The effects of Castilleja miniata's parasitic relationship with Delphinium nuttallianum on pollinator visitation and pollination success

Abstract

Castilleja miniata is a hemiparasite capable of taking up chemical toxins from its host plant. A unique relationship is C. miniata’s parasitism on Delphinium nuttallianum (which contains alkaloids); alkaloids from D. nuttallianum are taken up into C. miniata’s nectar which could negatively affect C. miniata’s pollinator visitation when compared to C. miniata parasitizing other plants. However, D. nuttallianum may have an increased visitation when parasitized by C. miniata should the pollinators prefer the alkaloid free nectar of the close-by D. nuttallianum over the alkaloid-containing nectar of its host. I observed pollinator visitation to two groups of C. miniata (one parasitizing D. nuttallianum and one not) and two groups of D. nuttallianum (one being parasitized by C. miniata and one not) for a total of eighty hours and performed herbivory assessments and hand-pollinations. I also assessed seed set for all treatments to determine if pollinator visitation dictated pollination success. There were no significant differences in flowers probed/open ratios or total visitation between C. miniata treatments or D. nuttallianum treatments, although the trends were in the direction expected for C. miniata (decreased visitation to C. miniata parasitizing D. nuttallianum) but not for D. nuttallianum (decreased visitation to D. nuttallianum parasitized by C. miniata). D. nuttallianum seed number and seed weight did not support pollination visitation determining pollination success; both seed number per plant and seed weight per plant negatively correlated with number of visits. C. miniata seed data has not yet been determined.

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