Rana ridibunda
This is the largest frog species native to Europe, which may grow up to 15 cm in length. It is a fairly robust species, found in a variety of freshwater ecosystems, including those on the Aegean island of Ikaria. Generally, the marsh frog is a diurnal species, although it can also be seen during the night. It is a very vocal species and it is more likely to be heard before it is seen. It is also a very social species, often forming large groups along river banks. At the moment, due to its large population and widespread distribution, the IUCN has classified it as Least Concern. Luckily it is a reasonably tolerant species, which can survive in polluted and saline environments. As a result, it should be a resident of freshwater ecosystems for a long time to come.
Nerium oleander
This is the only species found within its genus. This common, evergreen shrub grows along river banks and streams at low elevations. N. oleander can often be used as an indicator of the freshwater presence. Its length ranges between one meter and five meters and its long branches stand erect. It produces long, narrow fruits,which split open lengthwise to release seeds when the plant is mature. The flowers are normally pink, but can also be white or red. Oleanders flower during a long summer period. The IUCN has classified this species as Least Concern, because it is very widespread. However, without this species many freshwater ecosystems would not have the same ecological or aesthetic value.
Calopteryx virgo
Like all damselflies, this species is closely associated with freshwater habitats. It is a fairly large and robust species, measuring up to 49 mm in length. Male C. virgo are metallic blue in color, while their wings are dark purplish blue. The females are metallic green or brown and their wings have a white spot on the tips. They are more likely to be found upstream, in shaded habitats which are more open than the lower sections of rivers. More open habitats are likely to be inhabited by a similar species – Banded demoiselle (C. splendens). Beautiful demoiselles have not been included on the IUCN Red List of Threatened Species, because in many areas they are locally abundant and can easily be spotted on numerous streams.
Alnus glutinosa
A. glutinosa is a deciduous tree, which on the Greek islands can grow up to 20 m in height, yet in ideal conditions even up to 35 m. It has a straight trunk with spreading branches. At maturity, its bark begins to split, creating great fissures down the length of the trunk. The flowers group together in catkins, where the female ones are green and egg-shaped. Black alder grows in wet and damp habitats, so it is likely to be found alongside rivers, streams and ravines. It is perfectly capable of growing in marsh or wetland areas, where its roots are completely submerged. Despite this, it is most often found in semi-mountainous areas. The IUCN classifies this species as Least Concern. However, it is mentioned in the Habitats Directive (92/43/EEC Directive) Annex I (“Alluvial forests with Alnus glutinosa and Fraxinus excelsior”).