Rare or common? Developing protection schemes for bisexual-parthenogenetic species

Parthenogenetically reproducing species, which lack at least some of the genetic recombination mechanisms, are more vulnerable to loss of genetic diversity compared to sexually reproducing species. Investigating the role of sexual ancestor populations in maintaining genetic diversity and, consequently, the acclimation potential of parthenogenetic populations will provide the basis for developing effective conservation measures. Chara canescens has been chosen as the model organism to investigate this because of the relevance of this organism group. Charophytes play an important role as habitat engineers in mesotrophic to eutrophic water bodies by providing shelter for zooplankton and juvenile fish, allowing for efficient top-down control of phytoplankton and consequently stabilizing clear-water conditions, which enhances the ecosystem service provision. For coastal water lagoons, Chara canescens, as the only true brackish water species of charophytes, is the key element for stabilizing clear-water status. Until now, only parthenogenetic populations are known for coastal lagoons world-wide; sexual reproducing populations are restricted to Mediterranean and Pannonian inland brackish water sites, whereas the distribution maximum clearly is in the Baltic Sea region, requiring long-distance vectorial transport. Protecting the coastal stands only will not be effective, because their fitness depends to a high degree from connectivity with inland brackish water sites. Those inland sites are, if at all, protected for other reasons, mainly bird protection, which can result in conflicts of interests and even harm the charophyte stands. In order to develop effective transnational conservation strategies, it is necessary to provide the site managing authorities with the knowledge about niche structure to allow multi-target management of the sites bearing the extremely rare bisexual populations. Unravelling recent as well as past gene flow via stepping-stone habitats will allow for estimation of the effects of lost inland brackish water sites and identifying potential gaps which need to be restored. For this, niche structure differences between parthenogens and bisexuals as well as the restoration suitability of lost habitats needs to be assessed. The presentation (showing data from a Biodiversa+ project) will give an overview about the current state of knowledge, highlighting the role of diaspore banks as “hidden biodiversity elements”. These diaspore reservoirs are not only ensuring mid-term resilience of temporary or/and degraded habitats but could be also potentially useful for restoration initiatives.