Pikea californica

Division: Rhodophyta
Class: Rhodophyceae
Order: Gigartinales
Species name: Pikea californica Harvey
Synonyms: None
Common name: Captain Pike's weed
 
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.
 
Distribution
This species is restricted in Britain to the Isles of Scilly (Maggs & Ward 1996) and has not been recorded anywhere else in Europe.
 
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 insignificant.
 
Effects on commercial interests
Unknown.
 
Control methods used and effectiveness
None used.
 
Beneficial effects
None known.
 
Comments
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).
 
References
Abott, I.A. & Hollenberg, B.J. 1976. Marine algae of California. Stanford University Press, Stanford, California.
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 Unit.
 
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.