COS 13-6 - Does florivory affect reproduction in a night-blooming plant?

Background/Question/Methods

Florivory has received increased attention in the last two decades, but many aspects of this interaction remain unexplored. Most studies on florivory concentrate on diurnal flowering plants, whereas less work has investigated the effect of damage on night-blooming species. Datura wrightii (Solanaceae) produces flowers that open in the evening and suffer high levels damage by florivores, both to the corolla and primary reproductive organs. Night-active hawkmoths are the main pollinators of D. wrightii and could be undeterred by damage that affects visual displays, although previous research suggests that damage to the calyx can reduce levels of carbon dioxide, a gas that is often used by these moths to find flowers. Direct damage to the reproductive tissues may have a larger effect on fruit set than damage to the corolla or calyx. To investigate these hypotheses, we first recorded the location of florivory and insects associated with damage in the Sonoran desert. We conducted one experiment in which beetle florivores were bagged with flowers overnight after which fruit set was recorded. We also applied artificial floral damage to corollas, calyces, and floral tubes to a planted population of D. wrightii, once in 2004 and again in 2011, and measured fruit set.

Results/Conclusions

Damage to flowers was concentrated on the corolla tube and flare, with ants and scarab beetles being the most common insects associated with florivory. We found that direct damage to reproductive tissues by beetles resulted in lower fruit set vs. unmanipulated controls. There was no evidence that artificial damage to corollas or calyces had effects on fruit set. This suggests that damage to corollas has little effect on nocturnal pollination but direct damage to reproductive tissues can substantially reduce fitness. As this is one of the few studies looking the effects of florivory on night-blooming flowers, we hope that others will replicate these efforts in different systems.