Reproductive biology of Wahlenbergia (Campanulaceae) endemic to Robinson Crusoe Island (Chile)

The reproductive biology of W. berteroi, W. fernandeziana. and a putative h ybrid between W. fernandeziana and W. grahamiae, endemic to Robinson Crusoe Island (Juan Fernandez archipelago, Chile) was studied. Flowers are hermap hroditic, protandrous, offer nectar. and exhibit secondary pollen presentat ion involving pollen collecting hairs on the style. These features imply al logamy and biotic pollination. However, male and female phases overlap and no effective pollinators were observed. Experimental data indicate these ta xa are self-compatible and facultatively autogamous, a conclusion also sugg ested by the pollen/ovule ratios. Selfing is accomplished when the stigmati c lobes reflex and touch the style, except for W. berteroi where they do no t reflex completely. Autogamy is accomplished in the latter when pollen gra ins deposited on the inner surface of the corolla throat by the "pollen bru sh" are gathered by stigmatic lobes when shaken by wind. The degree of auto gamy, and perhaps self-compatibility, seems to be inconstant, as implied by the variable natural seed set (overall range 21-188 seeds per fruit). A mi xed mating system - primarily outcrossing/entomophilous, but also autogamou s must have been present in the continental ancestors of these taxa. Autoga my promoting self-fertilization is important now - on an island with scarce pollinators - and in the past - when the first founders arrived.