Contrasts in genetic structure and historical demography of marine and riverine populations of Atherina at similar geographical scales

Abstract

In this paper, we compare the genetic structure and the historical demography of two populations of the sand smelt Atherina boyeri from the rivers Tagus and Mondego (Portugal) with two groups of samples of the closely related marine Atherina presbyter collected on the shore at comparable latitudes. A. presbyter is a pelagic marine inshore fish, while A. boyeri is typically found in coastal lagoons, estuaries and freshwaters bodies. Analysis of mtDNA control region sequences showed that the marine A. presbyter did not display signs of genetic differentiation between sites some hundreds of kilometers apart. On the contrary, A. boyeri showed clear differences between populations. The populations of A. boyeri showed a much lower genetic diversity and younger coalescence times when compared with A. presbyter. We suggest that these differences reflect the interplay between differences in ecology between the two species and the historical impact of the glaciations. While A. presbyter likely moved to the south evading the cold periods, A. boyeri probably went extinct and its populations in Western Europe are recent recolonizations from western Mediterranean refugia.

Phylogeography and demographic history of Atherina presbyter (Pisces: Atherinidae) in the North-eastern Atlantic based on mitochondrial DNA

“…Indeed, the estimates derived from the samples of each location may not reXect what happened in the past in that area, but rather the signatures of the demographic events that took place in the locations where the populations survived during the glacial retreats. In the case of A. presbyter, it is plausible that the species might have simply moved south of Iberia, having recolonized the area in the current interglacial (Francisco et al 2006a(Francisco et al , 2008. It is interesting to note that for the southern Portugal population the data conform to the spatial expansion model and the demographic one is rejected.…”

“…between Fonte-da-Telha and Arade). For the same species, Francisco et al (2006a) did not Wnd genetic diVerentiation for smaller geographic scales (less than 250 km). Several other studies using the same marker and similar sampling eVort could not Wnd genetic diVerentiation, even for much wider spatial scales (several hundreds to thousands of kilometres) (e.g.…”

“…Although the adults of sand-smelt are active swimmers in the water column, their migratory movements are probably diYcult along exposed shores. Francisco et al (2006a) showed that along the Portuguese west coast Wsh collected in sites separated by 250 Km did not present signs of population diVerentiation. Meanwhile, a large number of sequences (128) of A. presbyter were obtained covering a much broader area in west Europe and the Canaries as well as some samples from the Azores (AstolW et al 2005;Francisco et al 2008).…”

Phylogenetic relationships of the North-eastern Atlantic and Mediterranean forms of Atherina (Pisces, Atherinidae)

“…The western European and Moroccan A. boyeri belongs to the same clade that occurs in the Western Mediterranean and Adriatic Seas and probably survived in the Mediterranean area re-invading Atlantic rivers and lagoons after the last glaciation (Francisco et al, 2006).…”

Some Marine Tunisian Atherina boyeri Populations (Teleostei) have Morphological and Molecular Characteristics of Lagoon Fishes

“…Recently, we have proposed an evolutionary pattern of the three species of the A. boyeri complex [20], including firstly sympatric speciations followed by a post-Pleistocene colonization of the lagoons. Similarly, it has been suggested that during the cold periods, fish of the A. boyeri complex probably went extinct from the Portuguese coasts and present populations are due to recent recolonizations from western Mediterranean refugia [21]. The presence of Atherina populations around the Tunisian Islands gave us the opportunity to obtain new data concerning the evolution of the A. boyeri species complex, constituting thus the aim of this study.…”