World Congress of Malacology Antwerp ... - Unitas Malacologica

Holocene molluscan successions from the Lake Baikal region, Siberia
Preece, Richard C. 1 ; White, Dustin 1,2 ; Shchetnikov, Alexander A. 3
1. Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK,
Email: rcp1001@cam.ac.uk
2. Department of Anthropology, 13-15 HM Tory Building, University of Alberta, Edmonton, Alberta
T6G 2H4, Canada,
Email: dw330@cam.ac.uk
3. Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences, Irkutsk
664033, Russia,
Email: shchet@crust.irk.ru
This paper reviews the Holocene molluscan successions from two well-dated sites in the Baikal
region of south-central Siberia, the most detailed yet reported from the entire eastern Palaearctic.
Floodplain sediments of the upper Lena River near Basovo, west of the northern tip of Lake Baikal,
yielded over 72 500 shells from at least 28 species of terrestrial and 23 species of freshwater mollusc,
an abundance and diversity far higher than previously reported from the region. The molluscan
assemblages are dominated by land snails, especially Vallonia, represented by five species including
V. tenuilabris and two poorly known taxa V. kamtschatica and V. cf. chinensis. Other noteworthy
species recovered include Gastrocopta theeli, Carychium pessimum, Vertigo extima (southernmost
record), V. microsphaera (fourth record) and the first Asian records of three other taxa (V. geyeri, V.
genesii and V. parcedentata). The molluscan assemblages show clear successional trends during the
early to mid Holocene, reflecting episodes of dryness/wetness on the floodplain. Drier conditions at
c. 6350 14 C yr BP coincide with major changes in the archaeological record seen at other sites in the
region but it remains unclear whether the two are linked. A prominent charcoal-rich horizon dated to
c. 2800 14 C yr BP marks a burning event in the catchment, which resulted in a twofold increase in
sediment accumulation rate. The faunal analyses have been integrated with a detailed pedological
study of the sedimentary profile and a chronology provided by means of twelve AMS radiocarbon
dates. The second site near Burdukovo lies east of Lake Baikal and it too has provided a clear
Holocene succession but somewhat less dynamic than that at Basovo. This study provides the first
detailed palaeoecological information relating to Holocene molluscan assemblages from the Baikal
region and lays the foundation for future work in the eastern Palaearctic.
Preliminary study of DNA sequence variation in the terrestrial snail Rumina decollata
Prévot, Vanya 1,2 ; Jordaens, Kurt 3 ; Backeljau, Thierry 1,3
1. Royal Belgian Institute of Natural Sciences, Vautierstraat 29, B-1000 Brussels, Belgium,
Email: vanya.prevot@naturalsciences.be; Thierry.Backeljau@naturalsciences.be
2. Laboratory of Evolutionary Genetics, Institute of Molecular Biology and Medecine (IBMM), Free
University of Brussels, rue des Professeurs Jeener et Brachet 12, B-6041 Gosselies, Belgium,
3. Evolutionary Biology Group, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp,
Belgium,
Email: kurt.jordaens@ua.ac.be
Rumina decollata (Gastropoda: Subulinidae) is a predaceous land snail that is native to countries
bordering the Mediterranean Sea and that has been widely introduced in many other areas. The
species presents a high degree of shell and colour polymorphism. Being a hermaphroditic species, R.
decollata is described as a complex of homozygous allozyme strains generated by a breeding system
of facultative self-fertilization. The North African form of R. decollata may be a separate species,
viz. R. saharica, which seems to be supported by the genital anatomy.
In order to (re-)interpret the taxonomy, population genetic structure and colonisation history of this
species, both in its native range and in areas where it was (recently) introduced by man, we started a
combined morphological and molecular genetic analysis on both micro- and macrogeographic scales.
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