Original Research
A new long-tubed subspecies of Pelargonium dipetalum (section Hoarea) (Geraniaceae) from the Albertinia-Swellendam area in Western Cape Province, South Africa
Submitted: 19 May 2014 | Published: 08 December 2014
About the author(s)
M. Marianne le Roux, National Herbarium, South African National Biodiversity Institute, South Africa; Department of Botany and Plant Biotechnology, University of Johannesburg, South AfricaJohn C. Manning, Compton Herbarium, South African National Biodiversity Institute, South Africa; Research Centre for Plant Growth and Development, University of KwaZulu-Natal, South Africa
Abstract
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.
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