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 mayflyBaetis gr. rhodanion the three largest north-western 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.

Direct analysis of vicariance in Neotropical mayflies (Ephemeroptera)

“…Furthermore, the barrier is more complex in Oligoneuriidae. We hope that future research dating the sister clades could test Cienc (2019) 91(4) e20181130 7 | 13 these hypotheses, nevertheless some studies have estimated divergence in mayfly sister species ranging 3 to 9 Mya (Sekiné et al 2013, Bisconti et al 2016. Zelusia Lugo-Ortiz and McCafferty (1998), with two described species, presents a similar vicariant pattern (Salles et al 2016).…”

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, 2016;Sekin e, Hayashi, & Tojo, 2013;Theissinger et al, 2011). 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, 2010).…”