Nectar shortage caused by aphids may reduce seed output via pollination interference

DEVEGILI, ANDRÉS M.; CHALCOFF, VANINA R.

OECOLOGIA

SPRINGER

Lugar: Berlin; Año: 2020

0029-8549

Herbivores decrease plant fitness by consuming reproductive tissues, limiting resources, and/or affecting mutualisms. Although these mechanisms were extensively tested for in chewing herbivores, the impact of other functional groups (e.g., sap-feeders) remains poorly understood. We investigated whether aphids (sap-feeding insects) affect the reproduction of Oenothera odorata and examined two possible mechanisms: resource limitation and/or pollination interference. We compared plant traits and seed set of naturally aphid-free vs. aphid-infested plants and then manipulated aphid presence and pollen receipt. Finally, we examined the relationships among variables using path models. Nectar volume and seed set of aphid-infested plants was 48% and 42% lower than that of aphid-free plants. After ~72 hrs of aphid removal, nectar volume restored to the level of aphid-free plants. When pollinators were excluded, seed set was similar between aphid-infested and aphid-free plants, suggesting that aphids were not affecting plant reproduction through resource limitation. Manual addition of pollen restored seed set of aphid-infested plants, suggesting that aphids could be interfering with pollination. Path analysis supported a negative association between aphids and seed set via nectar volume. This is one of the few reports showing in field conditions that sap-feeders may decrease plant reproduction through an effect on pollination via the impoverishment of a floral reward. Since aphids are crop pests and feed on a large number of animal-pollinated plants, the potential of these insects to influence pollination and plant reproduction is high. This study emphasizes the importance of sap-feeders to better understand the links between herbivory, pollination, and plant fitness.