Pollination biology of Erica aristata: First confirmation of long-proboscid fly-pollination in the Ericaceae

Abstract

Long-proboscid fly (LPF) pollination has been recorded in multiple plant lineages in South Africa. However in the large and morphologically diverse genus Erica, evidence for LPF pollination is limited to predictions based upon floral syndromes as well as anecdotal observation and limited citizen science records. Here we use breeding system experiments, pollinator exclusion, remote camera traps, spectral analysis and field observation in the Klein River Mountains, Western Cape Province, South Africa, to demonstrate this mode of pollination in the range-restricted taxon Erica aristata. This species has long narrow corolla tubes with narrow opening and contrasting white and crimson pink petals. Flowers were visited and pollinated exclusively by one long-proboscid fly species, Prosoeca rubicunda (Nemestrinidae) over four years at this study site. Breeding experiments showed that E. aristata is not self-compatible and pollinator exclusion experiments indicate that pollinator visits were required for seed-set. Low nectar volume and moderately high nectar sugar concentration were consistent with other long-proboscid fly-pollinated plant species in the Cape. This study represents the first confirmed instance of long-proboscid fly-pollination in the genus Erica.