Nursery pollinators lay eggs in the flowers they pollinate, and, the pollinator’s larvae feed on the developing seeds. If host plants abort a flower, all pollinator eggs within die. We investigated the egg-laying strategy of nursery pollinator Tegeticula yuccasella in response to variation in the probability of flower abortion of its host plant Yucca glauca. Yucca glauca are more likely to abort late-opening distal flowers in the presence of basal fruits. We tested the hypothesis that nursery pollinators invest fewer eggs in flowers with a higher probability of abortion. We manipulated Y. glauca inflorescences to obtain late-opening flowers either (1) without basal fruits, or (2) with hand-pollinated basal fruits. Using these inflorescences, we conducted behavioral trials to quantify the proportion of flowers with at least one oviposition (egg-laying event) and the total number of ovipositions by T. yuccasella in each treatment. If, in the presence of basal fruits T. yuccasella lay fewer eggs, we expect fewer larvae to emerge from fruits developed from those flowers. To test this, we determined whether T. yuccasella larvae emerging from distal fruits decreased with increasing number of basal fruits on naturally-pollinated inflorescences.
As expected, the presence of fruits significantly reduced the proportion of flowers that received at least one oviposition. This provides evidence that oviposition strategy of nursery pollinators is plastic and responds to the risk of flower abortion due to presence of fruits, which to our knowledge is a novel driver of a nursery pollinator’s oviposition strategy. Additionally, we detected the trend that the presence of fruits reduced the total number of ovipositions. This was not consistent with our observations of naturally-pollinated inflorescences where larval emergence was independent of the number of basal fruits present. A lower probability of accepting a flower as an oviposition site when fruits are present is likely adaptive for nursery pollinators as it reduces the loss of eggs to flower abortion. An egg-laying strategy that discriminates between flowers on inflorescences with and without fruits is particularly important in our study system because the frequency of flowers with and without the presence of fruits varies across space and time probably due to highly variable resource availability. Further, short-lived nursery pollinators like T. yuccasella are likely time-limited and should avoid wasting time ovipositing in flowers that have a high chance of being aborted.