دانلود رایگان مقاله نسبت ایزوتوپ پایدار در نمونه گرفته شده همراه شتاب دهی گرادیان

Abstract

Rock ptarmigan (Lagopus muta) and black grouse (Tetrao tetrix) are two closely related alpine bird species that form relict populations in the European Alps. Besides manifold anthropogenic influences in this region, global climate change is forecast to lead to significant changes in temperatures and precipitation. We here analysed stable isotope ratios (δ13C and δ15N) of feathers of both bird species and their potential dietary plants across a longitudinal precipitation gradient in south-east Switzerland. Plant δ13C was higher at higher altitudes and in drier areas (coinciding with higher longitudes) while plant δ15N did not differ geographically. Black grouse δ13C reflected the longitudinal pattern in precipitation and plant δ13C, and there was no indication for a change in dietary composition with precipitation (i.e. no significant changes in δ15N). In contrast, rock ptarmigan δ13C was independent of precipitation and plant δ13C values and showed a significant increase in δ15N towards drier areas, suggesting a potential dietary shift. In rock ptarmigan, we furthermore investigated intraspecific differences with age, between males and females and among years, and did not find any biologically meaningful intraspecific differences. Interspecifically, rock ptarmigan feathers had significantly higher δ13C and lower δ15N values than black grouse, reflecting a dietary segregation between both species. This may partly be due to the higher altitudinal distribution of rock ptarmigan in combination with an altitudinal gradient in plant δ13C. In addition, however, species also segregated in δ15N, most likely caused by a higher proportion of invertebrate diet in black grouse.

Conclusions/implications of this study

Alpine wildlife isseverely affected by anthropogenic influences, from land use patterns to global climate change that will affect temperature and precipitation patterns in the Alps. One aim of this study was therefore to investigate the dietary changes along a precipitation gradient within the central European Alps in both rock ptarmigan and black grouse. Overall, our data suggested a potential effect of precipitation on the diet of rock ptarmigan and no effect on black grouse. The more significant and slightly unexpected results of this study were, however, the dietary segregation of rock ptarmigan and black grouse.