Macaronesia, with the exception of the Azores, is one of the few Palearctic provinces where basic taxonomic information on the freshwater copepods is still lacking. We redescribed Eucyclops azorensis, a cyclopid crustacean so far known only in the Azores, and report the occurrence of this species in Algeria and Madeira Island. Eucyclops azorensis was formerly considered to be a subspecies of E. agiloides (East Africa); therefore, the latter species is redescribed here as well based on type and non-type material. Morphological comparisons between E. azorensis, E. agiloides and other taxa (E. serrulatus and E. roseus), assumed to be closely related to our target species, support a closer relationship between E. azorensis and E. serrulatus (Palearctic) than between E. azorensis and E. agiloides (Afrotropical). The slight differences between E. azorensis and E. serrulatus in the surface ornamentation of the antennal coxobasis and intercoxal sclerites of legs 1 and 4 suggest a relatively young separation of these lineages. Eucyclops agiloides is morphologically close to E. roseus (temperate and subtropical Asia, southeastern Europe, East Africa). The numerous and clear-cut differences indicate a species rather than subspecies-level differentiation between E. agiloides and E. roseus, unlike what was formerly proposed in the taxonomic literature.

Females and males of two South Palearctic Cyclops, C. ankyrae Mann, 1940 Mann, A. K. 1940. Über pelagische Copepoden türkischer Seen (mit Berücksichtigung des übrigen Planktons).. Internat Rev Hydrobiol., 40: 1–87. [Google Scholar] and C. abyssorum divergens Lindberg, 1936 Lindberg, K. 1936. Notes sur des Cyclopides (Crustacés Copépodes) de l'Iran.. Bull Mus R Hist Nat Belg., 12(17): 1–26. [Google Scholar] are redescribed, and their taxonomic relationships are discussed. Cyclops ankyrae can be distinguished from congeners by the spine formula of the terminal exopodal segments (2433), distinct anal operculum, bare proctodeum, presence of a longitudinal row of large spinules near the palp on the frontal surface of the mandibular coxopodite, spinule ornamentation of the maxilliped coxopodite, presence of hairs on the caudal surface of P3–P4 couplers, and lack of large spinules on the frontal surface of the P1 basipodite. Cyclops abyssorum divergens differs from C. abyssorum s. str. in the relatively short inner median caudal seta, reduced spinule ornamentation on the caudal surface of P4 coxopodite, and presence of large spinules on the maxillular palp. Cyclops singularis Einsle, 1996 is synonymized here with C. a. divergens Lindberg, 1936 Lindberg, K. 1936. Notes sur des Cyclopides (Crustacés Copépodes) de l'Iran.. Bull Mus R Hist Nat Belg., 12(17): 1–26. [Google Scholar] . The geographic distribution of C. a. divergens is revised.

Little is known about the insular diversity and its determinants in the freshwater invertebrates in comparison to land animals. Our goal is to obtain global-scale information on the insular diversity in Cyclopidae, test its relationships with the geographical variables in different types of islands, and compare the patterns to those observed in other organisms. In total 291 species and subspecies were reported in the 35 islands included in our analyses. The total and endemic species richness have strong positive correlations with surface area and maximum elevation of the islands; regression slopes are larger in the oceanic than in continental islands. Small-island effects occur in the relationships between the endemic species richness and area and elevation. Distance from mainland has negative correlations with the total and endemic species richness in the oceanic islands. Compositional similarity (in contrast to species richness) is determined by the geographic variables to only a minor extent, while space has stronger impact. The relationships found in Cyclopidae generally fit those observed in other predominantly terrestrial organisms, yet some characteristics (negative intercepts in the area–species and elevation–species relationships; large area and high elevation thresholds below which no endemic species occurs) are suggested to be specific to fresh waters.