Mitochondrial phylogeography of the European sprat (Sprattus sprattus L., Clupeidae) reveals isolated climatically vulnerable populations in the Mediterranean Sea and range expansion in the northeast Atlantic

Abstract

We examined the genetic structure of the European sprat (Sprattus sprattus) by means of a 530-bp sequence of the mitochondrial control region from 210 fish originating from seven sampling localities of its distributional range. Phylogeographical analysis of 128 haplotypes showed a phylogenetic separation into two major clades with the Strait of Sicily acting as a barrier to gene flow between them. While no population differentiation was observed based on analysis of molecular variance and net nucleotide differences between samples of the Baltic Sea, the North Sea and the Bay of Biscay nor between the Black Sea and the Bosporus, a strong population differentiation between these samples and two samples from the Mediterranean Sea was found. Further, the biggest genetic distance was observed within the Mediterranean Sea between the populations of the Gulf of Lyon and the Adriatic Sea, indicating genetic isolation of these regions. Low genetic diversities and star-like haplotype networks of both Mediterranean Sea populations point towards recent demographic expansion scenarios after low population size, which is further supported by negative F(S) values and unimodal mismatch distributions with a low mean. Along the northeast Atlantic coast, a northwards range expansion of a large and stable population can be assumed. The history of a diverse but differentiated Black Sea population remains unknown due to uncertainties in the palaeo-oceanography of this sea. Our genetic data did not confirm the presently used classification into subspecies but are only preliminary in the absence of nuclear genetic analyses.

Unexpected mosaic distribution of two hybridizing sibling lineages in the teleplanically dispersing snail Stramonita haemastoma suggests unusual postglacial redistribution or cryptic invasion

“…The flounder Plathichthys flesus (Borsa et al., 1997), the sprat Sprattus sprattus (Debes, Zachos, & Hanel, 2008), and the planktonic chaetognatha Sagitta setosa (Peijnenburg, Breeuwer, Pierrot‐Bults, & Menken, 2004) are examples of species with a discontinuous geographic distribution in the Northern Mediterranean Sea. For those three examples, genetic divergence between Atlantic and Mediterranean populations and between Northern Mediterranean pockets has been revealed.…”

Imprints from genetic drift and mutation imply relative divergence times across marine transition zones in a pan-European small pelagic fish (Sprattus sprattus)

“…Sampling density, however, differed between north and south, reflecting a more continuous distribution of spawning locations in the north, compared with the south where major populations presumably are presently restricted to the Gulf of Lion, the northern Adriatic Sea and the Black Sea Basins (Debes et al, 2008). Additional occurrences in estuarine areas around the Iberian Peninsula have been reported, but populations are thought to be in strong decline or even disappeared (Cabral et al, 2001).…”

“…Data from a total of 21 sampling stations representing 19 locations were included in the analysis (Figure 1). Of these, mtDNA variation was reported for seven locations in Debes et al (2008). Microsatellite data were compiled for 17 sampling stations: 11 stations as reported by Limborg et al (2009) and six additional stations extending the previous northerly dominated coverage southwards via the English Channel and the Atlantic into the Mediterranean and eastwards into the Black Sea (Figure 1).…”

“…Samples were, with few exceptions, collected on spawning sites during the spawning season, which differs among populations. Temporal replicates were collected from two locations (see Table 1, Debes et al (2008) and Limborg et al (2009) for more details on sampling).…”

“…A study using a mtDNA marker suggested a complex phylogeographic history with two major clades: one representing the clade that presumably colonised northern European waters following the LGM, and a second in the eastern Mediterranean and the Black Sea with a pre-or postglacial origin (Debes et al, 2008). A substructure was also evident within clades, with genetic differences within the 'western' clade between Atlantic-Baltic Sea and western Mediterranean populations, and within the 'eastern' clade between Adriatic Sea and Black Sea populations (Debes et al, 2008). A recent microsatellite study further demonstrated population structure across the Baltic-Atlantic transition zone (Limborg et al, 2009).…”