Notes on the flowering and pollination of the endemic grassland Aloe reitzii var. reitzii (Asphodelaceae)

Abstract

Background: Aloe reitzii var. reitzii is a succulent with a restricted distribution in the montane grassland of eastern South Africa. It is a summer (late January-March) flowering succulent that grows on rocky outcrops at 1000 m-1600 m, and the conspicuous inflorescences suggest a pollination system focused towards birds. Objectives: To understand more about the pollination biology of A. reitzii var. reitzii. Methods: Nectar standing crop (flower volume and concentration) and the proportion of plants flowering were recorded. Camera traps and observations were used to record visitors to A. reitzii var. reitzii inflorescences. Results: Nectar volume was 36 μL ± 27 μL per flower (range 6 μL-93 μL; n = 27) and concentration was 16.5% ± 1.7% (range 13.5% - 19.5%). Camera trap observations, where 18.9% of all plants were observed flowering, recorded the three bird species Cape Weaver, Ploceus capensis, Malachite Sunbird, Nectarinia famosa and Greater Double-collared Sunbird, Cinnyris afer (60.4%, 27.1% and 12.5% of plant visits, respectively) visiting inflorescences. Conclusion: Because birds are important pollinators for many Aloe species, it is assumed that the bird species detected visiting A. reitzii var. reitzii are similarly important pollinators. At least 10 invertebrate species and sengi (Elephantulus sp.) were also recorded as visitors to flowers, but they may be less important pollinators than specialist and generalist avian nectarivores. This study provides further insight into the pollination biology of a diverse, and ecologically important, succulent genus in Africa.