Molecular phylogenetic relationships in the aquatic snail genus Lymnaea , the intermediate host of the causative agent of fascioliasis: insights from broader taxon sampling

Abstract

Phylogenetic analyses were performed on partial mitochondrial (16S) gene sequences that included new 16S data for 23 exemplars of the freshwater pulmonate snail genus Lymnaea sensu lato and putative outgroup species. This procedure yielded relatively congruent patterns of evolutionary divergence and phylogenetic affinities, and greater resolution and support for many lineages at different levels of divergence than from a previous work based on fewer samples. It has also clarified the relationships between key taxa. Molecular differentiation was evident among genera. Lymnaeids with n=16 chromosomes are a distinct, well-supported monophyletic group of recent origin. The genus Radix appears to be paraphyletic. Among the indigenous North American lymnaeids, a closer alliance was found between Fossaria spp. and Stagnicola caperata, a member of the subgenus Hinkleyia, than between the latter species and members of the subgenus Stagnicola s.str. The North American population of Lymnaea stagnalis is likely to be of European origin as it clustered with its European counterparts. The relevance of the molecular findings to efforts aimed at controlling snail-transmitted trematode diseases is discussed.

Bridging gaps in the molecular phylogeny of the Lymnaeidae (Gastropoda: Pulmonata), vectors of Fascioliasis

“…We chose these three genes because they are highly variable and have been extensively used in phylogenetic studies of Lymnaeidae. They represent most known clades of this family ( e.g ., [6,7,9-11,41]). In addition, living individuals of 12 lymnaeid species and an additional outgroup, Physa acuta (Physidae), were collected in 13 populations sampled in a variety of countries/continents (Table 1).…”

“…We recorded the susceptible or not susceptible status for each species (Table 3). In addition, the haploid number of chromosomes (n) was obtained from previous publications [7,11,31,48]. …”

“…In contrast, the anatomy of their reproductive tracts (including prostate, penis and preputium) is extremely homogeneous ( e.g ., [1,27,28]). Immunological [29], cytogenetical [30,31], enzyme electrophoresis studies [25,32,33], and DNA-based approaches [7,10] have demonstrated extensive homoplasy in anatomical characters [12,26,34-38]. The difference between patterns in shell morphology and anatomy explains why lymnaeid systematics has been controversial [6].…”

“…Today, it is accepted that the total number of species might be less than 100 [1], with most occurring in the Palearctic and Nearctic regions [2]. Although some effort has been done to resolve their phylogenetic relationships, the small number of genes or species considered ( e.g ., a single gene in [7]) and limited geographical coverage ( e.g ., Neotropic in [10], Australasia in [11] and ancient European lakes in [39]) represent severe limitations and biases. Furthermore, some well-recognized species have never been considered ( e.g ., the Neotropical species Lymnaea cousini and L. diaphana ).…”

Conceptual shifts in animal systematics as reflected in the taxonomic history of a common aquatic snail species (Lymnaea stagnalis)

“…Already the first attempts to examine the internal diversity of L. stagnalis by molecular methods (Remigio and Blair 1997;Remigio 2002) revealed that its populations from different countries (Italy, Germany) and continents (Europe, North America) are separated by rather great genetic distances comparable with those separating distinct species of Lymnaeidae or even slightly exceeding them. Remigio (2002: 691) suggested that these populations "probably deserve at least subspecies status".…”