Does Breeding Site Fidelity Drive Phenotypic and Genetic Sub-Structuring of a Population of Arctic Charr?

Abstract

There is now increasing acceptance that divergence of phenotypic traits, and the genetic structuring that underlie such divergence, can occur in sympatry. Here we report the serendipitous discovery of a sympatric polymorphism in the upper Forth catchment, Scotland, in a species for which high levels of phenotypic variation have been reported previously, the Arctic charr, Salvelinus alpinus. Attempting to determine the proximate mechanisms through which this pattern of phenotypic variation is maintained, we examine the use of the available feeding resource and the genotypic and phenotypic structure of charr in this system. We show clear differences in head morphology between charr from three very closely connected lakes with no barrier to movement (Lochs Doine, Voil and Lubnaig) and also differences in muscle stable isotope signatures and in stomach contents. There were significant differences at 6 microsatelite loci (between Lubnaig and the other two lochs) and very low estimates of effective migration between populations. We conclude that, despite living in effective sympatry, strong genetic and phenotypic sub-structuring is likely maintained by very high levels of site fidelity, especially during spawning, resulting in functional allopatric divergence of phenotype.

Discrete prey availability promotes foraging segregation and early divergence in Arctic charr, Salvelinus alpinus

“…Loch Doine is located in one arm of the Forth catchment (56°20 0 N, 4°20 0 W), which drains a large part of east-central Scotland eastwards to the North Sea. It has an area of 0.54 km 2 with 20 m of maximum depth (for more details, see Adams et al, 2006).…”

“…Information about diet of the fish from Loch Doine was obtained from Adams et al (2006). The methodology that they used to determine diet was as follows: stomach contents from approximately 35 charr (mean fork length 169 mm; range 88-251 mm) captured during July using multi-mesh (Norden) gill nets were removed and placed in 70% ethanol.…”

Mitochondrial DNA diversity and relationships of endemic charrs of the genus Salvelinus from Lake Kronotskoye (Kamchatka Peninsula)

“…A characteristic peculiarity of charrs of the genus Salvelinus is sympatric existence of several species, forms, or ecotypes, which are reliably distinguishable on the basis of traditional morphological characters (Behnke, 1980(Behnke, , 1989Savvaitova, 1989;Glubokovsky, 1995;Alekseyev et al, 2000;Osinov, 2002;Adams et al, 2006). It has been shown that the observed phenotypic polymorphism of charrs is often genetically determined (Dynes et al, 1999;Gislason et al, 1999;Skúlason et al, 1999;Adams & Huntingford, 2002;Klemetsen et al, 2002;Westgaard et al, 2004;Wilson et al, 2004).…”

Genotypic variation does not explain differences in growth of mummichogs Fundulus heteroclitus from simple and complex tidal marsh landscapes

“…Adams & Huntingford 2004) even among sub-populations that are not geographically isolated. For example, Adams et al (2006) reported distinct differences at multiple microsatellite loci in sub-populations of the Arctic char Salvelinus alpinus from 3 closely connected lakes in Scotland. The authors proposed strong site fidelity, particularly in connection with spawning areas, as a likely mechanism producing genetic and phenotypic population sub-structuring from limited gene flow among locations even in the absence of effective physical barriers to movement.…”