Feeding ecology of thirteen syntopic species of anurans in a seasonal tropical environment

Summary Thirteen species of anurans belonging to three families forage diurnally for arthropods in the leaf litter of the lowland rainforest at the Río Llullapichis in Amazonian Perú. This paper investigates the diets and patterns of coexistence in this group of ecologically similar species. All thirteen species use the forest floor habitat without apparent differentiation. Most species take prey in proportions significantly different from those occurring in the leaf litter and comprise two specialist guilds: dendrobatids and bufonids that eat hard-bodied, slow-moving arthropods such as ants and mites; and leptodactylids that eat soft-bodied, mobile arthropods, primarily orthopterans and large spiders. Dendrobates femoralis (Boulenger) is a generalist, taking prey in proportions not significantly different from those in the leaf litter. Within specialist guilds, body sizes of species vary and are correlated with the size of prey taken. Foraging behavior and predator defense also correlate with the type and sizes of prey taken. Ant specialists tend to be poisonous and active searchers, taking many small prey per day. Non-ant specialists are cryptic, sit-and-wait foragers that take few large prey per day. Similarity in diet within guilds tends tobe lowest in the dry season when food is less abundant, suggesting that food is in short supply in the dry season.     

Common garden and natural selection experiments support ecotypic differentiation in the Dominican anole (Anolis oculatus)

The theory behind ecotypic differentiation and ecological speciation assumes a predominant role for natural selection working on characteristics with genetic variance, but experimental support for these assumptions is limited. Lesser Antillean anoles show marked ecotypic variation within islands and the potential for ecological speciation. Common garden rearing experiments on the Dominican anole (Anolis oculatus) suggest that the characters showing geographic variation have genetic variance and are not primarily determined by environmental plasticity. Replicated natural selection experiments using large-scale enclosures show that translocated montane samples experience significant (multivariate) directional selection in both wet and dry seasons in both males and females. The targets of selection appear to be spread among the various character systems. An experiment on 12 geographically segregated populations along a coastal xeric-montane rainforest gradient (four replicate enclosures) clearly showed that the magnitude of the directional selection intensity is positively related to the position along this gradient. The results of the common garden and natural selection experiments support the interpretation that the geographic differentiation is primarily driven by natural selection and are compatible with the potential for ecological speciation in this system.     

Seasonal pattern in food gathering of the weaver ant Oecophylla longinoda (Hymenoptera: Formicidae) in mango orchards in Benin

Prey capture and food scavenging activities of Oecophylla longinoda were monitored through regular weekly samplings during two consecutive years (2009–2010) in a large mango orchard of the Borgou Department of Benin, West Africa, a main mango production area located in the Sudan agro-ecological zone. In both years, interspecific competition with other ants occurred mainly during the dry season (January to March) resulting in increased captures of Formicinae, Myrmicinae and Ponerinae. More prey was caught during the rainy season (end April to end October) than during the rest of the year, with Diptera and Coleoptera prey peaking in May and June, respectively, along with the mango season. As insect prey quickly decreased during November to December weaver ants increasingly collected seeds and plant debris. A total of 241 species of insects were captured including 61 species (25.3%) associated with mango and a few with cashew, among which 48 mango pest species (78.7% of species associated with mango tree). Only five species (2.1%) of beneficial insects were captured. It is concluded that the presence of O. longinoda colonies is beneficial to perennial tree cropping systems such as mango and cashew.     

Lower thermal tolerance in nocturnal than in diurnal ants: a challenge for nocturnal ectotherms facing global warming

1. The thermal adaptation hypothesis proposes that because thermoregulation involves a high metabolic cost, thermal limits of organisms must be locally adapted to temperatures experienced in their environments. There is evidence that tolerance to high temperatures decreases in insects inhabiting colder habitats and microclimates. However, it is not clear if thermal limits of ectotherms with contrasting temporal regimes, such as diurnal and nocturnal insects, are also adapted to temperatures associated with their circadian activities. 2. This study explores differences in heat tolerance among diurnal and nocturnal ant species in four ecosystems in Mexico: tropical montane, tropical rainforest, subtropical dry forests, and high‐elevation semi‐desert. 3. The critical thermal maximum (CT_max), i.e. the temperature at which ants lost motor control, was estimated for diurnal and nocturnal species. CT_max for 19 diurnal and 12 nocturnal ant species distributed among 45 populations was also estimated. 4. Semi‐desert and subtropical dry forest ants displayed higher tolerances to high temperatures than did ants in tropical rainforest. The lowest tolerance to high temperatures was recorded in tropical montane forest ants. In general, among all habitats, the CT_max of nocturnal ants was lower than that of diurnal ants. 5. An increase in nocturnal temperatures, combined with lower tolerance to high temperatures, may represent a substantial challenge for nocturnal ectotherms in a warming world.     

The genus Paragehyra (Reptilia: Sauria: Gekkonidae) in southern Madagascar

Paragehyra Angel is a gekkonine genus endemic to Madagascar. From 1929 until the present, the genus was represented only by the holotype of the single known species. Paragehyra petiti. The type locality of P. petiti is in the driest part of Madagascar (south-west) where rainless periods may exceed 11 months and the original vegetation consists of thorn scrub or dry deciduous forest. No new individuals of P. petiti were observed. However, a second, undescribed species of the genus was discovered in October 1990 on the opposite side of the island (south-east) in primary-low montane rainforest. The new form was observed at four localities at the southernmost extremity of rainforest in Madagascar.     

Effects of habitat,season, and age on winter fat storage by migrant and resident birds in Jamaica

Most small birds wintering in the tropics should show little subcutaneous fat deposition (SFD), except in habitats where food availability may decline in late winter or, for some resident species, to prepare for incubation or brooding fasts. However, these predictions need re‐examination in light of a new, precise, cross‐validated method to compare SFD among habitats and species. We sampled 170 Nearctic‐Neotropical migrant and 279 resident birds during early and late winter in 1993 and 1994 in Jamaica, West Indies. Habitats, from greatest to least expected availability of insect prey, were (1) mangrove forest, (2) montane/foothills forest and cultivation, (3) dry limestone forest, and (4) acacia scrub. Percent lipid, estimated from multiple‐regression models using visual fat scoring (0–8 scale), total‐body electrical conductivity, and a variety of morphometrics, was categorized by percentile ranks to determine if SFD varied by habitat, season, or age for all species, resident species, migrant species, and several individual species. SFD averaged ~ 13% total mass for all birds, ranging from 8–24% for well‐sampled species. The few bird species in acacia scrub, primarily two facultative long‐distance migrants, averaged ~ 26% lipid content, significantly more than birds in other habitats. Most birds did not vary in SFD in the other three habitats, although Common Yellowthroats (Geothlypis trichas) had greater SFD in dry limestone habitat than in montane habitat. Bananaquits (Coereba flaveola) and Jamaican Euphonias (Euphonia jamaica) in montane habitat, especially in early winter, had higher SFD than other resident species. Contrary to our prediction, adults and juveniles had similar SFD, with the exception of juveniles having more SFD than adults in acacia scrub habitat. Winter fat deposition (or, in some cases, muscle‐protein catabolism) in the tropics may be an overlooked strategy, potentially important as a hedge against fasting for floaters, facultative migrants, some territorial migrants in habitats with seasonal declines in food resources, and some resident species prior to breeding.     

Mycorrhizas in the Kakadu region of tropical Australia

This research represents the first part of a study which aimed to characterize the role of mycorrhizal associations in undisturbed and disturbed habitats in the Alligator Rivers Region of the Northern Territory of Australia. This is a seasonally dry tropical region with a climate consisting of a long dry season and a monsoonal wet season. Intact soil cores were sampled from 22 sites in this region, representing eucalypt savanna woodland, wetland, rocky hill and rainforest habitats. Clover, sorghum and eucalypt seedlings were grown in these cores in bioassays to measure the inoculum potential of vesicular-arbuscular mycorrhizal (VAM) and ectomycorrhizal (ECM) fungi. Propagules of VAM fungi were concentrated in the surface horizon, and were not adversely affected by 6 months dry storage of soil. Bioassays detected VAM fungus propagules at all sites, but these were less numerous in three sites with sparse herbaceous vegetation (a shrub-dominated woodland site, a sandstone area and a disturbed gravel pit without topsoil), than in other woodland sites. Propagules of VAM fungi were particularly numerous in soil from a rainforest habitat, which had much denser plant cover than any of the savanna sites. Propagules of ECM fungi colonized eucalypt seedling roots in some cores from all sites, except two wetland areas and a disturbed area without eucalypt trees. Physical and chemical properties of soils varied between sites and some properties (texture, organic carbon, etc.) were correlated with the inoculum potential of VAM fungi.     

西双版纳热带雨林土壤与叶片生态化学计量特征的干湿度效应

基于地理格局对西双版纳热带雨林的干湿度梯度效应和生态化学计量学的研究思路,结合野外试验监测和室内分析,对西双版纳热带雨林土壤-植物系统元素化学计量特征对海拔和干湿度效应响应进行了研究探讨,结果发现:西双版纳热带雨林土壤和叶片碳氮磷化学计量特征均不同程度的受到海拔和干湿季影响。季雨林与山地雨林的水热梯度受海拔梯度重要影响,随海拔梯度升高,土壤含水率变化显著,且含水率在干湿季均对土壤有机碳(SOC)存在显著影响(P0.01),雨季其对土壤全氮(STN)和土壤全磷(STP)的影响要显著于干季;叶片全磷(TP)随含水率的增大而升高,而叶片全氮(TN)在干季会随含水率的升高而增大,雨季含水率升高到一定程度时会抑制TN含量的增加并出现单峰现象;而土壤C/P与海拔和干季土壤含水率的极显著相关性(P0.01)及干季叶片C/N与叶片含水率的显著相关关系(P0.05)说明,干季水分匮乏条件下,土壤含水率影响土壤P的矿化度和植物对P的吸收利用水平,而且叶片C/N对反馈植物水分含量具有明显指示作用。因此,水热梯度是土壤-叶片系统碳氮磷生态化学计量特征变化的重要驱动因素。此外,全球变化区域响应方面,多雨高温可能会削弱季雨林叶片C的同化能力,且叶N含量降低,但受氮沉降的影响,对C/N的影响尚无法确定;由于P循环对其他元素的耦合作用,雨林土壤-叶片系统的元素循环周期将会被缩短,但干季山地雨林植物生态系统P的限制作用有可能会减弱。     

The distribution, density and biomass of terrestrial reptiles in Dominica, West Indies

Fourteen species of reptiles have been recorded from the island of Dominica, Lesser Antilles. As part of a larger study of the ecology of Dominica's forests, the distribution, density and biomass of three widespread lizard species ( Anolis oculatus, Ameiva fuscata and Mabuya mabouya ) were estimated in all major vegetation types. No consistent differences between seasons occurred for any of the three species, and at no site was a definite breeding season detected. Densities, estimated mainly by plot counts, were highest in coastal woodlands where mean densities reached 2148 Anolis per hectare, 379 Ameiva per hectare, and 751 Mabuya per hectare. Densities in rain forest sites were often very low. Combined biomass for the three species also reached a maximum in coastal woodlands of 44.7 kg/ha. This value is amongst the highest recorded for terrestrial reptile assemblages, and suggests that Dominica's coastal woodlands are unusually favourable habitats for reptiles.
Previous studies of Caribbean lizards have suggested that either competition or predation from birds may influence lizard densities. The present study, however, found no such relationships, and it was concluded that lizard density was independent of bird density.     

Seed Dynamics in Relation to Gaps in a Tropical Montane Rainforest of Hainan Island, South China： （I） Seed Rain

Seed dynamics is an important part of stand dynamics in forest ecosystems. In this paper, 26 gaps were randomly selected to study the influence of gaps on the spatial and temporal patterns of seed rains in a tropical montane rainforest of Hainan Island, South China. Three zones for each gap, including outside gap zone （Non-gap）, transitional gap zone （EG-CG）, and central gap zone （CG）, were designed, and fourseed traps （each lm x lm in size） were placed in each zone. Seed rains were collected by these traps every 10 days from June 2001 to May 2002. Seed rain varied greatly with season and generally exhibited a pattern of unimodal change during the study period： seed abundance and species richness were both greater in the wet season than in the dry season. Gaps significantly influenced the temporal patterns of both species richness and density of seed rains. Gaps had no significant influences on the spatial distribution patterns of seed rain species richness, but significantly affected the spatial distribution pattern of seed rain densities. Among the three different zones of gaps, the outside gap zone generally received more seeds inputs than the two other gap zones.     

Intraguild interactions between spiders and ants and top-down control in a grassland food web

In most terrestrial ecosystems ants (Formicidae) as eusocial insects and spiders (Araneida) as solitary trappers and hunters are key predators. To study the role of predation by these generalist predators in a dry grassland, we manipulated densities of ants and spiders (natural and low density) in a two-factorial field experiment using fenced plots. The experiment revealed strong intraguild interactions between ants and spiders. Higher densities of ants negatively affected the abundance and biomass of web-building spiders. The density of Linyphiidae was threefold higher in plots without ant colonies. The abundance of Formica cunicularia workers was significantly higher in spider-removal plots. Also, population size of springtails (Collembola) was negatively affected by the presence of wandering spiders. Ants reduced the density of Lepidoptera larvae. In contrast, the abundance of coccids (Ortheziidae) was positively correlated with densities of ants. To gain a better understanding of the position of spiders, ants and other dominant invertebrate groups in the studied food web and important trophic links, we used a stable isotope analysis (¹⁵N and ¹³C). Adult wandering spiders were more enriched in ¹⁵N relative to ¹⁴N than juveniles, indicating a shift to predatory prey groups. Juvenile wandering and web-building spiders showed δ¹⁵N ratios just one trophic level above those of Collembola, and they had similar δ¹³C values, indicating that Collembola are an important prey group for ground living spiders. The effects of spiders demonstrated in the field experiment support this result. We conclude that the food resource of spiders in our study system is largely based on the detrital food web and that their effects on herbivores are weak. The effects of ants are not clear-cut and include predation as well as mutualism with herbivores. Within this diverse predator guild, intraguild interactions are important structuring forces.     

Seasonality of the activity pattern of Callithrix penicillata (Primates, Callitrichidae) in the cerrado (scrub savanna vegetation).

Two wild groups of Callithrix penicillata, the Black Pincelled Marmoset, were observed from January to September 1998, in two areas, one an area of dense scrub savanna vegetation (cerrado) and the other, a semidecidual woodland (cerrad?o), both within the boundaries of the Ecological Reserve of IBGE (Brazilian Institute of Geography and Statistics), in an environmentally protected area, the APA (Portuguese abbreviation for "environmental protected area") Gama/Cabe?a-de-Veado, Brasília, DF. The behavioral data collected during the rainy (January 15 to April 15) and dry season (June 1 to September 15) were compared. Because of the proximity to the Reserve facilities, the group from the dense scrub savanna vegetation (CD) was submitted to antropic impacts different from the group in the semidecidual woodland (CE), which was using as territory an area that had been suffering from man-made fires every two years as part of a long-term experimental project on fire impacts. The behavioral data was quantified by instantaneous cross-section ("scan sampling") every ten minutes with records of locomotion, rest, foraging for insects, use of exudate, and feeding. During the whole year, the greatest percentage of time spent by CE and CD was in foraging for insects, with 44% and 39%, respectively. It was evident when comparing the data for the two seasons that, for both groups, foraging for insects was more intense during the dry season, possibly to complement the shortage of food, and locomotion increased during the rainy season. The greater the availability and distribution of fruit in the areas, the greater the locomotion of the groups to obtain these resources. None of the other behavioral patterns, including the use of exudates, presented significant differences between the two seasons. Both groups foraged more frequently during the dry season and locomoted more during the rainy one.     

Seasonal variation in populations of panamanian litter frogs and their prey: A comparison of wetter and drier sites

Summary Various species of frogs and toads, belonging to the genera Bufo, Atelopus, Dendrobates, Colostethus, and Eleutherodactylus, occur in the leaf litter in rainforest in Panamá. This study compares the litter communities at two sites in Panamá: Pipeline Road, the drier site, and Carti Road, the wetter site. At both sites, frog abundance is greater in the dry season, when abundance of their prey, the litter arthropods, is greater. Species diversity does not change seasonally at either site; however, species diversity differs strikingly between sites, with Carti Road having the greater species diversity. Similarity in diet does not vary consistently with seasonal changes in food abundance at a single site or with differences in species diversity between sites. These results suggest that neither moisture nor food abundance alone influences the abundance or the diversity of litter frogs at these two sites in Panamá.     

Local trophic specialisation in a cosmopolitan spider (Araneae)

Trophic specialisation can be observed in species with long-term constant exploitation of a certain prey in all populations or in a population of a species with short-term exploitation of a certain prey. While in the former case the species would evolve stereotyped or specialised trophic adaptations, the trophic traits of the latter should be versatile or generalised. Here, we studied the predatory behavioural adaptations of a presumed myrmecophagous spider, Oecobius navus. We chose two distinct populations, one in Portugal and the other in Uruguay. We analysed the actual prey of both populations and found that the Portuguese population feeds mainly on dipterans, while the Uruguayan population feeds mainly on ants. Indeed, dipterans and springtails in Portugal, and ants in Uruguay were the most abundant potential prey. In laboratory trials O. navus spiders recognised and captured a wide variety of prey. The capture efficiency of the Portuguese population measured as components of the handling time was higher for flies than for ants, while that of the Uruguayan population was higher for ants. We found phenotypic plasticity in behavioural traits that lead to increased capture efficiency with respect to the locally abundant prey, but it remains to be determined whether the traits of the two populations are genetically fixed. We conclude that O. navus is a euryphagous generalist predator which shows local specialisation on the locally abundant prey.     

Can changes in ant diversity along elevational gradients in tropical and subtropical Australian rainforests be used to detect a signal of past lowland biotic attrition?

Increasing temperatures are predicted to have profound effects on montane ecosystems. In tropical forests, biotic attrition may reduce lowland diversity if losses of species due to upslope range shifts are not matched by influxes of warmer‐adapted species, either because there are none or their dispersal is impeded. Australian rainforests consist of a north–south chain of patches, broken by dry corridors that are barriers to the dispersal of rainforest species. These rainforests have repeatedly contracted and expanded during Quaternary glacial cycles. Many lowland rainforests are expansions since the Last Glacial Maximum and may, therefore, show a signal of historical biotic attrition. We surveyed ants from replicated sites along three rainforest elevational transects in eastern Australia spanning 200 to 1200 m a.s.l. and nearly 14° of latitude. We examined elevational patterns of ant diversity and if there was possible evidence of lowland biotic attrition. Each transect was in a different biogeographic region; the Australian Wet Tropics (16.3°S), the central Queensland coast (21.1°S) and subtropical south‐eastern Queensland (28.1°S). We calculated ant species density (mean species per site) and species richness (estimated number of species by incorporating site‐to‐site species turnover) within elevational bands. Ant species density showed no signal of lowland attrition and was high at low and mid‐elevations and declined only at high elevations at all transects. Similarly, estimated species richness showed no evidence of lowland attrition in the Wet Tropics and subtropical south‐east Queensland; species richness peaked at low elevations and declined monotonically with increasing elevation. Persistence of lowland rainforest refugia in the Wet Tropics during the Last Glacial Maximum and latitudinal range shifts of ants in subtropical rainforests during the Holocene climatic optimum may have counteracted lowland biotic attrition. In central Queensland, however, estimated richness was similar in the lowlands and mid‐elevations, and few ant species were indicative of lower elevations. This may reflect historical biotic attrition due perhaps to a lack of lowland glacial refugia and the isolation of this region by a dry forest barrier to the north.     

The invasion of Lantana camara L. in Forty Mile Scrub National Park,north Queensland

Abstract Seventy-three per cent of dry rainforest in Forty Mile Scrub National Park and large areas in adjacent savanna woodland have more than 5000 individuals per ha of lantana (Lantana camara L.). Transect studies in dry rainforest and savanna woodland across varying intensities of lantana infestation show a negative correlation between the density of lantana and tree cover in rainforest. The density of pig rooting is very high in areas of the dry rainforest on deep soil that was not heavily infested with lantana. It is suggested that the digging activities of these animals may cause tree death and subsequent increased light penetration, which favours lantana. The species richness of the dry rainforest declines as the density of lantana increases. However, the saplings and seedlings and the soil seed bank of dry rainforest and savanna woodland tree species have comparable densities in heavy and light lantana infestations. The proliferation of lantana results in the build up of heavy fuel loads across the boundary of dry rainforest and savanna woodland. Recent fires have killed the canopy trees in a large area of dry rainforest within the Park. Active management of Forty Mile Scrub National Park is urgent and some initiatives are suggested.     

FUCTIONAL RESPONSE AND PLANT PREFERENCE OF NEPHASPIS OCULATUS (COLEOPTERA: COCCINELLIDAE), PREYING ON BEMISIA ARGENTIFOLII (HOMOPTERA: ALEYRODIDM) IN THE LABORATORY

Abstract The predatory behavior and functional response of all larval stages and adults of Nephpis oculatus (Blatchley), a predacious coccinellid, on various egg densities of Bemisia argentgolii Bellows & Pemng, and prey preference of adult N. oculatus , were studied in the laboratory. Daily consumption of eggs of B. argentifolii by N. oculatus was evaluated at six different densities to obtain functional response curves for all active stages of the coccinellid. Bemisia argentifolii eggs were offered to N. oculatus on collard leaf disks in Petri dish arenas over a 24-h period at 26.7 ∀ 2°C: and a photoperiod of 14:10 (L: D) h. Linear relationship were observed between percentage prey consumed and prey density, with r ² values between 0.82–0.99 for all stages except for the fourth instar that had a smaller r² value (0.64). Functional response curves of prey consumption by N. oculatus against density of B. argentifolii eggs fitted the type II model of Holling's disc equation for all larval stages and both the male and female adults. Adult females consumed more prey than adult males. The maximum theoretical number of prey consumed per day increased with larval development. The fourth instar was the most effective larval predator, followed by the third instar, the second instar, and finally, the first instar. Based on the functional response parameters, a maximum of 321, 312, 237, 229, 73, and 34 B. argentifolii eggs could be attacked by an adult female, a fourth instar, an adult male, a third instar, a second instar, and a first instar of N. oculatus , respectively. Nephaspis oculatus adults strongly preferred collard to tomato, soybean, eggplant or sweet-potato for oviposition and foraging. Nephaspis oculatus did not deposit any eggs on soybean and tomato.     

Variations in bird abundance in tropical arid and semi-arid habitats

Temporal variation in bird abundance was studied during a complete annual cycle in a thorn scrub, a thorn woodland and a deciduous forest in northeastern Venezuela. Abundance of site-attached and transient birds from different feeding guilds was determined by mist-netting at 2-week intervals. Diets were investigated by regurgitated samples. The overall avifauna was characterized by a low number of species but they were present all year despite showing strong seasonal fluctuations in abundance. The number of bird species and individuals peaked before and after the reproductive period. These high values probably were associated with movement of species feeding on plant food during the late dry season and the post-breeding dispersion of juveniles. Bird richness and abundance were lowest during the breeding season and in the early dry season when food abundance was low. Birds from different feeding guilds showed distinct patterns of seasonal abundance which tended to be similar at all three sites. Transient birds represented a large portion of the avifauna, particularly in nectarivores, frugivores and granivores during the dry season. We used a canonical correspondence analysis to demonstrate that bird abundance was correlated with breeding activity, rainfall seasonality and food abundance, with the influence of each parameter varying according to feeding guilds, spatial behaviour of individuals and habitats. Despite a great turnover in the occurrence of the diverse food types available, species composition remained strikingly constant during the year, with birds responding to seasonal changes primarily through a generalist feeding habit and a highly variable rate of transience.     

Response of the foraging behaviour of red wood ants (Formica rufa group) to exclusion from trees

Abstract 1 Because of the large numbers within a colony and their aggressive nature, red wood ants (Formica rufa group) have a potential to greatly influence the cold‐temperate forest ecosystem. Wood ants are omnivorous and hunt in trees as well as on the forest floor. 2 A field experiment in a mixed forest in central Sweden was carried out to examine (i) the foraging behaviour of wood ants on the forest floor and (ii) the impact of increased numbers of wood ants on the soil fauna. The foraging behaviour of wood ants was manipulated by excluding the ants from their food resources in the tree canopy, with the intention to increase ant activity on the forest floor. To estimate this activity, the number of trees with foraging ants, the numbers of ants going to and from their nests and the prey carried by home‐running wood ants were determined during the summer period. Pitfall traps were placed in the soil to determine effects on mobile soil invertebrates. 3 When excluded from local trees, wood ants searched other trees further away from the nests rather than searching more intensively for prey on the forest floor. By contrast to the initial hypothesis, more soil‐living prey were caught by ants in the control plots than in the plots where the local trees were not accessible to the wood ants. The proportion of soil‐living to tree‐living prey tended to be greater in the control plots. 4 In the treated plots (no access to the trees), wood ants had a negative effect on the activity of Linyphiidae spiders. There was little effect of wood ants on other soil invertebrates. 5 This study suggests that the role of wood ants as top predators in the forest soil food‐web in central Sweden is limited.     

Elevational and geographic variation in army ant swarm raid rates

Geographic and elevational variation in the local abundance of swarm-raiding army ants has implications for the population dynamics of their prey, as well as affecting the profitability of army-ant-following behavior for birds. Here, we analyze systematically collected data on E. burchellii and L. praedator raid rates from geographically and elevationally wide-ranging sites, from lowland to montane forests. We show that raids of each species, and of both species pooled, reach peak densities at intermediate (premontane) elevations. These patterns suggest that army ant swarm raids are relatively abundant in Neotropical montane forests. Therefore, a paucity of ant raids does not explain the absence of obligate ant-following bird species, particularly true antbirds (Thamnophilidae), from montane forests. As army ant raids are relatively common at middle elevations, opportunities exist for other montane bird taxa to exploit army ant raids as a food source.