Pollen-ovule ratios and flower visitors of day-flowering and night-flowering Conophytum (Aizoaceae) species in South Africa

•Flower visitors were observed for 30 Conophytum (Aizoaceae) species in South Africa.•Pollen wasps (Quartinia: Masarinae) were main flower visitors in diurnal species.•In night-flowering species different moth species were observed as flower visitors.•Pollen-ovule ratios (P/O) were analyzed to characterize pollinator efficiency.•P/Os of diurnal and nocturnal species suggest similar pollinator efficiency.

In desert environments mutualistic relationships between plants and their pollinators are believed to be strongly synchronized by rainfall that triggers flowering periods. However, recent studies have shown that this might not always be the case and that the level of specialization may also play a role. Although spring is the main flowering season in Namaqualand, the winter-rainfall region of southern Africa's Succulent Karoo, a pronounced flowering peak occurs in autumn, outside of the normal winter–spring period. One example is the genus Conophytum where, in contrast to the vast majority of the Aizoaceae, most species flower in autumn before the winter rain. About 25% of the species in the genus are night-flowering, maybe as a consequence of the shift in the seasonal flowering time. We therefore studied flower visitors in 30 Conophytum species in South Africa and, for comparison of pollination systems, analysed pollen-ovule ratios in diurnal and nocturnal conophytums. Pollen wasps of the genus Quartinia (Vespidae: Masarinae) were found to be the main flower visitors in diurnal species, whereas in night-flowering species different moth species were observed. We found no significant differences between pollen-ovule ratios of diurnal and nocturnal Conophytum species, suggesting that diurnal and nocturnal pollinators are equally efficient.