spectrum. A significant difference was observed in the pollinator relationship among the ultraviolet floral patterns in invasive plants ({chi}2 = 63.98, df = 32, P < 0.001), whereas no significant variation was evidenced in the pollinator relationship among the ultraviolet floral patterns in non-invasive plants ({chi}2 = 19.50, df = 24, P = 0.724). Analysis of pollinator preference revealed that invasive species were mostly pollinated by bee and butterfly mediated pollination, whereas non-invasive species were mostly pollinated by bees and generalist insects. Intraspecific variations in the floral ultraviolet signal were observed among different morphs in a few flower color polymorphic species, especially in Lantana camara. The multispectral analysis of floral patterns revealed that plants utilize both the visible and ultraviolet spectrums to effectively communicate with pollinators. The results from the present study strongly suggest that the variation in the floral ultraviolet signature among invasive species might play a vital role in plant-pollinator interaction and invasion success.