World Congress of Malacology Antwerp ... - Unitas Malacologica

Genetic and morphological variability in fluviatile species of Tylomelania (Caenogastropoda:
Pachychilidae) from Southwest Sulawesi, Indonesia
Dames, Claudia; Glaubrecht, Matthias; von Rintelen, Thomas
Museum of Natural History, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin,
Germany,
Email: claudia.dames@museum.hu-berlin.de
The species of the endemic viviparous pachychilid gastropod Tylomelania Sarasin & Sarasin, 1897
form a prominent element of Sulawesi’s limnic biota. Tylomelania is widely distributed in rivers and
has radiated extensively in the ancient lakes of the island. In contrast to the c. 35 lacustrine species
only eight fluviatile taxa have been described to date. Extensive recent sampling has revealed a much
higher diversity of fluviatile species than previously anticipated, though.
Southwest Sulawesi harbours several endemic and distinct Tylomelania species. Most populations
can easily be assigned to a species by their shell morphology. Most of these species are local
endemics, just three are more widely distributed. Generally only one species occurs at each locality,
the only exception being the Balocci Valley in the western part of the peninsula. The three species
occurring syntopic there differ strongly in substrate preference and radula morphology, which is
otherwise rather uniform in fluviatile taxa.
Molecular data are in strong conflict with these morphology-based patterns. The sympatric and
syntopic species of the Balocci valley have identical mtDNA haplotypes, for example, while
haplotypes are very diverse in the most widespread and morphologically rather uniform species T.
perfecta “smooth”. Within this taxon haplotypes group with different clades not just between
individuals from geographically separated populations but frequently even within a single population.
Several alternative hypotheses may be invoked to explain this discrepancy between the observed
morphological and molecular patterns. The identical haplotypes of the morphologically distinct
species in the Balocci valley might be explained by incomplete lineage sorting due to rapid
speciation, while the highly divergent haplotypes of T. perfecta “smooth” might indicate cryptic
species. The latter assumption is rendered rather unlikely by the repeated occurrence of extremely
distinct haplotypey within single populations lacking any apparent geographic structuring, though.
Nuclear data are needed to resolve this conflict.
The evolution of co-operative behaviour:
a virtual ‘experiment’ using high-shore snails as a model system
Davies, Mark S. 1 ; Stafford, Richard 2 ; Williams, Gray A. 3
1. School of Health, Natural & Social Sciences, University of Sunderland, Sunderland, SR1 3SD,
UK, Email: mark.davies@sunderland.ac.uk
2. Cefas, Lowestoft Laboratory, NR33 7TH, UK,
Email: richardstafford@yahoo.co.uk
3. The Swire Institute of Marine Science, Department of Ecology & Biodiversity, The University of
Hong Kong, Hong Kong,
Email: hrsbwga@hkucc.hku.hk
Aggregation is a co-operative behaviour with demonstrated individual level selective advantages in
many animals. However, the evolution of co-operative behaviour through individual-based selection
mechanisms is unresolved. An individual gains no benefit from evolving an aggregation trait, unless
the trait is shared. We show that aggregation can occur as an emergent property of individually
beneficial traits, providing a fully individual-based mechanism to explain the evolution of cooperative
behaviours.
High-shore snails (Echinolittorina trochoides and E. radiata) were used as model animals. They
move upshore with the incoming tide to feed while awash. As the tide retreats, they move downshore,
forming complex aggregation patterns both in crevices and on smooth rock. We simulated downshore
movement patterns virtually, using three behavioural rules: an aggregation rule, where if two or more
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