[Taxacom] Ishavstaangen - the ice sea weed

Algologia algologia at telia.com
Wed Dec 16 05:24:29 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


A. Athanasiadis

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