Fragmentation in eucalypt woodlands promotes nest‐tree occupancy by a despotic species,the noisy miner (Manorina melanocephala)

The effects of habitat fragmentation as a threat to biodiversity are well known; decreased connectivity can potentially influence population processes and dynamics, resulting in smaller, isolated populations that may not function optimally. However, fragmentation may also increase the amount of edge or ecotone habitat available to open country species, benefiting their populations and enabling them to dominate remnant habitats. Noisy miners (Manorina melanocephala) are one such species, occupying eastern‐Australian eucalypt woodlands. They are considered a ‘despotic’ species, in that their presence negatively impacts woodland avifauna biodiversity due to their aggressive exclusion of other taxa from occupied areas. Despite this well‐known impact, little information exists on the patterns of nest‐tree occupancy by noisy miners within eucalypt woodlands. In the current study, we explored the patterns of nest‐tree occupancy by noisy miners across two successive years, aiming to identify preferences for breeding areas relative to vegetation structure. Our results show that both habitat fragmentation and the characteristics of individual eucalypt trees in an area influenced nest‐tree occupancy. Noisy miners constructed nests in trees near the edge of woodland patches more often than expected. Moreover, the nest tree chosen was a eucalypt that was significantly smaller than randomly selected trees from the surrounding area. The results highlight the importance of habitat management measures that may reduce the suitability of woodland patches as nesting sites for this species, in order to mitigate the severe effects of this despotic edge specialist.     

Fine‐scale habitat preferences and habitat partitioning by three mycophagous mammals in tropical wet sclerophyll forest,north‐eastern Australia

Abstract Fine‐scale habitat preferences of three co‐occurring mycophagous mammals were examined in a tropical wet sclerophyll forest community in north‐eastern Australia. Two of the three mammal species responded to fine‐scale variation in vegetation and landform around individual trap locations. At a broad scale, the northern bettong (Bettongia tropica), an endangered marsupial endemic to the Australian wet tropics region, showed a preference for ridges over mid‐slopes and gullies, irrespective of forest type. In contrast, the northern brown bandicoot (Isoodon macrourus), a widespread marsupial, displayed a preference for Eucalyptus woodland over adjacent Allocasuarina forest, irrespective of topographic category. The giant white‐tailed rat (Uromys caudimaculatus), a rodent endemic to the wet tropics, showed no particular preference for either forest type or topographic category. A multiple regression model of mammal capture success against three principal habitat gradients constructed from 21 habitat variables using principal component analysis indicated strong species‐specific preferences for fine‐scale vegetation assemblages. Bettongs preferred areas of Eucalyptus woodland with sparse ground cover, low densities of certain grass species, high density of tree stems and few pig diggings. Bandicoots, in contrast, favoured areas in both forest types with dense ground cover, fewer tree stems and greater numbers of pig diggings; that is, characteristics least favoured by bettongs. The striking differences in fine‐scale habitat preferences of these two mammals of similar body size and broad habitat requirements suggest a high degree of fine‐scale habitat partitioning. White‐tailed rats did not show preference for any of the habitat gradients examined.     

Ecological aspects of development of testacean complexes in nests of Formica lugubris and Formica exsecta (Hymenoptera, Formicidae)

Testacean population in the nests of Formica lugubris and F. exsecta was studied in a spruce forest and in a mixed birch forest. Samples of the nest material (spruce litter and grass fragments) were taken from the surface layers, the inner parts of the nests, and from underlying soil. In all, 33 species of testaceans were identified. The highest species diversity and abundance were observed in the Formica lugubris nests, in the upper layer of the F. exsecta nest, and in the spruce litter. In all the samples, 10 widespread aerophilic and edaphic species (Centropyxis aerophila, C. sylvatica, C. orbicularis, Cyclopyxis kahli, Trinema lineare, and others) were the most common, resulting in a uniform species composition in all the habitats studied. In the presence of the relevant substrate, this group is supplemented by species of appropriate ecological groups (bryophilic, acidophilic, and inhabitants of coarse humus). In the inner part of the Formica lugubris nest, the testacean population is characterized by a very high abundance of Plagiopyxis penardi, whereas the surface layer of the F. exsecta nest is characterized by abundant Cyclopyxis eurystoma and very low species diversity in the inner layers. The initial composition and decree of decomposition of plant remains due to ant activity are considered as the main factors responsible for the testacean species diversity, as well as the availability of substrates suitable for the development of different ecological groups of testaceans.     

Nest niche dynamics of Meyer's Parrot Poicephalus meyeri in the Okavango Delta,Botswana

Meyer's Parrot Poicephalus meyeri is the only cavity-nesting bird species that breeds during winter in the Okavango Delta. This is facilitated by exclusive access to arthropod larvae incubating inside and feeding on fruits and pods in their diet. To minimise predation risk and overcome low overnight temperatures they have specialised, non-random nest cavity preferences that restrict them to 4.5% of the available nest cavities in the study area. Here we evaluated the nest niche of Meyer's Parrot by studying the nest tree preferences and ecological context of all nest cavities to determine factors that may restrict breeding success in disturbed or altered habitat. Although specific nest tree preferences were significantly different between host tree species, Meyer's Parrot preferred trees greater than 14 m in height that were in relatively poor condition (e.g. portion of the canopy dead). A comparison of nest tree characteristics (n = 75) and the availability of these tree specifications in a representative sample of the different habitat types (n = 1 129) within the sample area indicated that Meyer's Parrot are dependent on riverine forest, Acacia-Combretum marginal woodland and dry mopane woodland for nesting opportunities. Disturbance to hardwood trees by African elephants Loxodonta africana and fungal attack (e.g. Coriolus versicolor) are likely important dynamics in supporting healthy Meyer's Parrot populations and cavity-nesting bird communities.     

Effect of host species,host nest density and nest size on the occurrence of the shining guest ant <Emphasis Type="Italic">Formicoxenus nitidulus</Emphasis> (Hymenoptera: Formicidae)

Understanding habitat requirements of species is important in conservation. As an obligate ant nest associate, the survival of the globally vulnerable shining guest ant, Formicoxenus nitidulus, is strictly tied to that of its hosts (mound building Formica ants). We investigated how host species, nest density, inter-nest distance and nest mound size relate to the occurrence of F. nitidulus. In total, 166 red wood ant nests were surveyed in SW Finland (120 Formica polyctena, 25 F. rufa, 14 F. aquilonia, 5 F. pratensis, and 2 F. lugubris). Overall, F. nitidulus was found in 60% of the nests. For the actual analysis, only F. polyctena and F. rufa nests were included due to the small number of other nests. F. nitidulus was more likely to be found among F. polyctena than F. rufa. Also, while inter-nest distance was not important, a high nest density, commonly found in polydomous (multi-nest) wood ant colonies, was beneficial for F. nitidulus. The guest ant was also more likely to be found in large host nests than small nests. Thus, our results show that the best habitat for the guest ant is a dense population of host nest mounds with a high proportion of large mounds. Conservation efforts should be directed at keeping the quality of the red wood ant habitats high to preserve their current populations and to increase colonization. This will not only benefit the guest ant, but also a plethora of other species, and help in maintaining the biodiversity of forests.     

A canopy dominant ant affects twig‐nesting ant assembly in coffee agroecosystems

One commonly studied driver of community assembly is the effect of dominant species on subordinate species. Dominant species may impact community assembly during competitive sorting, or recruitment. For ants, important and abundant species in the tropics, several factors may drive community assembly including competition, dispersal, priority effects, and environmental conditions. Although competition is a hallmark of ant ecology, few have examined the influence of patchily distributed dominant ants on other ant species and diversity, especially at the recruitment stage. Here, I consider the impacts of a canopy dominant ant species, Azteca instabilis, and changes in vegetation on twig‐nesting ant colony founding and ant community assembly in a coffee agroecosystem. I added artificial nests to coffee plants in areas with and without A. instabilis four times over a year, and then examined the occupation rate and identity of species colonizing nests. I also examined vegetation characteristics of sites where nests were added. The presence of A. instabilis on coffee plants drastically lowered colonization rates, but nest occupation increased with tree density, and with decreasing proportion of Inga spp. trees in the canopy. The presence of A. instabilis limited the number of nests occupied by six of the ten most common species; most rare species, however, were not affected by A. instabilis presence. Richness of colonizing ants in areas with A. instabilis was lower, but these effects did not significantly affect richness across broader scales. Despite large effects on individual species, species composition did not differ greatly in areas with and without A. instabilis, but some vegetation characteristics (basal area and tree richness) were predictive of ant composition. These results suggest that A. instabilis strongly affects founding events especially for common twig‐nesting species and that both vegetation and influences from this dominant species affect community assembly of twig‐nesting ants at the local scale.     

Size matters: nest colonization patterns for twig‐nesting ants

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The relocation of ant nest entrances: Potential consequences for ant-dispersed seeds

The rate at which ant nests relocate may affect the fate of ant-dispersed seeds by influencing nutrient and seed accumulation in localized areas. In this study, the movement of ant nest entrances was monitored in fixed quadrats in dry sclerophyll woodland in Kuringai Chase National Park, NSW. Changes in entrance location were rapid for most species, with few entrances remaining in use for more than 6 months. Approximately 30% of entrances that closed were subsequently re-opened. There was no obvious seasonal pattern in entrance relocation. After 1 year, between 5 and 40% of the ground surface of the quadrats had been within 10 cm of a nest entrance. New nest entrances did not cluster near old entrances, indicating that nest entrance relocation may be accompanied by changes in underlying nest structure. Nutrient levels in soil samples from active nests of Rhytidoponera metallica, Aphaenogaster longiceps, Pheidole sp. 1 and Iridomyrmex sp. 8 did not differ significantly from random locations. The rapid changes in entrance location and the lack of nutrient enrichment may be the result of continual and progressive underground shifts in nest location. Such shifts have three potential consequences for seeds that remain buried within the nests. First, seeds will not benefit following germination by being in a nutrient-rich microsite. Second, a proportion of seeds collected by harvester ant species may escape predation if left in an abandoned section of the nest. Third, concentrations of seeds in localized areas may be reduced, leading to a reduction in competition between establishing seedlings.     

Nest habitat selection by the Austral parakeet in north‐western Patagonia

Identifying habitat or nesting microhabitat variables associated with high levels of nest success is important to understand nest site preferences and bird–habitat relationships. Little is known about cavity availability and nest site requirements of cavity nesters in southern hemisphere temperate forests, although nest site limitation is suggested. Here we ask which characteristics are selected by the Austral parakeet (Enicognathus ferrugineus) for nesting in Araucaria araucana–Nothofagus pumilio forest in Argentine Patagonia. We compared nest plot and tree characteristics with unused plots and trees among areas of different A. araucana–N. pumilio density. We also examine whether nest plot and tree use and selection, and the associated consequences for fitness of Austral parakeets are spatially related to forest composition. Austral parakeets showed selectivity for nests at different spatial scales, consistently choosing isolated live and large trees with particular nest features in a non‐random way from available cavities. Mixed A. araucana–N. pumilio forests are ideal habitat for the Austral parakeets of northern Patagonia, offering numerous potential cavities, mainly in N. pumilio. We argue that Austral parakeet reproduction and fitness is currently very unlikely to be limited by cavity availability, although this situation may be rapidly changing. Natural and human disturbances are modifying south temperate forests with even‐aged mid‐successional stands replacing old growth forests. Cavity nesting species use and need old growth forests, due to the abundance of cavities in large trees and the abundance of larvae in old wood. Neither of the latter resources is sufficiently abundant in mid‐successional forests, increasing the vulnerability and threatening the survival of the Austral.     

The relationship between soil variables and leafcutter ant (Atta sexdens) nest distribution in the Colombian Amazon

We determined the relationships between several soil variables and the distribution of leafcutter ant (Atta sexdens) nests on the Colombian shore of the Amazon River. Seven habitats were identified in which nests were consistently present or absent. Soil samples for physiochemical analysis were taken near nest sites in three habitats where nests were present and from randomly selected sites in four other habitats where nests were absent. Percent canopy cover and soil resistance were also measured for each site. Almost all of the 20 identified soil variables were significantly different between habitats with and without A. sexdens nests, and the values of all variables were heterogeneous between the seven habitats. The most important variables correlated with leafcutter ant nest presence were percent canopy cover (positively), percent silt, soil resistance at 0–20 cm, and pH (all negatively). We deduced a binomial and a multinomial logistic regression which showed how each of these variables was related to nest presence and habitat, respectively. We describe how each variable may affect leafcutter ant nest development, especially in its earliest stages, and therefore influences nest distribution. We propose a suitable-soil hypothesis which, complementary to the palatable forage hypothesis, aims to explain patterns in leafcutter ant nest demography based on soil conditions.     

Nest site selection and nesting success of five species of passerines in a South American open Prosopis woodland

I analyzed nest site preferences and whether these preferences were linked to nest success of five bird species breeding in an arid area of southern South America. Most nests (90%) were located in three plant species (Geoffroea decorticans, Capparis atamisquea, and Atriplex lampa). Serpophaga griseiceps, Poospiza ornata, and P. torquata nested in plants with size significantly different from randomly selected plants. At the mesohabitat scale (i.e., habitat patch surrounding the nest), four species showed clear differences from random patches within the general habitat, and the remaining species (Saltatricula multicolor) showed a non-significant trend. The daily survival rate of S. griseiceps nests placed in the preferred plant species (i.e., G. decorticans) was lower than those in the other nest-plants. In the other four bird species, nest survival did not differ between preferred and other plants used for nesting. At the scale of microhabitat (i.e., plant size and location of the nest inside the plant), no significant differences were detected between unsuccessful and successful nests. Similarly, unsuccessful nest patches did not differ significantly in habitat features from those that were successful. High nest predation rates found in this habitat (around 85% for the total assemblage) and a relatively high diversity of predators (and of predation tactics) appear to impede the presence of safe sites for nesting (i.e., there are trade-offs between avoidance strategies).     

Microhabitat nest‐site selection by ducks in the boreal forest

The boreal forest is one of the North America’s most important breeding areas for ducks, but information about the nesting ecology of ducks in the region is limited. We collected microhabitat data related to vegetation structure and composition at 157 duck nests and paired random locations in Alberta’s boreal forest region from 2016 to 2018. We identified fine‐scale vegetation features selected by ducks for all nests, between nesting guilds, and among five species using conditional logistic regression. Ducks in the boreal forest selected nest sites with greater overhead and graminoid cover, but less forb cover than random sites. Characteristics of the nest sites of upland‐ and overwater‐nesting guilds differed, with species nesting in upland habitat selecting nests that provided greater shrub cover and less lateral concealment and species nesting over water selecting nests with less shrub cover. We examined the characteristics of nest sites of American Wigeon (Mareca americana), Blue‐winged Teal (Spatula discors), Green‐winged Teal (Anas crecca), Mallards (Anas platyrhynchos), and Ring‐necked Ducks (Aythya collaris), and found differences among species that may facilitate species coexistence at a regional scale. Our results suggest that females of species nesting in upland habitat selected nest sites that optimized concealment from aerial predators while also allowing detection of and escape from terrestrial predators. Consequently, alteration in the composition and heterogeneity of vegetation and predator communities caused by climate change and industrial development in the boreal forest of Canada may affect the nest‐site selection strategies of boreal ducks.     

From endogenous to exogenous pattern formation: Invasive plant species changes the spatial distribution of a native ant

Invasive species are a significant threat to global biodiversity, but our understanding of how invasive species impact native communities across space and time remains limited. Based on observations in an old field in Southeast Michigan spanning 35 years, our study documents significant impacts of habitat change, likely driven by the invasion of the shrub, Elaeagnus umbellata, on the nest distribution patterns and population demographics of a native ant species, Formica obscuripes. Landcover change in aerial photographs indicates that E. umbellata expanded aggressively, transforming a large proportion of the original open field into dense shrubland. By comparing the ant's landcover preferences before and after the invasion, we demonstrate that this species experienced a significant unfavorable change in its foraging areas. We also find that shrub landcover significantly moderates aggression between nests, suggesting nests are more related where there is more E. umbellata. This may represent a shift in reproductive strategy from queen flights, reported in the past, to asexual nest budding. Our results suggest that E. umbellata may affect the spatial distribution of F. obscuripes by shifting the drivers of nest pattern formation from an endogenous process (queen flights), which led to a uniform pattern, to a process that is both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. The number and sizes of F. obscuripes nests in our study site are projected to decrease in the next 40 years, although further study of this population's colony structures is needed to understand the extent of this decrease. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.     

Does land use change influence predation of bird nests?

Worldwide, many areas of agricultural land which were once covered with native vegetation have been converted to tree plantations. Such landscape transformation can influence the dynamics of wildlife populations through, for example, altering rates of predation (e.g. predation of nests of birds). Nest predation can influence reproductive success and, in turn, may alter populations by affecting juvenile recruitment. We quantified predation of bird nests in woodland remnants surrounded by two types of land use, grazing farmland and exotic Radiata pine (Pinus radiata) plantation. We also examined differences in predation rates between artificial and natural nests. We found both artificial and natural nests were more susceptible to nest predation in woodland remnants surrounded by a pine plantation than in woodland remnants located within farmland. Our study suggests that higher levels of nest predation may reduce occupancy of woodland remnants by small‐bodied birds over time, including species of conservation concern. This may have been occurred as a result of the conversion of semi‐cleared grazing land to exotic pine plantation.     

Leaf-cutting ant preferences for five native tropical plantation tree species growing under different light conditions

To examine the susceptibility of five Costa Rican tree species to leaf-cutter ants (Atta cephalotes L.: Formicidae, Attini), young and mature leaves from trees that were grown in a plantation under full sun and partial shade were offered to six leaf-cutter colonies located in full sun and six in patial shade. In addition to offering leaf disks to the ants, we offered large pieces of leaves to assess the effect of cutting leaves on food choices. Leaf-cutters responded differently to each plant species, preferring Virola koschyni Warburg (Myristicaceae) and Hyeronima alchorneoides Allemao (Euphorbiaceae) over Stryphnodendrum microstachyum Poeppig & Endlicher (Mimosoideae), Pentaclethra macroloba Willdenow (Fabaceae) and Vochysia ferruginea Martius (Vochysiaceae). In agreement with previous studies, interspecific differences among the tree species in water and saponin content appeared to account for the observed ant preferences among the five tree species: leaf-cutter ants preferred leaves and disks with more water and less saponins and the five tree species varied significantly in these traits. An observed positive correlation between preference and phenolic/nitrogen ratio appears to be spurious, and is instead due to a negative correlation between water content and nitrogen content. For the first time, Atta nest location has been shown to affect consumption: nests located in partial shade removed more leaf material than those from the sun plots. However, nest location had no effect on preference ranking of the tree species tested. Pieces of leaves from all the tree species grown in partial shade were significantly more removed than those trees grown in full sun. Leaf age, toughness, leaf specific weights, ant activity, and colony were not correlated with food choices. Because of the observed preferences, the five tree species should not be considered as equal candidates for plantation purposes. However, complete characterization of the candidate status of tree species for plantations in the neotropics must include information on the ability of such species to tolerate pest attacks in addition to their natural defenses to attack.     

Breeding habitat and nest‐site selection by an obligatory “nest‐cleptoparasite”, the Amur Falcon Falco amurensis

The selection of a nest site is crucial for successful reproduction of birds. Animals which re‐use or occupy nest sites constructed by other species often have limited choice. Little is known about the criteria of nest‐stealing species to choose suitable nesting sites and habitats. Here, we analyze breeding‐site selection of an obligatory “nest‐cleptoparasite”, the Amur Falcon Falco amurensis. We collected data on nest sites at Muraviovka Park in the Russian Far East, where the species breeds exclusively in nests of the Eurasian Magpie Pica pica. We sampled 117 Eurasian Magpie nests, 38 of which were occupied by Amur Falcons. Nest‐specific variables were assessed, and a recently developed habitat classification map was used to derive landscape metrics. We found that Amur Falcons chose a wide range of nesting sites, but significantly preferred nests with a domed roof. Breeding pairs of Eurasian Hobby Falco subbuteo and Eurasian Magpie were often found to breed near the nest in about the same distance as neighboring Amur Falcon pairs. Additionally, the occurrence of the species was positively associated with bare soil cover, forest cover, and shrub patches within their home range and negatively with the distance to wetlands. Areas of wetlands and fallow land might be used for foraging since Amur Falcons mostly depend on an insect diet. Additionally, we found that rarely burned habitats were preferred. Overall, the effect of landscape variables on the choice of actual nest sites appeared to be rather small. We used different classification methods to predict the probability of occurrence, of which the Random forest method showed the highest accuracy. The areas determined as suitable habitat showed a high concordance with the actual nest locations. We conclude that Amur Falcons prefer to occupy newly built (domed) nests to ensure high nest quality, as well as nests surrounded by available feeding habitats.     

The Importance of Where to Dump the Refuse: Seed Banks and Fine Roots in Nests of the Leaf‐Cutting Ants Atta cephalotes and A. colombica1

The location of the nutrient‐rich organic refuse produced by a leaf‐cutting ant colony varies among ant species. Atta cephalotes locate their organic refuse in subterranean chambers, whereas A. colombica place their organic refuse on the soil surface near the nest. We studied the effect of the absence or presence of external organic refuse on the abundance of fine roots and seed bank composition in the superficial horizons of ant nests. We sampled soils from ant nests or dumps and adjacent areas of 15 adult nests of A. cephalotes at La Selva (LS), Costa Rica, and of 15 of A. colombica nests on Barro Colorado Island (BCI), Panama. Soils from A. cephalotes nests did not differ from adjacent soils in abundance of fine‐root and seed diversity. In contrast, organic refuse from A. colombica nests was less diverse in seed composition (due to the great abundance of Miconia argentea) and had a greater abundance of fine roots than adjacent areas. Thus the external location of the ant‐nest organic refuse is potentially important in determining the different types of plant recolonization in abandoned or dead ant nests. The relative abundance of these Atta species may influence the structure and/or composition of tropical forests.     

Influence of nests of leaf‐cutting ants on plant species diversity in road verges of northern Patagonia

Abstract. It has been suggested that ant nests are the most frequent small‐scale disturbance that affect vegetation patterns. However, their effects on plant diversity are little studied. We document effects of nests of the leaf‐cutting ant Acromyrmex lobicornis on physical‐chemical soil properties and their influence on plant diversity near road verges in a desert steppe in NW Patagonia, Argentina. We analysed nest soils and controls for nitrogen, phosphorus, organic matter, moisture retention capacity and texture. We also analysed the vegetation on 42 nests (30 active and 12 abandoned or without life) and 42 areas without nests. Soil around nests had a greater nutrient content and capacity to retain moisture than control soils, which is mainly due to the presence of organic waste that the ants deposit on the soil surface. We found no association between the occurrence of nests and specific groups of plants, but plant diversity was higher at nest‐sites than at nearby non‐nest sites. This increased diversity – which is also found on abandoned nests – is mainly due to the occurrence of a larger number of native and exotic plant species on nest‐sites that are uncommon elsewhere in the study area. The most abundant plant species showed similar cover values at nest and non‐nest sites. This suggests that changes in diversity are associated to edaphic changes caused by nests rather than by changes in competitive balance caused by dominant species exclusion. We propose that the nests of Acromyrmex lobicornis, through increasing the availability of resources, generate favourable microsites that can function both as ‘refuges’ for less frequent native species, and as‘stepping stones’ for less frequent exotic plant species.     

Long-term impact of agriculture on the survival of wood ants of the <Emphasis Type="Italic">Formica rufa</Emphasis> group (<Emphasis Type="Italic">Formicidae</Emphasis>)

The impact of agriculture on wood ants of the Formica rufa group was investigated in a small-scale agricultural landscape with many woodland fragments in the east of the Netherlands. An inventory of nests was carried out in 1986, and repeated in 2014. The number of nests of F. rufa and F. polyctena had drastically decreased during the intervening 28 years, especially in small patches of woodland bordering a maize field. The species F. rufa, which mainly disperses by flight of the queen, seems to be better adapted to habitat fragmentation than F. polyctena, where dispersal is mainly by colony splitting. However, the flying strategy can only be successful in a landscape where most woodland fragments have a good quality habitat; in the study area, the habitat quality had deteriorated. This is ascribed to the development of a tall, nitrophilous vegetation, a result of considerable nitrogen deposition from the atmosphere and the spraying of manure. The regional survival of wood ants in the east of the Netherlands is at risk in the agricultural landscapes we studied. This is due to the increasing probability of colonies becoming extinct and the decreased probability of a queen colonizing habitat patches. However, the negative influence of agriculture on the edge vegetation of patches of woodland can be decreased by leaving a wide strip between the arable land and the woodland that receives no manure.     

Impact of Atta colombica Colonies on Understory Vegetation and Light Availability in a Neotropical Forest1

We quantified patterns of vegetation removal and light availability above Atta colombica nests on Barro Colorado Island, Panama. Ants cleared vegetation less than 1 cm in diameter from an area of 77 m², and up to 3 m above ground level. Overall light availability 1.5 m above ground level was 49 percent greater at ant nest sites than at sites in undisturbed understory. These higher light levels fell within the range known to enhance growth of both shade tolerant and pioneer species.