EYE ATTACHED HEMIPOLLINARIA IN THE HAWKMOTH AND SETTLING MOTH POLLINATION OF HABENARIA (ORCHIDACEAE) - A STUDY ON FUNCTIONAL-MORPHOLOGY IN 5 SPECIES FROM SUBTROPICAL SOUTH-AMERICA

Morphological adaptations to sphingophily and pollination by moths was studied in 5 South American Habenaria species. For H.gourlieana and H . hieronymi direct evidence of hawkmoth (Agrius cingulatus and Manduca sexta) and settling moth (Rochiplusia nu) pollination, respectively, by hemipollinaria attachment on the eyes, is presented. In two other s pecies (H. poucofilia, H. rupicola) pollination by settling moths and eye attachment of the hemipollinaria can be inferred by indirect evide nce (placement of scales and massulae on the flowers) and by flower st ructure. For the fifth species (H. montevidensis) pollination by small moths or mosquitoes with hemipollinaria attachment on the proboscis i s postulated. A comparative study in floral features revealed clear mo rphological divergence between sphingophilous and phalaenophilous spec ies. In addition to deeper spurs the former have slender, exerted, and upturned petal lobes (acting as mechanical guide to the hovering visi tors), a much developed median rostellar lobe (acting as deflecting su rface of the hawkmoths towards the viscidia), flexible and sinuous hem ipollinarium caudicles (appropriate for frontal strikes against the st igma when hemipollinaria are brought by the hawkmoths dangling against the flower). Male efficiency was compared between 4 species with over lapping flowering time in the same area. Male efficiency factors were unexpectedly low in all species. Only in one species (H. hieronymi) ea ch pollen donation accounted for more than one pollination. H. gourlie ana is part of a more or less rich sphingophilous flora interacting wi th the same two long-tongued hawkmoth species. Interspecific competiti on for pollen placement on the pollinator's body surface is probably l ow on account of different pollination mechanisms.