Mitochondrial DNA variability of the pipefish Syngnathus abaster

Abstract

This study provides data on the genetic structuring of the pipefish Syngnathus abaster in the western Mediterranean and Adriatic Seas. A total of 109 specimens were collected in brackish-water biotopes. The control region and three other regions of the mitochondrial genome were analysed. The most relevant result was the high genetic structuring found by Bayesian inference (BI), maximum likelihood (ML) and network analyses, which were consistent in showing three well-separated clusters of S. abaster populations. Furthermore, BI and ML did not support the monophyly of the taxon S. abaster. These results suggest the occurrence of a species complex in the study area, whose differentiation may have occurred since the Pleistocene. The results also show a very high genetic variability at the inter-population level, with no shared haplotypes among sites. Evolutionary forces due to the fragmented nature of the brackish-water habitats may account for the high genetic divergence found among the groups and populations. Finally, although dispersal by rafting over long distances may occasionally occur, this study suggests linear stepping-stone model of colonization to be most likely. The complexity of the results obtained suggests that further studies are needed to elucidate the phylogeny of S. abaster.

Phylogeography of Aphanius fasciatus (Osteichthyes: Aphaniidae) in the Mediterranean Sea, with a focus on its conservation in Cyprus

“…This is probably due to the absence of dispersal stages combined with the exclusively benthic adults; conversely, the potential for migration across stretches of sea allows a shallower structuring in A. fasciatus. A similar pattern of substantial isolation between populations occurring in different brackish-water bodies was retrieved in the pipefish Syngnathus abaster Risso, 1827, a species occurring mostly in brackishwater environments across the Mediterranean Sea and characterised by egg brooding in a ventral pouch and hatching of benthic juveniles (Sanna et al, 2013). However, unlike A. fasciatus, S. abaster shows as well a further structuring into three deeply divergent clades occurring in different areas of the Mediterranean Sea (Western Mediterranean, Tyrrhenian ?…”

Next‐generation phylogeography of the cockle Cerastoderma glaucum: Highly heterogeneous genetic differentiation in a lagoon species

“…Several mechanisms may cause genetic differentiation between marine species populations such as vicariance processes, caused by historical barriers, oceanographic discontinuities, local adaptation, and limited dispersal capabilities (Palumbi, ). The spatially isolated nature of costal lagoons, at both present and past sea levels, may lead to significant population differentiation in allopatry, as highlighted by the studies of the Mediterranean goby Pomatoschistus tortonesei (Mejri et al, ), the pipefish Syngnathus abaster (Sanna et al, ), and the lagoonal sand smelt Atherina lagunae (Trabelsi et al, ). Previous studies of lagoon species were based mainly on few genetic markers, but our genome‐wide SNP analysis indicated that genetic differentiation between geographically isolated populations can be widespread across the genome and that many of the loci exhibit concordant genetic structure.…”

Past and present drivers of population structure in a small coastal fish, the European long snouted seahorse Hippocampus guttulatus

“…Other syngnathid species, however display different distributions of genetic diversity, so species-specific characteristics need to be discerned and taken into account in management. The Mediterranean lagoon-dwelling pipefish Syngnathus abaster has a more complex haplotype network but no shared haplotypes between populations, and similar nucleotide diversity to seahorses (Sanna et al 2013), suggesting that the fragmented habitat and life history characteristics of the species have resulted in population isolation and breakdown of gene flow following the initial post-glacial expansion. One a larger geographical scale the seahorse H. erectus also demonstrates regionality and genomic divergence, with little connectivity between northern and southern populations occupying waters with very different environmental conditions (Boehm et al 2015).…”

“…A single recent study has assessed genetic variation in H. guttulatus across a small part of the species' geographic range (NW Iberian Peninsula), and found no significant barriers to gene flow (Lopez et al 2015), but studies of three other syngnathid species from areas more representative of the geographic range of H. guttulatus suggest more defined population differentiation in such species. Contemporary population structure of the pipefish Syngnathus typhle has been shown to be influenced by Pleistocene glaciations, with post glacial recolonisation effects evident in movement of the geographic range north and eastwards (Wilson & Eigenmann Veraguth 2010), whilst another pipefish (S. abaster) displays significant post-glacial fragmentation and differentiation (Sanna et al 2013). Similarly, both contemporary (i.e.…”