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33.
Wolfgang Forstmeier Dennis Hasselquist Staffan Bensch Bernd Leisler 《Behavioral ecology and sociobiology》2006,59(5):634-643
Song complexity is often regarded as a sexually selected trait that reflects the overall quality of a male. In many passerine
species, old males possess larger song repertoires than younger males. This may be either because individual males improve
their performance as they get older (longitudinal increase) or because poor singers have reduced viability and, hence, are
underrepresented in old age classes (cross-sectional increase). We studied the age dependence of repertoire size and other
song traits in a German and a Swedish great reed warbler (Acrocephalus arundinaceus) population. We found marked differences between longitudinal and cross-sectional approaches, as well as between the two
study populations. In the German population, we found that syllable switching, a measure of immediate versatility and strophe
length, increased with age in a cross-sectional analysis. This was not because birds improved with age (longitudinally) but
because syllable switching was positively correlated with male longevity. However, in Sweden, syllable switching seemed to
be unrelated to age and longevity. In the Swedish population, individual males increased their repertoire size as they got
older (longitudinal increase), but this did not happen in the German population. Hence, two populations, even when belonging
to the same subspecies, may differ in whether or not they show delayed song maturation. 相似文献
34.
Energy expenditure for mouthbrooding in a cichlid fish 总被引:1,自引:0,他引:1
Summary Energy costs of mouthbrooding were investigated in the East African maternal mouthbrooder Pseudocrenilabrus multicolor by measuring rates of oxygen consumption. Mothers with their brood in the mouth expended 15.7% more energy than mothers without their brood and 13.8% more than starving nonreproductive controls. After subtracting the energy expenditure of the brood, the excess is reduced to 4.7% and 3.2%, respectively, a difference that is not statistically significant. By contrast, feeding nonreproductive females expended more than twice as much energy as the other groups. We conclude that mouthbrooding is a low-cost strategy profiting from investments made during the preceding nonreproductive phase. The implications for the evolution of mouthbrooding are discussed within the context of ecological constraints. 相似文献
35.
A few species of the weakly electric snoutfish, the African freshwater family Mormyridae, have been reported to vocalise. However, allopatric populations of a single species were never compared. Members of three allopatric Marcusenius macrolepidotus populations, originating from the Upper Zambezi River in Namibia, the Buzi River (Mozambique), and the Incomati River system in South Africa, vocalised with pulsatile growl- and tonal hoot sounds in dyadic confrontation experiments. A high rate of growling accompanied territorial and agonistic interactions and also non-threatening interactions between males and females, which in one pair appeared to be courtship. Growl sound characteristics of M. macrolepidotus from the Incomati system differed from those of the Upper Zambezi in a significantly higher frequency of the first harmonic (mean, 355 Hz vs 266 Hz). The two vocalising males from the Buzi River generated growls about twice as long as the other fish. Furthermore, the growl pulse period was about 4 ms in M. macrolepidotus from the Upper Zambezi River and from the Incomati system, but 6 ms in M. macrolepidotus from the Buzi River. Hoots were only observed in agonistic encounters. Hoot oscillograms showed a sinusoidal waveform, and the mean duration of this sound was similar in Incomati system fish (mean, 161 ms), Upper Zambezi fish (172 ms) and Buzi fish (103 and 145 ms for the two vocalising individuals). The mean frequency of the first hoot harmonic was higher in Incomati system fish (326 Hz) than in Upper Zambezi fish (245 Hz). Both growl and hoot occurred only in the presence of conspecifics, probably signalling the presence and condition of an opponent, territory owner or potential mate. This is the first evidence for (1) sound production and acoustical communication in another species and genus, M. macrolepidotus, from southern Africa to be (2) geographically differentiated. 相似文献
36.
Summary Whirligig beetles aggregate in the daytime into dense single-and multispecies groups (rafts) of hundreds or thousands of individuals. On the 22km shoreline of Lake Itasca in northern Minnesota, these aggregations were on the average 0.8 km apart, and they were usually found day after day in the same ocations.Most beetles apparently do not home to the aggregation of their origin after dispersing at night because (a) the species composition of some aggregations changed greatly, and (b) paint-marked beetles (Dineutus horni) moved overnight from one aggregation as far as 4km, joining 11 of the 14 large (>300 beetles) D. horni groups on the lake.Throughout the night, the largest concentrations of beetles remained within 100m of the diurnal aggregation sites. Beetles reconvened into the compact rafts before daybreak, in part by following each other in sometimes long single files or trains. Their forward motion stopped after they joined large number of other beetles. We infer that following behavior enables those individuals that have dispersed from their original aggregations (during their nocturnal foraging) to find and join other aggregations before daylight.Naive fish ate the beetles despite their noxious secretions. However, fish living near rafting sites and feeding on insects on the water surface in daylight should soon learn to avoid the beetles. The rafting sites would then become safe places. We observed fish attacking only those beetles that had been either dispersed from their rafts or released into open water away from raft sites in the daytime. We speculate that the evolutionary significance of the aggregation behavior is related to predator (fish) avoidance. 相似文献
37.
We reconstructed the flora of a European region at a historical point in time from historical topographical maps that contain rather precise information about the condition and composition of habitats. The ecological information obtained from these maps can be enriched through the potential of broadly diversified archival information. This study is confined to grassland communities. Considerations in terms of phytosociology make historical lists of plant species a good starting point for the reconstruction of grassland communities. The combination of historical and scientific methods proves suitable for reconstructing specific historical environmental conditions. Taking into account the frequency of relevant historical sources in European archives as well as in archives abroad, this approach claims for far-reaching application to ecosystem restoration matters, especially if ecological information from natural sources is missing. 相似文献
38.
Significance of platinum group metals emitted from automobile exhaust gas converters for the biosphere 总被引:1,自引:0,他引:1
Intention, Goal, Scope, Background Following the introduction of automobile catalytic converters the platinum group metals (PGM) platinum (Pt), palladium (Pd)
and rhodium (Rh) gain on increasing interest in environmental research as these metals are emitted with exhaust fumes into
the environment. Consequently, elevated PGM levels were found in different environmental matrices uch as road dusts, soils
along heavily frequented roads, sediments of urban rivers etc. Accordingly, the effects of increasing PGM emissions on the
biosphere are controversially discussed.
Objective This paper summarizes the present knowledge on the biological availability of PGM to plants and animals. As biological availability
is one of the most decisive factors determining the toxicologi-cal potential of xenobiotics, this information is very important
to evaluate the possible threat of the noble metals to ecosystems.
Results and Discussion The availability of soluble as well as particle bound PGM to terrestrial plants was demonstrated in several studies. Experimental
investigations revealed uptake of Pt, Pd and Rh also by aquatic plants. Additionally, the biological availability of the noble
metals for animals has been verified in experimental studies using soluble metal salts, catalytic converter model substances,
sediments of urban rivers, road dust or tunnel dust as metal sources. These studies refer mainly to aquatic animals. Beside
of free living organisms, in particular worms parasitizing fish demonstrated a high potential to accumulate PGM. This could
be of great interest in respect of biomonitoring purposes. Generally, for plants as well as for animals Pd turns out to be
the best available metal among the PGM. Compared to other heavy metals, the biological availability of PGM from road dust
to zebra mussels(Dreissena polymorpha) ranged between that of Cd and Pb.
Conclusion Especially chronic effects of PGM on the biosphere can not be excluded due to (1) their cumulative increase in the environment,
(2) their unexpected high biological availability and bioaccumulation and (3) their unknown toxicological and ecotoxicological
potential. However, it appears that acute effects on ecosystems due to anthropogenic PGM emission are not likely.
Recommendation and Outlook Research on environmental PGM contamination of the biosphere, especially the fauna, and on long-term toxiciry of low PGM concentrations
is highly appreciated. These studies require very sensitive analytical techniques to determine PGM even in low sample amounts.
Research has to be done in particular on reliable determination of (ultra) trace levels of Pd and Rh as the lack of data on
these two metals is mainly due to analytical problems. 相似文献
39.
Bernd U Wiese María C Palancar José M Aragón Fernando Sánchez Roberto Gil 《Water environment research》2006,78(8):781-791
The Entrepe?as Reservoir is a monomictic reservoir located in River Tagus (Spain). The aim of this work is to establish a feasible model to predict the depth of the thermocline that is developed in the reservoir during the period of natural thermal stratification. Entrainment, eddy diffusion, inflow of external energy, and other factors are considered to calibrate the parameters of the model. The methodology involves the measure of actual temperature and electrical conductivity profiles, use of meteorological data and reservoir parameters, and selection and application of several models from the literature. The calculations and predictions are integrated to a software packet that is able to predict thermocline depth and water temperature profile during a 1-year period on a day-by-day basis. In the thermocline depth, the prediction error, on the basis of real data, is less than 6% and, in the water temperature, it is 2 degrees C. 相似文献