A bimodal pollination system enhances reproductive potential of translocated populations of an endangered grassland succulent

Abstract

Frithia humilis Burgoyne is an endangered, cryptic, dwarf succulent in the Aizoaceae (Burgoyne & Krynauw 2005; Burgoyne, Smith & Du Plessis 2000). It is endemic to the Rand Highveld Grassland of Gauteng and Mpumalanga in South Africa, specifically the area between Bronkhortspruit, Ogies and Middelburg. Here it is restricted to flat sandstone plates of the Dwyka and Ecca formations in microhabitats comprising aggregates of weathered rock and organic materials (Burgoyne & Hoffman 2011). The succulent leaves of the species generally grow from beneath the soil surface (a typical window plant), seldom protruding more than 20 mm above ground level. The leaves are contractile, allowing the plant to retract into the soil where it is protected from desiccation and frost in the winter months (Burgoyne et al. 2000). Consequently, leaves of this species are only visible during active growth, specifically when flowering during the summer months (Figure 1a).