PARENT SESSION
Poster Session #33: Rare, Threatened, and Endangered Species.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Response of hawkmoths and longhorn beetles to floral displays of the rare night-blooming cereus.

O'LEARY, JESSICA^*,1, STUBBEN, CHRIS¹, MILLIGAN, BROOK¹, ¹ New Mexico State University, Las Cruces, New Mexico

ABSTRACT- The night-blooming cereus, Peniocereus greggii var. greggii, is a cryptic cactus with large, tubular flowers that open for a single night. In May 2001, we monitored the 2-week blooming period of a small population in the San Andres Mountains of southern New Mexico to identify floral visitors and determine if fruit set was limited by the availability of pollinators. Few hawkmoths, including the white-lined sphinx moth (Hyles lineata) and the five-spotted hawkmoth (Manduca quinquemaculata), were seen visiting flowers and the number of visits by pollinators apparently did not increase with the size of the floral display. The probability of a flower setting fruit on the night with many open flowers (33 % fruit set) was lower than other blooming nights with few flowers (63 % fruit set). Additionally, the probability of a flower setting fruit on plants with many blooms on a single night was lower than plants with only a single open flower. While these results are consistent with pollinator limitation, an alternative hypothesis is that larger floral displays may attract more longhorn beetles (family Cerambycidae) that grazed the flowers, thus altering visitation rates by pollinators or preventing successful pollination caused by damage to the style and stigma. These initial results will be followed by a complete survey of all 350 known plants in the San Andres Mountains in 2002.

KEY WORDS: Floral display, pollinator limitation, Peniocereus greggii, fruit set