World Congress of Malacology Antwerp ... - Unitas Malacologica

Waddington´s widget in the field: Do different stress response strategies result in variations of
pulmonate shell variability?
Köhler, Heinz-R. 1 ; Lazzara, Raimondo 1 ; Dittbrenner, Nils 1 ; Krais, Stefanie 1 ; Capowiez, Yvan 2 ;
Mazzia, Christophe 2 ; Triebskorn, Rita 1,3
1. Animal Physiological Ecology, University of Tübingen, Konrad-Adenauer-Str. 20,
D-72072 Tübingen, Germany,
Email: heinz-r.koehler@uni-tuebingen.de
2. Invertebrate Ecology, INRA Avignon, Domaine St-Paul, site Agroparc, F-84914
Avignon cedex 9, France,
3. Steinbeis-Transfer Center for Ecotoxicology and Ecophysiology, Blumenstr. 13,
D-72108 Rottenburg, Germany
In a stable environment, stabilizing selection favours an average intensity of a phenotypic trait whilst
extremes are cut off from this trait´s variability curve. Consequently, stabilizing selection reduces
phenotypic variability which, however, is the prerequisite for all evolutionary processes. This is a
well-known dilemma in microevolutionary theory. A way to circumvent this dilemma is to accept
hidden variability which can occur in populations and species but is not subject to selection in its
hidden form, and is phenotypically expressed at certain occasions only. Besides inherited but
unexpressed characters (e.g. the potential variability of male characters in a mostly parthenogenetic
population), an epigenetic phenomenon which has been called Waddington´s widget may contribute
to often disguised but occasionally apparent phenotypic variability: the observation that variability
increases in populations undergoing stress. In recent years, it was discovered that stress proteins can
act as molecular capacitors of phenotypic variability and thus likely contribute to the Waddington´s
widget phenomenon. We investigated natural populations of different species of mediterranean
pulmonate snails (which showed different variability in their shell morphology) for their stress
protein (hsp70, hsp90) responses to environmental heat stress. In our dataset, a stress response
strategy which involved rather low levels of stress proteins correlated with a high morphological
variability in the colouration of the shell. This is the first evidence that a molecular process which is
thought to contribute to Waddington´s widget may condition morphological variability in natural
field populations.
Climbing the gene trees: a first molecular step towards elucidating the extreme morphological
variation within Abida secale
Kokshoorn, Bas 1 ; Gittenberger, E. 2
1. Institute of Biology, Leiden University, P.O.Box 9516, NL-2300RA Leiden, The
Netherlands,
Email: kokshoorn@naturalis.nnm.nl
2. National Museum of Natural History, P.O. Box 9517, NL 2300RA Leiden, The
Netherlands,
Email: gittenberger@naturalis.nnm.nl
The genus Abida Turton, 1831 (Pulmonata: Chondrinidae) consists of 10 currently known species.
All are obligate limestone dwellers, i.e. occurring exclusively in calcareous habitats. With the
exception of two species, viz. A. polyodon (Draparnaud, 1801) and A. secale (Draparnaud, 1801),
their distributional ranges are restricted to the Cantabrian mountains in NW Spain and the Pyrenees.
Abida secale occurs throughout Europe, from England in the west, Belgium and southern Germany in
the north and Slovakia and former Yugoslavia in the east. The southern part of its distribution
includes N. Italy, France and NE. Spain. The morphological differentiation is small over the largest
part of its range. An exception to this uniformity is found in the extreme southwestern part of the
species’ range. In SE. France and NE. Spain the species shows an extreme morphological
differentiation. This has led to the description of three subspecies in the French part of the Pyrenees,
one in Andorra and an astonishing eleven in the province of Catalunya, Spain.
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