World Congress of Malacology Antwerp ... - Unitas Malacologica

multiple factors including (i) the repeated challenges posed to fauna by environmental change in
the Quaternary; (ii) intra-specific reproductive characteristics and responses to selection; and (iii)
sporadic long-distance dispersal. Several studies of marine species have suggested that Quaternary
land-bridges between Tasmania and the mainland have had a prominent role in structuring genetic
diversity, but with paradoxical inferences about timing and a relatively minor effect on
morphological species distributions. No study has identified known major biogeographic boundaries
with phylogeographic discontinuities.
Studies of the two nominal species of the estuarine/lagoonal hydrobiid snail Tatea have revealed
novel diversity patterns implying high levels of population connectivity. In mitochondrial 12S rRNA,
the same common haplotype is found in both T. kesteveni and T. huonensis along more than 5000
kilometres of coastline. Variant haplotypes differ from the common form at few bases and have
restricted (although occasionally disjunct) distributions. In the nuclear gene ITS-1 also, the most
frequent haplotype is widely-distributed in both species. Two of the possible explanations of this
pattern of diversity are rapid expansions from Pleistocene refugia or a selective sweep through both
T. huonensis and T. rufilabris.
We will report on genetic investigations of other estuarine species (including the pulmonate
Amphiboloidea Phallomedusa and Salinator, and the mussel Xenostrobus securis) to determine
whether the Tatea pattern is general in molluscs from this environment. We will describe the nongenetic
methods for testing population connectivity that we are undertaking in the
Amphiboloidea.We will also report on genetic studies searching for correlations between
phylogeographic and biogeographic boundaries in marine species such as the mussels X. pulex and
Brachidontes rostratus and the snails Siphonaria spp., Austrocochlea spp. and Bembicium spp.
Phylogeography and evolutionary origins of Florida's native Apple snail, Pomacea paludosa
Collins, Timothy M. 1 ; Rawlings, Timothy A. 2 ; Choquette, Duane M. 1
1. Department of Biological Sciences, Florida International University
Miami, FL 33199, USA,
Email: collinst@fiu.edu, erlikbl@yahoo.com
2. Department of Biology, Cape Breton University, Nova Scotia B1P 6L2, Canada,
Email: Timothy_Rawlings@cbu.ca
The native Florida apple snail, Pomacea paludosa, is an important component of food webs within
the wetland marshes and rivers of Florida and has been designated a key indicator of the health of
freshwater ecosystems. Changes to Florida's wetlands including habitat loss, habitat fragmentation,
eutrophication of waterways, manipulation of the seasonal hydrologic regime of flooding and dry
downs, and the introduction of at least four exotic Pomacea species, however, have raised concern
over the long term survival of Pomacea paludosa within the State. Understanding the geographic
pattern of relationships among apple snail populations can provide critical information needed for
developing restoration models of Florida's wetland ecosystems and for charging park managers with
the task of restocking waterways devoid of native apple snails. Here we present an analysis of the
population genetic structure of Florida's native apple snail based on a 2.5 kilobase contiguous region
of mitochondrial (mt) DNA from more than 136 individuals from 35 different locations across the
Florida peninsula. Using both phylogenetic and nested cladistic approaches, we have found wellsupported
geographically structured populations, with branch lengths and topologies indicative of
recent range expansion over a large portion of the current range of this species. We have also used
mtdna sequences to evaluate competing scenarios concerning the origins and biogeography of P.
paludosa. Our results suggest that P.paludosa is more closely related to extant species within the
Caribbean Islands than to species found in Central America.
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