Experimental florivory and its effects on pollinators of Opuntia cantabrigiensis Lynch (Cactaceae)

Abstract

Florivores modify the attributes of flowers while feeding, that affects the behavior and frequency of pollinators that visit flowers and setting of fruits and seed as a result of low pollen deposition. We determined the effect of experimental florivory on pollinators visitations, fruit-set, and seed-set of Opuntia cantabrigiensis. Four treatments were applied on intact flowers during reproductive season: 1) removal of 50% of the perianth, 2) emasculated flower, 3) flower without stigma, perianth and stamens (stigma-perianth) and 4) intact flower-control; selected treatments mimic the types of florivory observed in the population. The frequency of visitation, activity and taxonomic identity of the pollinator were recorded. We found that frequency of pollinators decreased with damage to the flower, with the stigma-perianth treatment receiving the fewest visits. The most frequent pollinators were the solitary bees Macrotera sinaloana, Diadasia rinconis, and Lithurgopsis apicalis (Hymenoptera) that collect rewards and perch on the stigma of flowers. Pollinators responded differently to florivory; Ashmeadiella opuntiae avoided flowers with perianth damage, possibly associating it with a lack of rewards, while D. rinconis prefered such flowers, the removal of this structure facilitated access to floral rewards. Flowers in the stigma-perianth treatment produced seedless fruit. Intact flowers had higher seed production than those with perianth damage or emasculation due to low pollinator visitation and pollen deposition. Opuntia cantabrigiensis is a xenogamous species with dependence on biotic vectors, therefore the damage caused by florivores reduces the visit of their pollinators and its reproductive success, which could negatively affect the population persistence.