flowers in Angiosperms and the role of insect cognition in their evolution.
Second, this could help to explain why some "rewardless
" orchids are ignored consistently by their pollinators at certain sites (Neiland & Wilcock, 1998).
This may explain how polymorphisms in reward levels such as we have shown in Mimulus gutattus may persist and why rewardless
species or sexes are common in nature (Dafni 1984, Willson and Agren 1989).
The remaining two morphs only, blue and purple, were varied in frequency, and were rewardless
in one series of treatments, but controls where these morphs had rewards were also performed for comparative purposes.
Looking after the cattle, which is a major part of their work in life, became almost rewardless
. The matter becomes all the more serious under the scarcity situation of pulses and their high prices.