Optimising sampling methods for small mammal communities in Neotropical rainforests

相似文献   

Evaluation of collection methods for Culex quinquefasciatus,Aedes aegypti,and Aedes simpsoni in northeastern Tanzania

In East Africa, significant morbidity and mortality are caused by infections spread by Culex quinquefasciatus and Aedes aegypti. Sticky traps have been shown to be effective tools for sampling populations of Aedes mosquitoes and have been found to catch Cx. quinquefasciatus. Thus, they could potentially be used to sample populations of this species. This study compared Sticky ovitraps (SO) and MosquiTraps (MQT) with the CDC Gravid trap (CDC‐GT) for collection of Culex and Aedes mosquito populations in Tanzania. A follow‐up experiment was carried out using traps set for a 24‐h period to accommodate the oviposition habits of Aedes aegypti and Ae. simpsoni s.l. mosquitoes. The results showed that the CDC‐GT caught significantly more Cx. quinquefasciatus and Ae. aegypti than the SO or MQT, but there was no significant difference in the number of mosquitoes caught between the two sticky traps or of Ae. simpsoni s.l. caught among the three trap types. The results suggest that CDC‐GTs are the most appropriate in sampling of Cx. quinquefasciatus. Although CDC‐GTs collected more Ae. aegypti than the sticky traps, the simplicity and cost benefit of sticky traps facilitates large scale studies. All three trap types should be considered for monitoring Aedes mosquitoes.     

Attractiveness of baits to dung beetles in Brazilian savanna and exotic pasturelands

The Brazilian savanna is the second largest ecosystem in Brazil. It is also one of the most endangered, with only 20% of its habitat remaining unchanged. Agriculture and livestock have been indicated as the main agents of destruction of the Brazilian savanna. Brazilian livestock, for example, is the main reason for cultivation of exotic grasses such as Urochloa spp. (from Africa). Dung beetles are widely used in ecological assessment, mainly because they are recognized as bioindicators of environmental changes. Therefore, efficient sampling is required for any research involving the biodiversity of this group. In order to mitigate the lack of information on efficiency of the attractiveness of baits in the endangered Brazilian savanna and in exotic pasturelands, we sampled dung beetles in four native patches of the Brazilian savanna and in four areas of pastures with Urochloa spp. Dung beetles were captured with pitfall traps baited with carcass, cattle dung, human feces and pig dung, with a total sampling effort of 384 traps. We sampled 7544 individuals belonging to 43 species and 18 genera of dung beetles. Thirty‐eight species were collected in the Brazilian savanna and 24 species in exotic pastureland. In both ecosystems traps baited with human feces sampled greater abundance and species richness of dung beetles when compared with the other three baits used. Our results showed that human feces is a reliable, easy and inexpensive bait to sample greater abundance and species richness of generalist dung beetles in both native and exotic habitats, with clear structural differences.     

Efficacy of the pheromone (3Z)‐lactone and the host kairomone (3Z)‐hexenol at detecting early infestation of the emerald ash borer,Agrilus planipennis

The invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp., in its introduced range in North America. Field studies were conducted to quantify the efficacy of traps baited with kairomone and pheromone lures for early detection of A. planipennis infestation. A trapping experiment demonstrated that green traps baited with the kairomone (3Z)‐hexenol detected at least one adult A. planipennis in 55.3% of plots with ‘nil to low’‐density infestations and in 100% of plots with ‘moderate to high’‐density A. planipennis infestations. Mean trap captures increased significantly with increasing infestation density. In terms of the optimal number of traps per plot, when one (3Z)‐hexenol‐baited trap was placed per plot, the trap detected populations in 62% of the plots with ‘low to moderate’‐density infestations through branch sampling. Detectability was increased to 82% when two traps were placed per plot. Finally, addition of female‐produced (3Z)‐lactone pheromone to traps significantly increased detection rates at both the trap and plot level, as compared with traps baited with the host volatile, (3Z)‐hexenol, alone (88 vs. 60%, respectively). Our results are the first to demonstrate the efficacy of baited green sticky traps for detecting low‐density A. planipennis infestations, particularly when the (3Z)‐lactone pheromone is used. This combination is therefore recommended for development of early‐detection protocols against A. planipennis.     

Effects of pitfall trap size and sampling duration on collection of ground beetles (Coleoptera: Carabidae) in temperate forests

Pitfall trapping is a standard sampling method to compare the abundance or community structure of ground beetles. However, effects of sampling duration on biodiversity estimation of ground beetles according to different trap sizes have not been experimentally evaluated in temperate forests in Korea. Therefore, the objective of this study was to determine the interaction between trap sizes (SB, small‐sized bottle; MB, medium‐sized bottle; PC, plastic cup; PJ, plastic jar; PT, perforated type trap; FT, funnel‐type trap) and sampling duration (T1, 2 weeks × 2 sessions, 28 days; T2, 2 weeks × 4 sessions, 56 days; T3, 4 weeks × 2 sessions, 56 days) on estimation of ground beetle assemblages in Naejangsan National Park, a temperate forest in Korea. Funnel type and larger pitfall traps collected higher numbers of individuals and species than other trap sizes. Species composition of ground beetles was different by size of traps (SB, MB, and PC vs. PJ, PT, and FT). In particular, ground beetle composition in larger traps (PJ, PT, and FT) appeared to be influenced by environmental characteristics according to localities (e.g., soil characters and dominant tree species). These findings from our study support that pitfall trapping of ground beetles can be influenced by trap sizes per se as well as sampling durations and environmental characteristics. Thus, biodiversity monitoring in temperate forests should be conducted with long sampling duration (at least 28 days) using large‐sized traps (> 7.5 cm in diameter of trap mouthpart) considering expenses and study aims.     

An assessment of re-randomization methods in bark beetle (Scolytidae) trapping bioassays

1 Numerous studies have explored the role of semiochemicals in the behaviour of bark beetles (Scolytidae). 2 Multiple‐funnel traps are often used to elucidate these behavioural responses. Sufficient sample sizes are obtained by using large numbers of traps to which treatments are randomly assigned once, or by frequent collection of trap catches and subsequent re‐randomization of treatments. 3 Recently, there has been some debate about the potential for trap contamination to occur when semiochemical treatments (baits), and not trap‐treatment units (traps and baits), are re‐randomized among existing traps. Due to the volatility of many semiochemicals, small levels of contamination could potentially confound results. 4 A literature survey was conducted to determine the frequency of re‐randomizing semiochemical treatments (baits) vs. trap‐treatment units (traps and baits) in scolytid trapping bioassays. An experiment was then conducted to determine whether differences in the response of Dendroctonus brevicomis LeConte to attractant‐baited traps exist between the two methods. 5 The majority of papers examined reported use of a large number of fixed replicates (traps) rather than re‐randomization of treatments at frequent intervals. Seventy‐five percent of papers for which re‐randomization methods could be determined reported relocation of semiochemical treatments (baits) only. 6 No significant differences in trap catch were observed among multiple‐funnel traps aged with D. brevcomis baits (Phero Tech Inc., Canada) for 0, 30 and 90 days, suggesting that contamination did not influence the results. 7 It is concluded that re‐randomizing baits is a viable cost‐effective option to re‐randomizing trap and bait units.     

Quantifying responses of dung beetles to fire disturbance in tropical forests: the importance of trapping method and seasonality

Understanding how biodiversity responds to environmental changes is essential to provide the evidence-base that underpins conservation initiatives. The present study provides a standardized comparison between unbaited flight intercept traps (FIT) and baited pitfall traps (BPT) for sampling dung beetles. We examine the effectiveness of the two to assess fire disturbance effects and how trap performance is affected by seasonality. The study was carried out in a transitional forest between Cerrado (Brazilian Savanna) and Amazon Forest. Dung beetles were collected during one wet and one dry sampling season. The two methods sampled different portions of the local beetle assemblage. Both FIT and BPT were sensitive to fire disturbance during the wet season, but only BPT detected community differences during the dry season. Both traps showed similar correlation with environmental factors. Our results indicate that seasonality had a stronger effect than trap type, with BPT more effective and robust under low population numbers, and FIT more sensitive to fine scale heterogeneity patterns. This study shows the strengths and weaknesses of two commonly used methodologies for sampling dung beetles in tropical forests, as well as highlighting the importance of seasonality in shaping the results obtained by both sampling strategies.     

Colour-coded sampling: the pan trap colour preferences of oligolectic and nonoligolectic bees associated with a vernal pool plant

1. Pan traps or water traps have been used widely to sample agricultural insect pests, but no formal studies have assessed the utility of these traps as sampling devices for bees. 2. Coloured pan traps, used as flower models, can efficiently and selectively sample an oligolectic bee, Andrena (Hesperandrena) limnanthis, and other bees associated with white-flowered Limnanthes douglasii rosea. 3. Females and males of A. limnanthis unexpectedly exhibit different colour preferences. Females are strongly attracted to white and blue traps, but discriminate against yellow traps. Males prefer white traps over blue and yellow traps. Consequently, blue traps are selective for females only, while white traps are selective for both sexes. 4. Non-A. limnanthis bees were caught in significantly greater numbers in yellow than in blue or white traps. These bees included generalists, as well as specialists that are oligolectic on mostly yellow-flowered species. 5. Colour of traps had a significant effect on the numbers of A. limnanthis females and males, and non-A. limnanthis bees caught in traps. These results indicate that quantitative sampling of bees by pan trap methods can be highly sensitive to trap colour.     

The influence of trap type on evaluating population structure of the semifossorial and social rodent <Emphasis Type="Italic">Octodon degus</Emphasis>

Trap type may influence captures of individuals in different age-sex categories in small mammal studies, resulting in biased population and demographic information. We deployed 4 live trap types at burrow systems of the rodent, Octodon degus Molina, 1782, in central Chile to determine trap efficacy in capturing individuals of 6 demographic categories. We captured 2672 individuals in 17 709 trap days (15.1% trapping success). Tomahawks were the most efficient trap capturing half of individuals during both years, followed by mesh Sherman traps, large Sherman traps, and medium Sherman traps in 2005. All trap types equally sampled sexes. Large and medium Sherman traps provided similar demographic structure, where half of the individuals captured were pups; Tomahawk traps sampled more adults than pups. Relative captures of pups were similar across different trap types, suggesting that pups are equally sampled by each of the deployed trap types. Relative captures of adults were lower in Sherman traps, suggesting that this age class avoided solid-walled traps. For Octodon degus, the sole use of Tomahawk traps may produce sufficient, unbiased demographic data. Only 4 trap mortalities occurred (0.15%). Researchers may minimize trap mortality without compromising sufficient demographic sampling by trapping during peak animal activity.     

Artificial covering on trap nests improves the colonization of trap-nesting wasps

To evaluate the role that a trap‐nest cover might have on sampling methodologies, the abundance of each species of trap‐nesting Hymenoptera and the parasitism rate in a Canadian forest were compared between artificially covered and uncovered traps. Of trap tubes exposed at eight forest sites in six trap‐nest boxes, 531 trap tubes were occupied and 1216 individuals of 12 wasp species of four predatory families, Vespidae (Eumeninae), Crabronidae, Sphecidae and Pompilidae emerged over 2 years, and no bee species were found. Results indicated that artificial covering led to a significant increase in the number of nested tubes of Ancistrocerus adiabatus, Ancistrocerus antilope, Ancistrocerus campestris and Auplopus mellipes, and significant effects of covering were not found for the other species. No significant difference in the overall parasitism rate between covered and uncovered traps was noted. These suggested that the covering technique could provide more opportunities for some wasp species to colonize trap nests.     

Trapping intensities for sampling ants in Australian rangelands

Abstract I investigated the relationship between species richness and composition of ant faunas, and sampling intensity in two regions with different long‐term histories of grazing intensity in mulga (Acacia aneura) woodlands in northern New South Wales. There were two aims: (i) to examine the relationship between sampling intensity and species richness and composition; and (ii) to explore the differences in ant assemblages from two regions of markedly different grazing intensity when sampled at different intensities (i.e. when a higher proportion of the local ant fauna were collected). Ants were sampled in pit traps (120‐mm diameter) at densities of two, four, six and nine pits per 100 m². Each sampling‐intensity treatment was replicated three times within each region. Pit traps filled with preservative were opened for 3 days. Species richness was higher with each successive increase in sampling intensity but was not different between regions for a given trapping intensity. There was no obvious asymptote of the curve relating trapping intensity to cumulative species richness suggesting that even greater trap densities than those used in the present study would be needed to collect most of the species of ants using a patch of ground over a few days. Spatial replication of a low‐intensity sampling design did not capture as many species as one higher‐intensity sampling array with the same total number of pit traps. This result can be explained by aggressive numerically dominant species of ants monopolizing access to a greater proportion of the traps in low‐density arrays. Ordination reveals that regions and sampling‐intensity treatments could be discriminated and that differences between regions with different grazing histories were less apparent with high‐intensity sampling arrays than they were with low‐intensity sampling arrays. This suggests that differences between locations in space (or potentially samples in time) could be exaggerated by incomplete sampling of the patch‐scale fauna. Comparison of the present study with other studies suggests that most studies to date have used sampling intensities that would not give a thorough assessment of the patch‐scale ground‐dwelling fauna if sampled only by pit traps. The implications of the results for programmes of ant monitoring in rangelands are discussed.     

Optimum spacing of pheromone traps for monitoring the coffee leaf miner Leucoptera coffeella

Pest monitoring with pheromone traps is affected mainly by factors such as trap placement and pest biology. The intertrap distance can affect the capture due to competition among traps that are placed at short distances. We studied the interference among pheromone traps used to monitor males of the coffee leaf miner, Leucoptera coffeella (Guérin‐Méneville) (Lepidoptera: Lyonetiidae), with traps placed at various distances. Using geostatistical analysis, we determined at what distance captures were independent from other traps. Traps were placed in groups of 12 with distances among traps per group either 2, 5, 10, 15, or 30 m. Traps were checked for males every 4 days during 16 days. We found interference between traps when intertrap distances were shorter than 10 m. The range and magnitude of spatial dependence varied considerably among each sampling date and wind direction. For directions of 45° and 135°, the traps should be placed 110 and 177 m apart, respectively, to obtain spatially independent counts and therefore representative samplings for assessing the insect population in the area. These results have implications for developing sampling plans for managing L. coffeella with pheromone traps; the spatial analysis indicated that a trap density of one pheromone trap for every 3.5–4 ha would be adequate for the monitoring of the coffee leaf miner.     

Spatial distribution,sampling efficiency and Taylor's power law

1. A relationship between sampling efficiency and Taylor's power law (TPL) is derived and illustrated with data from gypsy moth samples taken in Pennsylvania. 2. It is shown that attractant traps such as pheromone and light traps may exhibit density‐dependent sampling efficiency which can influence the parameters of TPL. 3. Comparison of the light trap and pheromone trap sample data with those of a standardised suction trap enables the attractant traps to be standardised. 4. Rescaling male moth catches per trap to number per unit volume increases the slope, intercept and correlation coefficient while stretching the pattern of data points. 5. Density‐dependent sampling efficiency of attractant traps shows how TPL is sensitive to spatial aggregation behaviour as well as other life‐history variables.     

The Importance of Microhabitat for Biodiversity Sampling

Responses to microhabitat are often neglected when ecologists sample animal indicator groups. Microhabitats may be particularly influential in non-passive biodiversity sampling methods, such as baited traps or light traps, and for certain taxonomic groups which respond to fine scale environmental variation, such as insects. Here we test the effects of microhabitat on measures of species diversity, guild structure and biomass of dung beetles, a widely used ecological indicator taxon. We demonstrate that choice of trap placement influences dung beetle functional guild structure and species diversity. We found that locally measured environmental variables were unable to fully explain trap-based differences in species diversity metrics or microhabitat specialism of functional guilds. To compare the effects of habitat degradation on biodiversity across multiple sites, sampling protocols must be standardized and scale-relevant. Our work highlights the importance of considering microhabitat scale responses of indicator taxa and designing robust sampling protocols which account for variation in microhabitats during trap placement. We suggest that this can be achieved either through standardization of microhabitat or through better efforts to record relevant environmental variables that can be incorporated into analyses to account for microhabitat effects. This is especially important when rapidly assessing the consequences of human activity on biodiversity loss and associated ecosystem function and services.     

Efficiency of subaquatic light traps

Subaquatic light traps are often used for sampling of the aquatic insects; however, their efficiency has not been tested yet. Here, we describe the use of such traps, illustrate the design of a simple trap allowing standardised sampling, and present results of assessment of the light trap efficiency according to the different turbidity levels, as well as model insects’ escape rates. The effect of turbidity on the capture efficiency was not significant for Sigara lateralis (Leach, 1817), Notonecta glauca Linnaeus, 1758 and Corixa punctata (Illiger, 1807) and was marginally significant for Chaoborus sp. Escape rates were affected by the entrance size and daylight exposure time. Although subaquatic light traps are helpful for standardised sampling, their entrance should be adequate for the target species, and the traps should be removed soon after the dawn or the resulting specimen counts should be corrected for the daylight exposure time before the trap removal.     

Preferences by Rhagoletis indifferens (Diptera,Tephritidae) for rectangles of various yellow colours and fluorescence

Sticky rectangle traps of various yellow colours and fluorescence made of cardboard were field tested against western cherry fruit fly, Rhagoletis indifferens Curran, in paired trap preference experiments in Washington state. In a first experiment that involved comparisons of Alpha Scents (proprietary paint), Fluorescent Yellow (aerosol paint), Saffron Thread and Neon Light (semi‐gloss enamel paints) traps at two sites, the best performing trap was the Saffron Thread trap. In a second experiment comparing Citrus Splash (semi‐gloss enamel paint) with Alpha Scents and with Macaw and Lemon Zest (both semi‐gloss enamel paints) traps at a third site, the Citrus Splash trap outperformed the Alpha Scents trap. The Citrus Splash trap did not differ statistically from Saffron Thread and Lemon Zest traps, even though it caught 51% more flies than the Lemon Zest trap. The Alpha Scents trap caught significantly more non‐target Diptera than Fluorescent Yellow, Neon Light and Citrus Splash traps at two of three trap sites where non‐target Diptera populations were relatively high and overall it appeared less selective than the Citrus Splash trap. Results suggest that sticky rectangle traps painted semi‐gloss enamel Saffron Thread or Citrus Splash with low fluorescence could be highly useful for detecting R. indifferens.     

A carbon dioxide, heat and chemical lure trap for the bedbug, Cimex lectularius

Abstract A trap for the collection of bedbugs, Cimex lectularius Linnaeus (Hemiptera: Cimicidae), is described. The trap was baited with CO₂ (50–400 mL/min), heat (37.2–42.2 °C) and a chemical lure comprised of 33.0 μg proprionic acid, 0.33 μg butyric acid, 0.33 μg valeric acid, 100 μg octenol and 100 μg L‐lactic acid, impregnated into a gel. Laboratory studies, conducted in a square arena measuring 183 cm on each side, showed that traps with and without baits captured adult bedbugs, but traps with CO₂ emissions of 50–400 mL/min caught significantly (P < 0.05) more bedbugs than traps without CO_2. In an infested unoccupied apartment, traps with heat and with or without the chemical lure were tested without CO₂ on 29 trap‐days and with CO₂ on 9 trap‐days. The numbers of bedbugs captured were 656 and 5898 in traps without and with CO₂, respectively. The numbers of bedbugs of all development stages captured were significantly greater in traps with CO₂ (χ² = 15 942, d.f. = 1, P < 10^?9). A non‐parametric two‐way analysis of variance evaluation of six different traps with or without CO₂, heat or a chemical lure monitored over 19 trap‐days in an infested apartment showed that trap type was highly significant (n = 2833 bedbugs collected) (P < 10^?7). The trap with CO₂, heat and a chemical lure captured more bedbugs than the other traps, but only caught significantly more fourth and fifth instar nymphs than all other traps. Otherwise, the catches in this trap did not differ significantly from those caught by traps that contained CO₂ and heat only. The total numbers of bedbugs collected for each trapping date (pooling all six traps) followed an exponential decline over the trapping period. This type of trap, which caught bedbugs in unoccupied apartments with and without furniture, and in an occupied apartment, may have utility in studying the ecology of bedbugs, in detecting bedbug infestations and in reducing numbers of bites by trapping host‐seeking bedbugs.     

Migration to and dispersal from oilseed rape by the pollen beetle,Meligethes aeneus,in relation to wind direction

1 Host‐plant‐odour‐induced upwind anemotaxis is accepted as the main mechanism by which herbivorous insects find their host plant within an heterogenous environment, but field data supporting this hypothesis are scarce. 2 The flight directions of the pollen beetle Meligethes aeneus to and from a plot of winter oilseed rape and the direction of the wind were recorded concurrently. The beetles were sampled by eight double‐sided window traps encircling the plot. Distal sides of the traps, relative to the plot, sampled the beetles as they flew towards the plot, whereas the proximal sides of the traps sampled them as they flew away from the plot. Paired data on daily catch of beetles in distal or proximal traps and the volume of air impacting each trap were compared. 3 Correlations between daily catch of M. aeneus into distal traps and trap wind volume were negative, indicating that flights by both overwintered‐ and new‐generation insects towards the plot were upwind. 4 Correlations between daily catch of M. aeneus into proximal traps and trap wind volume varied with generation. Catch of overwintered‐generation M. aeneus was negatively correlated with trap wind volume, indicating that flight was upwind. Proximal trap catch of the new‐generation M. aeneus was weakly/modestly positively correlated with trap wind volume, indicating that flights were downwind or crosswind. 5 Understanding the effect of wind direction on flight of M. aeneus holds potential for improving the forecasting of their arrival and spatial distribution on the crop for integrated pest management.     

An experiment on ant predation in soil using a new bait trap method

To examine which species of ant are underground predators, we invented a simple bait trap using live mealworms as bait. A total of 75 bait traps were buried in soil at various depths (10, 20, 30 and 50 cm) to investigate the vertical distribution of predatory ants. The ants captured in approximately 50% of the traps were mostlyTetramorium caespitum andSolenopsis japonica. Solenopsis japonica was captured at greater depths (>30 m) thanT. caespitum. Eight kinds of soil invertebrate (the earthworm, wood louse, pill bug, millipede, adults of the dung beetle and carabid beetle, larvae of a cetoniine beetle and the earwig), placed in traps at a depth of 10 cm, varied greatly in attractiveness and vulnerability to ant predation. The earthworm and the wood louse were both attractive and vulnerable to ant predation, whereas the pill bug, the dung beetle and the millipede were attractive but not vulnerable. The larvae of a cetoniine beetle, the carabid beetle and the earwig were mostly unattractive.     

Spatial relationships between two Agriotes click-beetle species and wireworms in agricultural fields

1 The production of new insect pheromones for pest monitoring proceeds at a greater rate than their evaluation, with the consequential possibility of premature introduction. Fundamental to their successful deployment is the determination of a consistent relationship between adult male pheromone trap catches and pest damage. In the present study, adult pheromone traps and larval bait traps were used to examine spatial relationships between two species of Agriotes beetle and wireworms at the field scale. 2 The spatial distributions of adult male Agriotes lineatus and Agriotes obscurus in two fields were determined and compared with the distribution of their larvae. Data were assembled as spatially referenced trap counts, and analysed for evidence of aggregation and clustering using Spatial Analysis by Distance IndicEs (SADIE) methodology. Spatial stabilities of adult populations between sampling dates were tested using association tests. Spatial and quantitative linkages between adult and larval trap catches were also tested. Moreover, a new way of adapting SADIE methodologies is presented for situations where two datasets within an area do not share the same sampling points. 3 There was no significant difference in variance : mean relationships for the two species but there were differences in their spatial distributions, and this is a definitive example of the general argument stating that it is important to consider spatial as well as count data in ecological studies. The spatial distribution of A. lineatus varied between sampling occasions at both sites whereas A. obscurus had consistently significant SADIE indices over time at one site, and adult catches could also be linked to larval distributions and counts. It is proposed that observed differences between the two species can be explained by interference between traps and dissimilar movement rates. There was some evidence of an edge effect at the field boundaries. 4 The distance between pheromone traps is related to the time that elapses before adjacent traps interfere with trap captures and this limits the detection of statistically significant spatial patterns. It is shown that the current practice of adding trap counts for different Agriotes species and treating them as numerically equivalent is insufficiently robust to be recommended at this stage. 5 The implications for the use of sex pheromone traps in wireworm pest management are considered. It is concluded that pheromone traps, as currently used, will not reliably indicate where wireworms occur in a field, and that the complexity of interpreting adult male trap counts limits quantitative predictions of population size.