D’hondt, S.

Pinseel, E.

Sabbe, K.

Souffreau, C.

Van de Vijver, B.

Vanormelingen, P.

Verleyen, E.

Vyverman, W.

Open Marine Archive

113 
 
S02: Evolutionary history of terrestrial & marine biota  
Disentangling the evolutionary history of the diatoms in Antarctica: 
the Pinnularia borealis species complex as a case study 
Pinseel Eveline1,2,3, Pieter Vanormelingen1, Sofie D’hondt1, Caroline Souffreau1,4, Elie Verleyen1, Koen 
Sabbe1, Bart Van de Vijver2,3 and Wim Vyverman1 
1 Protistology & Aquatic Ecology, Ghent University, Krijgslaan 281/S8, 9000 Gent, Belgium 
E-mail: eveline.pinseel@ugent.be  
2 Botanic Garden Meise, Nieuwelaan 38, 1860 Meise, Belgium 
3 Ecosystem Management Research Group, University of Antwerp, Universiteitsplein 1, 2610 Wilrijk, 
Belgium 
4 Laboratory of Aquatic Ecology, Department of Biology, University of Leuven, Ch. De Bériotstraat 
32, 3000 Leuven, Belgium 
 
Because of their immense diversity, the systematics of protists, and diatoms in particular, is 
complex and challenging. As species taxonomy has far-reaching consequences for our 
understanding of diatom evolutionary history, ecology and biogeography, detailed studies into 
species limits and diversity are needed if we are to advance our understanding of the range 
dynamics and diversification of diatoms. However, the biogeography and ecology of (pseudo)cryptic 
diatom species is highly understudied and there are virtually no data available on the timing of 
lineage splitting within species complexes. This is especially the case for Antarctica for which 
molecular studies on diatoms are seldom undertaken. In the present study, we used the 
semiterrestrial diatom morphospecies complex Pinnularia borealis as a case study for speciation, 
evolutionary history and biogeography of terrestrial diatoms, and more generally microscopic 
eukaryotes, in Antarctica. 
 
During field campaigns on multiple continents, including the entire Antarctic Region, more than 
500 samples from (semi)terrestrial habitats were collected. From these, over 900 monoclonal 
cultures were established for DNA and morphology. Automatic species delimitation based on the 
cox1 and 28S rDNA genes revealed the presence of at least twelve Antarctic lineages and 93 
lineages worldwide. Of all Antarctic lineages, only two were recovered from other continents. A 
molecular clock analysis on a four marker dataset indicated that the diversification of P. borealis 
started in the late Eocene and strongly increased during the Miocene.  
 
The results indicate a high degree of hidden species diversity in P. borealis worldwide and the 
presence of regional endemics in Antarctica. The topology of the phylogenetic tree and the age of 
the lineage splitting does not support a radiation of the P. borealis species complex in Antarctica. In 
contrast, it suggests multiple independent colonization events in or out of the Antarctic Region 
during the past 20 million years. Together with the high levels of genetic diversity, these findings 
indicate that although the P. borealis complex is relatively successful in dispersal, this is not 
sufficient to prevent speciation. Altogether, our data provide evidence for the moderate endemicity 
hypothesis for micro-organisms and suggest that, whereas Antarctica is the most remote and 
hostile continent on the world, it has been reached and successfully colonized multiple times by 
terrestrial diatoms.  


Disentangling the evolutionary history of the diatoms in Antarctica: the <i>Pinnularia borealis</i> species complex as a case study

Disentangling the evolutionary history of the diatoms in Antarctica: the <i>Pinnularia borealis</i> species complex as a case study

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