^. \. «3 S.6M.I010 <^ GENERA -3 MAR Bulletin of the ^ LIBRAR British Museum (Natural History Botany series Vol 7 1979 British Museum (Natural History) London 1980 Dates of publication of the parts No 1 25 October 1979 No 2 25 October 1979 No 3 20 December 1979 ISSN 0068-2292 Printed in Great Britain by Henry Ling Ltd, at the Dorset Press, Dorchester, Dorset : ^ GENERAL ^^ .^^ 'i;. hV Contents Botany Volume 7 Page No 1 The distribution of Padina pavonica (L.) Lamour. (Phaeophyta: Dictyotales) on British and adjacent European shores J. H. Price, I. Tittley & W. D. Richardson No 2 Seaweeds of the western coast of tropical Africa and adjacent islands a critical assessment. Ill, Rhodophyta (Bangiophyceae) D. M. John, J. H. Price, C. A. Maggs & G. W. Lawson 69 No 3 A revision of the genus Anacyclus L. (Compositae : Anthemideae) C. J. Humphries 83 Bulletin of the British Museum (Natural History) The distribution of Padina pavonica (L.) Lamour. (Phaeophyta : Dictyotales) on British and adjacent European shores James H. Price, Ian Tittley and Walter D. Richardson Botany series Vol 7 No 1 25 October 1979 The Bulletin of the British Museum {Natural History), instituted in 1949, is issued in four scientific series, Botany, Entomology, Geology (incorporating Mineralogy) and Zoology, and an Historical series. Papers in the Bulletin are primarily the results of research carried out on the unique and ever-growing collections of the Museum, both by the scientific staff of the Museum and by specialists from elsewhere who make use of the Museum's resources. Many of the papers are works of reference that will remain indispensable for years to come. Parts are published at irregular intervals as they become ready, each is complete in itself, available separately, and individually priced. Volumes contain about 300 pages and are not necessarily completed within one calendar year. Subscriptions may be placed for one or more series. Subscriptions vary according to the contents of the Volume and are based on a forecast list of titles. As each Volume nears completion, subscribers are informed of the cost of the next Volume and invited to renew their subscriptions. Orders and enquiries should be sent to: Publications Sales, British Museum (Natural History), Cromwell Road, London SW7 5BD, England. World List abbreviation: Bull. Br. Mus. nat. Hist. (Bot.) Trustees of the British Museum (Natural History), 1979 ISSN 0068-2292 Botany series Vol 7 No 1 pp 1-67 British Museum (Natural History) Cromwell Road London SW7 5BD Issued 25 October 1979 The distribution of Padina pavonica (L.) Lamour. (Phaeophyta : Dictyotales) on British and adjacent European shores James H. Price Department of Botany, British Museum (Natural History), Cromwell Road, London SW7 5BD Ian Tittley Department of Botany, British Museum (Natural History), Cromwell Road, London SW7 5BD and Walter D. Richardson Department of Biological Sciences, Goldsmiths' College, University of London, New Cross, London SE 1 4 6NW Contents Synopsis .... 2 Introduction .... 2 General distribution and ecology 3 Life-history 4 Distribution along the coasts of the British Isles 11 Aberdeenshire 12 Essex. .... 14 Kent 14 Sussex .... 15 Isle of Wight 16 Dorset .... 18 Devon (South) 23 Cornwall .... 28 Devon (North) . 29 Glamorgan 30 Pembrokeshire . 30 Anglesey .... 30 Lancashire 31 Ayrshire .... 31 Argyllshire. 32 Ireland .... 32 Co. Galway 32 Co. Cork 32 Distribution along adjacent continental coasts 32 Benelux .... 33 33 Netherlands . Belgium .... 33 France .... 35 36 Nord [French Flanders] . 36 Pas de Calais . Somme .... 37 Seine Maritime 37 Eure .... 37 Calvados 38 Manche .... 39 Channel Islands 41 Issued 25 October 1979 Bull. Br. Mils, licit. Hist. (Bot.) 7(1) : 1-67 J. H. PRICE, I. TITTLEY & W. D. RICHARDSON Ille-et-Vilaine ..... 44 Cotes du Nord .... 44 Finistere. ..... 45 Morbihan ..... 46 Loire Atlantique; Vendee; Charente Maritime 47 Gironde; Landes .... 49 Basses Pyrenees .... 49 Iberia ...... 50 Northern Spain: Guipuzcoa to Pontevedra 50 Portugal ...... 51 Atlantic southern Spain . 52 Discussion ...... 53 Trends in distribution .... 53 Origins of populations and distribution foci 54 Reproductive patterns .... 55 Validity of earlier data 55 Variations between Britain and the adjacent continent 57 Periodicity of biological phenomena 58 Acknowledgements. .... 58 References ...... 59 Synopsis Padina pavonica is one of the few British marine algae for which there is a sufficiently long history of data, relatively plentiful and reliable, to p>ermit conclusions as to distributional variation in time and space. The species reaches its current northern limits along southern British and Irish shores; there is strong circum- stantial evidence that past, maybe ephemeral, populations occurred considerably further north. Contraction in distribution range, possibly one aspect of periodic or irregular regional response to environmental changes at range periphery, seems generally indicated. There may have been similar contraction on adjacent shores of Netherlands, Belgium and northern France. British foci of distribution are Devon (the earliest recorded), Dorset, and the Isle of Wight. Analogous foci can be recognised along northern French shores. Gametangial plants seem currently to be very rare outside the Mediterranean; even in it, gametangia seldom develop on plants in the first 0-5 m of the infralittoral. On British and perhaps adjacent continental shores, P. pavonica appears rarely to grow below that depth and this may accentuate gametangial scarcity. Tetrasporangia are much more common than gametangia on Atlantic shores, occurring especially in July to September. Basal perennation and vegetative spread remain very important. Plants seem to appear slightly earlier in the year in Atlantic areas near the Mediterranean. Introduction Many past British and Irish records of benthic marine algae are unsupported by representative specimens. Generally, the earlier the records, and in more recent times the more common the species, the more likely is the lack of material. The delimitation beyond reasonable doubt of phasic or irregular peripheral changes in distribution (expansion or contraction in range) over time for any long-established species therefore requires that the plants be both conspicuous enough to have been frequently noticed in the past and so distinctive that statements made in even the sketchiest of published data, however early, can be confidently accepted as relating to that species. Few British algae of distributional interest, the northern or southern limit or some characteristic and unusual discontinuity occurring here, qualify under such stringent requirements as regards data from the distant past, although more are susceptible to analysis in terms of the last 70- 80 years. Species such as Asparagopsis armata, Boimemaisonia hamifera, Colpomenia peregrina, and the more recent Sargassum muticum have established here during that time; recognition of these events was comparatively easier since by then phycological knowledge was more extensive and generally more accurate than in past eras, and the invasion by alien species is often more spectacular than long-term variations in the long-established flora. Jones (1974) provides the most recent broad review of distributional and floristic changes in the British marine benthic flora; his examples, for reasons given above, are mostly from the 20th century and even then concern less the ;: THE DISTRIBUTION OF PADINA PAVONICA 3 variations or loss of species than the spectacular introductions. Jones refers to a few instances, such as the fluctuations and periodic absences oi Nemalion helminthoides (Veil.) Batt. on Anglesey. There have been very few attempts to determine what changes have occurred, even within this century, in distribution of any species or genus over a wide geographical area and we have been unable to trace any detailed attempt to examine the situation for a particular species throughout its recorded history in the British Isles, although there has been generalisation on the subject. Those detailed comparisons that have been made (Price & Tittley, 1972 and in prep.; Edwards, 1975; Price et al., 1977a, b) have dealt with the relationship of past to present floras of restricted areas (mostly counties). During work on the Kent marine flora, two of us (J. H. P.; I. T.) became aware that, amongst the older-established British marine flora, one of the few good candidates for species-oriented study in distributional change at range periphery over recorded time is Padina pavonica* The only Padina species reported for the study area, P. pavonica has long possessed both an English name (Turkey-feather alga') and, previously, a pre-Linnean name {Fucus maritimus Gallopavonis pennas referens of C. Bauhin, 1620 et seq.) that were unequivocal and of common usage. General distribution and ecology Padina pavonica, indeed the whole genus Padina, is overwhelmingly of warmer water affinities. P. pavonica reaches its present European northern limit of distribution on the coasts of southern England and southern Ireland, and on the adjacent French coasts (Fig. 1). Sporadically, there have been reports of finds to the north and east of the limits as currently recognisable. The body of the paper presents detailed examination of the present European Atlantic distribution and of all the available evidence on previous occurrence. No attempt has been made precisely to delimit the world distribution of P. pavonica because of taxonomic uncertainties concerning some earlier