Reproductive biology of three co-occurring, primarily small-mammal pollinated Protea species (Proteaceae)

Abstract

This study investigated the role of vertebrates in the reproductive biology of a community of three co-occurring Protea species (Protea canaliculata, Protea sulphurea and Protea humiflora, Proteaceae) at Kraggashoek in the Western Cape, South Africa. Live-trapping, measures of facial and faecal pollen loads, and footage from remote cameras facing the inflorescences confirmed that all three are visited by small mammals and specialist nectarivorous birds. These plant species have bowl-shaped inflorescences that produce highly concentrated (34.1–42.9%) sucrose-rich nectar and a “yeasty” scent, typical traits of small-mammal pollinated plants. Camera footage indicated that 140 visits were made by eight small mammal species to an accumulative 19 inflorescences of the three Protea species. Small mammals thus made up 69% of total visits by all vertebrate species. Camera footage revealed that Micaelamys namaquensis visited flowers more frequently than any other vertebrate visitor (41% of total visitations by birds and mammals) but Elephantulus edwardii (10% of total visitations by birds and mammals) spent the longest time foraging on inflorescences (~28s per inflorescence). The ‘trap shy’ species, Graphiurus ocularis, was observed for the first time on camera, visiting Protea humiflora and Protea sulphurea inflorescences. Galerella pulverulenta (Cape gray mongoose) also visited inflorescences of P. canaliculata. The remaining 31% of total vertebrate visits, primarily to Protea humiflora, were by three species of specialist nectarivorous birds (the Cape sugarbird Promerops cafer, and the shorter-billed sunbirds, Anthobaphes violacea and Cinnyris chalybeus). Breeding system experiments with Protea sulphurea revealed that pollinators are needed for seed set, although exclusion of vertebrate pollinators only marginally lowered seed set of this partially self-incompatible species. These three Protea species had asynchronous flowering periods, supporting a wide range and relative abundance (overall live mammal trapping success rate of 22.7% nocturnal and 5.7% diurnal species) of vertebrate pollinators over a three month period in winter. That these Protea species co-occur suggests there is a community of vertebrate flower visitor species and primarily small mammal-pollinated plant species. The partitioning of nectar resources over a long period has conservation implications for both the plants and animals.