Rewardlessness in orchids: how frequent and how rewardless?

Area of Science:

• Botany
• Ecology
• Evolutionary Biology

Background:

• A widely cited estimate suggests one-third of orchid species attract pollinators through deception, lacking floral rewards.
• The empirical foundation for this 'one-third' estimate in scientific literature is often not explicitly stated or rigorously examined.
• Recent findings indicate some 'rewardless' orchids may offer minute sugar quantities, complicating the notion of absolute deception.

Purpose of the Study:

• To investigate the empirical basis of the common estimate that one-third of orchid species are rewardless.
• To explore the nuances of orchid pollination strategies, particularly the extent of deceit versus actual reward.
• To highlight the need for further empirical research on rewardlessness in orchids.

Main Methods:

• Tracing citation pathways to identify the origins of the 'one-third rewardless' estimate in botanical literature.
• Reviewing recent scientific measurements of floral rewards in orchids previously considered rewardless.

Main Results:

• The citation analysis revealed a surprisingly narrow empirical basis for the widely accepted 'one-third' estimate of rewardless orchids.
• Minute sugar quantities were detected in some orchids presumed to be rewardless, suggesting a strategy of partial or conditional deceit.
• While rewardlessness is common in orchids, its prevalence and variation require more extensive empirical verification.

Conclusions:

• The common assertion of one-third rewardless orchid species is based on limited empirical evidence.
• Orchid pollination may involve a spectrum of strategies, including significant deceit but not necessarily absolute rewardlessness.
• Further research is crucial to accurately quantify rewardlessness and its geographic/environmental variations in orchids.