NERI technical report no. 539: Anvendelse af molekylærgenetiske markører i naturforvaltningen. Andersen, L.W., Simonsen, V., Søgaard, B., Madsen, A.B., Pertoldi, C., Wind, P., Pihl, S., Fog, K., Damgaard, C.F. 66 p. 2005.
Summary
The objective of the report is to demonstrate how molecular genetic markers can be applied in nature management. The EU-Habitat Directive imposes on Denmark to ensure the survival of species that presently are vulnerable or threatened. The management of this obligation involves many considerations to be taken in order to fulfil the species demands from food availability, quantity and quality to space for different purposes like hunting, mating behaviour and parental care. Amongst the biggest threats to species survival is a reduction in population size, which can result in inbreeding and difficulties to adapt to a changing environment. The consequence of a reduction in population size and inbreeding is often reduced genetic variation, resulting in an increased genetic homogeneity among the individuals in the population. This can cause a reduction in viability and in the worse case result in extinction of the population. Another consequence of a low genetic variation as mentioned above is a reduction in the ability to adapt to changing environment. This can lead to a reduced ability to endure attacks from bacteria, vira or pesticides that are new to the species. The key to the species ability to compensate negative influence from outside is the individual’s genome. The more variable the genome is the better is the chance for the individual to survive. If a population has a high level of genetic variation the chances to survive is higher. It is therefore necessary to include the genetic composition of the population in the evaluation of the chances for a species to survive in a given area. The report shortly reviews the molecular genetic variation and its importance for the ability of the population to survive. Furthermore, it is described how human made effects can influence a population.
Investigations of fen orchid, the European otter and the European tree frog illustrates how the genetic composition of populations of the species can be applied in nature management. For fen orchid, the used techniques were not able to detect genetic variation. On this background, it was not possible to suggest management advice that would improve the survival of fen orchids in Denmark. For the European otter, the use of museum material made it possible to include a temporal perspective in the evaluation of the genetic variation. The results surprisingly demonstrated that the genetic variation in the present-day otters only was slightly reduced compared to the historic material. There were indications of genetic differentiation in the Danish otter population and that serious reduction in the population sizes had happened in former times. The material indicates that the recent otters have continued a negative development of genetic variation, which probably started in prehistoric time. Of course, migration between areas will reduce the negative development, but it is hardly likely that migration can stop the development. The European tree frog is analysed by comparing populations that former were assessed as having a favourable conservation status to populations having an unfavourable conservation status. The study showed that populations with favourable conservation status had a higher level of genetic variation than populations with unfavourable conservation status. Furthermore, it was shown that the tree frogs showed some degree of site fidelity. But the results also indicated that some individuals migrated from a source pond to new established ponds or nearby ponds located up to 5 km from the source pond. In one pond, a man-made artificial introduction of tree frogs was detected. The tree frogs in this pond were more closely related to tree frogs in a pond 20km away than to the frogs in the neighbour pond. In some isolated ponds a reduced survival of larva was detected which could be ascribed to an effect of genetic drift (random loss of genetic variation) and inbreeding. The population size in each pond was estimated counting calling males. A positive correlation between the number of calling males and the genetic variation was shown, i.e. the higher the number of calling males the higher the level of genetic variation. The results indicated that the genetic investigations did reflect the populations with favourable and the populations with unfavourable conservation status.
The implications for management reflected by the genetic analysis of the three species indicate that on the basis of the presented genetic analysis of fen orchid no dispersal corridors or other kinds of genetic exchanges would seem to improve the survival of the species. The genetic analysis of the European otter indicates that in Jutland the otter should be managed as one coherent population. To sustain the moderate genetic variation observed, an effective population size of 500 mature individuals is recommended, which indicates that the population size for the European otter ought to be 1,200 to 1,600 adults. The small population on Zealand should be managed in ways that allows the size to increase. For the European tree frog the genetic analyses indicate a significant correlation between the number of calling males and the level of genetic variation in the single pond. The detection of migration direction makes it possible to identify which populations are isolated and consequently direct the management effort specifically towards ensuring dispersal possibilities between groups of sub-populations. This will stabilise or increase the population size of the tree frogs and make it feasible for all groups to achieve a favourable conservation status.
Finally, a short review of the species on the EU-Habitat Directive Annex II and IV with unknown or unfavourable conservation status in Denmark is presented for which it would be beneficial to include analyses of the genetic variation in their management.
Full report in pdf format (1779 kB)
