World Congress of Malacology Antwerp ... - Unitas Malacologica

lesser known taxa such as land snails in conservation program. This is mainly due to lack of our
knowledge on ecology of this cryptic group. So there is urgent need to assess the distribution and
landscape ecology to conserve these lesser known but a very significant group of invertebrates before
they silently disappear due to anthropogenic activities such as habitat alteration and degradation,
pollution and climatic change.
Land snails versus mammals: chromosomal neighbourhood of genes drives the
„phylogenetic impact“ of DNA sequences
Armbruster, Georg F.J.
University of Basel, Section Plant Ecology, Schoenbeinstr. 6, CH-4055 Basel, Switzerland,
Email: G.Armbruster@Unibas.ch
DNA sequences evolve through mutation, recombination, selection and/or stochastic fixation in gene
pools and phylogenetic lineages. The A, T, G, and C digits of DNA sequences are source-codes in
molecular phylogenetics. I report on a particular process of nucleotide evolution: the loss of A and T
signals because of the influence of homologous gene “neighbours” along chromosomal positions.
The process is based on gene conversion, and is called GC3 drive. GC3 triggers the conversion of A
and T nucleotides towards G and C at the third codon position of protein-coding genes without
alteration of the amino acid sequence. Here, histone genes of land snails and mammals are used as
model systems for GC3 processes.
There is evidence that land snails’ histone genes do not undergo GC3 drive, presumably because of
fixed chromosomal arrangement of the loci. Hence, phylogenetically relevant A and T nucleotides
might still appear at the third codon position of land snails’ histone genes. A multiple sequence
alignment of the H3/H4 gene cluster of land snails is investigated for the appearance of A, T, G, and
C nucleotides at the third codon position. Mammals, however, have loose arrangements of
homologous and paralogous histone gene copies along chromosomes, and they show high GC3 drive
because of gene conversion of neighbouring loci. As a consequence, one should consider less A and
T signals in phylogenetic lineages of mammalian histone genes.
In conclusion, gene arrangement and gene conversion have impact in the search of appropriate
markers in molecular phylogenetics. I suppose single-copy loci as better targets for studying
molecular phylogeny, e.g. the large subunit gene of the RNA polymerase II or the
phosphoglucomutase-1 gene for “deep branch” phylogeny. Single-copy genes are attractive
phylogenetic tools because the pitfalls of chromosomal neighbourhood and GC3 drive are negligible.
Predicting the effects of a habitat restoration project on population viability of one threatened
and one endangered lotic gastropod
Arrington, Tristan; Richards, David
EcoAnalysts, Inc., Center for Aquatic Studies, 11 E Main Street; Suite M, Bozeman,
Montana USA,
Email: tarrington@ecoanalysts.com; drichards@ecoanalysts.com
Rare, threatened, and endangered taxa are often considered ‘umbrella taxa’. Their persistence in an
ecosystem is considered to reflect a ‘natural state’. River impoundments can often eliminate habitat
for aquatic threatened and endangered taxa and reduce population viability. The threatened Bliss
Rapids snail, Taylorconcha serpenticola, and the endangered Banbury Lanx, an undescribed Lanx
sp., survive as meta- and fragmented populations in the mid-Snake River drainage, Idaho, USA
including the Banbury Springs complex. Much of the lotic habitat in this spring complex has been
inundated by the manmade Morgan Lake: neither species occurs in the lake. Habitat restoration
projects in the Banbury Springs complex area have been implemented to reduce anthropomorphic
impacts on the native taxa and ecosystem, including the removal of Morgan Lake. Management goals
include: 1) reestablishment of lotic habitat for Lanx sp. and T. serpenticola, 2) increased dispersal
12