Beetle Pollination and Floral Thermogenicity inMagnolia Tamaulipana(Magnoliaceae)

• Published in: International journal of plant sciences Vol. 160; no. 1; pp. 64 - 71
• Main Authors: Dieringer, Gregg, Cabrera R., Leticia, Lara, Manuel, Loya, Larisa, Reyes‐Castillo, Pedro
• Format: Journal Article
• Language: English
• Published: The University of Chicago Press 01-01-1999
• Subjects: Ambient temperature; Beetles; Calyx; Flower stigma; Flowers; Odors; Petals; Pollen; Pollen tubes; Pollination
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/314099

The pollination biology involving floral thermogenicity ofMagnolia tamaulipanawas conducted at the El Cielo Reserve in Tamaulipas, Mexico, during May 1996. Our results indicate thatM. tamaulipanapossesses a highly specialized beetle pollination system involvingCyclocephala(Scarabaeidae: Dynastinae) and members of the Staphylinidae. Of the 366 insects visiting 213 flowers ofM. tamaulipana, 364 were beetles.Cyclocephala caelestisaccounted for 52% andMyrmecocephalussp. for 46% of the visits. Breeding system experiments indicated that the flowers were self‐compatible but only 44% of the open‐pollinated stigmas were pollinated.Cyclocephala caelestiswas frequently observed to feed on petals but never sepals. As a reward, flowers offered petals high in carbohydrate and low in fiber toCyclocephala. The protogynous flowers ofM. tamaulipanaopened at night, were viable for a maximum of 24 h, and were thermogenic. Flowers were hottest when they first opened and female. Floral temperatures gradually declined with time and hence sexual phase and, 24 h after anthesis, were not different from ambient. Excess floral temperatures ranged from 1.0° to 9.3°C for female‐phase flowers and from 0.2° to 5.0°C for male‐phase flowers. The two species of beetles showed differential visitation to trees associated with floral thermogenicity. Our data indicate that large‐flowered trees dissipate more heat and, therefore, more floral odor from their petals than small‐flowered trees, thereby attracting a greater number ofCyclocephala.