Stand structure and woody species diversity in relation to stand stratification in a subtropical evergreen broadleaf forest, Okinawa Island

Stand structure and woody species diversity in a subtropical evergreen broadleaf forest grown in a silicate habitat, Okinawa Island, have been investigated on the basis of stand stratification. The forest stand consisted of four layers. The floristic composition of the top and the lower three layers was only slightly similar, although approximately one-third of the species were common to them. Mean tree weight decreased from the top toward the bottom layer whereas tree density increased from the top downward. This trend resembled the mean weight–density trajectory of self-thinning plant populations. The relationship between mean tree height and tree density for the upper two layers supported Yamakuras quasi –1/2 power law of tree height. The values of the Shannon–Wiener index, H, and the equitability index, J, tended to increase from the top layer downward except for the bottom layer. The values of H and J were, respectively, 4.83 bit and 0.82 for trees taller than 0.10 m. The lower layers contained many species of smaller height. High species diversity of the forest depended on small trees in the lower layers. Conservation of small trees in the lower layers, especially the bottom layer, is indispensable for sound maintenance of Okinawan evergreen broadleaf forests.     

鼎湖山南亚热带常绿阔叶林不同成熟度群落特征的比较

研究不同成熟度群落物种的共存状态,了解群落演替过程中结构的动态变化,对揭示森林不同发育时期的群落构建机制具有重要意义。本研究基于鼎湖山南亚热带常绿阔叶林20 ha固定监测样地(以下简称鼎湖山大样地)2010年植被调查的数据,根据径级与林龄将鼎湖山大样地划分为成熟林和过熟林两个斑块,对其群落物种组成、区系特征及径级结构进行了初步的比较。研究发现:(1)成熟林和过熟林种类组成的群落相似性系数高、物种多样性指数相近,以及锥栗(Castanopsis chinensis)重要值相似,但物种数、密度、总胸高断面积、物种重要值等有所不同;(2)热带区系成分在两个斑块均占优势,但以过熟林的比例较高;(3)两个斑块虽然所有活立木径级结构分布均呈倒"J"型,但在同径级个体群重要值比较中,成熟林中径级个体群重要值较高,而过熟林则是大径级个体群重要值较高。由此可见,鼎湖山大样地的成熟林与过熟林虽属于同一类群落的演替顶极阶段,但群落结构上却存在差异,推测在林窗作用下不同发育时期的群落存在不同的构建过程。     

Density dependence is not very prevalent in a heterogeneous subtropical forest

There is a growing body of evidence demonstrating that tree survival is influenced by negative density‐dependence, but it is still controversial how the effect may vary with life‐stage, and to what extent it plays a role in regulating tree survival in heterogeneous subtropical forests. In this study, we investigated density‐dependent effects on tree survival of six tree species in a 5‐ha subtropical forest in eastern China. The roughly 45 000 individuals in the forest were fully censused in 2003 and 2008. For each of these species, we used an inhomogeneous pair‐correlation function to quantify the change in spatial distribution for different size classes, and a case‐control design to study seedling–adult associations in 2003. Autologistic regression was used to determine the influence of neighborhood factors on individual survival from 2003 to 2008. We found that seedlings of five species were repulsed by distance to nearest conspecific adults in terms of their survival, consistent with predictions of the Janzen–Connell mechanism. By contrast, only the least shade‐tolerant Schima superba had a negative relationship with individual survival and conspecific distance‐weighted basal area. This suggests that the Janzen–Connell effect is only prevalent at the early seedling stage or seed‐to‐seedling phase. The strength of clustering significantly declined at sapling–pole and pole–adult transitions for Sycopsis sinensis and at seedling–sapling transition for Cleyera pachyphylla. Correlations between individual survival and conspecific abundance for these species were consistent with trends in the strength of clustering. These results suggest that density dependence plays a limited role in individual survival and species spatial structure beyond the early seedling stage (i.e. after true leaves growing) in this forest. In addition, this study indicates that including individuals from early life‐stages and factoring out potential confounding factors such as habitat preference are important in studies that seek evidence for density dependence in forest trees.     

Understorey versus canopy: patterns of vertical stratification and diversity among Lepidoptera in a Bornean rain forest

We studied the vertical distribution of Lepidoptera from a canopy walkway within a dipterocarp rain forest at Kinabalu Park (Borneo) using three different methods: (1) Bait traps to survey fruit-feeding nymphalid butterflies, (2) standardized counts for predominantly flower-visiting butterflies and their potential predators, aerial-hawking birds, and (3) attraction by blacklight for hawk- and tiger moths. There was a distinct decrease in the abundance of fruit-feeding nymphalids towards the canopy, probably due to a reduced and less predictable availability of rotting fruits in higher strata. These constraints might also be responsible for a higher abundance variation in the canopy, and a significant shift in size from larger species in the understorey to smaller ones in the canopy. Changes of microclimate and the conspicuous increase of insectivorous aerial-hawking birds from ground to canopy layer may be responsible for the prominent change in species composition of fruit-feeding nymphalids between 20 and 30 m. Nectar-feeding Lepidoptera showed a reversed abundance pattern. One main factor contributing to the much higher abundance of flower-visiting butterflies and moth taxa in the canopy, such as Sphingidae and some Arctiinae, might be the increase of nectar resources available in upper vegetation layers. A distinctly higher diversity in hawkmoths was also found in the canopy. A higher abundance of insectivorous aerial-hawking birds in the canopy might contribute to the shift in body design of fruit-feeding nymphalids from more slender bodies at lower vegetation layers to stouter ones (i.e. species which are stronger on the wing) in the canopy. Larval resources could play an additional role in specialisation on but a small part of the vertical gradient. This may explain stratification pattern of the nymphalid subfamilies Morphinae and Satyrinae. Monocotyledoneous larval food plants of both taxa, whose flight activity is largely restricted to the understorey, occur mostly in lower vegetation layers. Our observations on a wide taxonomic and ecological range of butterflies and moths indicate that tropical forest canopies hold a distinct and unique Lepidoptera fauna, whose species richness and abundance patterns differ from lower strata. However, the notion of tropical forest canopies as peaks of terrestrial diversity does not hold uniformly for all taxa or guilds.     

EcM fungal community structure, but not diversity, altered in a Pb-contaminated shooting range in a boreal coniferous forest site in Southern Finland

Boreal forests contain diverse fungal communities that form essential ectomycorrhizal symbioses with trees. To determine the effects of lead (Pb) contamination on ectomycorrhizal fungal communities associated with the dominant pine (Pinus sylvestris L.), we surveyed sporocarps for 3 years, analyzed morphotyped ectomycorrhizal root tips by direct sequencing, and 454-sequenced fungal communities that grew into in-growth bags during a 2-year incubation at a shooting range where sectors vary in the Pb load. We recorded a total of 32 ectomycorrhizal fungi that formed conspicuous sporocarps, 27 ectomycorrhizal fungal phylotypes from 294 root tips, and 116 ectomycorrhizal fungal operation taxonomic unit (OTUs) from a total of 8194 internal transcribed spacer-2 454 sequences. Our ordination analyses by nonparametric multidimensional scaling (NMS) indicated that the Pb enrichment induced a shift in the ectomycorrhizal community composition. This was visible as indicative trends in the sporocarp and root tip data sets, but was explicitly clear in the communities observed in the in-growth bags. The compositional shift in the ectomycorrhizal community was mainly attributable to an increase in the frequencies of OTUs assigned to genus Thelephora and to a decrease in the OTUs assigned to Pseudotomentella, Suillus, and Tylospora in Pb-contaminated areas when compared with the control. While the compositional shifts are clear, their functional consequences for the dominant trees or soil ecosystem function remain undetermined.     

Genetic diversity affects productivity in early but not late stages of stand development

Recent declines in the genetic diversity of populations have stimulated research on the importance of genetic diversity for the functioning of natural communities. Current studies on this topic are based on the exploration of a limited number of clones and do not allow distinctions to be made between the effects of genetic identity and genetic diversity per se and to evaluate the effects of genetic diversity in genetically diverse communities. Also, most information comes from short-term studies, which are insufficient for evaluating the long-term effects relevant in relatively undisturbed communities of perennial species.We explored the importance of clone diversity vs. clone identity for stand productivity and the changes of the pattern over time. We used 18 clones of a perennial grass, Festuca rubra, to establish a set of communities composed of 1, 6 or 18 clones in two environments and studied the effects of genetic diversity on stand productivity over 3 years.Genetic diversity had a significant effect on stand productivity in the 1st year but not in the 2nd or 3rd year. In most cases, the observed yield was not significantly different from the total expected yield. The biomass of the mixtures never outperformed the biomass of the most productive clone, suggesting that clone identity is an important determinant of total biomass.The results indicate that the effects of genetic diversity on stand productivity may be transient and suggest that the conclusions of short-term studies on diversity effects should be evaluated carefully. They also suggest that individual clones are not complementary and that the properties of the stands are mainly additive results of the properties of the constituent clones.     

Spatial structure and diversity of woody plants and ectomycorrhizal fungus sporocarps in a natural subtropical forest

Spatial patterns of ectomycorrhizal fungi, ectomycorrhizal plants, and non-ectomycorrhizal plants were investigated in a natural subtropical forest using second-order analysis. The results of spatial pattern analysis showed that the degree of clumping of woody plants and ectomycorrhizal sporocarps were correlated. There was a significantly positive correlation of relative aggregation indices between ectomycorrhizal fungi and both non-ectomycorrhizal trees and ectomycorrhizal saplings. Correlations between percentage of ectomycorrhizal trees and sporocarp occurrence of ectomycorrhizal fungi and between diversities of woody plants and ectomycorrhizal fungi were distance-dependent or scale-related. A significantly high percentage of ectomycorrhizal trees was found only at relatively short distance from ectomycorrhizal fungal sporocarps, and significantly positive correlation of the diversity between woody plants and ectomycorrhizal fungi was found only at relative long distance, which implied that ectomycorrhizal sporocarps prefer ectomycorrhizal-tree-dominant micro-sites at near distances and at relatively large scales, diverse ectomycorrhizal sporocarps could be found in woodlands with high diversity of woody plants. Important factors affecting the spatial distribution, occurrence, and diversity of ectomycorrhizal fungi include spatial pattern of ectomycorrhizal plants and non-ectomycorrhizal plants, percentage of ectomycorrhizal plants, and plant diversity in a natural forest.     

Effect of forest fragment size on tree diversity and population structure of humid subtropical forest of Meghalaya,India

The present study was conducted in subtropical humid forests of Meghalaya to study the distributional pattern of species, floristic composition, community structure and tree population structure.Forest fragments of varying sizes(0.5 ha, 1 ha, 2 ha and 5 ha) were used in the study.All of the forest fragments are distributed within the same altitudinal range, and had similar rainfall and temperature regimes.Four forest fragments were sampled using random quadrats to analyze the impact of fragment size on tree...     

Arthropods in epiphytes: a diversity component that is not effectively sampled by canopy fogging

Insecticide fogging is often used to document arthropod species richnessin forest canopies, but this technique may not effectively sample invertebratesthat are concealed within a variety of microhabitats. We quantified the effectsof fogging on invertebrates in canopy epiphyte mats of a Costa Rican cloudforest by extracting arthropods from 18 paired pre- and post-fogging samples.Mean abundance and morphospecies richness of living arthropods were respectivelyreduced by 33 and 30% in epiphyte material after fogging, but most organismssurvived the treatment. Relative abundances of major taxa were unaffected byfogging. Herbivores were less abundant after fogging than other trophic groups,and the median body length of non-mite arthropods present in epiphytes wassignificantly smaller after fogging. Examination of seven post-fogging samplesshowed that many arthropods killed by insecticide remained trapped within theepiphyte material. These results provide the first quantitative assessment of aspecific component of arboreal arthropod biodiversity that is missed by thefogging technique.     

Species-specific traits predict genetic structure but not genetic diversity of three fragmented Afrotropical forest butterfly species

The Upper Guinean forests of Ghana, West Africa, are considered among the most threatened and fragmented in the world. Little is known about the genetic consequences of fragmentation on Ghana’s forest-associated species, but this genetic signature is generally expected to differ across species. We compared patterns of mtDNA cytochrome oxidase I (COI) variation of three Nymphalid forest butterfly species that differ with respect to their relative dispersibilities (Aterica galene: high habitat fidelity, low dispersal ability; Euphaedra medon: high habitat fidelity, strong dispersal ability; Gnophodes betsimena: relaxed habitat fidelity, low dispersal ability). Individuals were collected from two large forest reserves and five small sacred forest groves. Patterns of differentiation across species were broadly coincident with our predicted hierarchy of relative species dispersibility and suggested that genetic connectivity is most compromised by strict fidelity to forest habitat rather than by raw capacity for sustained flight. Connectivity was uncorrelated with geographic distance, but instead seemed best explained by urbanization and the sequential pattern of forest loss. Genetic diversity was dramatically different among species and not easily explained by either species-specific traits or effects of fragmentation. Aterica galene, the species most impacted by fragmentation, exhibited very high diversity, whereas G. betsimena, a broadly distributed, very common species, with relaxed habitat fidelity, was genetically depauperate. There was limited evidence of genetic erosion from the sacred groves despite these small forest patches accounting for less than 1–10 % of the total area of the forest reserves, which indicates these forest relics have high conservation value.     

Considerable MHC diversity suggests that the functional extinction of baiji is not related to population genetic collapse

To further extend our understanding of the mechanism causing the current nearly extinct status of the baiji (Lipotes vexillifer), one of the most critically endangered species in the world, genetic diversity at the major histocompatibility complex (MHC) class II DRB locus was investigated in the baiji. Nine highly divergent DRB alleles were identified in 17 samples, with an average of 28.4 (13.2%) nucleotide difference and 16.7 (23.5%) amino acid difference between alleles. The unexpectedly high levels of DRB allelic diversity in the baiji may partly be attributable to its evolutionary adaptations to the freshwater environment which is regarded to have a higher parasite diversity compared to the marine environment. In addition, balancing selection was found to be the main mechanisms in generating sequence diversity at baiji DRB gene. Considerable sequence variation at the adaptive MHC genes despite of significant loss of neutral genetic variation in baiji genome might suggest that intense selection has overpowered random genetic drift as the main evolutionary forces, which further suggested that the critically endangered or nearly extinct status of the baiji is not an outcome of genetic collapse.     

Density dependence is prevalent in a heterogeneous subtropical forest

Although negative conspecific density dependence among neighbours is widely studied, the general prevalence of the effects is still poorly understood due to a lack of studies from zonal forests other than the tropics. In addition, the detection of density dependence may be confounded by the influence of habitat heterogeneity. Here we examined the spatial distributions of 47 common tree species (diameter at breast height≥1  cm) using the pair-correlation function g(r) in a fully mapped 24-ha subtropical forest in China. We first investigated whether habitat heterogeneity influenced tree distributions, and then examined the conspecific tree patterns and density dependence after removing the effects of habitat heterogeneity. We found that the forest plot exhibited strong large-scale heterogeneity in the distribution of both large adult trees of different growth forms and individual species. After the habitat heterogeneity was accounted for, 39 of the 47 species (83.0%) were found to exhibit density dependence predominantly at close distances among neighbors. Our findings highlight density dependence as a prevalent mechanism for regulating the population spatial structure of most tree species in the species-rich subtropical forest studied here. Furthermore, the occurrence of density dependence is closely associated with species abundance and the strength of conspecific aggregation at local scales. Abundant species with high strength of conspecific aggregation tend to show density dependence.     

Study on canopy disturbance regime and mechanism of tree species diversity maintenance in the lower subtropical evergreen broad-leaved forest,South China

ABSTRACT

The canopy disturbance, the gap environment, gap regeneration and maintenance of tree species diversity in the lower subtropical evergreen broad-leaved forest (LSEBF) of South China were studied in this paper. The most common manner of gap formation in the forest was by stem breakage. Most gaps were formed by two gap makers. The sizes of most expanded gaps (EG) and canopy gaps (CG) were in the range of 100 – 300 m² and 50 – 100 m², respectively. The ecological factors in gaps were analysed on the basis of contrasting measurement of the microclimatic regimes in gaps of different sizes and in non-gap stands. Tree species in the LSEBF were classified into 5 ecological species groups on the bases of their changes in order of importance values in gaps and in non-gap stands. Most of the species reached their peak of regeneration density around the gap sizes of 100 m² and 500 m². The curves of regeneration density vs. gap age for major species revealed two types. Regeneration densities of most species, and species diversity indices in gaps were greater than those in non-gap stands.     

Abundance and diversity of Homoptera in the canopy of a tropical forest

Abstract. 1. A series of samples of Homoptera was obtained by fogging the canopy of Luehea seemannii trees in tropical forest in the Panama Canal Zone at three different times of the year.
2. The peak of abundance occurs around July (at least 11.8 individuals/m²), in the early wet season, at a time when most of the trees in the forest, including Luehea are producing new leaves.
3. Minimum abundance occurs in March (at least 3.5 individuals/m²), in the late dry season.
4. The samples obtained are some 35% richer in species per given number of individuals than light trap samples taken simultaneously in a similar forest some 6 km away from the present sampling site.
5. The data show that the effect of intensive light trapping on the populations of Homoptera in the forest is virtually negligible.
6. For a given sample size the tropical samples are many times richer in species than samples from temperate areas.     

How the diversity,abundance, size and climbing mechanisms of woody lianas are related to biotic and abiotic factors in a subtropical secondary forest,Taiwan

Lianas are woody vines that play an important role in forest dynamics in tropical and subtropical areas. Their relationship to various biotic and abiotic conditions is, however, not yet wholly clear. We explored how the size, climbing mechanisms, diversity and abundance of woody lianas is related to host plant size, environmental factors and topography. Liana assemblages were examined in twenty 20 × 20 m plots in each of three topographic sites (valley, slope and ridge) in a subtropical secondary forest in southeastern Taiwan. The valley site had the highest abundance and species richness of lianas. The abiotic factors, soil pH and rock cover, were related to different topographic sites. Larger lianas were always found on larger host trees, while smaller lianas were found in smaller trees; no lianas with a DBH greater than 10 cm were found. Significantly more adhesive lianas were found on larger trees whereas twining and leaning-hook lianas were found in smaller trees. In conclusion, this study demonstrates that the species of liana is associated with the size and type of tree growing under different topographic conditions.     

Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest

Canopy structure and light interception were measured in an 18-m tall, closed canopy deciduous forest of sugar maple (Acer saccharum) in southwestern Wisconsin, USA, and related to leaf structural characteristics, N content, and leaf photosynthetic capacity. Light attenuation in the forest occurred primarily in the upper and middle portions of the canopy. Forest stand leaf area index (LAI) and its distribution with respect to canopy height were estimated from canopy transmittance values independently verified with a combined leaf litterfall and point-intersect method. Leaf mass, N and A _max per unit area (LMA, N/area and A _max/area, respectively) all decreased continuously by over two-fold from the upper to lower canopy, and these traits were strongly correlated with cumulative leaf area above the leaf position in the canopy. In contrast, neither N concentration nor A _max per unit mass varied significantly in relation to the vertical canopy gradient. Since leaf N concentration showed no consistent pattern with respect to canopy position, the observed vertical pattern in N/area is a direct consequence of vertical variation of LMA. N/area and LMA were strongly correlated with A _max/area among different canopy positions (r²=0.81 and r²=0.66, respectively), indicating that vertical variation in area-based photosynthetic capacity can also be attributed to variation in LMA. A model of whole-canopy photosynthesis was used to show that observed or hypothetical canopy mass distributions toward higher LMA (and hence higher N/area) in the upper portions of the canopy tended to increase integrated daily canopy photosynthesis over other LMA distribution patterns. Empirical relationships between leaf and canopy-level characteristics may help resolve problems associated with scaling gas exchange measurements made at the leaf level to the individual tree crown and forest canopy-level.     

Weak vertical canopy gradients of photosynthetic capacities and stomatal responses in a fertile Norway spruce stand

Wildfire severity in forests is projected to increase with warming and drying conditions associated with climate change. Our objective was to determine the impact of wildfire and clearcutting severity on the ectomycorrhizal fungal (EMF) community of Douglas-fir seedlings in the dry forests of interior British Columbia, Canada. We located our study within and surrounding the area of the McLure fire (August 2003). We hypothesized that disturbance would affect EMF community assembly due to reductions in fungal inoculum. Five treatments representing a range of disturbance severities were compared: high severity burn, low severity burn, screefed clearcut (manual removal of forest floor), clearcut, and undisturbed forest. EMF communities in the undisturbed forest were more complex than those in all disturbance treatments. However, aspects of community assembly varied with disturbance type, where the burn treatments had the simplest communities. After 4 months, regenerating seedlings in the burn treatments had the lowest colonization, but seedlings in all treatments were fully colonized within 1 year. EMF communities were similar among the four disturbance types, largely due to dominance of Wilcoxina throughout the study period. However, forest floor retention influenced community assembly as the EMF in the clearcut treatment, where forest floor was retained, had levels of diversity and richness comparable to the undisturbed forest. Overall, the results suggest that increasing forest floor disturbance can alter EMF community assembly in the first year of regeneration. A correlation between poorly colonized seedlings and seedling productivity also suggests a role for productivity in influencing community assembly.     

CENP-C is necessary but not sufficient to induce formation of a functional centromere.

CENP-C is an evolutionarily conserved centromeric protein. We have used the chicken DT40 cell line to test the idea that CENP-C is sufficient as well as necessary for the formation of a functional centromere. We have compared the effects of disrupting the localization of CENP-C with those of inducibly overexpressing the protein. Removing CENP-C from the centromere causes disassembly of the centromere protein complex and blocks cells at the metaphase-anaphase junction. Overexpressed CENP-C is associated with an increase in errors of chromosome segregation and inhibits the completion of mitosis. However, the excess CENP-C does not disrupt the native centromeres detectably and does not associate with another conserved centromere protein, ZW10. The distribution of the excess CENP-C changes during the cell cycle. In metaphase, the excess CENP-C coats the chromosome arms. At the metaphase-anaphase transition, the excess CENP-C clusters, and during interphase it is present in large bodies which form around pre-existing centromeres which are also clustered. These results indicate that CENP-C is necessary but not sufficient for the formation of a functional centromere and suggest that the structure of CENP-C may be regulated during the cell cycle.     

Tree diversity promotes generalist herbivore community patterns in a young subtropical forest experiment

Stand diversification is considered a promising management approach to increasing the multifunctionality and ecological stability of forests. However, how tree diversity affects higher trophic levels and their role in regulating forest functioning is not well explored particularly for (sub)tropical regions. We analyzed the effects of tree species richness, community composition, and functional diversity on the abundance, species richness, and beta diversity of important functional groups of herbivores and predators in a large-scale forest biodiversity experiment in south-east China. Tree species richness promoted the abundance, but not the species richness, of the dominant, generalist herbivores (especially, adult leaf chewers), probably through diet mixing effects. In contrast, tree richness did not affect the abundance of more specialized herbivores (larval leaf chewers, sap suckers) or predators (web and hunting spiders), and only increased the species richness of larval chewers. Leaf chemical diversity was unrelated to the arthropod data, and leaf morphological diversity only positively affected oligophagous herbivore and hunting spider abundance. However, richness and abundance of all arthropods showed relationships with community-weighted leaf trait means (CWM). The effects of trait diversity and CWMs probably reflect specific nutritional or habitat requirements. This is supported by the strong effects of tree species composition and CWMs on herbivore and spider beta diversity. Although specialized herbivores are generally assumed to determine herbivore effects in species-rich forests, our study suggests that generalist herbivores can be crucial for trophic interactions. Our results indicate that promoting pest control through stand diversification might require a stronger focus on identifying the best-performing tree species mixtures.     

Spatial structure of litter-dwelling ant distribution in a subtropical dry forest

Understanding the spatial patterns of species distribution is essential to characterize the structure of communities, to optimize species inventories and to evaluate the impact of biotic and abiotic variables. Here we describe the spatial structure of the distribution of leaf litter ant species, and of biotic factors that could explain it, in a subtropical semi-deciduous forest of the Argentinian Chaco, characterized by a dense understorey of shrubs and terrestrial bromeliads. Environmental variables (leaf litter quantity and ground bromeliad density) were measured and ants were collected in 1 m² quadrats distributed along two 200 m transects at intervals of 1.25 m. Overall 87 species were collected. Sixteen positive associations and a single negative association were observed between the 11 most frequent species taken pair-wise. Our results suggest that the spatial distribution of leaf litter ants was determined at two different scales. At a small scale (period below 10 m) a periodic spatial structure, likely due to intraspecific competition, produced a succession of peaks of abundance separated by gaps. At a larger scale (period around 50 m), periodically distributed environmental factors induced aggregates of colonies of species responding positively to these factors. A high quantity of leaf litter and, to a lesser extent, a high density of ground bromeliads promoted a high density and a high species richness of ants. Numerically dominant ants being generally positively associated, interspecific competition was apparently weak. All ant species whose abundance was correlated with an environmental factor were not completely spatially structured by it. This suggests that some other factors, such as intraspecific competition, may have counter-effects. Received 14 March 2005; revised 26 April 2005; accepted 10 May 2005.