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1.
Costs of plant defences to herbivores have been extensively studied, but costs of chemical defences to carnivores are less well understood. We examine the costs to Australian keelback snakes (Tropidonophis mairii, Gray 1841) of consuming cane toads (Bufo[Rhinella]marinus Linnaeus 1758). Cane toads (an invasive species in Australia) are highly toxic. Although keelbacks can consume toads without dying (unlike most Australian snakes), we show that cane toads are poor quality prey for keelbacks. Toads are of low net nutritional value, take longer to consume than do native frogs and reduce the snake's locomotor performance for up to 6 h after ingestion of a meal. These latter effects may increase a snake's vulnerability to predation. Nutritional content of vertebrate prey is not the only factor driving the evolution of foraging behaviour; other more subtle costs, such as risk of predation, may be widespread.  相似文献   

2.
Records of the Arabian Toad (Duttaphrynus arabicus) and the Dhofar Toad (Duttaphrynus dhufarensis) in the UAE and adjacent areas of northern Oman are mapped and some recent observations presented. The Arabian Toad is more widely distributed in more mesic habitats and benefits from the increase in artificially irrigated habitats. The Dhofar Toad is able to live in drier areas but its distribution pattern suggests it may be outcompeted by the Arabian Toad in wetter areas with greater availability of surface water.  相似文献   

3.
It is widely assumed that winter is a critical time for homeotherms because of decreased ambient temperatures coupled with reduced food supply. Shrews are excellent models for investigating overwintering strategies, not only because of their particularly small size, high energy requirements relative to their size and short fasting endurance, but also the dramatic reduction in body size (Dehnel's phenomenon) exhibited by soricine shrews in northern temperate winters. The cause of Dehnel's phenomenon is poorly understood but food supply is implicated. To test the hypothesis that winter at higher latitudes is a period of food shortage for small homeotherms, we compared feeding habits of common shrews, Sorex araneus, and abundance and biomass of their prey in winters and summers in northeastern Poland using scat analysis combined with pitfall and ground core sampling for invertebrates. Ground‐surface activity and numbers of invertebrates in pitfall traps were greatly reduced in winter but, contrary to prediction, no significant differences between winter and summer were found in total numbers and biomass of prey invertebrates in ground core samples. However, certain prey types changed seasonally with respect to numbers, biomass and distribution in the soil profile, which was reflected in shrews’ food composition and foraging behaviour. Dehnel's phenomenon appears not to be caused by reduction in total prey numbers and biomass, at least in our study area. Smaller body mass coupled with lowering of absolute food requirements may have important survival value in winter with its reduced numbers of certain major prey coupled with increased difficulty of locating and extracting invertebrates within the soil profile resulting in higher energetic costs of foraging.  相似文献   

4.
The distribution and ecological roles of ground-dwelling invertebrates colonizing dry beds of temporary rivers are poorly known, due in part to the lack of tested sampling methods. Sampling efficiency and completeness and detection biases associated with pitfall-trap and quadrat samples were compared at six sites in the dry beds of two New Zealand rivers. On average, pitfall-trap samples contained 3.5 times more taxa than quadrat samples, and pitfall traps required less time to collect as many taxa as quadrats. Among all taxa collected, 80% were exclusive to pitfall traps and 4% to quadrat samples. Among-sites differences in invertebrate composition were greater in pitfall-trap samples than in quadrat samples. Rarefaction curves indicated that eight to eleven pitfall traps/100 m2 were necessary to collect most of the common taxa in the study sites. Differences in the performance of pitfall traps and quadrats in dry riverbeds may be due to the absence of vegetation, to the large range of taxa considered, and to diel movements of some taxa. The large number of samples required at our study sites to reach a high level of sampling completeness suggests that the diversity of ground-dwelling invertebrates in dry riverbeds has probably been underestimated in previous studies.  相似文献   

5.
Mire degradation due to drainage for forestry results in the loss of mire specialist species. To halt the loss in biodiversity, ecological restoration is needed and already implemented. However, a major challenge in ecological restoration is whether actions taken have the desired outcome. Key abiotic and biotic conditions for the successful restoration of invertebrate communities can be identified by testing the “Field of Dreams” hypothesis, which postulates that if a habitat is successfully restored, species will return. This study was conducted in nine boreal mires located in Eastern Finland, 1–3 years after restoration. Parts of each mire were drained for forestry during the 1960s and 1970s, and restored in 2003–2006. Two 250 m transects were established in each of three treatments (pristine, drained, restored) per mire. We used pitfall trapping to sample carabid beetles and spiders, sweep netting to sample micromoths and crane flies and counts along the transects to sample macromoths. Vegetation cover, water table level, and climatic variables were measured along all transects. Mire specialist species and invertebrate communities responded positively to restoration and negatively to drainage, whereas generalists showed varied responses. In addition, mire specialists were associated with high cover of Sphagnum mosses and with low numbers of tall trees (>3 m). Therefore, to successfully restore populations and communities of mire specialist invertebrates, maintaining environmental conditions that favor the growth of Sphagnum mosses, rewetting the sites and removing larger trees are necessary measures.  相似文献   

6.
Pheidole megacephala is an exotic ant species that has severely affected native invertebrate biodiversity throughout the tropics. Its impacts have been documented extensively in relatively depauperate invertebrate communities, but not in species-rich habitats such as tropical rain forests. Here we describe the local distribution of P. megacephala and its impacts on native invertebrate assemblages in and around a rain forest patch at Howard Springs, in Australia's monsoonal tropics. P. megacephala was found to be confined to a single area of approximately 25 ha, with its distribution centered on drainage lines and the rain forest. Significant but weak correlations were found between its abundance and vegetative canopy cover (positive) and distance from the rain forest (negative). In the most heavily infested area within the rain forest, the abundance of P. megacephala was 37–110 times that of total native ant abundance found within uninfested plots, as measured by pitfall traps. The abundance and richness of native ants and other invertebrates were significantly reduced in litter samples, pitfall catches and foliage beats where P. megacephala was present, inversely relative to the abundance of P. megacephala. Only two individuals of a single native ant species were found within the most infested plot, with native ant richness being reduced to about half in the least infested plot. The most persistent functional groups of native ants in infested plots were Cryptic species, which forage primarily within soil and leaf litter, and Opportunists, which exhibit highly generalised foraging behaviour. The highest abundance of P. megacephala corresponded with a 42–85% decrease in the abundance of other native invertebrates. Insect larvae were totally absent from foliage beats collected at the most heavily infested plot. P. megacephala was found overall to be expanding its range, averaging 12 m range expansion in the dry season and contracting 7 m in the wet season. It is able to spread into surrounding savanna habitats by occupying relatively sheltered microsites, such as beneath logs and at the bases of trees. However, it is unlikely to attain high population densities in open savanna habitats because of its relative intolerance of desiccation, and the prevalence of behaviourally dominant native ant species. Howard Springs is currently the only rain forest patch in monsoonal Australia known to be infested by P. megacephala, but clearly this ant is a serious potential threat to the region's rain forest invertebrate fauna. Received: 19 August 1998 / Accepted: 12 May 1999  相似文献   

7.
A critical component in the effort to restore the Kissimmee River ecosystem is the reestablishment of an aquatic invertebrate community typical of free‐flowing rivers of the southeastern United States. This article evaluates early responses of benthic and snag‐dwelling macroinvertebrates to restoration of flow and habitat structure following Phase I construction (interim period) of the Kissimmee River Restoration Project. Replicate benthic and snag samples were collected from remnant river channels in Pool A (Control site), and Pool C, the site of the first phase of restoration (Impact site). Samples were collected quarterly for 2 years prior to construction (baseline) and monthly or quarterly for 3 years following Phase I construction and restoration of flow. Baseline benthic data indicate a community dominated by taxa tolerant of organic pollution and low levels of dissolved oxygen, including the dipterans Chaoborus americanus (Chaoboridae) and the Chironomus/Goeldichironomus group (Chironomidae). Baseline snag data indicate a community dominated by gathering‐collectors, shredders, and scrapers. Passive filtering‐collector invertebrates were rare. Following restoration of flow, benthic invertebrate communities are numerically dominated by lotic taxa, including bivalves and sand‐dwelling chironomids (e.g. Polypedilum spp., Cryptochironomus spp., and Tanytarsini). Snags within the Phase I area support an invertebrate community dominated by passive filtering‐collectors including Rheotanytarsus spp. (Chironomidae) and Cheumatopsyche spp. (Hydropsychidae). Results indicate that restoration of flow has resulted in ecologically significant changes to the river habitat template not observed in Pool A. Observed shifts in benthic and snag macroinvertebrate community structure support previously developed hypotheses for macroinvertebrate responses to hydrologic restoration.  相似文献   

8.
The distribution, habitat occurrence and feeding ecology of Crocidura montis and Lophuromys flavopunctatus coexisting in the afro‐alpine zone on Mt. Elgon, Uganda, are described. Crocidura montis was the only shrew species occupying the afro‐alpine zone, but was not found in forested habitats below 3200 m. While there was considerable overlap in habitat occurrence between the two species, C. montis was most abundant in the montane grassland and in drier sites while L. flavopunctatus occupied a wider range of habitats and wetter sites. C. montis ate a diversity of invertebrates, the most important being Coleoptera, Araneae and Lumbricidae. Invertebrates, mostly Diptera larvae, Lumbricidae and Coleoptera, formed a major component of the L. flavopunctatus diets, plus plant material (particularly Hepaticae and monocots). The arthropod components of the diets reflected their abundance in pitfall samples.  相似文献   

9.
Understanding the factors that affect an invasive species’ viability and distribution has vital implications for biocontrol. In Australia, invasive cane toads (Rhinella marina) are anecdotally reported to utilise commercial beehives as a prey resource, but that interaction has never been studied in detail. We investigated the impact of apiaries on cane toads in northern New South Wales via mark-recapture surveys, dissections, and camera-trap observations. Cane toads were the most frequent visitors to apiaries, followed by bandicoots and corvid birds. Cane toads at apiaries were more abundant and in better body condition (i.e., larger mass relative to snout-urostyle length) than were toads at nearby control sites. Toads at beehives contained more prey items per stomach (mostly bees, which were never recorded in the stomachs of toads from other sites), and adult female toads at beehives had larger livers and ovaries relative to body size. We conclude that commercial apiaries attract cane toads, influence their diets, and increase their feeding rates and reproductive capacity. Like other habitat modifications wrought by agricultural activities, honey bee colonies provide resources that facilitate the spread of cane toads through an otherwise harsh landscape matrix. Minor modifications to beehives could exclude toads, thereby eliminating their positive impact on the invader.  相似文献   

10.
Replicated plots were established in pear thrips-infested sugar maple stands. They were treated withBeauveria bassianaas an emulsifiable concentrate and a nutrient-based granular formulation and withMariannaeasp. as a wettable powder. Postapplication invertebrates moving across plots were collected daily for 10 days in pitfall traps. Collected individuals were identified, held for 10 days, and then evaluated for the presence of fungal infection and other potential pathogenic microorganisms. A total of 3615 invertebrates were collected and identified. Of the invertebrate population in treated plots that fell into pitfall traps, 2.8% became infected with eitherB. bassianaorMariannaeasp. The fungi applied also occur naturally in sugar maple forest soils; therefore, it was impossible to confirm whether the infection we observed in treated plots was a result of contact with the spores we applied. Because we obtained infection among invertebrates collected from control plots, it is likely that these fungi do attack invertebrates under natural forest conditions. Of the 2584 invertebrates examined further for obligate internal pathogens, 2.5% were infected with entomophthoralean fungi, protozoans, and/or nematodes. Results suggest thatB. bassianaandMariannaeasp. could be applied to forest soil without a significant negative impact on the forest-dwelling invertebrate population.  相似文献   

11.
Epigeal movement of smoky shrewsSorex fumeus (Miller, 1895) following precipitation was examined in two habitats with different moisture conditions. Shrews and invertebrates were collected in pitfall traps over several consecutive nights each month from August to November 1996 and from March to August 1997. Capture rates of smoky shrews significantly increased following rainfall at dry ridgetop sites (p=0.001) but not at moist streamside sites (p=0.335). In mesic environments, favorable conditions on the forest floor not associated with precipitation may increase movements of shrews. Available invertebrate biomass did not increase significantly with rainfall in either habitat type (p=0.121 and 0.368). Increased surface activity by smoky shrews after rain events is probably related more to their ecophysiology than to increased prey availability.  相似文献   

12.
Soil and litter arthropods represent a large proportion of tropical biodiversity and perform important ecosystem functions, but little is known about the efficacy of different tropical forest restoration strategies in facilitating their recovery in degraded habitats. We sampled arthropods in four 7‐ to 8‐year‐old restoration treatments and in nearby reference forests. Sampling was conducted during the wet and dry seasons using extractions from litter and pitfall samples. Restoration treatments were replicated in 50 × 50‐m plots in four former pasture sites in southern Costa Rica: plantation – trees planted throughout the plot; applied nucleation/islands – trees planted in patches of different sizes; and natural regeneration – no tree planting. Arthropod abundance, measures of richness and diversity, and a number of functional groups were greater in the island treatment than in natural regeneration or plantation treatments and, in many cases, were similar to reference forest. Litter and pitfall morphospecies and functional group composition in all three restoration treatments were significantly different than reference sites, but island and plantation treatments showed more recovery than natural regeneration. Abundance and functional group diversity showed a much greater degree of recovery than community composition. Synthesis and applications: The less resource‐intensive restoration strategy of planting tree islands was more effective than tree plantations in restoring arthropod abundance, richness, and functional diversity. None of the restoration strategies, however, resulted in similar community composition as reference forest after 8 years of recovery, highlighting the slow rate of recovery of arthropod communities after disturbance, and underscoring the importance of conservation of remnant forests in fragmented landscapes.  相似文献   

13.
Abstract Despite widespread concern about the ecological impacts of invasive species, mechanisms of impact remain poorly understood. Cane toads (Chaunus [Bufo] marinus) were introduced to Queensland in 1935, and have now spread across much of tropical Australia. One plausible impact of toad invasion concerns competition between toads and native frogs, but there has been no previous experimental evaluation of this possibility. We examined interactions between toads and a morphologically similar species of native frog (Cyclorana australis) by manipulating toad and frog densities within large outdoor enclosures beside a floodplain in the wet‐dry tropics of the Northern Territory. Toads differed from frogs significantly in dietary composition and feeding rates, even in comparisons controlling for body‐size differences between these two taxa. Perhaps reflecting the abundant insect biomass, manipulating anuran densities or the presence of the putatively competing species did not influence food intake or dietary composition. However, the presence of toads suppressed activity levels of native frogs. The degree to which the invasion of cane toads influences attributes such as the activity levels, food intake and dietary composition of native frogs warrants further study, but our study suggests that competitive effects are likely to be minor compared with other pathways (such as direct poisoning during ingestion attempts) by which toads can affect frog populations.  相似文献   

14.
1. van Duinen et al. (Freshwater Biol., 2006) raise an interesting point regarding Mazerolle et al.’s (Freshwater Biol., 2006, 51 , p. 333) conclusion on the ability of invertebrates, especially sedentary species, to colonise newly created bogs pools. We wish to clarify that Mazerolle et al. (2006) targeted large arthropods and the absence of smaller sedentary species was purely a result of sampling design. 2. van Duinen et al. (2006) postulate that colonisation rates by bog specialists should be higher in Canada than in the Netherlands, given the extensive amount of intact peatlands in Canada. Here, we emphasise the importance of taking the regional context into account when assessing restoration success as our study site occurs in a landscape where most bog pools have been drained. 3. An evaluation of restoration efforts should focus on both sedentary and vagile invertebrates, to resolve the importance of persistence and colonisation. Such patterns are difficult to interpret, however, when sampling designs and analyses do not account for the probability of detection: an absence may be due to non‐detection or true absence. We strongly urge investigators to directly estimate detection probability in addition to the parameters of interest (e.g. presence, abundance) to provide the best information possible regarding restoration success.  相似文献   

15.
Canebrakes (bamboo grasslands dominated by Arundinaria spp.) were once a widespread ecosystem across the Southeastern United States, and many species of wildlife depended upon them. Early settlers replaced this system with subsistence agriculture and today few canebrakes remain. The restoration of canebrakes is critical to the recovery of several wildlife species; however, restoration is complicated because (1) seed is uncommon and often predated, (2) competition from hardwood species, including the exotic Chinese privet (Ligustrum sinesnse), often prevent cane establishment, and (3) cane depends on disturbance regimes that have been disrupted in the Southeast. We investigated the tolerance of Switch cane (Arundinaria tecta) to four commonly used herbicides that are effective at controlling privet and other hardwoods: hexazinone (Velpar‐L), glyphosate (Razor Pro), triclopyr (Garlon 3A), and imazapyr (Chopper). We also investigated the possibility of transplanting cane culms, and the factors affecting successful transplant. Cane tolerated hexazinone and triclopyr but was damaged or killed by glyphosate and imazapyr. Although many measures of weather and cane condition were not predictors of transplant success, the Keetch–Byram drought index was a strong predictor, and is available through most state forestry offices. Selective herbicides and deliberately timed transplantation may be important canebrake restoration tools.  相似文献   

16.
Ants are an incredibly diverse and ubiquitous group of invertebrates in most terrestrial ecosystems. Although extensively sampled, the majority of ant inventories do not evaluate the effect of different sampling techniques in capturing nontraditional metrics of diversity. We aimed to quantify TD (taxonomic) and FD (functional) diversities for a local ant assemblage by integrating metrics and evaluating complementarity of pitfall traps and Winkler extractors for the leaf litter versus epigeic ant faunas and to determine the effect of sampling techniques on functional composition (community-weighted means of 11 morphological traits) and functional diversity (multi-trait morphospace measured with three different metrics). We sampled the local community in an Atlantic Forest fragment using week-long pitfall traps and 1m2 leaf litter samples submitted to Winkler extractors and quantified the contribution on the technique to uniquely capture the ant morphospace by applying a new index (PWindex). Although ant TD overlapped, FD was significantly affected by the sampling technique. By controlling for TD effects, the community collected by each technique was differentially structured. Higher TD did not translate into wider morphospace for Winklers. Pitfalls recovered more functionally overdispersed assemblages. Pitfalls and Winklers overlapped in the sampling of the overall community, but each sampling method contributed with a unique spectrum to the ant morphospace. Our results suggest the importance of incorporating FD metrics in local ant inventories and the importance of sampling techniques when measuring the magnitude of FD and community structure. Our PWindex further illuminates sampling effects for ant assemblages. Abstract in Portuguese & Spanish is available with online material.  相似文献   

17.
The Hackensack Meadowlands District is a large heavily degraded, brackish marsh system in the urbanized northeastern region of New Jersey, USA. Six study sites were used, three of which were restored (Mill Creek, Skeetkill Creek and Vince Lombardi), and three others were unrestored (Richard DeKorte Park, Cedar Creek and Kingsland Creek). Highly significant differences were found with respect to snail abundance and gill parasite abundance. In the three restored sites, significantly more Littoridinops tenuipes were found, and Fundulus heteroclitus had significantly more digenean trematode metacercariae gill infections than at unrestored sites. As habitat quality improves following restoration, the number of suitable digenean trematode parasite hosts multiplies as substrate for benthic invertebrates (first intermediate host) increases and usage by other species, such as Fundulus spp. (second intermediate host), is encouraged, which then attracts more wading birds (definitive host). Though the restoration process enhances trophic complexity, including primary consumers (gastropods), secondary consumers (fish) and tertiary consumers (wading birds), and ultimately parasite diversity, restoration also helps facilitate parasite life cycles.  相似文献   

18.
Impact of Regional Species Pool on Grasshopper Restoration in Hay Meadows   总被引:1,自引:0,他引:1  
Agri‐environment schemes are the most widely adopted political measure to maintain and restore farmland biodiversity in Europe. However, abiotic and biotic factors often limit the success of ecological restoration. Among the biotic factors, the size of the local and regional species pool is a major constraint. This is only well documented for plants. We therefore wanted to know if a small regional species pool can also limit restoration efforts of invertebrates. Specifically, we tested if by relocating grasshoppers from further away, we could overcome regional species pool limitations on hay meadows under the Swiss agri‐environment scheme, so‐called Ecological Compensation Area meadows (ECA meadows). All meadows had been under restoration for 6 years and were formerly intensively used hay meadows. Two grasshopper species, Euthystira brachyptera and Mecostethus parapleurus, were selected; E. brachyptera was not found in the regional species pool and M. parapleurus had nearly disappeared. In 2004, 1,400 grasshopper individuals of each species were taken from the nearest large source populations and distributed equally on seven ECA meadows and seven control meadows. In 2005, we evaluated whether the species had successfully established. Only one individual of M. parapleurus was found. We conclude that a small regional species pool is not the only constraint for the reestablishment of grasshoppers on restoration meadows. Also, other factors such as habitat quality appear to constrain the reestablishment of grasshoppers on restoration meadows. Additional restoration efforts specifically targeted at grasshopper restoration are needed, and innovative techniques have to be developed to overcome the relocation constraints.  相似文献   

19.
1.  There is still considerable debate about the most effective methods of sampling invertebrates in monitoring and assessment programmes.
2.  The above-ground invertebrates of a limestone grassland in north-east England were compared between samples from pitfall traps and from a D-vac suction trap combined with a lightweight swish net (SW/DV).
3.  Over 14 000 individuals were captured, with similar numbers in the pitfall and SW/DV samples. A total of 480 species of Hemiptera, Coleoptera, Diptera and Araneae was identified and placed into 14 taxa for further analysis.
4.  The pitfall sample produced species/specimen curves from which it was possible to estimate species richness for all the Coleoptera and Araneae taxa and the calypterate Schizophora. The SW/DV sample was adequate to estimate the species richness of Hemiptera, most Diptera taxa, herbivorous Coleoptera and Linyphiidae.
5.  The proportion of Coleoptera and Araneae taxa that were method-unique was higher in the pitfall sample than the SW/DV sample and vice versa for the Hemiptera and Diptera taxa. Nevertheless, a relatively high proportion of method-unique species of most taxa was found in both sample types, indicating that they can each contribute to assessing species assemblages in grasslands.
6.  Both pitfall traps and SW/DV samples are needed to estimate species richness in grasslands for all taxa except Heteroptera, Homoptera and Lycosidae. Herbivorous Coleoptera and Linyphiidae were collected in numbers adequate for assessing richness in both sample types, but more specimens were required in one or other sample for the remaining taxa.  相似文献   

20.
The evaluation of the success of restoration efforts is an essential step for environmental monitoring programs, providing reliable and intricate information on the response of biotic and abiotic elements of ecosystem following the restoration programs adopted. The aim of this study was to evaluate the efficacy of different rehabilitation efforts after gold mining activities using ants as bioindicators. We tested the following hypotheses: (1) the ant species richness and composition vary with the technique of revegetation and (2) the number of epigaeic and hypogaeic ant species increases with resources. We selected four tailing dumps from gold mining, one spontaneously revegetated (“Natural”) and the other three areas with different rehabilitation techniques, namely: Grassy 2005—rehabilitation with grasses in 2005; Grassy 2006—rehabilitation with grasses in 2006, and Shrubby 2004—rehabilitation with grasses, herbaceous, and shrubs in 2004. Ants were sampled using epigaeic and hypogaeic pitfall traps. Species accumulation curves show that the “Natural” area has a higher number of species. We found differences in species composition of epigaeic and hypogaeic ants among the different areas sampled. We conclude that Camponotus fastigatus can be taken as a good indicator of environmental rehabilitation in areas impacted by mining activities. Moreover, Ectatomma edentatum, Dorymyrmex brunneus, Crematogaster evallans, and Solenopsis invicta can also indicate that the rehabilitation process is not yet completed.  相似文献   

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