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There are two likely scenarios as to whether floral colours in Australia have evolved independently to those of Europe and the Middle East. First, angiosperms evolved after Australia separated from Gondwana. Hence, parallel evolution may have occurred where similar flower colours were being selected by hymenopteran trichomatic vision. The second possible scenario is that angiosperms evolved before Australia separated from Gondwana and radiated out to all continents. 

 Thus, flowering plants drifted with the moving land masses and evolved in a similar way to European and Middle Eastern flowers. Scenario 1, in this regard, seems more likely as the evolution of flowers in Australia is likely to be independent, based on work by Kevan and Backhaus (1998) who estimate that early angiosperms were most likely to be a pale yellow pollen colour and later evolved highly coloured signals to lure important pollinator vectors. It is estimated that the earliest angiosperm fossil dates at 132 million years ago (mya), around the early Cretaceous (Crane, Donoghue et al. 1989; Crane, Friis et al. 1995). Towards the end of the Cretaceous, Australia separated from Gondwana (Rich and Rich 1993). However, the time scales are too imprecise to conclusively resolve this question. Additional data is needed on biogeographical relationships and how this relates to floral reflectance data for other continents such as Africa, South America, Asia and North America to understand this question.

The foraging success of a bee is dependent on the colour vision receptors being able to relialy distinguish flower species from each other (Chittka and Menzel 1992). There is a mutual benefit here as the pollinator’s foraging efficiency is increased if it can distinguish flowers from the surrounding background; and the plant is more likely to be pollinated if it appears distinct from its surroundings (Chittka and Menzel 1992). It is known that bees can discriminate colour stimuli best at 400 and 500 nm (Helversen 1972). So why, then, do we see a third peak at 600 nm (fig. 4b)? One reason could be that biological material (including leaves) reflect infrared radiation above 600 nm (Chittka, Shmida et al. 1994). There is also the possibility that insects with red receptors such as butterflies and beetles (Menzel and Backhaus 1991; Peitsch, Fietz et al. 1992) might also be important pollination vectors influencing the evolution of some Australian flower colours. Currently, there is very little information within Australia about the vision of insects with long wavelength sensitive receptors, but this would provide an interesting avenue for future research.

It was really important to not bias my data set by specifically picking species that are pollinated by only hymenopterans. Thus, I took a broad approach of including every flowering plant species available at my sampling site to best represent the colour distribution of Australian flowering plants that have evolved. This enabled me to test whether hymenopteran colour vision has been a major driving force shaping the evolution of floral colours. In spite of the fact that the dataset included a broad sample of plants (some of which would likely not even be pollinated by hymenopterans), strong pa本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。