Extreme variation in floral characters and its consequences for pollinator attraction among populations of an Andean cactus.

SCHLUMPBERGER, B.; COCUCCI, A.A.; MORÉ, M.; SÉRSIC, A.N.; RAGUSO, R.

ANNALS OF BOTANY

OXFORD UNIV PRESS

Año: 2009 vol. 103 p. 1489 - 1500

0305-7364

† Background and aims A South American cactus species, Echinopsis ancistrophora (Cactaceae), with dramaticamong-population variation in floral traits is presented.† Methods Eleven populations of E. ancistrophora were studied in their habitats in northern Argentina, and com-parisons were made of relevant floral traits such as depth, stigma position, nectar volume and sugar concentration,and anthesis time. Diurnal and nocturnal pollinator assemblages were evaluated for populations with differentfloral trait combinations.† Key Results Remarkable geographical variations in floral traits were recorded among the 11 populationsthroughout the distribution range of E. ancistrophora, with flower lengths ranging from 4.5to24.1 cm. Otherfloral traits associated with pollinator attraction also varied in a population-specific manner, in concert withfloral depth. Populations with the shortest flowers showed morning anthesis and those with the longest flowersopened at dusk, whereas those with flowers of intermediate length opened at unusual times (2300 – 0600 h).Nectar production varied non-linearly with floral length; it was absent to low ( population means up to 15 mL)in short- to intermediate-length flowers, but was high ( population means up to 170 mL) in the longest tubedflowers. Evidence from light-trapping of moths, pollen carriage on their bodies and moth scale deposition onstigmas suggests that sphingid pollination is prevalent only in the four populations with the longest flowers, inwhich floral morphological traits and nectar volumes match the classic expectations for the hawkmoth pollinationsyndrome. All other populations, with flowers 4.5 – 15 cm long, were pollinated exclusively by solitary bees.† Conclusions The results suggest incipient differentiation at the population level and local adaptation to eitherbee or hawkmoth ( potentially plus bee) pollination.Key words: Pollination, floral biology, Echinopsis ancistrophora, cactus, Cactaceae, hawkmoth, bee.