Persistence of phylogeographic footprints helps to understand cryptic diversity detected in two marine amphipods widespread in the Mediterranean basin

Abstract

Amphipods of the genus Gammarus are a vital component of macrozoobenthic communities inEuropean inland and coastal, marine and brackish waters of the Mediterranean and the Black Sea. Exceptional levels of cryptic diversity have been revealed for several widespread freshwater Gammarus species in Europe. No comprehensive assessment has yet been made for brackishwater counterparts, such as Gammarus aequicauda and G. insensibilis, which are among the most widely dispersed members of the so-called "G. locusta group" in the Mediterranean and in the Black Sea. Here we probe the diversity of these morphospecies examining the partitioning of mtDNA and nDNA across multiple populations along their distribution range and discuss it within the regional paleogeographic framework.We gathered molecular data from a collection of 166 individuals of G. aequicauda and G. insensibilis from 47 locations along their distribution range in the Mediterranean including the Black Sea. They were amplified for both mitochondrial COI and 16S rRNA as well as the nuclear 28S rRNA. All five MOTU delimitation methods applied revealed deep divergence between Black Sea and Mediterranean populations in both G. aequicauda and G. insensibilis.There were eight distinct MOTUs delimited for G. aequicauda (6-18% K2P) and 4 MOTUs for G. insensibilis (4-14% K2P). No sympatric MOTUs were detected throughout their distribution range. Multimarker time-calibrated phylogeny indicated that divergence of both G. aequicauda and G. insensibilis species complexes started already in the late Oligocene/early Miocene with the split between clades inhabiting eastern and western part of the Mediterranean occurring in both species at the similar time.Our results indicate a high cryptic diversity within Mediterranean brackishwater Gammarus, similar to that observed for freshwater counterparts. Moreover, the phylogenetic history combined with the current geographic distribution indicate that the evolution of both studied Gammarus morphogroups has been strongly connected with the geological events in the Mediterranean Basin and it reflect the turbulent history of the area. The results also point out the possibility of the existence of monopolization and yet unknown biogeographical barriers in the Mediterranean that might inhibit the sympatry and the dispersal of the existing lineages.

Molecular data suggest multiple origins and diversification times of freshwater gammarids on the Aegean archipelago

“…These findings confirm the recently observed high cryptic diversity and lack of monophyly in numerous widespread European freshwater gammarids [e.g. [19][20][21][22]26,78,79 ]. Interestingly, our data also support the polyphyly of Gammarus uludagi.…”

Macaronesian islands as promoters of diversification in amphipods: The remarkable case of the family Hyalidae (Crustacea, Amphipoda)

“…Verification of the taxonomic status and possible species‐level splits among these populations would require acquisition of additional data, among other, nuclear DNA sequence data. Nevertheless, extensive evidence has been compiled showing that specimens in well‐sorted CO1 MOTUs have been frequently confirmed as separate taxa (i.e., species) after using complementary genetic, morphological, biogeographic and/or ecological data (Borges et al, ; Cabezas, Cabezas, Machordom, & Guerra‐García, ; Delić, Trontelj, Rendoš, & Fišer, ; Hupalo et al, ; Jörger & Schrödl, ). Therefore, until further data are available, the MOTUs here reported could be regarded as possible candidates for species status on their own.…”

“…Detected cases typically involve geographically distant populations or populations separated by obvious phylogeographic barriers. However, cases of unusually deep divergence have also been reported among populations apparently connected and geographically close to each other (Hupalo et al, ; Lobo et al, ). Although some studies surveyed more or less comprehensively the genetic structure and diversity of the amphipod fauna in NE Atlantic (Costa, Henzler, Lunt, Whiteley, & Rock, ; Lobo et al, ; Raupach et al, ), the Macaronesian islands have been somewhat overlooked in those surveys.…”

Phylogeography of Acartia tonsa Dana, 1849 (Calanoida: Copepoda) and phylogenetic reconstruction of the genus Acartia Dana, 1846

“…Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12526-020-01043-1) contains supplementary material, which is available to authorized users. mitochondrial markers such as mtCOI, have been used to identify cryptic species in numerous marine organisms, including copepods (Lee 2000;Rocha-Olivares et al 2001;Dawson and Jacobs 2001;Lee and Frost 2002;Caudill and Bucklin 2004;Holland et al 2004;Hare 2008, 2011;Johnson et al 2008;Dippenaar et al 2010;Marrone et al 2010;Blanco-Bercial et al 2014;Cornils and Held 2014;Oyama et al 2019;Govender et al 2019;Han et al 2019;Hupało et al 2019;Figueroa et al 2019;Chan et al 2019). A comprehensive review of DNA barcoding of copepods based on mtCOI is presented by Blanco-Bercial et al (2014), where they show that this marker was able to accurately identify to species level 1381 sequences for 195 species of copepods, showcasing the utility of this marker for taxonomic research.…”