Seasonal succession of a microphagotroph community in a small pond during litter decomposition

Temporal dynamics of a lentic microphagotroph community were studied during leaf litter decomposition from December to May. Small plastic vessels containing leaf litter were placed on a pond bottom. They were sampled periodically to collect microphagotrophs. Three abiotic factors and abundance of two food items were also measured to analyze the autogenic and allogenic phenomena during a microphagotroph succession. Three behavior types were recognized in dominant taxa: a free-swimming type, a vagile (creeps on substratum, sometimes swims) type, and a voluntarily fixed type. Dominant taxa changed from the free-swimming to the vagile type up to mid-March, and the reverse change occurred from mid-April. Principal component analysis (PCA) indicated four factors affecting the dynamics of the community: water temperature as a seasonal factor, detritus volume on the litter surface as a habitat factor, and densities of bacteria and small flagellates as food factors. Taxa replacement appeared to occur through two mechanisms. (1) Dominance of small holotrichs, a free-swimming type, was brought about by a high bacterial density caused by seasonal events, i.e., leaf fall in December and detritus formation by litter feeders in mid-April. This is an allogenic aspect of community dynamics. (2) The free-swimming type was replaced by the vagile one during the period with high taxa diversity. This replacement occurred through intertaxa competition for scarce food and/or selective predation by larger microphagotrophs. It is an autogenic process within the community.     

Leaf litter processing and energy flow through macroinvertebrates in a woodland pond (Switzerland)

Energy generated by leaf litter processing and its flow through the associated macroinvertebrate community was quantified in a pond near Geneva (Switzerland). Annual density, biomass, and production on oak (Quercus robur) leaf litter were assessed for all macroinvertebrate taxa with emphasis on predators. Empirical energetic relations provided an energy budget for the macroinvertebrate community. On 1 m² of pond bottom, the processing of 5641 kJ of oak leaf litter resulted in 8.5% of leachate (6 days), and after 1 year 32% of material remained; the other 59.5% was biologically (animal or microbial) converted, including 11.2% processed by shredders. The mean annual density of associated macroinvertebrates was 51374 individuals, mean biomass was 3.53 g (dry mass) and production was about 1451 kJ (or 65 g). Predator production was 170 kJ/m², non-chironomid primary consumer production was 101 kJ/m² (including 57 kJ from shredders) and chironomid primary consumer production was estimated at 1180 kJ/m². Predators contributed to a high proportion of total biomass (39%) but to a smaller amount of production (12%) or density (6%). In this two-stepped food-chain mainly based on detritus, the transfer coefficient between first level (detritus + primary producers) and third level (secondary consumers) was high (2–2.5%) and indicated efficient conversion of energy. This high efficiency was partly related to the reutilization of fine particulate organic matter by the collectors. The production estimate measured on leaf litter was compared with two other predominant substrates (Typha latifolia stems and Chara sp.), and exhibited the highest value. This study shows how leaf litter can constitute a direct source for high secondary production and be an efficient energy source in freshwater ecosystems. It is also demonstrated that a woodland pond can support a high macroinvertebrate production as compared with other freshwater ecosystems.     

The Quantitative Importance of the Benthic Microfauna of an Arctic Tundra Pond

The microfauna (protozoa and micrometazoa) and bacteria and microalgae of the sediment of an arctic tundrapond at Barrow, Alaska were quantified through the summer. Very small protozoans (i.e. zooflagellates) and burrowing micrometazoans were found to be the most important components of the microfauna, whereas ciliates play a smaller role. This composition of microfauna is attributed to the mechanical property of the detrital sediment.Through a combination of laboratory experiments and field observations the grazing rates of protozoa for bacteria and microalgae in the field were estimated; protozoa were found to be important as bacterial grazers, but they consume only a modest fraction of the microalgae. An estimate of the grazing activity of the micrometazoans, based on indirect considerations, is also offered. It is of the same magnitude as that of protozoans but microalgae play a relatively larger role for the former. Based on previous studies on the pond it is estimated that microfaunal grazing constitutes about 30% of that of the detritus feeding macrofauna and that all categories of grazers together do not consume the total microbial production. The reasons for this results and the fate of this surplus production of algae and bacteria are discussed.     

Microspatial heterogeneity in the distribution of ciliates in a small pond

Five transects of contiguous samples from the surface of a small pond and one transect from its bottom were collected in order to quantify microspatial heterogeneity in the distribution of ciliated protozoa. Examination of the frequency-abundance relations for these transects suggests that they can be approximated by negative binomial distributions with a commonk of 1.87. Contagiousness or crowding increases with population density.Mean patch size and mean interpatch distance were measured for 4 transects as 1.5 to 2 cm and 3 to 4 cm, respectively. This heterogeneity is suggested to arise from behavioral aggregation about discrete food sources and be very ephemeral.Blocking of adjacent contiguous samples was used to investigate the effect of sample size on the apparent correlation between the numbers of pairs of taxa. In all cases examined, taxa were relatively independent in their distribution at small sample sizes and became more negatively or positively associated as samples were combined. This may reflect that the small scale patches are essentially monospecific.     

Riparian leaf litter decomposition on pond bottom after a retention on floating vegetation

Allochthonous (e.g., riparian) plant litter is among the organic matter resources that are important for wetland ecosystems. A compact canopy of free‐floating vegetation on the water surface may allow for riparian litter to remain on it for a period of time before sinking to the bottom. Thus, we hypothesized that canopy of free‐floating vegetation may slow decomposition processes in wetlands. To test the hypothesis that the retention of riparian leaf litter on the free‐floating vegetation in wetlands affects their subsequent decomposition on the bottom of wetlands, a 50‐day in situ decomposition experiment was performed in a wetland pond in subtropical China, in which litter bags of single species with fine (0.5 mm) or coarse (2.0 mm) mesh sizes were placed on free‐floating vegetation (dominated by Eichhornia crassipes, Lemna minor, and Salvinia molesta) for 25 days and then moved to the pond bottom for another 25 days or remained on the pond bottom for 50 days. The leaf litter was collected from three riparian species, that is, Cinnamomum camphora, Diospyros kaki, and Phyllostachys propinqua. The retention of riparian leaf litter on free‐floating vegetation had significant negative effect on the carbon loss, marginal negative effects on the mass loss, and no effect on the nitrogen loss from leaf litter, partially supporting the hypothesis. Similarly, the mass and carbon losses from leaf litter decomposing on the pond bottom for the first 25 days of the experiment were greater than those from the litter decomposing on free‐floating vegetation. Our results highlight that in wetlands, free‐floating vegetation could play a vital role in litter decomposition, which is linked to the regulation of nutrient cycling in ecosystems.     

Leaf litter species identity alters the structure of pond communities

The input of leaf litter resources is a major driver of ecosystem processes in terrestrial and freshwater habitats. Although variation exists in the quantity and composition of litter inputs due to natural and anthropogenic causes, few studies have examined how such variation influences the structure and composition of aquatic food webs. Using outdoor mesocosms, we examined the bottom–up effects of 10 chemically distinct tree litter species on microbial, algal, invertebrate and vertebrate fauna found in temperate ponds. We hypothesized that individual litter species, which differ in their traits, would differentially and predictably affect abiotic and biotic elements of pond communities. We further hypothesized that the presence of leaf litter, regardless of species, would elevate resource supply and increase the biomass of community members. Finally, we hypothesized that a mixture of litter species would have non‐additive effects on community responses. We followed the system for > 4 months and measured > 30 abiotic and biotic responses related to primary and secondary production. The different species of leaf litter had major effects on abiotic and biotic responses, including phytoplankton, periphyton, zooplankton, snails, amphipods and tadpoles. Most biological responses were negatively associated with soluble carbon content of litter, or litter decay rate. Other litter traits, including phenolic concentrations and litter C:N were of secondary importance but did exhibit both positive and negative associations with several responses. The absence of litter had pervasive effects on abiotic attributes, but did not promote substantial changes in organism biomass. Most responses to the litter mixture were additive. Our results suggest that changes in temperate forest composition can strongly affect pond communities.     

青冈林土壤动物群落结构在落叶分解过程中的演替变化

１９９３年５月－１９９５年４月,采用落叶袋法研究了中亚热带青冈（Ｃｙｃｌｏｂａｌａｎｏｐｓｉｓｇｌａｕｃａ）林土壤动物在落叶分离过程中的演替,变化,用多样性指数,演替指数,相似系数分析土壤动物群落结构的季节变化和在落叶分解过程中的演替,分解出现的类群,密度最高的为蜱螨目（Ａｃａｒｉｎａ）其次为弹尾目（Ｃｏｌｌｅｍｂｏｌａ）,二者个体数之和占总数的９２．７％,其他依次为：双翅目（Ｄｉｐｔｅｒａ）膜翅     

Complex responses to invasive grass litter by ground arthropods in a Mediterranean scrub ecosystem

Plant invasions have tremendous potential to alter food webs by changing basal resources. Recent studies document how plant invasions may contribute to increased arthropod abundances in detritus-based food webs. An obvious mechanism for this phenomenon—a bottom-up effect resulting from elevated levels of detritus from the invasive plant litter—has not been explicitly studied. We examined the effects of an annual grass invasion on ground arthropod assemblages in the coastal sage scrub (CSS) of southern California. Bottom-up food web theory predicts that the addition of detritus would increase generalist-feeding arthropods at all trophic levels; accordingly, we expected increases in fungi, Collembola, and common predators such as mites and spiders. For the common ant taxa, habitat alteration may also be important for predicting responses. Thus we expected that Forelius mccooki and Pheidole vistana, the most common ant species, would decline because of changes in soil temperature (F. mccooki) and habitat structure (P. vistana) associated with litter. We studied trends observationally and conducted a 3-year experiment in which we manipulated litter quantity. In contrast to other published studies, most detritus-based arthropod taxa declined in areas of high grass invasion, and, within trophic levels, responses often varied idiosyncratically. For the two most common taxa, a native ant (F. mccooki), and predatory mites in the Anystidae, we experimentally linked declines in abundance to increased levels of invasive grass litter. Such declines, especially those exhibited by the most common ant taxa, could have cascading effects on the CSS ecosystem, where ants are numerically dominant and thus may have broad influences on food web and ecosystem properties. Our results highlight that accurately predicting arthropod responses to invasive plant litter requires careful consideration of the structural and food resources provided by detritus to each particular food web.     

Leaf litter input mediates tadpole performance across forest canopy treatments

Understanding the mechanisms limiting the distributions of organisms is necessary for predicting changes in community composition along habitat gradients. In many areas of the USA, land originally cleared for agriculture has been undergoing a process of reforestation, creating a gradient of canopy cover. For small temporary wetlands, this gradient can alter abiotic conditions and influence the resource base of wetland food webs by affecting litter inputs. As distributions of amphibians and many other temporary wetland taxa correlate with canopy cover, we experimentally manipulated shade levels and litter types in pond mesocosms to explore mechanisms limiting species performance in wetlands with canopy cover. Most differences between ponds were mediated by litter type rather than direct effects of shading. Although all three amphibian species tested are open-canopy specialists, spring peepers were the only species to show decreased survival in shaded ponds. Pond litter type generally had strong effects on growth and development rates, with tadpoles of two species in grass litter ponds growing to twice the size of, and metamorphosing 7 days earlier than, those in leaf litter ponds. Contrary to our initial hypothesis, shade level and litter type showed very few significant interactions. Our results indicate that the effects of shading cannot be considered in isolation of vegetation changes in pond basins when evaluating the effects of forest succession on temporary pond communities.     

Habitat background selection by colonizing intermittent pond invertebrates

Habitat selection processes by organisms colonizing freshwater bodies have not been commonly studied, despite their obvious relevance to wetland ecology and management. We monitored, weekly, all organisms that appeared in tanks with different backgrounds (brown; white) and substrate/food availability treatments (control; added leaf litter; added algae) floating on the water surface of a natural intermittent pond. The experiment lasted for 14 weeks, from pond filling to pond drying, during which time we collected around 9,000 colonizing insects per m² (e.g., Diptera, Coleoptera, Hemiptera, and eggs) and a similar number of colonizing non-insects (e.g., Acari, Crustacea, Gastropoda, and ephippia). Non-insects exhibited greatest colonization early in the hydroperiod, correlated with major rain-fall events. Insect colonization was low at first, peaked in late May, and thereafter remained high until the pond dried. Most ovipositing female insects (especially chironomids) were attracted to tanks with a dark background or those containing decomposing dark leaves, although there were exceptions related to taxon (e.g., beetles) and hydroperiod. Non-insects showed treatment preferences similar to the insects, with cladoceran ephippia appearing more in the Leaf treatment. Colonization mechanisms were deemed ‘active’ for insects and largely ‘passive’ for the microcrustaceans, and the various possibilities for the latter (heavy rainfall, wind, wildlife) are discussed. For highly dispersive taxa, such as adults of the beetles Helophorus sp. and Anacaena sp. colonization densities at the pond surface were calculated to attain maxima of around 26 and 33 m⁻² respectively, in early May. Handling editor: S. Declerck     

Processing of leaf litter in two northern jarrah forest streams,Western Australia: II. The role of macroinvertebrates and the influence of soluble polyphenols and inorganic sediment

The long-term processing of jarrah (Eucalyptus marginata) leaves was examined in a small forest stream to determine the role played by macroinvertebrates and the influence of soluble polyphenols in the leaves. The widely used exponential model of litter processing was inadequate in describing the fate of jarrah leaves. Decomposition occurred in three distinct phases and was best described by a quadratic model. After a substantial and rapid loss due to leaching, processing was virtually inhibited during summer and autumn, with no associated increase in the organic nitrogen content. Macroinvertebrates played a significant role in the latter part of the year, processing approximately 25% of the initial leaf mass.High levels of soluble polyphenols in the leaves had an inhibitory effect on the microbial colonization of jarrah leaves, as indicated by the organic nitrogen content. However, pre-leaching of these compounds had no effect on the rate of decomposition nor on the leaf bag fauna. Polyphenols released into the stream during summer, when flows are low, may reach high concentrations and contribute to the slow processing at this time. Leaf litter processing in a nearby sedimented stream was compared with that in the undisturbed stream. Sediment disrupted litter processing, virtually eliminating the contribution made by invertebrates. Smothered leaf bags became anoxic, restricting microbial activity and reducing leaf quality. The low processing rate of leaves in the sedimented stream was attributed to differences in the leaf bag fauna. Leaf bags in the sedimented stream had more animals but shredders were poorly represented and predators were the most abundant feeding group. The low density of shredders was more likely to be a result of the reduced availability of detritus rather than selective predation. Whatever the reason, invertebrates in the sedimented stream were denied access to an important source of energy. Inorganic sediment can have a profound effect on stream function by interfering with the shredder-CPOM pathway.     

Reproductive characteristics of free-livingCalomys venustus (Rodentia, Muridae)

Calomys venustus showed a cyclic seasonal pattern of reproductive activity characterized by a period of repose and a variable length of the period of sexual activity between August—September to May—June. The study was done from 1983 to 1999. During this time the population density increased from October—November to the end of autumn and sharply decreased in winter. Three peaks in rate of pregnancy were recognized in the breeding period: spring, summer and late summer. The average litter size was different among the three peaks in rate of pregnancy. The reproductive pattern had a peak at the beginning of the spring produced by overwintering animals, and another peak in summer-autumn caused by the reproductive activity of young born in the same period in which they breed. The spring cohort exhibited the greatest breeding contribution suggesting that this cohort is principally responsible for the yearly peak in abundance.     

Studies on the bottom fauna in a tropical freshwater fish pond

Summary Quantitative samples of the bottom fauna obtained from a tropical freshwater fish pond during a period of two years were studied with regard to species composition, zonal variation and seasonal fluctuation. Two different zones with differences in faunal composition could be distinguished. The littoral zone was dominated by Mollusca, whereas Oligochaetes were predominant in the profundal zone. Most of the organisms showed their peaks in the months January to April. Breeding activities ofVivipara bengalensis, Digoniostoma cerameopoma, Melanoides granifera andPisidium clarkeanum as evidenced by presence of younger length groups in the populations were also observed during the same period (January to April). The influence of environmental factors as temperature, alkalinity and food were discussed as probable causes for the peaks in abundance. The average number of total organisms per square metre was found to be comparatively high indicating a high standing crop. Differences observed in the total number of organisms present have been attributed to inflow of water resulting in sudden alteration of the nutrient condition of the bottom mud. The seasonal variations of the standing crop of bottom fauna during both the years have been found to be influenced by fluctuations of the bivalve mollusc,Lamellidens corrianus. The availability of sufficient amount of benthic fauna for consumption by bottom feeding fishes has been indicated.This work formed part of a thesis submitted for the Degree of Doctor of Philosophy to the University of Calcutta, India in 1964.     

Protozoan grazing of bacteria in soil—impact and importance

Interactions between bacteria and protozoa in soil were studied over 2-week periods in the field and in a pot experiment. Under natural conditions the total biological activity was temporarily synchronized by a large rainfall, and in the laboratory by the addition of water to dried-out soil, with or without plants. In the field, peaks in numbers and biomass of bacteria appeared after the rain, and a peak of naked amoebae quickly followed. Of the three investigated groups—flagellates, ciliates, and amoebae—only populations of the latter were large enough and fluctuated in a way that indicated a role as bacterial regulators. The bacterial increase was transient, and the amoebae alone were calculated to be able to cause 60% of the bacterial decrease. The same development of bacteria and protozoa was observed in the pot experiment: in the presence of roots, amoebic numbers increased 20 times and became 5 times higher than in the unplanted soil. In the planted pots, the amoebic increase was large enough to cause the whole bacterial decrease observed; but in the unplanted soil, consumption by the amoebae caused only one-third of the bacterial decrease.     

Rainforest litter invertebrates decimated by high severity burns during Australia's gigafires

Climate change is increasing the frequency of extreme fires. In 2019–2020, extreme fires burned 97 000 km² of native vegetation in south-eastern Australia, affecting many areas of rainforest, which has historically burned less frequently. One year post-fires, we surveyed litter macroinvertebrates in 52 temperate rainforest sites. Sites had experienced increasing levels of fire severity (unburnt, medium severity and high severity). We asked how fire severity affected: (1) litter macroinvertebrate habitats; (2) the abundance of litter macroinvertebrate taxa per unit area; and (3) abundance relative to litter habitat (volumetric density). We also estimated the loss of litter macroinvertebrates across rainforests in the study region. High severity burns supported only a fifth of the litter volume and canopy cover as unburnt sites, lower soil moisture and higher herb cover. Medium burns were intermediate. Macroinvertebrate abundance declined with burn severity: high severity burns supported only 26% of the abundance in unburnt sites; medium severity burns supported 80% of that in unburnt sites. Patterns were similar for all taxa, with millipedes declining most. High severity fires resulted in up to 1.90 million fewer macroinvertebrates per hectare; 0.53 million fewer per hectare of medium burn rainforest. Across the study region, we estimate that 60 billion fewer litter macroinvertebrates persisted in temperate rainforests alone. Volumetric densities of many litter macroinvertebrate taxa in high severity burns were marginally higher than in unburnt sites, suggesting nutrients may be more available post-fire, or that persisting individuals become concentrated in the leaf litter. For less desiccation-tolerant groups (e.g., amphipods), density declines with increasing severity may reflect the combined impact of low soil moisture and reduced litter cover. Many taxa persisted following high severity fires, but declines were substantial, and taxa differed in their vulnerability. Longer-term monitoring is required to understand the recovery trajectory and impacts on ecological function.     

Benthic-pelagic trophic interactions within the fish assemblage in the western Bering Sea shelf area according to stomach content analysis and ratios of C and N stable isotopes

The composition, abundance, diet and trophic status of zooplankton, bottom invertebrates, fish and nekton were analyzed based on the data collected by the staff of the TINRO-Center during complex bottom trawl catches on the Bering Sea shelf in the fall of 2004. The stomach contents of mass fish species were analyzed and the nitrogen and carbon isotopic composition of 36 mass species of plankton, benthos, nekton and nektobenthos, which together make up the basis of pelagic and bottom communities, was determined. It was found that zooplankton noticeably differ from benthic invertebrates in carbon isotopic composition: δ¹³C values in zooplankton varied from −20.3‰ to −17.9‰; in benthos—from −17.5‰to −13.0‰; and in fish—from −19.2‰ (juvenile walleye pollock) to −15.3‰ (saffron cod). The levels of ¹³C isotope in the tissues of fish depended mostly on the share of pelagic or benthic animals in their diet. δ¹⁵N values in the studied species ranged from 8.6‰ (in sea urchins) to 17.2‰ (in large Pacific cods), which corresponds to a trophic level of 2.8. Obviously the δ¹⁵N values reflect the degree of predation and generally show the ratio of primary, secondary and tertiary consumers in a fish’s diet. Trophic interactions manifest a high degree of interdependence between benthic and pelagic communities (even without taking into account such lower components of the food web as phytoplankton, bacteria, and protozoa) occurring in most nektonic species that depend on both bottom and pelagic food.     

Fine‐scale five‐year vegetation change in boreal bog vegetation

Abstract. Within an ombrogenous part of N. Kisselbergmosen, Rødenes, SE Norway, fine‐scale changes in species abundance, successional trends relative to the main gradients (as represented by DCA axes), and co‐ordinated change within pairs of the bottom layer species are studied. Data sets were sampled twice with a five‐year interval, and included species abundance and cover of mud bottom, naked peat and litter in 436 sample plots (16 cm× 16 cm), and species abundance in 6976 subplots (4 cm× 4 cm). Depth from the surface of subplots to the water table was estimated in 1991. Most summers and growing seasons were somewhat drier than normal in the 5‐yr period. The area covered by mud‐bottom, naked peat and litter increased significantly, as did the frequencies of the dwarf shrubs Calluna vulgaris and Andromeda polifolia in hummocks and upper lawn. Sample plots were significantly displaced downward the peat productivity gradient (DCA 2), reflecting the reduced cover of many bottom layer species, including all Sphagnum spp. Significant coordinated changes in cover of bottom layer species are described. The changes observed in hummocks support the existence of a local regeneration cycle, as suggested by other researchers. Some of the vegetation changes seem parallel to those reported from areas with a higher nitrogen deposition, but it is not likely that nitrogen deposition alone is the major cause of the observed changes. Between‐year variation in population size and climatic fluctuations may as well explain the observed changes.     

Vertical Micro‐Zonation of Testate Amoebae and Ciliates in Peatland Waters in Relation to Potential Food Resources and Grazing Pressure

The aim of this study was to examine the community structure and vertical micro‐distribution of testate amoebae and ciliates in a raised bog in eastern Poland, as well as to assess the influence of potential food resources (Chl‐a, bacteria, heterotrophic flagellates) and predators (rotifers and copepods) on protozoa communities. Samples were taken from surface, bottom and interstitial waters. At each type of micro‐habitat and each sampling date water was sampled using a plexiglass corer or mini‐piezometers. Additionally, in order to evaluate grazing pressure, field enclosures were used in which metazoan abundance and composition was manipulated by size‐fractionation. Over experiments, metazoan populations shifted from dominance of rotifers to copepods. In the first experiment, with rotifers dominating, metazoa had only a modest predatory impact on the protozoa. In contrast, the second experiment, with copepods prevailing, demonstrated a clear top‐down control of the protozoa communities by metazoan. The density and biomass of protozoa significantly differed between the studied stations, with the lowest numbers in the interstitial water and the highest in the surface water. Surface sampling were dominated by mixotrophic taxa, whereas the deepest sampling level was characterized by increase in the proportion of bacterivore species. These differences between micro‐habitats may be due to differences in environmental conditions (food resources and grazing pressure). Ordination analysis revealed that bacteria can strongly regulate the abundance and taxonomic composition of protozoa in the bottom and interstitial waters. Metazoan predators could be the main regulators of protozoa communities in surface water. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The influence of dispersal on the realized trajectory of a pond metacommunity

Dispersal rates play a critical role in metacommunity dynamics, yet few studies have attempted to characterize dispersal rates for the majority of species in any natural community. Here we evaluate the relationship between the abundances of 179 plankton taxa in a pond metacommunity and their dispersal rates. We find the expected positive relationship between the regional abundances of phytoplankton, protozoa and metazoan zooplankton, which is suggestive of dispersal being a density‐independent per capita rate for these groups. When we tested to see if the rates of dispersing taxa predicted changes in community composition, we found that dispersers had no measurable impact on the short‐term trajectory of local pond communities or mesocosm communities established experimentally (assembled communities), but became increasingly represented in the overall pond metacommunity during the course of the full growing season. In comparison, the composition of experimental mesocosms that lacked any initial zooplankton community (unassembled communities) were found to be driven by dispersal measured at the local pond community but not by dispersal observed across the overall metacommunity. These results suggest that the role of dispersal may shift from a contributor to local, ecological dynamics to that of metacommunity‐wide, colonization–extinction dynamics as communities assemble.     

Ants on the Move: Resource Limitation of a Litter‐nesting Ant Community in Costa Rica1

The leaf litter of tropical wet forests is replete with itinerant ant nests. Nest movement may help ants evade the constraints of stress and disturbance and increase access to resources. I studied how nest relocation and environmental factors may explain the density, size, and growth of leaf litter ant nests. I decoupled the relationships among litter depth, food abundance, and nest availability in a 4‐mo manipulation of food and leaf litter in a community of litter‐nesting ants in a lowland wet forest in Costa Rica. Over 4 mo, 290 1 m² treatment and control plots were sampled without replacement. Nest densities doubled in response to food supplementation, but did not decrease in response to litter removal or stress (from litter trampling). The supplementation of food increased the utilization of less favored nesting materials. In response to food supplementation and litter trampling, arboreal ants established nests in the litter, and growth rates of the most common ants (Pheidole spp.) increased. Colony growth was independent of colony size and growth rates of the most abundant ants. In general, I conclude that litter‐nesting ant density is driven primarily by food limitation, that nest relocation behavior significantly affects access to resource and the demographic structure of this community, and that nest fission may be a method to break the growth–reproduction trade‐off.