World Congress of Malacology Antwerp ... - Unitas Malacologica

considered a member of the acavid genus Ampelita. He considered that the small embryonic shell of
H. covani was not consistent with a position in the Acavidae. Instead, he referred it to the Rhytididae
on account of ‘its rounded, regularly expanding whorls, coarse sculpture and unreflected apertural
lip’, provisionally placing it in the genus ‘Rhytida’. Emberton’s proposal has been accepted by
subsequent authors keen to see another Gondwanan fragment added to the geographic range of the
Rhytididae. Nevertheless, Emberton based his transfer of Helix covani from Ampelita to ‘Rhytida’
solely on shell characters, pointing out the need for anatomical observations to confirm this.
In relation to on-going phylogenetic studies of the Rhytididae of southern Africa (Herbert &
Moussalli), the occurrence of a putative rhytidid species in Madagascar is of considerable
significance. We therefore set out to obtain living material of Helix covani for anatomical study and
molecular analysis, so as to acquire more reliable phylogenetic information regarding the
relationships of this enigmatic taxon and test the hypothesis that the family Rhytididae is present in
Madagascar. The species is evidently rare and restricted to montane rainforest remnants in eastern
Madagascar, but we were successful in obtaining living material and here report on the results of our
observations. Whilst the shell of Helix covani is very similar to that of some rhytidids, the anatomical
and molecular data clearly show that is not a member of the Rhytididae and that in all probability its
prior referral to the Acavidae was correct.
Ancient vicariance and recent dispersal of springsnails (Hydrobiidae: Pyrgulopsis) in the Death
Valley System, California-Nevada
Hershler, Robert 1 ; Liu, Hsiu-Ping 2
1. Department of Invertebrate Zoology, Smithsonian Institution, P.O. Box 37012, NHB W-305, MRC
163, Washington, D.C., 20013-7012, USA,
Email: hershlerr@si.edu
2. Department of Biological Sciences, University of Denver, Denver, CO 80208, USA,
Email: hsiupingliu@comcast.net
The Death Valley system (southeastern California and southwestern Nevada) contains a highly
endemic aquatic biota that has long been the subject of compelling biogeographic speculation, yet
remains little studied phylogenetically. Springsnails (Hydrobiidae: Pyrgulopsis) are one of the most
diverse elements of this fauna, and are thought to have evolved in association with late Tertiary
rearrangements of landscape and drainage. We assembled a molecular phylogeny for this fauna to
investigate its evolutionary development in relation to regional geological history. Sequences for two
mitochondrial genes were obtained from 80 populations representing 13 of the 14 Death Valley
system springsnail species, and 31 extra-limital congeners. Combined analyses of the 1188 base pair
dataset consistently depicted the Death Valley system fauna as a polyphyletic assemblage of eight or
nine lineages. Based on a molecular clock, the six lineages endemic to the Death Valley system were
estimated to be minimally Pliocene in age, which is concordant with inception of regional
topographic closure during this time period. The single endemic lineage having a well resolved sister
relationship was closest to a species from the upper Gila River basin, which also suggests an old
divergence event. Three other lineages shared a pattern of shallow structuring (divergence events <
0.7 Ma) across multiple drainage basins, some of which have long been isolated. This suggests that,
contrary to previous thought, regional springsnail biogeography has been shaped in part by
geologically recent (Pleistocene) dispersal, and in some places occurred by means other than spread
through continuous reaches of aquatic habitat.
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