Environment or Pollinators? Factors Shaping Breeding System and Spatial Variation in Nectar Properties and...

Interaction with pollinators has been proposed as one of the most important factors shaping the diversity of flowering plants. Spatial variation in the directions of the selective pressure exerted by pollinators drives the evolution of adaptive differentiation. Across-population studies of flower traits and plant-pollinator interaction are therefore an important step to understanding the diverse selective pressures that drive floral evolution in zoogamous angiosperms. Here we combine observational data and field experiments to describe the assemblages of pollinators, breeding systems, and reward properties in studied populations of the Middle East geophyte, Fritillaria persica. Natural populations of this species include two floral color morphs with greenish or purple flowers; in both morphs, the nectaries of the outer whorl are covered by the tepals of the inner one. Our study documented geographical variation in the pollination system of two color morphs of F. persica. Visitors recorded in both populations were similar qualitatively; however, their contribution varied. Nectar sugar concentration and profile were generally constant in studied populations; we recorded differences only in nectar volume and concentration of amino acids. These results suggest that the observed variation in nectar production is likely to be a result of environmental factors rather than pollinator-mediated selection. In the context of reward, we also tested how uncovering the hidden nectar reward from outer tepals influences potential pollinators. Uncovering hidden reward did not change the time spent in one flower or inflorescence penetration; however, it increased the number of seeds produced. Nectar properties and the pollinator assemblages similarity suggest that in the context of pollination, F. persica represents a rather generalistic strategy, and observed differences may be caused by abiotic factors.