Determination of an Optimal Pitfall Trap Size for Sampling Spiders in a Western Australian Jarrah Forest

Pitfall trapping is a sampling technique extensively used to sample surface foraging invertebrates for biological diversity studies and ecological monitoring. To date, very few invertebrate studies have considered what trap size is optimal for sampling spiders. This study presents preliminary findings from a single short sampling period on the role of trap size in sampling spiders in a Western Australian Jarrah forest. Four different trap diameters (4.3, 7.0, 11.1 and 17.4 cm) were examined (4 trap sizes × 15 replicates = 60 traps). Two-way ANOVAs revealed no significant interaction effects between trap size or the spatial positioning of transects within the study site along which the pitfall traps were arranged. Post-hoc tests revealed abundance, family richness and species richness increased with increasing trap sizes for traps 7.0 cm. No significant differences in these dependent variables occurred between 4.3 and 7.0 cm traps, or for species richness between 11.1 and 17.4 cm traps. Determination of an optimal trap size was undertaken by bootstrapping and calculating species accumulation curves for increasing numbers of traps used. Three different criteria were considered: equivalent number of traps (15), standardized sampling intensity (cumulative trap circumference, approximately 207 cm) and standardized cumulative handling time (approximately 1 hour 17 minutes). The largest trap size (17.4 cm) was most efficient in terms of number of traps and trap circumference. For the same number of traps, it caught 19 species whereas all other trap sizes caught ten species. At the standardized circumference, it caught seven species whereas all other trap sizes caught five. For handling time, however, the two largest trap sizes (17.4 and 11.1 cm) were optimal. Both caught nine species whereas all other traps caught 相似文献   

Developing a branch-mimicking trap for adult plum curculios

We conducted field and semi-field experiments to determine the most visually stimulating and acceptable version of a branch-mimicking trap (PVC cylinder topped with an inverted screen funnel) to capture adult plum curculios, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae) foraging within canopies of host trees. Cylinder traps (25 cm tall × 6 cm diam) coated with different colors of gloss or flat latex paint captured similar numbers of feral adults in field tests. Tall cylinder traps (50 cm tall × 6 cm diam) captured significantly more feral adults in field tests in 1999 than cylinder traps of lesser height and/or different diameter, and significantly more released adults arrived at traps with these dimensions compared to cylinder traps of lesser height in semi-field tests. In field and semi-field tests, respectively, significantly more adults were captured by and numerically more adults arrived at tall cylinder traps (50 cm tall × 6 cm diam) attached in an upright, standard position to a horizontal limb than attached at angles of 45°, 90°, 135°, or 180° to horizontal limbs.     

Stream-bank shade and larval distribution of the Philippine malaria vector Anopheles flavirostris

The principal malaria vector in the Philippines, Anopheles flavirostris (Ludlow) (Diptera: Culicidae), is regarded as 'shade-loving' for its breeding sites, i.e. larval habitats. This long-standing belief, based on circumstantial observations rather than ecological analysis, has guided larval control methods such as 'stream-clearing' or the removal of riparian vegetation, to reduce the local abundance of An. flavirostris. We measured the distribution and abundance of An. flavirostris larvae in relation to canopy vegetation cover along a stream in Quezon Province, the Philippines. Estimates of canopy openness and light measurements were obtained by an approximation method that used simplified assumptions about the sun, and by hemispherical photographs analysed using the program HEMIPHOT. The location of larvae, shade and other landscape features was incorporated into a geographical information system (GIS) analysis. Early larval instars of An. flavirostris were found to be clustered and more often present in shadier sites, whereas abundance was higher in sunnier sites. For later instars, distribution was more evenly dispersed and only weakly related to shade. The best predictor of late-instar larvae was the density of early instars. Distribution and abundance of larvae were related over time (24 days). This pattern indicates favoured areas for oviposition and adult emergence, and may be predictable. Canopy measurements by the approximation method correlated better with larval abundance than hemispherical photography, being economical and practical for field use. Whereas shade or shade-related factors apparently have effects on larval distribution of An. flavirostris, they do not explain it completely. Until more is known about the bionomics of this vector and the efficacy and environmental effects of stream-clearing, we recommend caution in the use of this larval control method.     

A comparison of Lucitraps and sticky targets for sampling the blowfly Lucilia sericata

The Lucitrap (Miazma Pty Ltd, Queensland, Australia) combined with a synthetic odour bait, Lucilure (Miazma Pty Ltd, Queensland, Australia), is a commercially available trap for sampling and control of Lucilia cuprina (Wiedemann) in Australia. It was tested in Hungary against Lucilia sericata (Meigen) (Diptera: Calliphoridae), a cause of sheep strike throughout temperate Europe. The standard Lucitrap was tested against black or yellow sticky target traps. Both trap types were baited with either Lucilure or liver and 10% w/v sodium sulphide solution. With Lucilure as bait, L. sericata were caught on sticky traps but not in Lucitraps. With liver and sodium sulphide as bait, sticky traps caught 500-1500 times more L. sericata than Lucitraps. An adhesive sheet fitted to the top of a Lucitrap captured 30-300 times more L. sericata then were captured inside an unaltered Lucitrap. Direct observation of metallic green calliphorids (92.1% L. sericata) alighting on Lucitraps indicated that most flies stayed for a short while (modal class 2-4 s) and only a few stayed longer, to an observed maximum of 28 s. Flies explored a mean of 1.5 entry holes (range 0-7) during a visit but only 6% entered the trap. Size of L. sericata was not a physical barrier to Lucitrap entry, because many larger species were captured. However, L. sericata captured inside Lucitraps were significantly smaller than those captured on sticky traps, demonstrating that size was of behavioural importance. The data demonstrate that the Lucitrap is not effective as a trap for L. sericata in Hungary, due mainly to a failure of flies to enter the trap in large numbers. In Australia and South Africa, L. sericata is commonly caught in Lucitraps baited with Lucilure, although L. cuprina is more numerous. Our study highlights the potential for diversity of fly behaviour between different geographical populations of the same species. Such diversity can have a significant effect on the functioning of systems for fly sampling and control, when these systems depend for their success on certain behavioural responses of the target species.     

Oak canopy effects on the distribution patterns of two annual grasses: the role of competition and soil nutrients

Within the oak woodlands of California there is often a distinct shift in the botanical composition between the open grassland and the herbaceous understory beneath oak canopy. Botanical sampling at two woodland sites indicated that the annual grass Bromus diandrus was dominant under deciduous blue oak canopy, while a congener, Bromus hordeaceus, was dominant in open grassland. We examined the relative importance of congeneric competition and edaphic factors in creating these differences in species distribution in two separate field experiments that manipulated both congeneric and intraspecific competition, as well as soil type. We used the demographic measure of relative reproductive rate as an index of population growth. In general, demographic performance correctly predicted the distribution of the two annual grasses in the field. Our results indicate that reduced abundance of B. hordeaceus under canopy reflects the negative effects of competition with B. diandrus. In contrast, B. diandrus is little affected by competition from B. hordeaceus. The reduced abundance of B. diandrus in open grassland may result, in part, from its inability to adapt as well as B. hordeaceus to lower nutrient availability in soils of the open grassland.     

Effects of Canopy Gaps,Topography, and Soils on the Distribution of Woody Species in a Central Brazilian Deciduous Dry Forest1

The interrelationships between the distribution of woody species and environmental variables were investigated in an area of deciduous dry forest in Santa Vitöria, central Brazil. This is the first study of a vanishing type of dry forest which grows on base-rich soils originating from the basalt bedrocks of southern Goiás and western Minas Gerais. A survey of topography, soil properties, canopy gaps and woody plants (≥5 cm diameter at the base of the stem) was conducted in 50–15 × 15 m quadrats. The soils were classified into the following soil series: Hapludolls → Haplustolls → Haplustolls → Ustropepts → Rhodustalfs. This series corresponded to a gradient of increasing elevation and effective soil depth and decreasing slope gradient, soil organic matter and total exchangeable bases. A canonical correspondence analysis and a detrended correspondence analysis indicated that plant species’abundance distribution was significantly correlated with both the relative area of canopy gaps in the quadrats and the soil-topography gradient. Presumably, the critical factors involved in these two gradients are, respectively, light and ground water regimes. The influence of canopy gaps (i.e., light) was surprising and has not been documented previously for tropical deciduous dry forests.     

Seasonal Foliage Changes in the Eastern Amazon Basin Detected from Landsat Thematic Mapper Satellite Images1

Seasonal changes in tropical forests are difficult to measure from the ground, especially in areas of high species diversity and low phenological synchrony. Satellite images, which integrate individual tree canopies and cover a large spatial extent, facilitate tests for stand-level canopy phenology. Variability in near-infrated radiance (TM bands 4 and 5) of several distinct vegetation types was used to detect seasonal changes in a series of three Landsat Thematic Mapper (TM) images from the wet season to the dry season in Marabá, Brazil (eastern Amazon basin). Despite different atmospheric and instrumental conditions among the images, spectral changes were distinguishable. A phenological process (leaf aging, leaf drop, water stress) was determined from the spectral changes for each vegetation type. Changes in the spectral properties suggest that during the dry season, upland terra firme forest increased the rate of leaf exchange and some riparian vegetation was deciduous. Terra firme forest that had been altered by penetration of fires from nearby pastures increased in leaf biomass over a 14-month period. This study shows that a time series of images can provide information on temporal changes in primary vegetation and guide field studies to investigate seasonal changes that may not be detectable from the ground.     

Pattern and Performance of Understory Bamboos (Chusquea spp.) under Different Canopy Closures in Old-Growth Oak Forests in Costa Rica1

The effect of canopy closure on spatial and morphological patterns of three understory Chusquea species was studied in pristine upper montane oak forests. Plots with either Chusquea talamancenis Widmer & L.G. Clark or C. tomentosa Widmer & L.G. Clark were set out in gaps, under intermediate tree canopy and under closed canopy. The third species Chusquea foliosa L.G. Clark was only found in gap and intermediate canopy sites in the study area. Clumps of all bamboo species tend to be few and large under open conditions and numerous and small under more shady conditions. The larger size of clumps in gaps is reflected in the number of culms per clump, the diameter of the culms and, as a consequence, clump basal area, clump crown area, and biomass (index of plant volume) compared to intermediate and closed canopy. The smaller clump density in gaps compared to closed canopy implies that there is more intraspecific competition and density dependent mortality (self-thinning effect) when a bamboo species is dominant under favourable light conditions. Parameters of performance like culm length, number of nodes per culm, number and length of primary branches, and number of branch nodes seem not to be affected by the light regime, unlike total number of branches, total branch length, and the branching pattern. Species differ in their response to the light environment: C. tomentosa and C. foliosa have a higher degree of morphological plasticity than C. talamancensis, which in turn, appears to be more shade tolerant. No difference between species has been found regarding their contribution to vegetation, parameters reflecting abundance per unit area (site clump area, site crown area and site index of clump volume) were similar for all three species.     

Injury and short term mortality of benthic stream fishes – a comparison of collection techniques

Small benthic fish such as darters are frequently collected for stream inventory purposes or to document habitat use, with the intent of releasing the fish unharmed following enumeration. The purpose of this study was to examine the injury and short term mortality (8 d) of greenside darters captured by live wire pot trapping and electrofishing, using two different settings (80Hz, 6ms and 60Hz, 6ms). Two different electrofishing techniques were used, spot electrofishing and sweep electrofishing. Short term mortality was highest for fish collected in live pot traps. Abrasion from the wire traps appeared to remove scales and irritate the skin. By the conclusion of the study, 74% of the fish caught in live pot traps were dead from fungal lesions. Greenside darters captured by all electrofishing methods exhibited low short term mortality (< 10%). The only initial mortality, hemorrhaging and spinal damage, occurred for fish collected using 80Hz, 6ms sweep technique, although the short term mortality was still far less than that observed among trapped fish. The spot electrofishing technique resulted in no injury, with either of the settings. Live trapping produces little initial mortality, and thus may be wrongly viewed as a safe alternative for the collection of threatened benthic stream fishes, compared to electrofishing. We suggest that researchers studying small fish in warmwater systems use caution when collecting and handling fish for subsequent release. This revised version was published online in July 2006 with corrections to the Cover Date.     

Vascular Epiphyte Communities in the Inner-Crown of Hyeronima alchorneoides and Lecythis ampla at La Selva Biological Station, Costa Rica

The community composition and percent cover of vascular epiphytes were examined in relation to photosynthetic photon flux density (PFD), temperature, vapor pressure, and tree characteristics in the inner-crown of two emergent tree species, Hyeronima alchorneoides and Lecythis ampla, at La Selva Biological Station, Costa Rica. A total of 53 species were found in a total sampled branch area of 32 m² in eight trees—four trees per species. Community composition varied both among individuals of the same tree species and between tree species. However, percent cover patterns of vascular epiphytes were significantly different between the two tree species; Hyeronima had a significantly greater percent cover of epiphytes than Lecythis . The higher percent light transmittance as well as lower humidity in Lecythis are likely causes of its lower percent cover of epiphytes.