Succulents in the family Apocynaceae
Stapelia belongs to Apocynaceae, subfamily Asclepiadoideae. Fleshy stems are adapted to water storage, while the greatest diversity of reproductive characters is visible in the flowers. Pollen remains joined in pollinia, transferred by insects through a specialized attachment apparatus. [Meve and Liede 1994] [Bruyns et al. 2014]
Relationships and the broad treatment of Ceropegia
Molecular studies showed stapeliads nested within the broader Ceropegia lineage. In 2017, Bruyns and coauthors proposed including stapeliad genera in an expanded Ceropegia, divided into sections. POWO still accepts the genus Stapelia, so both treatments occur in current literature. An example is Stapelia hirsuta var. hirsuta, studied in 2026 as Ceropegia pulvinata var. pulvinata. [Bruyns et al. 2017] [Shuttleworth et al. 2026] [2-WWW]
Scent and touch
In stapeliad flowers, scent substances are produced in living secretory tissues called osmophores. Analyses of different species show different proportions of volatile sulphur compounds, phenols, aldehydes and organic acids. Attraction effectiveness depends on a mixture of chemical signals and flower-surface characters. [Jürgens et al. 2006] [Płachno et al. 2010]
In S. hirsuta var. hirsuta, experimentally removing hairs shortened the time flies spent probing the flower. Differences between yellow and burgundy flowers in the population studied were less significant for insect behaviour. Results show the functional role of structural details, which can be tested by manipulating an individual character. [Shuttleworth et al. 2026]