High genetic diversity but limited gene flow in Flemish populations of the crested newt, Triturus cri status

Habitat destruction and fragmentation are among the major causes of amphibian decline. We investigated to what extent geographic distance and barriers affect the genetic composition of the crested newt, Triturus cristatus in Flanders (North Belgium), causing inbreeding or loss of genetic diversity. Data from seven microsatellite loci and 170 individuals from seven meta-populations up to 180km apart revealed heterozygosities of 0.53 to 0.67 within populations and moderate levels of genetic divergence between populations (F-ST values from 0.074 to 0.141, harmonic means of D-est between 0.070 and 0.189). In all Flemish meta-populations, more than 90\% of the individuals from a given geographic region were assigned to the same genetic cluster indicating little genetic exchange, even in De Panne where the two populations Oosthoek and Westhoek are only a few kilometres apart. Such sub-structuring on a micro-scale has also been described in other amphibians. Unique alleles in most populations further support the probability that genetic drift has already led to some isolation. With the exception of the Oosthoek population, however, we found no significant evidence for bottlenecks. Connectivity within pool clusters seems essential to the maintenance of genetic diversity in crested newts as is indicated by our findings from Tommelen, the population with the largest number of pools in close proximity, which also shows the highest levels of heterozygosity (H-e and H-o) and the second highest number and richness of alleles. In conclusion, our study indicates that dispersal and migration rates between the Flemish populations of Triturus cristatus are limited at the geographic scale studied here but that habitat fragmentation has not yet led to a significant loss of genetic diversity of the studied Flemish populations, possibly because crested newts are relatively long-lived, fragmentation of their habitat is relatively recent in Flanders, and most investigated pools are still connected at the local scale.