Table 1 Summary of the molecular and population genetics literature for European and American eels

Allozymes

Fine et al.[24]

Candidate markers for eel species differentiation: transferrins

Fine et al.[25]

Heterogeneity among North Atlantic eels (not significant**)

Sick et al.[26]

Polymorphism in American eels only, monomorphy in European eels

Pantelouris et al.[27]

Differentiation among European continental and Icelandic eels (significant**)

Pantelouris et al.[28]

Differentiation among American continental and Icelandic eels (significant**)

de Ligny & Pantelouris [20]

First available diagnostic marker: MDH;

Differentiation among American and European continental eels (significant**);

No differentiation among eels from Azores and Europe.

Williams et al.[29]

Latitudinal clines at three allozyme markers (MDH invariable)

ADH & SDH clines establish at larval American eel stages

PHI cline establishes during freshwater residency of American eels

Koehn & Williams [30]

Latitudinal clines at SDH & PHI loci temporally stable

ADH cline unstable and allele frequencies vary among years

Comparini & Rodinò [31]

Evidence for two eel species at spawning grounds in the Sargasso Sea

Williams et al.[32]

First indication of genetic hybrids in Iceland

Avise et al.[12]

Evidence for an eel hybrid zone: cyto-nuclear disequilibrium in Iceland

Maes & Volckaert [33]

Evidence against panmixia in European eels: IBD (r =0.78; P = 0.030)

Maes et al.[34]

No interannual differentiation in European eels: no IBT (r = 0.0050, P > 0.05)

Mitochondrial DNA

Avise et al.[21]

Strong evidence for two eel species in the North Atlantic

Avise et al.[12]

Evidence for an eel hybrid zone: cyto-nuclear disequilibrium in Iceland

Lintas et al.[35]

Extensive variability in European eels

Daemen et al.[36]

Latitudinal haplotype diversity cline in European eels

AFLP

Albert et al.[37]

Quantification of total fraction of hybrid eels in Iceland (15.5%);

Latitudinal gradient of hybrid portions in Iceland;

Evidence for high portion of later generation hybrids (30%);

Indication of higher survival rates of hybrid eels in Iceland.

Gagnaire et al.[38]

Evidence for selection and non-neutral introgression

Microsatellites

Daemen et al.[36]

Low, significant genetic differentiation in European eels (F _ST  = 0.040; P < 0.050)

Wirth & Bernatchez [39]

Evidence against panmixia in European eels: IBD (r = 0.46; P < 0.0070);

Low, significant genetic differentiation in European eels (F _ST  = 0.0017; P = 0.0014);

Genetic intermediacy of Icelandic eels among North Atlantic locations.

Wirth & Bernatchez [40]

Evidence for long-term population decline in North Atlantic eels;

Differentiation among North Atlantic eels (F _ST  = 0.018; P < 0.0010);

No evidence against panmixia in American eels: no IBD (r = 0.0030; P > 0.40).

Mank & Avise [41]

Mild genetic differentiation among North Atlantic eels (G _ST  = 0.055; SE = 0.0049);

Genetic intermediacy of Icelandic eels among North Atlantic locations.

Dannewitz et al.[42]

Temporal instability of IBD pattern in European eels;

Low genetic differentiation in European eels (F _ST  = 0.0014; P < 0.010);

Temporal genetic variation exceeds geographic variation.

Maes et al.[34]

Evidence for interannual differentiation in Europe: IBT (r = 0.18; P = 0.043);

Contradicts allozyme pattern: no IBT, but IBD.

Palm et al.[43]

No genetic differentiation among same-aged silvering eels between a northern and a southern European locality (F _ST  = −0.00003; P =0.61);

Als et al.[44]

No evidence against panmixia in American or European leptocephali

(F _ST  = 0.00019, P = 0.4755): no IBD, nor IBT;

Evidence for inter-species hybridization in the Sargasso Sea

Côté et al.[45]

No evidence against panmixia in the American eel (F _ST  = 0.00009; P = 0.998);

Effective population size for American eels: N _E =10 532 (CI95%: 9 312–11 752)