Molecular evolution in Panagrolaimus nematodes: origins of parthenogenesis, hermaphroditism and the Antarctic species P. davidi
Open Access
- 16 January 2009
- journal article
- Published by Springer Science and Business Media LLC in BMC Evolutionary Biology
- Vol. 9 (1), 15
- https://doi.org/10.1186/1471-2148-9-15
Abstract
As exemplified by the famously successful model organism Caenorhabditis elegans, nematodes offer outstanding animal systems for investigating diverse biological phenomena due to their small genome sizes, short generation times and ease of laboratory maintenance. Nematodes in the genus Panagrolaimus have served in comparative development and anhydrobiosis studies, and the Antarctic species P. davidi offers a powerful paradigm for understanding the biological mechanisms of extreme cold tolerance. Panagrolaimus nematodes are also unique in that examples of gonochoristic, hermaphroditic and parthenogenetic reproductive modes have been reported for members of this genus. The evolutionary origins of these varying reproductive modes and the Antarctic species P. davidi, however, remain enigmatic. We collected nuclear ribosomal RNA gene and mitochondrial protein-coding gene sequences from diverse Panagrolaimus species and strains, including newly discovered isolates from Oregon, to investigate phylogenetic relationships in this nematode genus. Nuclear phylogenies showed that the species and strains historically identified as members of Panagrolaimus constitute a paraphyletic group, suggesting that taxonomic revision is required for Panagrolaimus and related nematode lineages. Strain-specific reproductive modes were mapped onto the molecular phylogeny to show a single origin of parthenogenesis from a presumably gonochoristic ancestor. The hermaphroditic strains were all placed outside a major monophyletic clade that contained the majority of other Panagrolaimus nematodes. Phylogenetic analyses of mitochondrial sequences showed that substantial molecular and geographic diversity exists within the clade of parthenogenetic strains. The Antarctic species P. davidi was found to be very closely related to two Panagrolaimus strains from southern California. Phylogenetic and molecular clock analyses suggested that P. davidi and the California strain PS1579 shared a common ancestor in the very recent evolutionary past. Our study provides a phylogenetic framework for understanding the evolutionary origins and diversification patterns of varying reproductive modes within Panagrolaimus and important insights into the origin of the Antarctic species P. davidi. Panagrolaimus offers a powerful nematode model for understanding diverse evolutionary phenomena including the evolution of asexuality and the adaptive evolution of extreme cold tolerance.Keywords
This publication has 53 references indexed in Scilit:
- Widespread Genetic Incompatibility in C. Elegans Maintained by Balancing SelectionScience, 2008
- Systemic RNAi mediated gene silencing in the anhydrobiotic nematode Panagrolaimus superbusBMC Molecular Biology, 2008
- Muller's Ratchet and compensatory mutation in Caenorhabditis briggsae mitochondrial genome evolutionBMC Evolutionary Biology, 2008
- Phylogeny of the nematode genus Pristionchus and implications for biodiversity, biogeography and the evolution of hermaphroditismBMC Evolutionary Biology, 2007
- A persistent mitochondrial deletion reduces fitness and sperm performance in heteroplasmic populations of C. elegansBMC Genomic Data, 2007
- Phylogeny of Cephalobina (Nematoda): Molecular evidence for recurrent evolution of probolae and incongruence with traditional classificationsMolecular Phylogenetics and Evolution, 2006
- Genetic Flexibility in the Convergent Evolution of Hermaphroditism in Caenorhabditis NematodesDevelopmental Cell, 2006
- Egg development in parthenogenetic nematodes: variations in meiosis and axis formationThe International Journal of Developmental Biology, 2006
- High mutation rate and predominance of insertions in the Caenorhabditis elegans nuclear genomeNature, 2004
- DnaSP, DNA polymorphism analyses by the coalescent and other methodsBioinformatics, 2003