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 Linnean Society

Wiley

Año: 2006 vol. 88 p. 579 - 592

1095-8312

The pollination of Caesalpinia gilliesii  (Fabaceae), a legume species with long, brush-type flowers, was studied inwild populations in Argentina. A total of 341 hawkmoths (Sphingidae), belonging to 10 species, with tongues rangingfrom 1.5 to 13.5 cm in length, were captured by means of light traps. Hawkmoths could be classified in four sig-nificantly different tongue-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 of the hawkmoths, belonging to seven species, car-ried pollen of Cae. gilliesii, mainly on their venter. Successful contact with anthers while drinking nectar dependedupon hawkmoth tongue length. The relative frequency of pollen-carriage and the mean tongue length of each specieswere positively and significantly correlated. Considering a null hypothesis of nonspecialization, in which hawkmothscarrying pollen are distributed at random among individuals of the four guilds, long-tongued hawkmoths carriedCae. gilliesii pollen more frequently than would be expected by chance. In contrast, short- and medium-tonguedguilds carried pollen less frequently than is predicted by random expectation. Individuals with short tonguesaccessed nectar from below without touching the anthers, whereas very long-tongued hawkmoths, with tongueslonger than the length range of the flower reproductive organs, can probably reach nectar without touching the fer-tile organs. Results show that a pterotribic pattern of pollen deposition on the body of long-tongued hawkmoths isoperating in this species. This suggests that brush-type blossoms are not necessarily unspecialized, despite popularbelief. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 579–592.