The general objective of this project is to understand underlying causality of observed patterns in the transition from sexuality to asexuality, and the maintenance of asexual lineages, using Eucypris virens as a unique model organism

1. To identify proximate mechanisms determining reproductive mode in non-marine Ostracoda
2. To test for the predicted genetic and genomic consequences of long-term asexuality and to consider mechanisms that might alleviate their effects
3. To determine dynamic genetic cohesiveness of a species with mixed reproduction.
4. To determine how different reproductive modes can coexist and how asexual lineages can persist.
5. To link extant distribution patterns of reproductive modes, such as geographical parthenogenesis, to historical and evolutionary causality.



The SEXASEX network will use Eucypris virens to address the following fundamental questions:

1. how are gender and reproductive mode determined in non-marine ostracods? What is the mechanism of asexual egg production? What are the roles of hybridisation and polyploidy?
2. are the predicted (long-term) effects of reproductive mode on genetic structure and genomic features identifiable, or, if not, can special mechanisms that counter them be identified?
3. can asexual lineages only persist over longer timeframes through close connection with sexual roots?
4. what is the genetic cohesiveness of this species, which consists of a cluster of sexual and asexual lineages?
5. how can both types of reproductive modes persist sympatrically? Is there ecological cohesion or spatial and temporal segregation between sexual and asexual females? Are there selective advantages of either reproductive mode in different ecological conditions?
6. how important was historical contingency in the formation of present-day spatial patterns of sexuality and asexuality within this species, and of the distribution of clonal diversity?

There is an urgent need for a more pluralistic approach in this field of evolutionary research, but so far this has only been reflected in a few papers, which have tried to model the impact of combined genetic and parasitic effects on asexual populations. The fundamental goal of SEXASEX is to thoroughly integrate the different empirical and theoretical disciplines into one research programme. SEXASEX has three interactive levels:

1. Combine different disciplines. Our new approach not only links several (sub-) disciplines of genetics and ecology, but expands the integration further by including also geographical, palaeontological, biochemical and morphological analyses.
2. Combine empirical and theoretical approaches. SEXASEX has both empirical and theoretical components. A key feature of this interaction will be to consider the assumptions of available models and ask whether they are applicable to real systems, specifically the ostracod model. New models will be constructed with assumptions provided by the model organism and parameterised with data from empirical parts of the project.
3. Compare different organisms. The present network concentrates on one species only. However, recently obtained funding from ESF will initiate the creation of an European platform on parthenogenesis, in which teams working on a wide variety of organisms will be able to exchange information. SEXASEX will be actively involved in this ESF network (called PARTNER).