[Taxacom] Ishavstaangen - the ice sea weed

Athanasios Athanasiadis Athanasios.Athanasiadis at marecol.gu.se
Wed Dec 16 05:37:13 CST 2009

The earliest notification of climatic changes affecting seaweed  
distribution was published by the late Peter Dixon  
(Biol.Signif.Clim.Changes in Britain: 113. 1965), where temperature  
is postulated to be the cause of recent re-invasions in Europe, and  
there are several examples in Scandinavian waters. Apart from those  
mentioned by Dixon, the warm-temperate red alga Sphaerococcus  
coronopifolius Stackhouse is presently considered to be an  
established species in Sweden - the first confirmed records dating  
since the 90's (and unconfirmed ones suggesting conspecifity with  
Lyngbye's Desmia hornemanii described in 1819 from Oeresund). Several  
European Delesseriaceae such as Hypoglossum Kuetzing and  
Haraldiophyllum Zinova are new members of the Scandinavian flora  
since a few decades. The possibility that such southern species could  
be in fact glacial survivals exists but is remote. If so, we would  
expect to see endemics as well - but to find the latter we have to  
'botanize' along the maximum ice cover, apparently both in the south  
and the northern border of the latest glaciation (Nord.J.Bot.24:  
469-499. 2007; Taxon 57: 223-230. 2008).
Yet, the case of Fucus evanescens C. Agardh 1820 stands as unique.  
Here we have a supposed Arctic species that in the past 100 years  
expanded its distribution in the opposite direction. Until 1890, its  
southern limit was near the polar circle (Kjellman,  
Handb.Skand.havsalgfl.: 67. 1890), but in 1894 it was reported from  
Oslofjord - a 'natural' jump of about 7°. Within 30 years it had  
reached the Swedish west coast, and after another 70 years it was  
recorded in Kiel's Bay (nearly 12° below the polar circle). The  
arctic-like conditions of the Baltic might explain this event, but  
the species was also reported from the Faeroes (Boergesen,  
Mar.Alg.Faeroes: 465. 1902, as F. inflatus) and the Shetlands (Powell  
in J.mar.bio.Assoc.U.K.36: 664-5. 1957, as subsp. edentatus).  
Recently, Baltic hybrids with local F. serratus Linne have been  
reported - although the two species coexist for thousands of years  
above the polar circle. It was hypothesized that local hybridization  
could be due to differences between the (isolated) Baltic F. serratus  
and the polar populations (Proc.R.Soc.Lond.269: 1829-34. 2002), but  
was that F. evanescens the same species originally described from  
Kamtchatka, genetically more related to F. gardneri Silva from the  
North Pacific (J.phycol.35: 389. 1999), and currently 'synonymized'  
with F. inflatus Linne 1753 (type locality: Norway), F. edentatus  
Pylaie 1829 (type locality: New Foundland), and F. bursigerus J.  
Agardh 1868 (type locality: Spitsbergen) ?

A few months ago, several Fucus specimens surfaced unexpectedly in a  
closet. They were sent away from a herbarium, thankfully not thrown  
away without consultation. A closer look showed that they were  
collected by D. Hylmoe at Varberg, on the Swedish west coast, between  
February 1933 and April 1934. Lenghty comments on the labels such as  
'Fucus serratus L. x inflatus..', 'Fucus inflatus L. x  
vesiculosus...', '...x...', '...x...', '...x...', '...x...', reveal a  
burning interest and intensive effort to find out. They were given a  
place as the first collections of an introduced species in that part  
of Sweden, deserving thorougher attention.
Was it the Arctic seaweed ?

with best wishes for the Holidays and the New Year,
and a reminder of the field courses the coming summer

Dr. A. Athanasiadis
University of Gothenburg
Marine Botany
P.O. Box 461
SE 405 30 Gothenburg, Sweden
Fax int-31-7862727

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