Do Beetles Prefer the Odor of Female-Stage to Male-Stage Flowers in Atemoya, a Cantharophylous Protogynous Fruit Tree (Annonaceae)?

Abstract

The flowers of annonaceous fruit trees such as cherimoya (Annona cherimola) and atemoya (A. cherimola x squamosa) exhibit protogynous dichogamy. Their main pollinators are sap beetles (Coleoptera: Nitidulidae). However, pollination by beetles is usually not sufficient for commercial fruit production, so costly hand pollination is required in many areas. Beetles are thought to visit the female-stage flower, remain inside it, and leave the flower when it has transitioned to the male stage; however, no study has as yet directly elucidated the visiting behavior of the beetles. In this study, we examined this hypothesis using olfactometer testing in the field. Both male and female sap beetles, Carpophilus marginellus, were significantly attracted to the odor of female-stage flowers, but not to the odor of late male-stage flowers. We conclude that the beetles prefer the odor of female-stage flowers to that of late male-stage flowers. These findings support the above hypothesis describing beetle pollination behavior.