This project involved work undertaken to provide up to date information on the current distribution and conservation status of Mathez’s water-starwort (Callitriche mathezii). All sites for which there were records (except south-west of Tetouan), as well as a range of other wetlands in the area east from Rabat to the plateau of the Moyen Atlas around Timahdit. Prior to this survey, C. mathezii had been reported from four sites: Central Plateau. Akzou (Agziou), south-west of Aguelmous and of Jbel Mtourzgane (Torziane), Oulmès, between Tiflet and Maaziz and SW of Tetouan. The origins of the records from between Tiflet and Maaziz and SW of Tetouan are unclear and unless material from this region can be confirmed, it is probably best to dismiss this record. 

During this project, C. mathezii was found in a total of seven main areas, three (Oulmès, Aguelmous - Mante and Aguelmous - Akzou) on the Central Plateau and four (Aguelmam Afennourir and sites between Jbel Hebri and Timahdite) in the Moyen Atlas. It must therefore be considered endemic to a very small area of Morocco. C. mathezii appears to be fairly abundant within a limited area, however the vulnerability of many of the sites where it occurs, combined with the limited number of sites and extremely restricted range mean that it should still be classed as Endangered.

Biometric data collected on fresh material show that the taxon treated as C. mathezii includes significant variation, which in other members of the genus could justify it being split into at least two taxa. This can only be resolved through further morphological and molecular research. This work has also confirmed that C. mathezii is capable of persisting in a terrestrial form and appears to be able to undergo fertilisation under water.

C. mathezii was recorded in four main habitat types: cupular pools in rock outcrops, seasonal pools on soil at medium altitude, seasonal pools in rocky desertic habitats at high altitude and a stream flowing over soil. It occurred in a wide range of habitats but notably did not occur in permanent water bodies. In each habitat it occurred with a different range of species, with no associates occurring in all the habitats.