Trends in the prey size-based trophic niches of feral and House Cats Felis catus L.

House Cats Felis catus L., whether attached to human households or not, appear to be versatile opportunistic predators. Their principal prey in most areas are mammals (rodents and rabbits), with bird prey secondary. Trophic niche breadth, as measured by the standard deviation of the spectrum of logarithmically transformed prey sizes ('SLH'), shows a latitudinal trend, being greater in low latitudes: it is also greater in periods of high prey availability. This appears to be influenced by inclusion of very small prey, especially insects, in areas and seasons when they are available. Both the niche breadth and the mean prey size (niche position) appear to be constant as population mean cat size increases. The most common prey size for cats is about 1% of their own body weights, which is much less than most previously reported values for carnivores.     

生态学假说试验验证的原假说困境

试验方法是生态学假说的主要验证方法之一,但也存在由原假说引发的质疑.Quinn和Dunham(1983)通过对Platt(1964)的假说-演绎模型进行分析,主张生态学不可能存在可以严格被试验验证的原假说.Fisher的证伪主义与Neyman-Pearson(N-P)的非判决性使得统计学原假说不能被严格验证;而生态过程中存在的不同于经典物理学的原假说H₀(α=1,β=0)与不同的备假说H₁′(α′=1,β′=0)的情况,使得生态学原假说也很难得到严格的实验验证.通过降低P值、谨慎选择原假说、对非原假说采取非中心化和双侧验证可分别缓解上述的原假说困境.但统计学的原假说显著性验证(NHST)不应等同于生态学假说中有关因果关系的逻辑证明方法.因此,现有大量基于NHST的生态学假说的方法研究和试验验证的结果与结论都不是绝对的逻辑可靠的.     

Production and storage of mealworm beetle as prey for predatory stinkbug

Arthropod predators can be produced using alternative prey, but the availability of a constant supply of prey at low cost is necessary to support large-scale production. The use of stored prey can be advantageous for maintaining a constant food supply, but its quality may decline in storage. Thus, we tested the effect of using stored pupae of the alternative prey Tenebrio molitor L. at low temperature (mean of 3.6°C) on the performance of predatory stinkbug Podisus nigrispinus (Dallas). The treatment conditions we tested were: pupae stored for exactly 30 days before being used as prey (30-d pupae); pupae stored for either 20 or 35 days prior to the initiation of their use as prey, with continued storage during nymphal and adult stages (20-d+ or 35-d+ pupae); and 2-day-old newly moulted pupae as the control treatment. The duration of the nymphal stage of females and the weight of males were lower for nymphs fed 20-d+ and 35-d+ pupae, respectively. The pupal weight consumed and the rate of eggs and nymphs produced per gram of consumed pupae were also lower for adult females fed 35-d+ pupae compared to females that were fed 2-day-old pupae. These measures, however, were similar for females fed 30-d and 20-d+ pupae. The greatest consumption of pupae was observed for 20-d+ and 35-d+ treatments during nymphal and adult stages, respectively. The use of stored T. molitor pupae supported the development and reproduction of P. nigrispinus, regardless of the period of storage but with variable results among treatments. Therefore, among any of the tested treatments those pupae that were stored for exactly 30 days produced the highest fitness for P. nigrispinus.     

Do earthworms help to sustain the slug predator Pterostichus melanarius (Coleoptera: Carabidae) within crops? Investigations using monoclonal antibodies

Earthworms provide a major potential source of alternative food for polyphagous predators, such as carabid beetles, that are natural enemies of slugs, aphids and other agricultural pests. Non-pest prey may foster larger numbers of natural enemies, which then help to control pests, or alternatively may help to divert the predators away from pest control. An earthworm-specific monoclonal antibody was developed to study carabid-earthworm interactions in the field and assess the role of earthworms as alternative prey. The antibody could identify as little at 7 ng of earthworm protein in an ELISA, and could detect earthworm remains in the foregut of the carabid beetle Pterostichus melanarius for 64 h after consumption. Thirty-six per cent of field-collected beetles contained earthworm remains. Quantities of earthworm proteins in the beetle foreguts were negatively related to total foregut biomass, suggesting that earthworm consumption increased as total prey availability declined. There was also a negative relationship between foregut biomass and beetle numbers, but both quantities and concentrations of earthworm proteins in beetle foreguts were positively related to beetle numbers. This suggests that as beetle activity-density increased, total prey availability declined, or, as prey availability declined, beetles spent more time searching. In these circumstances, beetles fed to a greater extent on earthworms, an acceptable but nonpreferred food item. Earthworms may, therefore, provide an ideal alternative prey for P. melanarius, helping to sustain it when pest numbers are low but allowing it to perform a 'lying-in-wait' strategy, ready to switch back to feeding on pests when they become available.     

The smell of danger: chemical recognition of fish predators by the invasive crayfish Procambarus clarkii

1. Since avoiding predation can compromise animal fitness, prey are expected to respond to different predator species with an intensity appropriate to the level of risk. In fresh waters, the threat of predation is typically assessed by chemical cues, in particular by odours released by either injured/disturbed conspecifics (conspecific alarm odour) or predators (predator odours). Here, we used the most widely distributed crayfish in the world, the invasive North American Procambarus clarkii, to investigate the relative effectiveness of odours emitted by fish predators compared with conspecific alarm odour. We also tested whether P. clarkii is able to discriminate between fish predators of which it has ‘experience’ (either recent, via introduction to the same water body, or old, by sharing a native range), as well as between fish predators that pose low or high risk. 2. The study was carried out on introduced populations of P. clarkii from two sites, characterised by different fish assemblages: the Malewa River (a tributary of Lake Naivasha, Kenya) and Lake Trasimeno (Italy). Laboratory experiments consisted of three sequential phases (‘water’, ‘food’ and ‘smell’ phases) and five treatments. Treatments differed in the odour presented during the smell phase, i.e. no odour (plain water) and odours from either injured conspecifics or three fish species per site. Crayfish from the Malewa River population were confronted with the odours of largemouth bass (Micropterus salmoides), common carp (Cyprinus carpio) and tilapia (Tilapia zillii) (all introduced to Lake Naivasha but absent from the Malewa River), and those from the Lake Trasimeno population with the odours of the introduced largemouth bass and carp and the native chub (Squalius cephalus). Largemouth bass is the only predator that imposes a high risk to crayfish, and it also shares its native range with P. clarkii. We analysed the time spent by crayfish feeding, in locomotion and in adopting a raised or lowered posture. A reduction in the time spent feeding and in locomotion, and an increase in the time spent in the lowered posture were considered to indicate alarm. 3. Crayfish from both populations responded with a more pronounced reduction in feeding to conspecific alarm odour rather than to predator odours. Crayfish from the Malewa River reacted with the same intensity to the odours of the three fish species tested, whereas, in Lake Trasimeno, the odour of largemouth bass was significantly more threatening than the odours of the other two species. 4. Procambarus clarkii seems to perceive a general fish odour that alerts it to possible predation risk without the need of either a direct recent experience or via sharing a common native range. However, where they coexist with fish, crayfish become able to distinguish among species, adapting the intensity of their response to the effective risk. Our results confirm the relatively high learning capacity of P. clarkii reported in previous studies and suggest the existence of mechanisms that make predator recognition particularly efficient in this extraordinarily successful invader.     

Predator functional response and prey survival: direct and indirect interactions affecting a marked prey population

1. Predation plays an integral role in many community interactions, with the number of predators and the rate at which they consume prey (i.e. their functional response) determining interaction strengths. Owing to the difficulty of directly observing predation events, attempts to determine the functional response of predators in natural systems are limited. Determining the forms that predator functional responses take in complex systems is important in advancing understanding of community interactions. 2. Prey survival has a direct relationship to the functional response of their predators. We employed this relationship to estimate the functional response for bald eagle Haliaeetus leucocepalus predation of Canada goose Branta canadensis nests. We compared models that incorporated eagle abundance, nest abundance and alternative prey presence to determine the form of the functional response that best predicted intra-annual variation in survival of goose nests. 3. Eagle abundance, nest abundance and the availability of alternative prey were all related to predation rates of goose nests by eagles. There was a sigmoidal relationship between predation rate and prey abundance and prey switching occurred when alternative prey was present. In addition, predation by individual eagles increased as eagle abundance increased. 4. A complex set of interactions among the three species examined in this study determined survival rates of goose nests. Results show that eagle predation had both prey- and predator-dependent components with no support for ratio dependence. In addition, indirect interactions resulting from the availability of alternative prey had an important role in mediating the rate at which eagles depredated nests. As a result, much of the within-season variation in nest survival was due to changing availability of alternative prey consumed by eagles. 5. Empirical relationships drawn from ecological theory can be directly integrated into the estimation process to determine the mechanisms responsible for variation in observed survival rates. The relationship between predator functional response and prey survival offers a flexible and robust method to advance our understanding of predator-prey interactions in many complex natural systems where prey populations are marked and regularly visited.     

Where biology meets; or how science advances: Presidential Address to the Linnean Society delivered at the Anniversary Meeting, 24th May 1985

Major advances in 'unrestricted' sciences like biology commonly occur when individual scientists (or techniques) cross conventional discipline boundaries; intra-discipline studies are essential for the consolidation and progress of the science, but are less likely to produce significant insights. 'Restricted' (or exact) sciences ignore variation, and are probably less sensitive to warping from specialization. This generalization is illustrated by recent controversies in evolutionary biology, particularly the neutralism debates of the 1970s, where over-rigid adherence to theoretical models and unjustified assumptions about the effects of gene action were made. The consequence of some of these is shown by considering genetic changes in house mouse (Mus domesticus) populations which were used to demonstrate apparent drift operating on neutral traits, whereas longitudinal studies of closed populations proved that strong natural selection may operate; a proper understanding of genetical forces requires a knowledge both of the history of particular populations and of environmental pressures varying in time and space.     

East asian hemoglobin type (Hbb p) in wild populations of the house mouse in Israel

Electrophoretic studies of hundreds of individuals showed that all wild populations of the house mouse in Israel are polymorphic for alleles Hbb^d and Hbb^pof the hemoglobin locus. No mouse carrying Hbb^swas found. This finding contradicts the notion that Hbb^pis limited to East Asian house mice.     

Evidence for X linkage of the mouse tear protein system-3 (Mtp-3) with mosaic expression in heterozygous females

Electrophoretic variations exhibited by some tear proteins have been observed using 20 strains of mice. Fifteen to twenty protein components were detected in tears, and one of the proteins, designated Mtp-3 (mouse tear protein system-3), is found only in the NZB strain. NZB animals were crossed to BALB/c animals with no Mtp-3 and the results showed that Mtp-3 was controlled by a pair of alleles on the X chromosome. Mosaic expression was detected in females heterozygous for the Mtp-3 alleles when tear samples were examined separately from the right or left eye. This report supports Lyon's hypothesis and shows that mouse tears are useful for genetic research.     

Murine liver arylsulfatase B processing influenced by region on chromosome 17

SM/J liver arylsulfatase B has a more rapid electrophoretic mobility and occurs as a series of more acidic isozymes following electrofocusing in narrow pH gradients than the liver enzyme from C57BL/6J mice. The SM/J and C57BL/6J electrofocusing patterns were both converted to a single isozyme with similar isoelectric points by pretreatment with neuraminidase, suggesting that the SM/J and C57BL/6J isozymes differed with respect to their sialic acid content. Arylsulfatase B electrofocusing and thermostability phenotypes segregated independently among progeny of SM/J×C57BL/6J crosses, suggesting that the electrofocusing phenotypes were not determined by different alleles at As-1, the putative structural locus for arylsulfatase B. Comparison of the joint segregation of hepatic acid phosphatase electrophoretic patterns and liver arylsulfatase B electrofocusing profiles revealed that the electrofocusing profiles may be determined by a region on chromosome 17 near or identical to Apl. Kidney, brain, and spleen arylsulfatase B electrofocusing patterns did not appear to differ between SM/J and C57BL/6J mice.This research was supported in part by Biomedical Sciences Research Support Grant RR-07030, by NIGMS Grant 1-RO1GM27707-01, and by Grant 1–570 from the National Foundation/March of Dimes.     

Comparative biochemistry of murine arylsulfatase B

Arylsulfatase B was purified 4500-fold from liver and kidney of C57BL/6J mice. Hepatic and renal arysulfatase B are apparently determined by a single structural locus; however, posttranslational modification introduces inter- and intratissue microheterogeneity. Partially purified enzyme from C57BL/6J, A/J, C3H/HeJ, and SWR/J mice has similar catalytic properties. The 4500-fold-purified arylsulfatase B from SWR/J and C3H/HeJ mice was more thermostable than that from C57BL/6J and A/J mice, strongly suggesting that the thermostability difference reflects an alteration of the primary structure of the enzyme. Thermal stability of arylsulfatase B was pH dependent and markedly influenced by buffer anion. Variation of thermostability did not appear accountable for the observed activity variation among these strains; however, this possibility cannot be rigorously excluded by presently available data. Thirty-five murine strains were found to possess the As-1 ^a allele (thermostable enzyme), while As-1 ^b was largely restricted to A and C57 strains.This research was supported by PHS Biomedical Sciences Research Support Grant RR-07030.