Comparative diversity and evolutionary age of desert nematode communities (B08)

• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268236062

Nematodes are thought to be one of the most diverse animal phyla and frequently inhabiting extreme environments. They are globally distributed and an important constituent of many soil ecosystems, but their diversity has so-far not been studied in detail in the Atacama or Namib deserts. Genomic biodiversity assessment in nematodes has mostly focused on few model-species. Thus, the extent of genomic diversity in the vast phylum remains understudied. In this project, we will first study the diversity of nematodes in hyper-arid deserts, including by establishing field-based genomic biodiversity assessment. These data will allow us to investigate the evolution of parthenogenesis, and the causes and consequences of variation in mutation rates in species with different modes of reproduction.The theory of geographical parthenogenesis holds that asexual organisms have an evolutionary advantage in more challenging environments. This theory has not been systematically tested and more data comparing the distribution and genomic variability of asexual taxa is urgently needed. We will make use of the relatively high frequency of asexual and sexual sister species in nematodes, and the hyper-arid desert systems analysed in the CRC1211 to sample and analyse such data.Recently it has been found that mutation rates are not constant within species, but that they might evolve as a quantitative trait underlying the principles of local adaptation. Mutation rates might differ between sexual and asexual species of the same genus. We will study if the variability of mutation rates is necessary for the existence of life under extreme conditions, and analyse to which degree they differ between sexual and asexual species.Implementations of a molecular clock to infer species age depend on paleontological calibration. In taxa with poor fossil records and substantial heterogeneity of nucleotide substitution rates, such as nematodes, the clock is inaccurate. The knowledge of a species’ mutation rate can allow for a precise molecular clock, but for highest resolution and accuracy past rates need to be modelled in accordance to paleo-environmental factors. As a final part of the project we will link mutation rates in nematodes to geological history of the landscape to develop a new method to obtain a precise molecular clock. This will feedback into modelling geological history of the desert environments.In summary, the proposed project will establish field-based biodiversity genomics assessment of soil invertebrates in one of the most extreme habitats on Earth and investigate long-standing questions of evolutionary biology and ecology, i.e. the theory of geographical parthenogenesis and the eco-evolutionary dynamics of mutation rates.

• DFG Programme: Collaborative Research Centres
• Subproject of: SFB 1211: Earth - Evolution at the Dry Limit
• Applicant Institution: Universität zu Köln
• Project Heads: Dr. Philipp Schiffer; Professorin Dr. Ann-Marie Waldvogel