Introduced ascidians along the coast of South Africa: water temperature as a predictor of their geog

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Introduced ascidians along the coast of South
Africa water temperature as a predictor of
their geographical distributionMarc Rius1,
Charles L. Griffiths2, Xavier Turon1
1Departament de Biologia Animal, Universitat de
Barcelona, Av. Diagonal 645, 08028, Barcelona,
Spain2Department of Zoology, University of Cape
Town, Rondebosh, Cape Town 7700, South Africa
Known introduced / cryptogenic ascidians species
on the South African coastline Introduced
Clavelina lepadiformis, Diplosoma listerianum,
Ciona intestinalis, Ascidia sydneiensis,
Ascidiella aspersa, Botrylloides leachi,
Cnemidocarpa humilis, Styela plicata, Microcosmus
squamiger Cryptogenic Trididemnum cerebriforme,
Didemnum granulatum, Didemnum psammathodes,
Didemnum rodriguesi, Corella eumyota, Botryllus
schlosseri, Polycarpa insulsa, Styela canopus
Surveys in winter 2007 covering all main
harbours, marinas and an oyster farm
SOUTH AFRICA
Benguela Current
Agulhas Current
ATLANTIC OCEAN
INDIAN OCEAN
Cape Agulhas where the Indian and Atlantic
Oceans meet
Cape Agulhas
Survey sites
v - Rare vv - Common vvv - Dominant
Tolerant to a wide temperature range
v
Dominant in cold waters
Dominant in warm waters

Cross fertilization For C. intestinalis and A.
aspersa (following Havenhand Svane 1991) and
for S. plicata and M. squamiger (Marshall
Keough 2003)

• Larval development (within 24 hours) depending on
  the temperature (N 5 individuals)
• Four dominant species
• West of the Cape (C. intestinalis, A. aspersa)
• East (S. plicata, M. squamiger)

Settlement patterns followed the same trend
according to temperature