The recognition of cryptic parasite species has implications for evolutionary and
population-based studies of wildlife and human disease. Echinostome trematodes are
a widely distributed, species-rich group of internal parasites that infect a wide
array of hosts and are agents of disease in amphibians, mammals, and birds. We utilize
genetic markers to understand patterns of morphology, host use, and geographic distribution
among several species groups. Parasites from >150 infected host snails (Lymnaea elodes,
Helisoma trivolvis and Biomphalaria glabrata) were sequenced at two mitochondrial
genes (ND1 and CO1) and one nuclear gene (ITS) to determine whether cryptic species
were present at five sites in North and South America. Phylogenetic and network analysis
demonstrated the presence of five cryptic Echinostoma lineages, one Hypoderaeum lineage,
and three Echinoparyphium lineages. Cryptic life history patterns were observed in
two species groups, Echinostoma revolutum and Echinostoma robustum, which utilized
both lymnaied and planorbid snail species as first intermediate hosts. Molecular evidence
confirms that two species, E. revolutum and E. robustum, have cosmopolitan distributions
while other species, E. trivolvis and Echinoparyphium spp., may be more geographically
limited. The intra and interspecific variation detected in our study provides a genetic
basis for seven species groups of echinostomes which will help accurately identify
agents of disease as well as reveal cryptic aspects of trematode biology.
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