THE DISTRIBUTION OF PADINA PAVONICA 



variations or loss of species than the spectacular introductions. Jones refers to a few instances, 

 such as the fluctuations and periodic absences ofNemalion 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., 19770, 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 

 refer ens 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 

 records. 



In the Mediterranean, apparently the centre of its distribution, P. pavonica is exclusively an 

 infralittoral alga, occurring over a wide depth range. Plants are present, often in considerable 

 abundance, in depths from about m down to 20 m; in some areas (e.g. the Straits of Messina), 

 they continue down to at least 40 m. Ramon & Friedmann (1966) reported the alga from to 2-5 m 

 at various Mediterranean localities; Zavodnik (1977) regarded it as characteristic in the Adriatic 

 upper infralittoral in semi-exposed and well-illuminated localities; Feldmann (1937) recorded it to 

 20 m in the Banyuls region. No systematic search for the alga has been made in the infralittoral 

 around British and adjacent continental shores, although the frequency and extent of recent 

 infralittoral studies in southern Britain would suggest that if P. pavonica were commonly present 

 it would have been noted. In those areas, the vertical distribution of Padina apparently extends 

 from shallow pools and damp areas just below MHWS into the shallow infralittoral, 0-5 m below 

 MLWS. With one possible exception, for which the data do not provide information more precise 

 than 'dredged in Plymouth near Duke rock', records have never been established along British and 

 adjacent continental coasts from greater depths. If this is a true, rather than an apparent, vertical 

 amplitude, the constraints may lie with available light or with temperature levels (cf Liddle, 1975; 

 Allender, 19770, b). In Britain, the most prolific growth of this alga has been detected in the lower 

 littoral, either on very wet rock or similar surfaces, or in shallow pools. 



* The latest International Code of Botanical Nomenclature (Stafleu et al, 1978) recognises in its list of Nomina 

 Conservanda (entry for Padina Adanson, Appendix III : 270) that the correct name to be applied to that species of 

 Padina occurring along European shores is P. pavonica. The current British check-list (Parke & Dixon, 1976) 

 continues to list the species as P. pavonia (L.) Lamour. Since both forms of the specific epithet are non-standard (not 

 accepted forms of adjectives derived from pavo), that form first used by Linnaeus (Fucus pavonicus, Spec. pi. . . .'. 

 1162, 1753) has to be accepted (Silva, in lift., 12 Oct. 1977; Papenfuss, 1977). We diverge from the opinions of Drs 

 Silva and Papenfuss only on the point of whether pavonius(Syst. not., ed. 10 : 1345, 1759) and pavonicus are distinct 

 or variant forms. They, with Thivy (in Taylor, 1960 : 234-235), regard them as distinct, therefore accepting the 

 authorities for the combination P. pavonica as (L.) Thivy in W. R. Taylor. By contrast, we regard them as variants 

 of the same epithet ; the combination is therefore here cited as Padina pavonica (L.) Lamour. (Hist, polyp. ...1816: 

 304). Although virtually all relevant authors [for details see Silva, 1952 : 276] back to Adanson (1763 : 586) had 

 clearly indicated their intention to recombine Fucus pavonicus L. in Padina Adanson or elsewhere, those prior to 

 Lamouroux (1816) made their statements in such a way as not to meet the requirements of Article 33 of the Code 

 (Stafleu et al., 1978). 



