Beschreibung
Hesse designates by law 20 red deer management areas in which the red deer can move freely. Outside these areas, only crowned deer over 5 years of age may cross the boundaries of the areas without being ordered to be shot. The increasing landscape fragmentation, especially by cities/settlements, traffic routes and agriculture lead to the steady decrease of habitat and habitat quality and to the isolation of the red deer populations. Based on the results of preliminary studies, the present study aimed to characterize genetic diversity and connectivity within and between Hessian red deer populations.
Samples from 1291 animals from the 19 important red deer management areas in Hesse were collected, genotyped based on 16 microsatellite markers and analysed. In particular, animals from the 2018/2019 hunting season were studied.
14 of the examined red deer management areas could be combined into four red deer regions, because there is still genetic exchange within these regions. Despite the geographical proximity to neighboring areas Knüll, Krofdorfer Forst, Wattenberg-Weidelsburg, Reinhardswald and Odenwald must be considered as isolated from the remaining red deer management areas.
The genetic effective population size was below 100 in ten of the red deer populations. This is an internationally and scientifically recognized threshold below which populations cannot cope with inbreeding depression in the short term. Effective population sizes of 500 to 1000 are necessary for long-term evolutionary development and adaptation to environmental influences. None of the 19 red deer populations exceeded this long-term threshold by itself. However, calculations of effective population size strictly apply only to smaller, isolated populations, so no definitive statement can be made for the larger red deer management areas where genetic exchange still exists. The occurrence of cases with mandibular shortening (Brachignatia inferior) in the areas Wattenberg-Weidelsburg, Knüll, Odenwald and Korfdorfer Forst starting in December 2018, together with the outlined inbreeding levels are indications for existing inbreeding depressions.
Consistent with the current view of the International Union for the Conservation of Nature, the common occurrence of a species and its habitats is obviously not sufficient to ensure the long-term existence of populations, if the genetic diversity of subpopulations cannot be maintained by isolation.
The relevance of this statement is proven with regard to the situation of the red deer population ‘Hasselbusch’ in Schleswig-Holstein, which can no longer be kept healthy in the long term due to massive inbreeding depression. Therefore, in regions where the implementation of silvicultural concepts is hampered by red deer populations, hunting and management measures must be taken, which also take into account the situation of red deer scientifically presented in this study.
