A review on the distribution and habitat features of Chara canescens in the Iberian Peninsula: sexual populations revisited

Abstract

Chara canescens, mainly distributed in Europe and the African Mediterranean coast, is the only Charophyceae species capable of reproducing parthenogenetically, the asexual populations being common; however, the sexual ones are rare. In this study we compile all the literature and herbaria data concerning the presence of C. canescens in the Iberian Peninsula and the Balearic Islands over several decades, analysing the historical and spatial distribution of the species and the limnological characteristics of its habitats. A decline in the number of records in the literature and herbarium sheets since 2010 was detected. Most of the populations are concentrated in Castilla-La Mancha, Andalucía and Castilla-León. The species lives in brackish waterbodies, both in coastal areas and endorheic shallow small lakes, and the majority of these locations do not exhibit a good conservation status. The only three locations with sexual populations previously cited in the literature (Bodón Blanco –Valladolid- and Las Eras –Segovia- lakes and Lucio Largo –Doñana-) were revisited in June 2023. Sexual populations of C. canescens in the two former lakes occurred, but the lake in the Doñana National Park was completely dry. Two new sexual populations of the species were found in La Iglesia and Caballo Alba lakes (Segovia), increasing the citation to five sexual populations. A description of population (coverage, male:female ratio) and individual (reproductive features) variables for the four C. canescens sexual populations are provided. The analysed limnological variables (water chemistry, other hydrophytes and marginal vegetation) showed that the lakes harbouring these populations exhibited signs of pollution, altered and unstructured marginal vegetation, etc. The genetic diversity of the species depends on the sexual populations, which are very rare in Europe, and are mainly concentrated in Spain. Therefore, the preservation of these inner brackish-water habitats is essential for the implementation of transnational effective conservation measures to protect this relevant and particular species.