Specialized use of pollen vectors by Caesalpinia gilliesii, a legume species with brush type flowers.

MORÉ, M.; SÉRSIC, A. N.; COCUCCI, A. A.

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2006 vol. 88 p. 279 - 292

0024-4066

The pollination of Caesalpinia gilliesii (Fabaceae), a species with long brush-type flowers, was studied in wild populations of Argentina. A total of 341 hawkmoths belonging to 10 species with probosces ranging from 1.5 to 13.5 cm were captured by means of light traps. Hawkmoths could be classified in four significantly different proboscis length classes or guilds: short (15.35 ± 1.11 mm), medium (30.23 ± 2.24 mm), long (55.85 ± 4.98 mm) and very long (95.61 ± 13.63 mm). A total of 133 hawkmoths belonging to 7 species carried pollen of C. gilliesii, mainly on their venter. Successful contact with anthers while drinking nectar depends upon hawkmoths tongue length. The relative frequency of pollen-carriage and the mean proboscis length of each species were positively and significantly correlated. Considering a null hypothesis of non-specialization, in which hawkmoths carrying pollen are distributed at random among individuals of the four guilds, long-tongued hawkmoths carried C. gilliesii pollen more frequently than expected by chance. In contrast, short and medium tongued guilds carried pollen less frequently than was predicted by random expectations. Individuals with short probosces accessed nectar from below without touching the anthers, whereas very long-tongued hawkmoths with tongues over the length range of the flower reproductive organs probably can reach nectar without touching the fertile organs. Results show that a pterotribic pattern of pollen deposition on the body of long-tongued hawkmoths is operating in this species. This suggests that brush-type blossoms are not necessarily unspecialized, despite popular belief. ADDITIONAL KEY WORDS: Fabaceae – long-tongued hawkmoth pollination – pollinator guild – pterotribic pollen deposition – Sphingidae.