TY  - JOUR
A1  - Schenk, Mariela
A1  - Mitesser, Oliver
A1  - Hovestadt, Thomas
A1  - Holzschuh, Andrea
T1  - Overwintering temperature and body condition shift emergence dates of spring-emerging solitary bees
JF  - PeerJ
N2  - Solitary bees in seasonal environments must align their life-cycles with favorable environmental conditions and resources; the timing of their emergence is highly fitness relevant. In several bee species, overwintering temperature influences both emergence date and body weight at emergence. High variability in emergence dates among specimens overwintering at the same temperatures suggests that the timing of emergence also depends on individual body conditions. However, possible causes for this variability, such as individual differences in body size or weight, have been rarely studied. In a climate chamber experiment using two spring-emerging mason bees (Osmia cornuta and O. bicornis), we investigated the relationship between temperature, emergence date, body weight, and body size, the last of which is not affected by overwintering temperature. Our study showed that body weight declined during hibernation more strongly in warm than in cold overwintering temperatures. Although bees emerged earlier in warm than in cold overwintering temperatures, at the time of emergence, bees in warm overwintering temperatures had lower body weights than bees in cold overwintering temperatures (exception of male O. cornuta). Among specimens that experienced the same overwintering temperatures, small and light bees emerged later than their larger and heavier conspecifics. Using a simple mechanistic model we demonstrated that spring-emerging solitary bees use a strategic approach and emerge at a date that is most promising for their individual fitness expectations. Our results suggest that warmer overwintering temperatures reduce bee fitness by causing a decrease in body weight at emergence. We showed furthermore that in order to adjust their emergence dates, bees use not only temperature but also their individual body condition as triggers. This may explain differing responses to climate warming within and among bee populations and may have consequences for bee-plant interactions as well as for the persistence of bee populations under climate change.
KW  - Wild bees
KW  - Timing
KW  - Fitness
KW  - Hibernation
KW  - Climate change
KW  - Mechanistic model
KW  - Osmia
KW  - Body weight
KW  - Body size
KW  - Pollinators
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228544
VL  - 6
ER  - 
TY  - JOUR
A1  - Cornelius, C.
A1  - Leingärtner, A.
A1  - Hoiss, B.
A1  - Krauss, J.
A1  - Steffan-Dewenter, I.
A1  - Menzel, A.
T1  - Phenological response of grassland species to manipulative snowmelt and drought along an altitudinal gradient
N2  - Plant communities in the European Alps are assumed to be highly affected by climate change since temperature rise in this region is above the global average. It is predicted that higher temperatures will lead to advanced snowmelt dates and that the number of extreme weather events will increase. The aims of this study were to determine the impacts of extreme climatic events on flower phenology and to assess whether those impacts differed between lower and higher altitudes. In 2010 an experiment simulating advanced and delayed snowmelt as well as drought event was conducted along an altitudinal transect ca. every 250m (600-2000 m a.s.l.) in the Berchtesgaden National Park, Germany. The study showed that flower phenology is strongly affected by altitude; however there were few effects of the manipulative treatments on flowering. The effects of advanced snowmelt were significantly greater at higher than at lower sites, but no significant difference was found between both altitudinal bands for the other treatments. The response of flower phenology to temperature declined through the season and the length of flowering duration was not significantly influenced by treatments. The stronger effect of advanced snowmelt at higher altitudes might be a response to differences in treatment intensity across the gradient. Consequently, shifts in the date of snowmelt due to global warming may affect species more at higher than at lower altitudes since changes may be more pronounced at higher altitudes. Our data indicate a rather low risk of drought events on flowering phenology in the Bavarian Alps.
KW  - Biologie
KW  - Advanced snowmelt
KW  - Alps
KW  - BBCH
KW  - Climate change
KW  - Delayed snowmelt
KW  - Flowering
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-77969
N1  - ist zugleich: IV. Kapitel der Dissertation von Bernhard Hoiß
ER  -