Genetic diversity

To date, the genetic composition of L. ghigii* populations of the streams of Apolakkia, Loutanis, Gadouras, Argiros, Kremastinos, Kontaris and Chas, as well as of that of the Agia Eleoussa reservoir has been studied. The techniques used were RAPD and RFLP-PCR, which examine total and mitochondrial DNA (mtDNA), respectively.

Analysis of the results, obtained with both techniques, revealed an exceptionally low intra-population genetic diversity and a much higher inter-population diversity, with fixation of different alleles of nuclear DNA and of haplotypes of mtDNA in all populations. This implies total genetic isolation of the populations, with absence of gene flow among them (through stockings) and/or recent "bottleneck" phenomena (sudden massive reduction of population size) that increase the degree of inbreeding and lead to the total loss of certain genomes or haplotypes and to the fixation of others. The reduction of the genetic diversity imposes a serious threat to a population, as it also reduces its ability to cope with future adverse environmental changes.

The RAPD method provided several diagnostic markers, namely alleles absent from all the individuals of a population and present in all those of another. Using the appropriate combinations of these diagnostic markers, a gizani specimen can be assigned with 100% reliability to a given population.

According to the results of genetic analyses, the populations of Apolakkia and Agia Eleoussa are the most highly differentiated compared to the rest (possessing different haplotypes), suggesting a long period of complete isolation, with absence of gene flow and (at least of major) stocking operations with fish from other populations.

Genetic analyses also prove that the fish of Agia Eleoussa were not transferred there from the Loutanis stream (as reported in previous studies), but from a local stream that today is almost completely dry. The Eleoussa stream was once connected to the Platis stream (located at the western part of the island) in which no fish are found. Thus the gizani inhabiting the Eleoussa water reservoir must be the only fish that survive (in a semi-natural environment) out of a population that lived in the Platis system but is now extinct. Therefore, the Eleoussa fish should be considered as an autonomous conservation unit and enhancement stockings with fish from other populations should be prohibited.

The gizani populations from Argiros and Kremastinos streams are identical in terms of their mitochondrial DNA (having the same unique haplotype) and considerably similar in terms of their nuclear DNA. The Chas and Kontaris populations seem to be considerably similar in their mitochondrial DNA, but differ in their nuclear DNA.

Considering the geographic patterns and the present genetic information, the different gizani populations seem to follow different evolutionary pathways and therefore they should be considered as autonomous conservation units and should be managed and conserved separately.