MUTUALISTIC INTERACTIONS BETWEENUPIGA VIRESCENS(PYRALIDAE), A POLLINATING SEED-CONSUMER, ANDLOPHOCEREUS SCHOTTII(CACTACEAE)

Abstract

Pollinating seed-consuming interactions are rare, but include fig–fig wasp and yucca–yucca moth interactions, both of which are thought to be coevolved. Conditions favoring such mutualisms are poorly known but likely include plants and pollinators whose life cycles are synchronized. In this paper, we describe a new pollinating seed-consumer mutualism between a Sonoran Desert cactus, Lophocereus schottii (senita cactus), and a pyralid moth, Upiga virescens (senita moth). We compare this mutualism with the yucca mutualism in terms of life history traits, active pollination, and selective abortion. Senita cactus flowers were pollinated nearly exclusively by nocturnal senita moths, but a few halictid bees also pollinated flowers. Only 40% of flowers set fruit during the years of study, apparently due to resource limitation. All phases of the senita moth’s life history were associated with the senita cactus. During flower visitation, female senita moths collected pollen, actively pollinated flowers, and oviposited one egg. After flowers closed, emerging larvae bored into the tops of developing fruit, where they consumed seeds and fruit tissue. However, not all seeds/fruit were consumed by larvae because only 20% of eggs produced larvae that survived to be seed/fruit consumers. Senita cactus and senita moth interactions were mutualistic. Moths received food resources (seeds, fruit) for their progeny, and cacti had a 4.8 benefit-to-cost ratio; only 21% of developing fruit were destroyed by larvae. Life history traits important to this mutualism included low survival of senita moth eggs/larvae, several moth generations per flowering season, host specificity of senita moths, active pollination, oviposition into flowers, and limited seed/fruit consumption. Active pollination by senita moths in the presence of co-pollinators supports the prediction that active pollination can evolve during a period of coexistence with co-pollinators. The specialization of both senita and senita moths in the presence of co-pollinators makes the senita mutualism quite remarkable in comparison with fig–fig wasp and yucca–yucca moth mutualisms.