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Different Temperature Regimes (different + temperature_regime)
Selected AbstractsAge-Related Microhabitat Segregation in Willow Tit Parus montanus Winter FlocksETHOLOGY, Issue 11 2000Lluís Brotons It is expected that through flexibility in behaviour, flock living birds respond to the asymmetries in resource access derived from dominance relationships. We analysed the microhabitat use of willow tits in winter flocks and assessed possible factors which shape habitat segregation between adults and juveniles in different temperature regimes. When foraging in mild conditions (ambient temperature >,0°C), flocks split up into subgroups with adults foraging in inner parts of trees more often than juveniles. However, no differences were recorded in the vertical position occupied in trees. In harsh conditions (< , 4°C), flocks re-united and juveniles further moved to outer parts of trees, increasing horizontal segregation between age classes. In mild conditions, vigilance behaviour was not related to the position of birds in trees, but in harsh conditions, scanning frequency was higher in outer parts of trees only for adults. In mild weather, juvenile position in trees was associated with body size and mass. The foraging microhabitat segregation detected in harsh conditions fits the age-related hoarding distribution previously described in the same population. This supports the hypothesis that hoarded food is important in determining future foraging habitat use. Adult preference and intraspecific competition for safer or richer inner parts of trees as foraging sites during harsh conditions seems to determine the habitat segregation between adults and juveniles. Furthermore, we suggest that in mild weather, when foraging in the absence of adults, juveniles balance the costs of using a potentially dangerous microhabitat with the benefits of building energetically cheap and large food reserves through hoarding. The expected patterns of microhabitat segregation may differ in parids, depending on whether predation risk or other factors such as food availability are the main factors controlling habitat quality. [source] Grazing impact and phenology of the freshwater sponge Ephydatia muelleri and the bryozoans Plumatella emarginata and Fredericella sultana under experimental warmingFRESHWATER BIOLOGY, Issue 5 2009ANDREAS VOHMANN Summary 1.,Both the clearance rates (CR) and abundances of the freshwater sponge Ephydatia muelleri and the bryozoans Plumatella emarginata and Fredericella sultana were investigated from autumn to spring under different temperature regimes. The experiments were performed in bypass channels of the River Rhine (Cologne, Germany) in which temperature could be manipulated. 2.,The impact of temperature increase on CRs depends upon the grazer: E. muelleri showed a clear increase in CRs with increasing temperature whereas P. emarginata was not significantly affected by experimental warming. 3.,Distinct differences in food preference were found for the sponge (which is an efficient grazer of bacteria and small algae) and for the bryozoan P. emarginata (which feeds primarily on large algae, and with no significant grazing on bacteria). 4.,In contrast to their temperature-related patterns in CR, respiration of both P. emarginata and E. muelleri increased with temperature between 19 and 32 °C, suggesting that the risk of experiencing energy deficiency at high temperatures due to increased metabolic rates is particularly high for the bryozoan. 5.,A temperature elevation of 3 °C above the natural Rhine temperature resulted in a delay in the disappearance of active tissue and formation of resting stages for E. muelleri in autumn. This delay ranged from 8 (beginning of gemmulation) to 22 days (termination of gemmulation). In contrast, there was no distinct effect of warming on the disappearance of active zooids of the two bryozoan species in autumn. However, warming can positively affect the maintenance of active zooids during winter in F. sultana. In spring, the appearance of active zooids of P. emarginata was clearly stimulated by temperature elevations, whereas the hatching of both F. sultana and E. muelleri was hardly affected by warming. 6.,The study demonstrated different patterns in the thermal ecology of the two freshwater bryozoans and the sponge in comparison to other filter feeders, particularly mussels. Such patterns need to be considered when predicting the impact of temperature on pelagic-benthic coupling in aquatic habitats. [source] A model for predicting the emergence of dragonflies in a changing climateFRESHWATER BIOLOGY, Issue 9 2008OTTO RICHTER Summary 1. Precise models for the phenology of different species are essential for predicting the potential effects of any temporal mismatch of life cycles with environmental parameters under different climate change scenarios. Here we investigated the effects of ambient water temperature on the onset and synchrony of emergence for a widespread European riverine dragonfly, Gomphus vulgatissimus. 2. Long-term field data on the annual emergence from two rivers in northern Germany, and additional data from a laboratory experiment with different temperature regimes, were used to develop a model that predicted the onset of emergence by using mainly the temperature sum (degree days) as a parameter. 3. Model predictions of the onset of emergence fitted the observations well and could be transferred between localities. This was particularly so when weighting early winter temperature data by using a day length and a temperature-response function, implying potential additional control mechanisms for the onset of emergence. 4. We simulated effects of different winter temperature regimes on the emergence curves in order to predict the effects of climate change. These indicated an acceleration of emergence by 6,7 days per 1 °C temperature increase, which is corroborated by the laboratory data and is in the upper range of data published for other dragonflies. [source] The use of size,frequency diagrams to characterize prehistoric fish catches and to assess human impact on inshore fisheriesINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2001Foss Leach Abstract Archaeological collections of fish bones from previously excavated sites in New Zealand are being re-examined and selected bones measured in order to estimate original fish size, reconstruct prehistoric fish catches and assess human impact on the fishery over the course of about 800 years of New Zealand prehistory. Several problems hamper this research, such as small sample sizes, lack of significant stratigraphy at many sites, inconsistent field collection strategies and failure to retain all of the material after initial analysis. Although some common fish species show a significant decline in mean size between pre-European and early historic samples on the one hand, and modern populations on the other, we have found little support for the common belief that there was a decline in mean fish size during the pre-European period. We have observed increases over time in the mean size of snapper (Pagrus auratus), blue cod (Parapercis colias) and undifferentiated species of Labridae from several sites scattered throughout New Zealand. Distinguishing between changes in fish population structures owing to natural processes, such as surface sea water changes, and those which are the result of human over-fishing is not simple, because both processes can operate simultaneously. We draw on modern fish quota management models to separate these processes. Important factors for each species are inshore biomass and the recruitment rate at different temperature regimes. In the case of blue cod, we find that there are signs in the catch diagrams of changes in fishing technology, and that 30,80% of catches are undersized fish in terms of modern management criteria. Copyright © 2001 John Wiley & Sons, Ltd. [source] Butterfly life history and temperature adaptations; dry open habitats select for increased fecundity and longevityJOURNAL OF ANIMAL ECOLOGY, Issue 1 2005BENGT KARLSSON Summary 1Evidence suggests that changes of temperature-related performance curves can trigger a selective response in life-history traits. Hence, it should be expected that insects adapted to different temperature regimes should exhibit optimal performance at the temperature to which they are adapted. 2To test this idea we investigated how fecundity and longevity are influenced by ambient temperatures in a set of satyrine butterflies adapted to live in dry open landscapes or in closed forest landscapes, respectively, by keeping egg-laying adult females at five different constant temperatures ranging between 20 and 40 °C. 3We studied four species, two of which are confined to dry and hot open habitats, namely the grayling (Hipparchia semele) and the small heath (Coenonympha pamphilus), and two of which are shade dwelling, namely the ringlet (Aphantopus hyperantus) and the speckled wood butterfly (Pararge aegeria). 4As predicted, the results showed that lifetime fecundity exhibited bell-shaped curves in relation to temperature with the open landscape group peaking at a higher temperature, 30 °C, compared with the shade-dwelling group that peaked at 25 °C. Longevity decreased with increasing temperatures among all species, but the open landscape living species survived better at higher temperatures. Moreover, although the magnitude of reproductive effort measured as lifetime egg mass did not differ between the two ecological groups, lifetime fecundity did with open landscape species laying more and smaller eggs than the shade-dwelling species. 5This difference in life-history character traits suggests either that dry and relatively warm open habitats open life-history opportunities in terms of higher fecundity and longevity that remain closed to butterflies adapted to cooler temperatures, or that life in dry open habitats actively selects for higher fecundity and survival as a result of increased offspring mortality. [source] Energy reserves during food deprivation and compensatory growth in juvenile roach: the importance of season and temperatureJOURNAL OF FISH BIOLOGY, Issue 1 2005P. L. M. Van Dijk The effect of 21 days of starvation, followed by a period of compensatory growth during refeeding, was studied in juvenile roach Rutilus rutilus during winter and summer, at 4, 20 and 27° C acclimation temperature and at a constant photoperiod (12L : 12D). Although light conditions were the same during summer and winter experiments and fish were acclimated to the same temperatures, there were significant differences in a range of variables between summer and winter. Generally winter fish were better prepared to face starvation than summer fish, especially when acclimated at a realistic cold season water temperature of 4° C. In winter, the cold acclimated fish had a two to three-fold larger relative liver size with an approximately double fractional lipid content, in comparison to summer animals at the same temperature. Their white muscle protein and glycogen concentration, but not their lipid content, were significantly higher. Season, independent of photoperiod or reproductive cycle, was therefore an important factor that determined the physiological status of the animal, and should generally be taken into account when fish are acclimated to different temperature regimes. There were no significant differences between seasons with respect to growth. Juvenile roach showed compensatory growth at all three acclimation temperatures with maximal rates of compensatory growth at 27° C. The replenishment of body energy stores, which were utilized during the starvation period, was responsible for the observed mass gain at 4° C. The contribution of the different energy resources (protein, glycogen and lipid) was dependent on acclimation temperature. In 20 and 27° C acclimated roach, the energetic needs during food deprivation were met by metabolizing white muscle energy stores. While the concentration of white muscle glycogen had decreased after the fasting period, the concentrations of white muscle lipid and protein remained more or less constant. The mobilization of protein and fat was revealed by the reduced size of the muscle after fasting, which was reflected in a decrease in condition factor. At 20° C, liver lipids and glycogen were mobilized, which caused a decrease both in the relative liver size and in the concentration of these substrates. Liver size was also decreased after fasting in the 4° C acclimated fish, but the substrate concentrations remained stable. This experimental group additionally utilized white muscle glycogen during food deprivation. Almost all measured variables were back at the control level within 7 days of refeeding. [source] Selection and sharing of sheltered nest sites by ants (Hymenoptera: Formicidae) in grasslands of the Australian Capital TerritoryAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2008Wayne A Robinson Abstract, In this study, it was investigated whether ants nesting under artificial rocks in a mesic south-eastern Australian grassland showed preference for nest sites with different temperature regimes. The study also allowed evaluation of competition between species for nest sites and observations of seasonality in brood and alate production in the nests of four common ant groups. On every sampling occasion more than 90% of nests were either Iridomyrmex spp., Rhytidoponera ,metallica', Paratrechina sp. or Pheidole spp. Soil underneath thinner artificial rocks had higher average temperatures and warmed up earlier in the day and Iridomyrmex spp. and R. ,metallica' showed preference for establishing nests under these. While all ant nests had summer peaks in brood production, Iridomyrmex spp. and R. ,metallica' had brood observed throughout the year. Winged reproductives were commonly encountered in Iridomyrmex spp., R. ,metallica' and Paratrechina sp. nests, but only occasionally Pheidole spp. nests. Alates were present in the nests from February but released by all taxa after spring rains and were scarcely recorded in November, December and January when brood production was observed in most nests. Nest sites that offer protection from predators are an obvious advantage, but improved reproductive success can be gained in cool regions such as the mesic grasslands of the Australian Capital Territory by choosing nest sites with an optimal thermal regime. [source] | |||||||||||||