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Institut Sophia Agrobiotech

UMR INRA - Univ. Nice Sophia Antipolis - Cnrs

The global population diversity of evolutionarily young parthenogenetic nematodes and their affinity to extreme environments

ednesday, June 8 - 11:00 - Sophia Antipolis - Inra PACA - Room A010

Scientific seminar
As part of the scientific activities of the Institut Sophia Agrobiotech, IPN team invite Philipp H. Schiffer, University College London, GEE, Telford lab: "The global population diversity of evolutionarily young parthenogenetic nematodes and their affinity to extreme environments"


Almost all parthenogenetic animals reside on terminal phylogenetic branches and are thus thought to be evolutionarily young and evolving towards fast extinction. Yet, most research efforts into "the Queen of Evolutionary Questions", why sex is the predominant mode of reproduction, have been invested into the few, old "evolutionary scandals". Thus, the diversity, and evolutionary origin and trajectory of most parthenogenetic animals remains enigmatic. In this study we analyse the fitness and genomic mutation rates of parthenogenetic nematodes in the genus Panagrolaimus in a comparative mutation accumulation (MA) lines experiment. We also develop a new method to access the evolutionary age of species and populations and analyse the population diversity between globally sampled isolates.
Panagrolaimus nematodes are well adapted to frequent desiccation (anhydrobiosis) and at least one parthenogenetic species inhabits the Antarctic continent. Using full genomic data from several species we analyse the connection between parthenogenesis and the adaptation to such extreme environments, i.e. the power of parthenogenesis to act as a disperser.
We find elevated mutation rates in parthenogenetic species in MA experiments. In agreement with this, their levels of population differentiation in the wild are higher than in sexual con-geners. The parthenogenetic species in Panagrolaimus appear to be evolutionarily young, but we observe a pronounced fitness loss after only very few generations under MA conditions. We find signatures of the adaptation to extreme environments in the genomes of Panagrolaimus, namely gene-family inflations and horizontally-acquired genes that could enhance desiccation tolerance. However, this does not seem to be more pronounced in the parthenogenetic than the sexual ones.
Our results show that parthenogenetic species have the potential to diversify quickly, but are on a steep mutationally driven trajectory to extinction that is most likely only temporarily buffered by large population sizes.