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821.
Martin?HeilEmail author Birgit?Baumann Ralf?Krüger K. Eduard?Linsenmair 《Chemoecology》2004,14(1):45-52
Summary. Myrmecophytic plants use obligate ant mutualists as a constitutive
indirect defence mechanism. These plants often produce cellular food bodies (FBs) to
nourish their resident ants. Lipids, proteins, and even highly specialised compounds
such as glycogen have been reported from FBs, but detailed chemical analyses of FB
composition have so far been presented only for Southeast Asian Macaranga
and Central American Piper myrmecophytes. Here we
report the chemical composition of FBs of five myrmecophytic Acacia
(Fabaceae) species from Mexico using HPLC (carbohydrates and proteins) and GC-MS
(lipids). Feeding experiments revealed no hints on any use of external food sources
by the inhabiting Pseudomyrmex ants. These ants
obviously rely completely on FBs and extrafloral nectar provided by their hosts.
The total content of nutrients in Acacia FBs was 15-25% of FB
dry mass, being much lower than in Macaranga or
Piper FBs. Proteins were dominating (8-14 % dm)
in Acacia FBs and thus were present in higher amounts than in
Macaranga FBs, yet in lower amounts than in
Piper. Lipids contributed 1-9 %
of dry mass, showing a lower proportion than in FBs of Macaranga
or Piper. Carbohydrates made up 3-11 % dm, reaching
in most Acacia species the same range as observed in
Macaranga and in Piper FBs.
Water content was 18-24 % of FB fresh mass, and structural tissue obviously made up
a much higher proportion in Acacia FBs than in
Macaranga or Piper
FBs. Both characters might represent an adaptation to producing FBs unprotected at
the leaf tips under dry conditions. Acacia FBs
contain all amino acids and all fatty acids that are considered essential for
insects, and their contents of lipids and proteins are higher than in the leaves
from which they are ontogenetically derived. This indicates a putatively adaptive
enrichment of nutritionally valuable compounds in structures functioning as ant-food. 相似文献
822.
Changes in chemistry and vertical distribution of35S were investigated in column experiments using intact topsoil and repacked mineral soil horizons 1 to 20 weeks after tracer application (901 kBq35S-SO4
2– per column 6.5 cm in diameter). Horizons O, A, AE and Bvs of an Orthic Podzol were incubated at 20°C and wetted twice a week with 11 mm of natural throughfall precipitation (38.5 mg S04
2– L–1-, pH 3.3). The top 35 cm of the soil contained 1,290 kg S ha–1, or 18 times more than is the annual atmospheric S input (71.4 kg S ha–1 yr–1). Of this amount, 17.8 % was stored as inorganic sulphate S, 4.6 % as reduced inorganic S, and 77.6 % as organic S. In O + A and AE, free sulphate was the most abundant35S form, while in Bvs the 35S activity of free and adsorbed sulphate was similar. The proportion of adsorbed sulphate increased with depth, averaging 23, 30 and 47 % of total inorganic sulphate35S in O + A, AE and Bvs, respectively. Total specific activity of chemically transformed35S (i.e., of reduced inorganic S and organic S) constituted 3.4, 3.8 and 105 % of inorganic sulphate35S activity in O + A, AE and Bvs, respectively, in averaged weeks 2–4, and 7.5, 6.4 and 39.6 % in averaged weeks 11–13 in O+A, AE and Bvs, respectively. The turnover time of C-bonded35S was shorter than that of ester sulphate35S. An increase in FeS2–
35S with time indicated anaerobic conditions suitable for bacterial sulphate reduction. After 13 weeks, 68 % of the tracer was found deeper than 8 cm below soil surface. 相似文献
823.
Minimum viable metapopulation size, extinction debt, and the conservation of a declining species. 总被引:2,自引:0,他引:2
Caroline R Bulman Robert J Wilson Alison R Holt Lucia Gálvez Bravo Regan I Early Martin S Warren Chris D Thomas 《Ecological applications》2007,17(5):1460-1473
A key question facing conservation biologists is whether declines in species' distributions are keeping pace with landscape change, or whether current distributions overestimate probabilities of future persistence. We use metapopulations of the marsh fritillary butterfly Euphydryas aurinia in the United Kingdom as a model system to test for extinction debt in a declining species. We derive parameters for a metapopulation model (incidence function model, IFM) using information from a 625-km2 landscape where habitat patch occupancy, colonization, and extinction rates for E. aurinia depend on patch connectivity, area, and quality. We then show that habitat networks in six extant metapopulations in 16-km2 squares were larger, had longer modeled persistence times (using IFM), and higher metapopulation capacity (lambdaM) than six extinct metapopulations. However, there was a > 99% chance that one or more of the six extant metapopulations would go extinct in 100 years in the absence of further habitat loss. For 11 out of 12 networks, minimum areas of habitat needed for 95% persistence of metapopulation simulations after 100 years ranged from 80 to 142 ha (approximately 5-9% of land area), depending on the spatial location of habitat. The area of habitat exceeded the estimated minimum viable metapopulation size (MVM) in only two of the six extant metapopulations, and even then by only 20%. The remaining four extant networks were expected to suffer extinction in 15-126 years. MVM was consistently estimated as approximately 5% of land area based on a sensitivity analysis of IFM parameters and was reduced only marginally (to approximately 4%) by modeling the potential impact of long-distance colonization over wider landscapes. The results suggest a widespread extinction debt among extant metapopulations of a declining species, necessitating conservation management or reserve designation even in apparent strongholds. For threatened species, metapopulation modeling is a potential means to identify landscapes near to extinction thresholds, to which conservation measures can be targeted for the best chance of success. 相似文献
824.
Mating behaviour and mating patterns are affected to a large extent by body size in both hermaphrodites and gonochorists.
Detailed research on mating patterns, mate choice, pre- and post-copulatory sexual selection in marine pulmonates is wanting,
thus warranting more attention as a study system in the future. The simultaneous hermaphroditic limpet Siphonaria capensis (Pulmonata: Basommatophora) shows size-dependent fecundity, and acts as a suitable organism to test the effects of body size
on mating patterns, mating success, gender expression and reciprocity in hermaphroditic marine gastropods. We mainly used
bootstrap resampling techniques to estimate the effects of different factors on mating patterns. In the populations studied,
a strong size-assortative mating pattern was observed, where small-scale spatial distribution of potential mating partners
(the mate availability hypothesis) could explain 65% of this pattern, while mate choice and mating constraints explaining
the rest. No significant difference in mating success between limpets with different body size was found, even though in one
population, the sperm recipients were larger than the non-copulating limpets. Interestingly, we found that intromission was
non-reciprocal during copulations. This may mean that this species does not conform to the common rule of reciprocity predicted
for hermaphrodites, unless there is sex-role alternation between individuals in a mating pair. The mating partners consisted
of similar sized, acting males and females, thus without any indication of the body size determining the gender expression.
The matings took place in early mornings only at spring tides and the animals were observed laying egg masses only during
neap tides. Since siphonariid limpets possess both a spermatheca and a seminal vesicle, which may have either a sperm storing
and/or digestive function, post-copulatory sexual selection (e.g., sperm competition) cannot be dismissed. 相似文献
825.
Michael Wink Angelika Hofer Martin Bilfinger Elke Englert Martinus Martin Dietrich Schneider 《Chemoecology》1993,4(2):93-107
Summary The palatability of plants was studied in young, immature and adult geese of three species,Anser anser, Anser indicus andBranta canadensis, with respect to secondary plant metabolites. In their first 1–4 weeks of life, hand-reared goslings feed on a wide variety of plants, more or less irrespective of their allelochemical contents. Older birds become more selective, but still consume plants which are normally considered to be unpalatable or even toxic for other animals. Choice experiments were performed with pure secondary metabolites which were offered on otherwise highly palatable food items, such as leaves ofTaraxacum officinale. These experiments revealed a similar trend, in that very young goslings discriminate their food much less than older goslings or adult geese. In general, food contaminated with essential oils was rejected, whereas alkaloids, glycosides, amines and sulfur compounds were tolerated to a remarkable degree. In consequence, especially young, but also adult geese must have a high capacity to tolerate and/or to detoxify dietary allelochemicals. Another detoxification mechanism became evident during the experiments: geese ingest soil and mud quite regularly. It could be shown experimentally that the respective soil had a high capacity to bind alkaloids. We assume that geophagy is a means (besides a presumed active detoxification in the liver) to adsorb and thus reduce the contents of dietary allelochemicals. 相似文献
826.
Martin?N.?MullerEmail author Richard?W.?Wrangham 《Behavioral ecology and sociobiology》2004,55(4):332-340
Field studies of endocrine function in a range of social mammals suggest that high dominance rank is commonly associated with elevated glucocorticoid production. This is puzzling, because in stable dominance hierarchies, high status is normally associated with social control and predictability, key predictors of low psychological stress. One solution to this problem may be that high rank is commonly associated with elevated energetic expenditure, leading to increased metabolic stress and glucocorticoid secretion. We conducted behavioural observations and non-invasive hormone sampling of male chimpanzees in Kibale National Park, Uganda, to examine the relationship between cortisol, dominance and stress in wild chimpanzees. Results indicate that male dominance rank positively correlated with urinary cortisol excretion in a stable dominance hierarchy. Cortisol excretion also correlated positively with rates of male aggression. We suggest that the relationship between cortisol and rank in chimpanzees may be driven by energetic factors rather than psychosocial ones. This interpretation is supported by the observation that urinary cortisol levels correlated negatively with food availability. These findings suggest that dominant chimpanzees experience significant metabolic costs that must be set against the presumed reproductive benefits of high rank. Metabolic stress may mediate the relationship between rank and cortisol in other social mammals.Communicated by L. Sterck 相似文献
827.
Martin?ReichardEmail author Pavel?Jurajda Carl?Smith 《Behavioral ecology and sociobiology》2004,56(1):34-41
We investigated the consequences of male-male interference competition associated with alternative male mating tactics in a freshwater fish, the European bitterling (Rhodeus sericeus). Male bitterling defend territories around living mussels and attract females to lay their eggs in the gill cavities of mussels. We experimentally manipulated spawning-site abundance and male density at two spatial scales. We showed that the total number of eggs spawned by females was constrained by the number of mussels available for oviposition. The effect was mediated by behavioral interactions among competing males because of variation in the Operational Sex Ratio (OSR) in close proximity to a mussel and not by a direct limitation in mussel capacity to accommodate the eggs. Both total and local male densities affected spawning behavior, and interacted in their effect on female spawning rate. Territorial male aggression caused courtship interruptions that prolonged the time until successful spawning and increased with male density. However, territoriality broke down at the highest male density, with a consequent stabilizing effect on spawning rate.Communicated by J. Krause 相似文献
828.
Stephen J. Martin Nicolas Châline Falko Drijfhout Graeme R. Jones 《Behavioral ecology and sociobiology》2005,59(1):24-29
In queen-right honeybee colonies workers detect and eat the vast majority of worker-laid eggs, a behaviour known as worker policing. However, if a colony becomes permanently queen-less then up to 25% of the worker population develops their ovaries and lay eggs, which are normally reared into a final batch of males. Ovary development in workers is accompanied by changes in the chemical secretion of the Dufour's gland with the production of queen-like esters. We show that ester production increases with the period that the colony is queen-less. The increased ester production also corresponds to an increase in persistence of worker-laid eggs in queen-right colonies, since the esters somehow mask the eggs true identity. However, in a rare queen-less colony phenotype, workers always eat eggs indiscriminately. We found that the egg-laying workers in these colonies were unusual in that they were unable to produce esters. This apparently maladaptive egg eating behaviour is also seen in queen-less colonies prior to the appearance of egg-laying workers, a period when esters are also absent. However, the indiscriminate egg eating behaviour stops with the appearance of ester-producing egg-laying workers. These observations suggest that esters are providing some contextual information, which affects the egg eating behaviour of the workers. 相似文献
829.
Polybrominated diphenyl ethers in whitefish from Swiss lakes and farmed rainbow trout 总被引:2,自引:0,他引:2
A method for trace analysis of polybrominated diphenyl ethers (PBDE) in fish based on gas chromatography/electron ionization high resolution mass spectrometry (GC/EI-HRMS) was developed, and levels of PBDE were determined in whitefish (Coregonus sp.) from eight Swiss lakes and in rainbow trout (Oncorhynchus mykiss) from four Swiss fish farms. PBDE concentrations (sum of PBDE congeners BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) in filet from whitefish between 36 and 165 ng/g lipid weight (lw) were found, corresponding to wet weight (ww) concentrations of 1.6-7.4 ng/gww. PBDE contents in filet from farmed rainbow trout were significantly lower than in wild whitefish (12-24 ng/glw, 0.74-1.3 ng/gww), and the PBDE congener patterns were different for both species (a higher BDE-47 to BDE-99 ratio for farmed rainbow trout compared to wild whitefish was found). Whitefish PBDE levels [ng/glw] correlate better with the surface/volume ratio of the respective lakes (r(2)=0.70) than with other lake properties such as catchment area (size or number of inhabitants) or residence time, suggesting atmospheric deposition as an input pathway for PBDE. Based on an average daily consumption of 20 g whitefish (Switzerland) with a PBDE content of 7.4 ng/gww (highest PBDE concentration detected in this study), a maximum daily intake of 0.15 microg PBDE was estimated (0.026 microg/day for farmed trout). This number corresponds to the lower end of the estimate for the total PBDE intake of the Nordic consumer of 0.2-0.7 microg/day. 相似文献
830.
Water-conducting faults and fractures were studied in the granite-hosted Äspö Hard Rock Laboratory (SE Sweden). On a scale of decametres and larger, steeply dipping faults dominate and contain a variety of different fault rocks (mylonites, cataclasites, fault gouges). On a smaller scale, somewhat less regular fracture patterns were found. Conceptual models of the fault and fracture geometries and of the properties of rock types adjacent to fractures were derived and used as input for the modelling of in situ dipole tracer tests that were conducted in the framework of the Tracer Retention Understanding Experiment (TRUE-1) on a scale of metres. After the identification of all relevant transport and retardation processes, blind predictions of the breakthroughs of conservative to moderately sorbing tracers were calculated and then compared with the experimental data. This paper provides the geological basis and model calibration, while the predictive and inverse modelling work is the topic of the companion paper [J. Contam. Hydrol. 61 (2003) 175].The TRUE-1 experimental volume is highly fractured and contains the same types of fault rocks and alterations as on the decametric scale. The experimental flow field was modelled on the basis of a 2D-streamtube formalism with an underlying homogeneous and isotropic transmissivity field. Tracer transport was modelled using the dual porosity medium approach, which is linked to the flow model by the flow porosity. Given the substantial pumping rates in the extraction borehole, the transport domain has a maximum width of a few centimetres only. It is concluded that both the uncertainty with regard to the length of individual fractures and the detailed geometry of the network along the flowpath between injection and extraction boreholes are not critical because flow is largely one-dimensional, whether through a single fracture or a network. Process identification and model calibration were based on a single uranine breakthrough (test PDT3), which clearly showed that matrix diffusion had to be included in the model even over the short experimental time scales, evidenced by a characteristic shape of the trailing edge of the breakthrough curve. Using the geological information and therefore considering limited matrix diffusion into a thin fault gouge horizon resulted in a good fit to the experiment. On the other hand, fresh granite was found not to interact noticeably with the tracers over the time scales of the experiments.While fracture-filling gouge materials are very efficient in retarding tracers over short periods of time (hours–days), their volume is very small and, with time progressing, retardation will be dominated by altered wall rock and, finally, by fresh granite. In such rocks, both porosity (and therefore the effective diffusion coefficient) and sorption Kds are more than one order of magnitude smaller compared to fault gouge, thus indicating that long-term retardation is expected to occur but to be less pronounced. 相似文献