Staminode evolution in

Staminodes are infertile stamens that have evolved numerous times across angiosperms; however, little is known about the evolutionary transitions of staminodes, especially among close relatives. We studied staminode evolution in Mentzelia section Bartonia to determine how many times staminodes have been gained or lost. A maximum-likelihood approach identified ten transitions, in which staminodes evolved at least five times and were reversible. We then examined the consequences of the evolution of staminodes by quantifying how staminodes affect visitation rates. A population of Mentzelia multiflora was used in an experimental study in which visitation of control flowers (staminodes present) was compared to that of treatment flowers (staminodes removed). The only pollinator was Apis mellifera (Apidae), which hovered above and landed on control flowers significantly more often than treatment flowers. Despite the preference for landing on staminodial flowers, once landed, pollinators spent an equal time on control and treatment flowers. We hypothesize that the increased visitation of staminodial flowers probably offsets the loss of the reproductive function in stamens.