Date of introduction and origin
Pikea californica was first recorded from the Isles
of Scilly off south-west England in 1983 (Hiscock 1984), although
examination of herbarium specimens showed that the population was
present in 1967 (Maggs & Guiry 1987). This species is known
from the west coast of North America. It is thought to have been
introduced from California (Maggs & Guiry 1987), possibly
having arrived during World War II.
Method of introduction
Flying boats flew directly from California to the Isles of
Scilly during World War II and Crisp (1958) reported that seaplane
hulls and floats are occasionally fouled by algae. This species may
have been transferred by Catalinas employing canvas sea
anchors (stored in the hull while flying which would consequently
have been damp but aerated), since it appears to be physiologically
robust and, furthermore, the planes flew at relatively low
altitudes (Maggs & Guiry 1987). However, Maggs & Ward
(1996) have carried out a recent survey of the Californian coast
and report that Pikea californica does not currently occur
around San Diego, where the seaplanes were manufactured. They have
no other suggestions concerning the vector used for transporting
this species from California.
Reasons for success
The limited temperature range in the Isles of Scilly may
favour this species (see Maggs & Guiry 1987).
Rate of spread and methods involved
Pikea californica has not been found elsewhere in
Great Britain and may be confined to favourable conditions found in
the Isles of Scilly.
This species is restricted in Britain to the Isles of Scilly
(Maggs & Ward 1996) and has not been recorded anywhere else in
Factors likely to influence spread and distribution
This species is possibly limited by winter temperatures in
Britain (Maggs & Guiry 1987).
Effects on the environment
Possible displacement of native species, but likely to be
Effects on commercial interests
Control methods used and effectiveness
In order to recognise this species, examination of the
distinctive anatomical detail is required (D.A. Birkett pers.
comm.). Recent research has shown that Japanese populations of
'Pikea californica' are in fact another species (Maggs
& Ward 1996).
Abott, I.A. & Hollenberg, B.J. 1976. Marine algae of
California. Stanford University Press, Stanford,
Crisp, D.J. 1958. The spread of Elminius modestus
Darwin in north-east Europe. Journal of the Marine Biological
Association of the United Kingdom, 37: 438-520.
Hiscock. K. 1984. Sublittoral survey of the Isles of
Scilly. Pembroke Field Studies Council, Oil Pollution Research
Maggs, C.A., & Guiry, M.D. 1987. An Atlantic population of
Pikea californica (Dumontiaceae, Rhodophyta). Journal
of Phycology, 23: 170-176.
Maggs, C.A., & Ward, B.A. 1996. The genus Pikea
(Dumontiaceae, Rhodophyta) in England and the North Pacific:
comparative morphological, life history, and molecular studies.
Journal of Phycology, 32: 176-193.
Acknowledgements (contributions from questionnaire)
Dr C.A. Maggs, Queen's University of Belfast.