Cryptic diversity and multiple origins of the widespread mayfly species groupBaetis rhodani(Ephemeroptera: Baetidae) on northwestern Mediterranean islands

Abstract

How the often highly endemic biodiversity of islands originated has been debated for decades, and it remains a fervid research ground. Here, using mitochondrial and nuclear gene sequence analyses, we investigate the diversity, phylogenetic relationships, and evolutionary history of the mayfly Baetis gr. rhodani on the three largest northwestern Mediterranean islands (Sardinia, Corsica, Elba). We identify three distinct, largely co‐distributed, and deeply differentiated lineages, with divergences tentatively dated back to the Eocene–Oligocene transition. Bayesian population structure analyses reveal a lack of gene exchange between them, even at sites where they are syntopic, indicating that these lineages belong to three putative species. Their phylogenetic relationships with continental relatives, together with the dating estimates, support a role for three processes contributing to this diversity: (1) vicariance, primed by microplate disjunction and oceanic transgression; (2) dispersal from the continent; and (3) speciation within the island group. Thus, our results do not point toward a prevailing role for any of the previously invoked processes. Rather, they suggest that a variety of processes equally contributed to shape the diverse and endemic biota of this group of islands.

A DNA barcode library for Germany′s mayflies, stoneflies and caddisflies (Ephemeroptera, Plecoptera and Trichoptera)

“…In addition, the coexistence of multiple mitochondrial haplotypes can lead to sequence variability in a single organism (heteroplasmy) and can impede correct species identification (Kang, Kim, Park, Kim, & Kim, ; Magnacca & Brown, ). Finally, other demographic processes, for example, migration driven by major climate changes such as glaciation events or bottleneck events, can have a huge impact on the variability of the mtDNA, which was reported among other orders for mayflies, caddisflies and stoneflies (Williams, Ormerod, & Bruford, ; Lehrian, Pauls, & Haase, ; Kubow, Robinson, Shama, & Jokela, ; Bálint et al., ; Vuataz et al., ; Theissinger et al., ; Bisconti et al., ; Gattolliat et al., ). Despite such potential complications, there is evidence from many large‐scale studies that DNA barcoding is a highly effective tool for species identification.…”

“…() (Appendix S4). However, because several former species in this genus have been synonymized with B. rhodani (Gattolliat & Sartori, ; Müller‐Liebenau, ), there is a strong possibility that there may be more than one valid species (Bauernfeind & Soldán, ; Bisconti et al., ; Rutschmann, Gattolliat, Hughes, Sartori, & Monaghan, ). Another species with apparently difficult taxonomy is B. vernus Curtis, 1834, which was represented by four clusters in a paraphyletic group with B. liebenauae Keffemuller, 1974 that was previously considered as belonging to the B. vernus species group (Savolainen, Drotz, Hoffsten, & Saura, ; Ståhls & Savolainen, ) based on allozyme electrophoresis.…”

Metabarcoding of freshwater invertebrates to detect the effects of a pesticide spill

“…High intraspecific variation (>3% divergence in cox1 ) is a well‐established observation in the case of Asellus (Sworobowicz et al., ). Three BOLD‐OTUs were assigned to Baetis rhodani (Ephemeroptera), which is also reflected in the incomplete taxonomy of this species complex (Bisconti et al., ; Williams, Ormerod, & Bruford, ).…”

Evolutionary divergence in freshwater insects with contrasting dispersal capacity across a sea of desert

“…Speciation in mayflies has been associated with other kinds of obstacles to gene flow. For example, species‐level divergence in groups has been associated with changes in sea levels, continental uplift and glaciation (Bisconti et al., ; Sekiné, Hayashi, & Tojo, ; Theissinger et al., ). One of the few desert mayfly species studied genetically, Callibaetis americanus , represented a diverse cryptic species complex, with significant restriction of gene flow and considerable CO1 divergence between populations in spring habitats (Stutz, Shiozawa, & Evans, ).…”