Mayflies are among the most ancient winged insects, spending most of their lives as aquatic nymphs before emerging as adults that live for mere hours or days. The order Ephemeroptera comprises roughly 4,000 species in about 500 genera and 40 families. Within the Palaearctic region, however, the family Leptophlebiidae is surprisingly depauperate, with only 60 species recorded across four subfamilies. The genus Habrophlebia accounted for nine of the 25 Palaearctic species in the subfamily Habrophlebiinae before this study, six of them already known from the Maghreb: two from Algeria and four from Morocco. That picture has now changed dramatically.

The new research emerged from intensive surveys conducted between 2018 and 2022 across rivers and streams in northeastern Algeria, a region that has recently gained recognition as a hotspot of freshwater biodiversity and a refugium for both cold-adapted mountain species and Afrotropical relicts. The Numidia region, stretching across northeast Algeria and northwest Tunisia, harbours a wide range of wetlands supporting endemic waterbirds, fish, and amphibians, along with a diverse assemblage of aquatic insects. Lowland wetlands there sustain relict dragonflies such as Urothemis edwardsii, while montane zones shelter cold-stenothermic taxa including the dragonfly Aeshna cyanea and the damselfly Pyrrhosoma nymphula.

To untangle the true diversity of Habrophlebia, the team, led by Michel Sartori, Laurent Vuataz, and Boudjéma Samraoui, integrated molecular and morphological evidence. They analysed a 658-base-pair fragment of the mitochondrial cytochrome oxidase subunit 1 gene, or COI, combining 91 previously published West Palaearctic sequences with 27 newly generated ones from Algerian specimens, for a total of 118 sequences. DNA was extracted non-destructively, allowing the same specimens to be used for both genetic and microscopic study. The resulting gene tree, reconstructed with Bayesian inference in BEAST using a relaxed molecular clock, revealed that sequences from each of the five new species formed distinct, well-supported clades.

Three contrasting species delimitation methods were applied to the COI dataset: the distance-based ASAP, the tree-based mPTP, and the single-threshold GMYC approach. All three identified the same five molecular operational taxonomic units matching the five new species. Pairwise genetic distances told a striking story: within the five newly described species, mean divergence was just 0.4 percent, while between species it averaged 15.6 percent, ranging from 4.6 to 19.7 percent. The smallest gap, 4.3 percent between Habrophlebia callensis and H. annaba, still far exceeds typical intra-species thresholds in mayflies, confirming that these are genuinely separate evolutionary lineages rather than mere colour variants.

The five new species are Habrophlebia callensis, named after the historic fortress town of El Kala; H. ghora, after Mount Ghora on the Algerian-Tunisian border, itself named for the coot, known locally as Ghor; H. seybouse, after the ancient river Ubus, now the Oued Seybouse; H. annaba, after the city once known as Hippo Regius, the episcopal see of Saint Augustine; and H. edough, after the massif that Procopius called Mons Pappua. Each species was diagnosed through painstaking dissection and slide-mounting of nymphal mouthparts, legs, and gills, supplemented by scanning electron microscopy of eggs, whose chorionic ribs and micropyles provide species-specific signatures.

The morphological evidence is as compelling as the genetic. Four of the five new species share a rare character: the setae on the upper face of the hind femora are always entire, never feathered, a trait otherwise known only in the European H. fusca and H. lauta. Habrophlebia callensis possesses a tarsal claw with 18 to 21 teeth, rivalling only H. hassainae. H. ghora and H. seybouse have the fewest claw teeth of any species in the genus, 12 to 14, and gills with remarkably few filaments. H. edough occupies a peculiar position, bearing feathered setae on the hind femora and on the second segment of the maxillary palp, unlike any other species treated in the study, and it coexists with H. annaba in the same streams but flies in late summer and autumn while its neighbour emerges in spring.

Each Maghrebian Habrophlebia species appears geographically restricted, a pattern of true microendemism. H. annaba and H. edough occur in the Edough Mountains; H. callensis in the El Kala northern hills; H. ghora in the Kroumiria Mountains spanning Algeria and Tunisia; H. seybouse in the Seybouse and Collo regions; H. hassainae in northwestern Algeria; H. djurdjurensis in the Djurdjura Mountains; and the Moroccan species in the High Atlas and Rif. The authors link this checkerboard distribution to the region’s complex topography, Quaternary glacial refugia, and Miocene marine transgressions that fragmented freshwater habitats and isolated upland streams. The distributional patterns support an east-west divide within the Maghreb, most likely shaped by distinct glacial refugia, a break also seen in dragonflies, other mayfly genera, and ribbed newts.

Mayflies are poor dispersers. Adults live only hours to days and have weak flight, restricting movements to local or catchment scales. Combined with the genus’s narrow ecological tolerance, or stenoecy, and preference for headwater streams at elevations of 200 to 900 metres with moderate current, these limitations foster allopatric speciation within montane refugia. The result is a genus that now comprises 19 West Palaearctic species, 14 of them exclusive to the Maghreb, with at least three additional undescribed taxa already known from the Djurdjura Mountains and four distinct genetic Euro-Mediterranean lineages awaiting formal description. The concentration of endemism extends well beyond mayflies to caddisflies, stoneflies, amphipods, crabs, and vertebrates such as the Maghreb bleak and the tree frog Hyla carthaginiensis.

The study also carries a conservation warning. North African wetlands deliver essential ecosystem services yet face escalating anthropogenic pressures that place a substantial proportion of Maghrebian freshwater species at risk of extinction. Because Habrophlebia species persist only in isolated headwater streams largely unaffected by human disturbance, they may serve as reliable bioindicators of relict mountain ecosystems. The authors provide an updated identification key to the nymphs of all Habrophlebia species in the western Palaearctic, a tool they hope will sharpen future monitoring. Whether European members of the genus originated from Maghrebian ancestors dispersing northwards across the Strait of Sicily, or whether an ancestral lineage entered the Maghreb from Europe and diversified in isolation, remains an open question, one that these five new Algerian endemics now make impossible to ignore.

Subject of Research: Biodiversity and Taxonomy

Article Title: Endemism and hidden diversity of Habrophlebia , Eaton, 1881 in Algeria’s Northeastern Mountains ( Ephemeroptera , Leptophlebiidae )

Article References: Samraoui, B., Vuataz, L., & Sartori, M. (2025). Endemism and hidden diversity of Habrophlebia, Eaton, 1881 in Algeria’s Northeastern Mountains (Ephemeroptera, Leptophlebiidae). Alpine Entomology, 9, 113-151. https://doi.org/10.3897/alpento.9.171490

Image Credits: AI Generated

DOI: 10.3897/alpento.9.171490

Keywords: mayflies, Habrophlebia, Algeria, endemism, freshwater biodiversity, cryptic species, Maghreb, biogeography, hidden, diversity, Eaton, Northeastern