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Abstract:
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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. |
