A new long-tubed subspecies of <i>Pelargonium dipetalum</i> (section <i>Hoarea</i>) (Geraniaceae) from the Albertinia-Swellendam area in Western Cape Province, South Africa

• Main Authors: M. Marianne le Roux, John C. Manning
• Format: Article
• Language: English
• Published: South African National Biodiversity Institut 2014-12-01
• Series: Bothalia: African Biodiversity & Conservation
• Subjects: Ecotype; New subspecies; Pelargonium dipetalum L’Hér.; Pollination; Section Hoarea (Sweet) DC.
• Online Access: https://abcjournal.org/index.php/abc/article/view/163
• ISSN: 0006-8241; 2311-9284

Background: Field studies confirmed that unusually long-tubed populations of Pelargonium dipetalum from between Swellendam and Albertinia, Western Cape Province, South Africa, are a distinct ecotype adapted to pollination by the long-proboscid fly, Prosoeca longipennis. The geographical and morphological isolation of these populations suggests that they are reproductively isolated from short-tubed populations, which are pollinated by bees. Objectives: To determine and describe the floral variation in P. dipetalum, with a view to recognising the long-tubed populations at some taxonomic level. Method: All available collections were measured and compared. Results: Populations of P. dipetalum were segregated into a short-tubed form with hypanthium 3 mm – 24 mm long and mostly pink petals that occurs from Betty’s Bay to Knysna, and a long-tubed form with the hypanthium 34 mm – 54 mm long and consistently white petals that is restricted to a small area east of Swellendam between Suurbraak and Albertinia. We described the long-tubed form as the new subspecies P. dipetalum subsp. stenosiphon. Conclusion: The new subspecies increases our understanding of the diversity in P. dipetalum and represents a new taxon of conservation concern.