Evolution and island endemism of morphologically cryptic Baetis and Cloeon species (Ephemeroptera, Baetidae) on the Canary Islands and Madeira

The Canary Islands and Madeira are reportedly home to seven recognised species of baetid mayflies (Ephemeroptera, Baetidae), two of which also occur on the European mainland. Their species status remains unsure, and loss of habitat suggests they are of conservation concern. We applied morphological characters and a general mixed Yule-coalescent (gmyc) model analysis of the cytochrome c oxidase subunit 1 (cox1) gene to delineate putative species within morphologically cryptic species groups Baetis (Rhodobaetis) and Cloeon dipterum s.l. We used a three-gene mitochondrial data set (1450 base pairs) to infer phylogenetic relationships and a molecular clock calibrated using island geological ages to infer colonisation history. Genetic and morphological evidence indicated the presence of 12 putative species, 11 of which were endemic to the islands. Only Baetis atlanticus, on Madeira, also occurs on the European mainland. Two lineages (B.pseudorhodani s.l. and B. canariensis s.l.) appear to have arisen in the past 15 million years (mya) and diversified in parallel throughout the Canary Islands. Within the canariensis lineage, sister species occur on the island of Gran Canaria and in North Africa. Pronounced island endemism contradicts previous taxonomic work, which reported a depauperate fauna that included several mainland species. Recent diversification among islands and a close link to North Africa suggest a complex evolutionary history. Owing to their small population size and ongoing habitat alteration, several of these island endemics are among the most endangered aquatic insects in Europe.