Drought reduces floral traits of Solanum rostratum but does not impact plant-pollinator interactions

Sammanfattning

Climate change is a global issue that threatens ecosystems. The slow temperature rise in recentyears are causing an increase in drought severity and frequency. This reduction in wateravailability can be decisive for the survival of plants. For flowering plants their survival dependson managing vegetative growth and on attracting pollinators, which is crucial for flowering plantspecies. Flowering plants rely on floral display, floral rewards, and volatile emissions to attractanimals that act as pollinators, but these plant traits can be affected by drought. This researchexplores the effects of drought on floral traits of Solanum rostratum (Solanaceae), a nectarlessplant that offers pollen as a reward for visiting pollinators, and the subsequent effects on plantpollinatorinteractions, a topic that has been sparsely researched. In this study I employed agreenhouse experiment with S. rostratum plants grown under two watering treatments: The controltreatment consisted of plants grown under daily watering, while the drought treatment consistedof plants grown under induced drought stress via limited watering. I utilised behaviour assays withBombus terrestris to assess the behaviour of a bee when exposed to a mix of flowers gathered fromplants of both watering treatments. I determined flower size, anther lengths, and the number ofovules for each flower used in the assays and compared them between treatments. My resultsshowed that drought-treated plants produced smaller and fewer flowers as well as shorter antherscompared to plants grown in well-watered conditions, but they had a similar number of ovules.Additionally, I found that the peak flowering time was advanced by one week among the droughttreatedplants. Furthermore, I found that visitation rate was positively correlated with flower sizeand that visit duration was influenced by whether the bee buzzed or not. These findings suggestthat S. rostratum responds to drought stress by producing an earlier, smaller floral display whilemaintaining ovule number per flower. This study also shows that drought can indirectly influencethe behaviour of visiting pollinators by causing the production of smaller flowers in droughtstressedplants, which may ultimately affect plant survival and long-term ecosystem dynamics.Understanding how plant-pollinator interactions are affected by the changing climate is crucial forpredicting and mitigating future disruptions in natural and agricultural ecosystems.