Untersuchungen zur Variabilität von Geweihmerkmalen beim Rotwild (Cervus elaphus, L.)
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Beschreibung
The antler structure of red deer (Cervus elaphus L.) follows a general genetic construction plan, although there can be considerable phenotypic differences in antler characteristics from year to year within the same individual. The variability of different antler characteristics depending on age, side, origin, and existing environmental conditions has been studied in a large number of papers. However, comparisons of only a limited number of antler parameters, primarily CIC traits, have been conducted to date. Furthermore, the trophies and cast antlers of previous studies came from different deer. The aim of the present study was to compare cast antler series and to investigate the variability of antler characteristics depending on animal, age, side and origin in order to quantify the constancy of the different antler characteristics and how they can be influenced by environmental conditions.
The basis for this study was a total of 377 cast antlers and 10 trophies from a total of 35 different red deer stags. Drill samples of all cast antlers and trophies were examined to validate that they belonged to the same deer. DNA isolation from the bone chips was performed using an isolation kit. PCR amplificates were obtained from the DNA samples using 16 microsatellites in 4 multiplex approaches. Subsequently, capillary sequencing and electrophoresis of the fluorescence-labelled PCR products were performed. The accuracy of phenotypic assignment of the antlers to the same deer was 95 %. A Hand-held scanner was used to create 3D models of trophies and cast antlers, which were subsequently measured using a CAD program. Thus, a total of 93 measured or calculated parameters per antler were included in the statistical evaluation. This was done by using a generalized linear model taking into account the effects of stag, origin, age and side. The distribution of the parameters was also considered.
Of all the traits examinated, the distances between the tips of brow and bay tine, brow and tray tine as well as bay and tray tine, the branching angles of the main tines, the direct distances between the nodes of brow and bay tine, brow and tray tine as well as bay and tray tine, the bend of the main been where the tray tine branches off, the angle between brow tine and the plane consisting of the nodes of the tray and brow tine as well as the point on the tray tine before the bending begins, the relative lengths of the main tines to the beam length, the specific weight, the proportion of antlers with bay tine, the quotient between the precise and the rough coronet circumference, the bending of the bay tine from the side and from above as well as the curvature of the main beam are the most constant traits. These are characterised by a high variance explained by the stag and a low variance explained by the age, what makes them particularly well suited to distinguish stags from each other. On the other hand, the length of the brow tine according to CIC, the direct length from the node to the tip of the brow tine, the circumference of the tray tine, the upper beam circumference according to CIC, the smallest circumference between the tray tine and the base of the crown, the weight, the colour, the pearls as well as the ends of the tines according to CIC turned out to be the most variable traits, characterised by a high age dependence and a marginal effect of the stag. Overall, the crown traits were explained very little by the effects studied, suggesting a high variability of the crown, the cause of which remains unexplained so far.
Based on the surveys of antler characteristics, it was possible to test various hypotheses, some of which were self-generated and some of which came from the literature. That the number of tines is not a good indicator of age and that angular tines cannot serve as a recognition feature for deer could be confirmed. The claim that the convexity/concavity of the seal can serve as a recognition feature for deer could only be confirmed to a limited extent, as this feature turned out to be strongly age-dependent. That the presence of a bay tine is variable could be confirmed, but the markedness of the bay tine remains relatively constant except for the circumference, which increases with age. Contrary to the hypothesis, there was no correlation between the presence of a bay tine and lower beam circumference. The claim that hunting selection influences antler traits in the population could only be confirmed to a limited extent, since only a few traits (see above) were found to be particularly constant, and thus could in principle be influenced by selection. Spacing between main tines and tine angles may serve as recognition traits for deer, contrary to the hypotheses put forward. The claim that the curvature of the main beam and the main tines is highly variable could be rejected, because the curvature of the main beam was found to be a constant trait. For the curvature of the main tines, on the other hand, the hypothesis could be confirmed. The presence of a split brow and tray tine was found to be independent of age, contrary to the hypothesis. Another assumption is that the crown shape is highly variable and that there is no basic shape. The high variability could be confirmed here, however, the crown with single front end and multiple forked rear end turned out to be a kind of universal form, from which all other crown forms can emerge. Contrary to the assumed hypothesis, the tines differed in their dependence on the origin. Their lengths, circumferences, relative lengths to the main beam length, and curvatures were found to be more influenced by the effect of origin the more distally the tine was located. Beam circumferences behaved similarly. Contrary to the hypothesis, the upper beam circumference was more strongly dependent on the origin than the lower beam circumference. The previously only assumed increasing complexity of the crowns with age and distinct variability could be scientifically proven and quantified for the first time.
The results shed light on the suitability of the multiple traits studied for individual identification and age estimation of individuals under practical conditions. The antler traits show considerable differences in the degree of variation within and between individuals. The results were only made possible by the availability of cast antlers from several years from individual deer, which could be correctly assigned by DNA analysis. In summary, it can be seen that the genetic blueprint of the antlered deer is surprisingly stably maintained over the years for certain traits (see above - constant traits), while such a blueprint is hardly recognizable for other traits (see above - variable traits). The identification of largely constant traits in antler development made in this work opens up approaches and opportunities for follow-up work to generate new insights into the genetic architecture of antler structure.
Autor*in
Katharina Bils