World Congress of Malacology Antwerp ... - Unitas Malacologica

New inventory and conservation methods of the threatened freshwater bivalve Unio crassus
Valovirta, Ilmari
Finnish Museum of Natural History, P.O.Box 26, FIN-00014 University of Helsinki, Finland,
Email: ilmari.valovirta@helsinki.fi
Finnish Museum of Natural History acting together with the WWF-Finland joined in 1996 the
inventory of Unio crassus into the Margaritifera working group. The main object is to inventory and
study the distribution, ecology, morphology and protection of these species. Unio crassus is protected
by law in Finland and it belongs to the Annex II and IV of the EU Habitats directive and is strict
protected in the European Union.
Sub-aqua work is very prominent in the research of this group. We have inventoried one meter wide
underwater research transect by SCUBA divers more than 2500 km. This inventory project is one of
the largest and most accurate in Europe. It gave lot of new information about the methods how to
inventory natural and seminatural environments of U. crassus. The importance of the right water flow
and the natural continuity of different river habitats, macro- meso- and microhabitats, have been
turned out as a very important reason for a successful conservation of U. crassus.
Two of the largest calculated U. crassus populations in Europe exists in Finland in the river
Mustionjoki and in the river Vantaa. In both of these there are more than one million specimens. The
former river belongs to the Natura 2000 network being set up under the EU Habitats Directive. The
river Vantaa flows through the capital of Finland, Helsinki and it is not yet in the Natura 2000. There
are only four rivers of the 20 known inhabited by U. crassus which are inside Natura network in
Finland. The mussels working group has checked U. crassus populations also in some rivers in
Estonia and Latvia.
The Turkana mollusks reconsidered: punctuational evolutionary events or biological
invasions?
Van Bocxlaer, Bert 1 ; Van Damme, Dirk 1 ; Feibel, Craig S. 2
1. Research Unit Palaeontology, Department Geology and Soil Science, Ghent University, Krijgslaan
281 (S8), B-9000 Ghent, Belgium,
Email: Bert.VanBocxlaer@ugent.be; Dirk.VanDamme@ugent.be
2. Department of Geological Sciences, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854-
8066, USA,
Email: Feibel@rci.rutgers.edu
A controversial concept in current evolutionary thought is Eldredge & Gould’s punctuated
equilibrium model, which proposes long periods of morphological stasis interspersed with rapid
bursts of dramatic evolutionary change. The validity of the punctuated equilibrium model remains
contested, with various high-profile studies often cited in support of its veracity. One of the most
iconic pieces of research in support of punctuated equilibrium is the work of Williamson on the
Cenozoic molluscs of the Turkana Basin. This study claimed to have found firm evidence for three
episodes of rapid evolutionary change separated by long periods of stasis in a 35 ka high resolution
sequence. Most of the discussions following this report centered on the topics of (eco)phenotypy vs
genotypy and the possible presence of preservational and temporal artefacts. The debate remains
largely unsettled, leaving Williamson’s reports as one of the empirical foundations of the paradigm of
punctuated equilibrium. Here we conclusively show Williamson’s original interpretations to be
highly flawed. The supposed rapid bursts of punctuated evolutionary change are in fact artefacts
resulting from the invasion of extrabasinal faunal elements in the Turkana palaeolakes during Plio-
Pleistocene East African wet phases. The new results emphasize the importance of taking into
account geological, climatological, hydrogeographical and ecological parameters when considering
faunal successions in an evolutionary context. The punctuated equilibrium model loses herewith
empirical palaeontological support.
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