World Congress of Malacology Antwerp ... - Unitas Malacologica

To live or not to live in mud: The Neogastropod side of the story
Fortunato, Helena
Institute für Geowissenschaften Universität Kiel, Ludewig-Meyn-strasse 10, D-24118 Kiel,
Germany, Email: fortunatomh@hotmail.com
Although muddy substrates are often viewed as flat and featureless environments, the abundance of
nutrient rich material provide an optimal habitat for many infaunal and epifaunal organisms. In the
Gulf of Panama (eastern Pacific coast) the dominant habitat type is fine, silty mud, often with
terrigenous component. Few sandy patches (carbonate sand, incrusting algae, some coral rubble) are
found mostly surrounding islands.
A series of field surveys in two consecutive years (dry and wet season) were conducted to compare
the community structure of muddy, sandy, and ‘maerl’ type habitats. For this study, 50 samples were
analyzed in relation to the gastropod fauna.
Mud communities were less structured, inhabited predominatly by thin shelled taxa, whereas sanddy /
‘maerl’ type communities were often multilayered.
Concerning paterns of diversity and abundance, mud communities were less diverse even though they
had higher abundances. Preliminary results show that collectively, gastropod densities were higher in
muddy habitats (averaging 30 specimens per sample). This could relate to the higher abundances of
both bivalve prey and detritus found here and used as food sources. Over 100 taxa were recorded,
most of them relatively rare. Only 10 taxa could be considered abundant (≥ 25 specimens per
habitat). Turrids and nassarids were most abundant / diverse in muddy habitats, whereas buccinids
and columbellids predominated in sandy areas.
Feeding guild analysis indicated few differences among habitats. Mud communities showed a higher
trophic diversity. Predatory carnivores and detritivorous taxa (turrids, conids, olivs, nassarids) were
predominant in muddy habitats, whereas herbivores and some browsing carnivores (columbellids,
buccinids) were more abundant in sandy / ‘maerl’ type areas. Predation levels, as shown by numbers
of drilled shells, was much higher in muddy habitats than in sandy patches.
Evolution and biogeography of Southeast Asian viviparids (Gastropoda: Caenogastropoda)
Franke, Helena 1 ; Riedel, Frank 2 ; Glaubrecht, Matthias 1 ; Köhler, Frank 1 ; von Rintelen,
Thomas 1
1. Museum of Natural History, Humboldt University Berlin, Invalidenstrasse 43, 10115 Berlin,
Germany,
Email: helena.franke@museum.hu-berlin.de
2. Free University Berlin, Dept. of Geosciences, Institute of Geol. Sciences, Malteserstr. 74-100,
Building D, 12249 Berlin, Germany
The freshwater gastropod group Viviparidae is widely distributed in continental and insular Southeast
Asia and Australia, occurring on both sides of Wallace’s line and thus making it potentially
interesting for biogeographic hypothesis testing. With at least 23 described and morphologically
distinct genera, the region is the hotspot of viviparid diversity. Minor species radiations have been
reported from ancient lakes in Myanmar and Sulawesi. The taxonomy of the Asian taxa both at the
generic and species level is still largely based on shell morphology and rather confuse, though,
making it difficult to gain deeper insights into their evolution and biogeography at present.
In this study we have used a molecular phylogeny based on mtDNA sequences (cytochrome oxidase
I) of a wide range of viviparid species from the Southeast Asian mainland, the Malayan Archipelago
and Australia (i) to test the monophyly of previously established genera, (ii) to investigate
biogeographical relationships in the region, and (iii) to gain insights into the nature of the alleged
ancient lake radiations.
The molecular phylogeny indicates that the current shell morphology-based viviparid taxonomy does
not reflect the phylogenetic relationships of species, particularly among the large group of smoothshelled
taxa from the Asian mainland and the large Sunda Isles. The data also support a distinct and
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