Community structure of saproxylic arthropods along an urbanization gradient

doi:10.21203/rs.3.rs-1989983/v1

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Community structure of saproxylic arthropods along an urbanization gradient

https://doi.org/10.21203/rs.3.rs-1989983/v1

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Saproxylic arthropods play essential roles in the detritus food chains of forest ecosystems by contributing to wood decomposition and nutrient cycling. Here, we examined saproxylic arthropod communities along a gradient from large forests to urban fragmented forests to clarify the effects of urbanization on the structure and composition of these communities. We found that communities could be allocated to three groups on the basis of species composition, and the groups were correlated with the urbanization gradient represented by forest size. The fragmented urban forest community had large numbers of individuals of few facultative saproxylic species, whereas many obligate saproxylic species—proportional to the abundant dead wood volume— occurred in the large forest community. As result, species richness was significantly lower in communities in fragmented urban forests than in those in large forested areas, as determined by using rarefaction curves based on the number of individuals. However, this difference was not significant when the curve was based on wood volume.

Implications for insect conservation

Our result suggested that forest size as urbanization scale was the most important environmental factor influencing the saproxylic arthropod communities because species composition and species diversity were affected by forest area. We need to protect large forests to conserve the overall diversity of saproxylic arthropods.

Saproxylic arthropod

Urbanization

Species richness

Functional structure

Individual density

Saproxylic arthropods living in dead wood play essential roles in the detritus food chains of forest ecosystems. They contribute to wood decomposition and nutrient cycling through their activity (Harmo et al. 1986; Stokland et al. 2012). Saproxylic arthropods form a highly diverse group that includes a large proportion of forest arthropod fauna (Grove 2002; Speight 1989). In Japan, some of the large saproxylic beetles with large mandibles (e.g. of the family Lucanidae) are popular with collectors and have high cultural and market value (Kameoka and Kiyono 2003).

Saproxylic species are in decline because of environmental changes caused by human activity (Cálix et al. 2018; Nieto and Alexander 2010). Because of the importance of saproxylic beetles and their sensitivity to habitat change, Two Red Lists specific to these beetles has been published in Europe in 2010 and 2018 (Cálix et al. 2018; Nieto and Alexander 2010). According to these Red Lists, the factors influencing saproxylic beetle populations are logging and harvesting, agricultural expansion, and urban sprawl.

Urbanization is a major threat to biodiversity (McDonald et al. 2013; McKinney 2002). Habitat loss, fragmentation, and isolation within urban areas all affect arthropod communities (Ishitani et al. 2003) and their contributions to ecosystem functions (Kotze et al. 2011), and saproxylic species are no exception to this threat. However, little is known about the effects of urbanization on saproxylic arthropod communities.

Studies of saproxylic arthropods in urban areas have dealt only with limited taxa, such as endangered beetle species, including Osmoderma eremita, Lucanus cervus, and tenebrionid beetles (Carpaneto et al. 2010; Fattorini and Galassi 2016; Fremlin 2009). Community-level studies have not been conducted in urban forests, which are important remnant habitats for such species (Horák 2011; Jones and Leather 2012) and are important elements for humans, for example by providing ecosystem services (Wolch et al. 2014).

The aim of our research was to clarify the effects of urbanization on the structure and composition of saproxylic arthropod communities. This is the first study of saproxylic arthropod communities in urban areas. We sampled dead wood from forests along an urban–rural–forest landscape gradient, and we collected arthropods dependent on the dead wood. We then analyzed the composition and structure of the saproxylic arthropod communities.

Saproxylic arthropods

Saproxylic arthropods are defined as species that are “dependent, during some part of their life cycle, upon the dead or dying wood of moribund or dead trees (standing or fallen), or upon wood-inhabiting fungi, or upon the presence of other saproxylics” (Speight 1989). Saproxylic species are associated with dead wood to different degrees. Obligate saproxylic species strictly require dead wood for their life cycles. In contrast, facultative saproxylic species (i.e. habitat generalists) use dead wood but can also use other resources (Stokland et al. 2012).

Wood decay is driven primarily by microbial activity, but arthropods are also thought to play a role (Ulyshen and Wagner 2013). For instance, fragmentation, tunneling, and digestion by arthropods facilitate wood decomposition (Rayner and Boddy 1988; Ulyshen 2016; Walker and Wilson 1991).

Study sites

We performed the study within a warm–temperate zone of Japan. In this climatic zone, areas with various levels of urbanization exist around the Tokyo metropolitan area. We selected nine forests have different area due to be surrounded by different levels of urbanization (see result) in the south-west region of the Tokyo metropolitan area (Table 1). The mean annual temperature of the region ranges from 16.9 to 20.5 °C, and annual precipitation ranges from 1342.5 to 1874.0 mm. The potential natural vegetation is evergreen broad-leaved forest (Miyawaki 1986) dominated by Castanopsis sieboldii and by Quercus acuta and other evergreen oaks. Coppice forest exists as secondary vegetation dominated by deciduous Quercus serrata.

In each forest, we set a survey line across two ridges and valleys in the dominant vegetation stand in the forest, and on each line we chose three sampling sites approximately 80 m distant from each other. Vegetation and dead wood accumulation were surveyed at each site.

Dead-wood sampling and arthropod identification

Dead wood on the forest floor was sampled and examined for the presence of saproxylic arthropods. We randomly sampled a maximum of 10 (13 at site FGY) pieces of dead wood (diameter ³3 cm and length ³30 cm) in each of three sampling plots (10 ´ 10 m; each set up at the center of a vegetation survey plot; see Table 2 and below) from December to May in 2016 and 2017 (we surveyed each plot one time). We sampled one time at each plot during this period. We broke the wood pieces and collected arthropods Pieces of dead wood longer than 250 cm or greater than 5000´p cm³ in volume were too large to break the whole and were cut into lengths of 30 to 50 cm or volumes of no more than 1250´p cm³and used as three separate samples (upper, middle, lower) for sampling of the wood. These dead wood samples were used to compile both site arthropod datasets and single-wood-sample arthropod datasets (Table 2).

Collected arthropods were identified to species level. If this was not possible, the specimens were classified into morphospecies on the basis of their morphology. We also classified the arthropods into three functional groups—1) obligate saproxylic, 2) facultative saproxylic, and 3) non-saproxylic—and six food habit groups—1) xylophage (feeding on wood or phloem or both), 2) carnivore, 3) fungivore, 4) omnivore, 5) detritivore (excluding wood and fungus eaters), and 6) parasite of arthropods. Because of the massive numbers of social arthropods, including ants (Formicidae) and termites (Termitidae), in these cases we counted the number of colonies (i.e. the number of genet). We therefore excluded termites and ants from those analyses that were based on the number of individuals. We obtained many single dead-wood-based community data, 27 sets of arthropod plot-based community data, and nine sets of forest site-based community data.

We recorded seven features for each dead wood sample: 1) diameter (m), 2) length (m), 3) decay type (white, brown or soft), 4) decay stage (1 - 5), 5) strength (0 - 1), 6) occurrence of bark (0 - 100%), and 7) wood posture (standing or fallen) (Table 2). We excluded tree species identification of dead wood samples because of its difficulty, for example no leaves or a little bark. Strength was calculated by the depth of knife penetration (cm) per wood sample diameter (cm). Decay type and the percentage of bark present were observed visually. We followed the decay stages of Fukasawa et al. (2009). We evaluated stage from strength, bark and other visual features. For example, Stage 1 is wood hard, penetrable with a knife to only a few mm, bark and twigs (diameter <1 cm) intact. Stage 5 is wood disintegrating either to a very soft crumbly texture or is flaky and fragile, penetrable with a knife to more than 10 cm, original log circumference barely recognizable or not discernable (Fukasawa et al 2009).

Vegetation survey and survey of dead wood accumulation

We obtained vegetation data at the same locations as where we had collected the arthropod samples. At each forest site we set up three 15 ´ 15-m quadrats and recorded the species, height, and diameter at breast height of every tree in the quadrat (Table 2) to obtain site datasets for vegetation. The vegetation survey was conducted from October to November in 2016 and 2017.

We established two extra survey lines that were parallel to the first sampling line and on each side of it at a separation distance of at least10 m, and we set up three plots (7 ´ 7 m) along each new line, giving a total of six plots in each forest (Table 2). We measured the volume of dead wood (diameter ³3 cm and length ³30 cm) in the forest in cm³ as a resource for saproxylic arthropods, thus obtaining dead-wood accumulation datasets. The seven above-described features of the wood were also recorded in these plots. This survey was conducted in winter (December to February) from 2016 to 2019 (we surveyed each plot one time).

Urbanization scale

We used the maximum inscribed circle as an indicator of forest area to consider the edge effects in forests of various shapes (Primack 1995; Soga 2013). Correlation coefficients to the percentages of surrounding urban land cover in 1000 m and 2000 m buffer were calculated to confirm validity of the maximum inscribed circle of the forest as an urbanization scale. Forest area (maximum inscribed circle area) was log transformed before this analysis. We performed these calculations by using ArcGIS 10.3.1 (ESRI, Redlands, California, USA).

A principal component analysis was conducted to summarize the vegetation in each forest. We used the sums of the basal areas (m²) of each family for this analysis. Fagaceae, Ericaceae, and Cornaceae had both evergreen and deciduous species, which we considered as separate groups (i.e., evergreen Fagaceae and deciduous Fagaceae were considered separately). The vegetation variable was the first principal component (PC1). (The proportion of variance was 0.89.)

Arthropod community analysis

We conducted a hierarchical cluster analysis to classify nine forest-based arthropod communities by using a Bray-Curtis dissimilarity matrix with arthropod abundance. We considered species collected from at least three dead-wood arthropod plots in order to exclude the noise potentially contributed by the presence of rare species.

To detect those environmental factors affecting community division, we analyzed environmental factors of vegetation and urbanization scale by using one-way ANOVA followed by Tukey’s HSD test.

We compared species richness between community types. We used both arthropod-individual-based and wood-volume-based rarefaction curves to compare the species richness of the different community types by using the accumcomp function of the Biodiversity R package (Kindt and Coe 2005).

To compare arthropod diversity and abundance by volume of wood, we used a Poisson regression with the number of species or individuals as the response variable and the community type as the categorical explanatory variable, with wood sample volume as an offset term. This analysis was based on the single dead-wood-sample-based dataset (see Table 2). The number of arthropod species and the number of individuals in each food habit group and with obligate or facultative saproxylicity were also analyzed.

To detect the species characteristic of each community type, we performed Poisson regressions for each arthropod species. The response variable was abundance in each dead wood sample; community type was the categorical explanatory variable and deadwood volume was the offset term. The single dead-wood-based dataset was used, and we considered only those arthropod species for which we collected more than 10 individuals in the whole study.

Wood property preference was analyzed for those arthropod species having significant correlations with arthropod community types. The response variable was the number of individuals of each arthropod species in a single dead-wood-sample; the wood properties were explanatory variables, and single dead-wood-sample volume was the offset term.

In all regression models, the best model was chosen on the basis of the Akaike information criterion, and all statistical analyses were conducted in R (R Development Core Team 2018, version 3.3.2).

Urbanization scale

A strong negative correlation was found between the forest area (maximum inscribed circle area) and surrounding urban land cover area (r = –0.81 in 2000-m buffer; r = –0.74 in 1000-m buffer); we therefore used forest area as indicator of urbanization in the following analysis.

Field survey

A total of 2125 arthropod individuals belonging to 98 species were collected from 290 individual dead wood samples in 27 dead-wood-arthropod plots in nine forest sites. The species collected in all forest sites were Dorcus rectus, Reticulitermes speratus, Uloma marseuli as obligate saproxylic and xylophagous species; and Scolopocryptops rubiginosus, and Bothropolys asperatus as a facultative saproxylic and carnivorous species. Plesiophthalmus nigrocyaneus—as obligate saproxylic and xylophagous species—was collected at eight of the nine forest sites.

Community types

Communities at the nine forest sites were classified into three types: community types A, B, and C (Fig. 1). Forest area differed significantly between community types A and C (P = 0.002; Table 3), not significantly in A and B, B and C. Average number of tree species, vegetation type (as PC1 in the vegetation analysis), and average dead wood accumulation did not differ significantly among community types (Table 3). Community type A was located in large forests, type C in small urban forests, and type B in intermediate forests.

The proportions of obligate and facultative saproxylic individuals differed among communities (P < 0.001, Fisher’s exact test), although the number of species did not differ significantly (P = 0.55, Fisher’s exact test) (Fig. 2). In urban community type C, more than 65% of individuals were facultative saproxylics, which can use other habitats such as leaf litter; this value was only 26% in large forest community A and 43% in intermediate type B (Fig. 2).

Only carnivorous and detritivorous species were found among the facultative arthropods sampled on the dead wood, although a variety of food habit types were found among the obligate species. In the obligate species, the proportions of individuals in different food habit groups clearly differed significantly among communities (P < 0.001, Fisher’s exact test), but the proportions of species in different food habit groups did not (P = 0.29, Fisher’s exact test) (Fig. 3). Among the facultative species, the proportion of detritivorous individuals was highest in community type C (P < 0.0001, Fisher’s exact test) (Fig. 3). Food habit group did not differ significantly in terms of the number of species (P = 1, Fisher’s exact test).

Functional type composition in single dead-wood-based data set

After removal of the effect of wood volume by regression analysis, the total numbers of species and individuals in a single wood sample were significantly larger in urban community type C and intermediate community type B than in large forest community type A (Table 4); this was also true for both obligate and facultative species, with the exception of obligate species in community B versus those in community A.

When food habit was considered in more detail, numbers of species and individuals in a single wood sample were significantly larger in urban community type C and intermediate community type B than in large forest community type A in terms of all food habit groups of facultative species and in terms of xylophagous and fungivorous obligate species, with the exception of fungivorous species in community B versus community A. On the other hand, there were no significant differences among communities in the case of carnivorous or omnivorous obligate saproxylic species, with the exception of the number of individuals in community C versus community A for omnivorous obligate saproxylics (Table 4).

Species richness

Rarefaction curves based on the number of individuals showed richer diversity in community type A than in type C (Fig. 4). However, in those based on wood volume, the three community types were similar in richness. In the curves based on number of individuals, community type C had a small number of facultative species with a huge number of individuals, whereas community type A had a large number of individuals of obligate species.

Species typical of each community type

There were significantly more individuals of Pseudopyrochroa vestiflua, D. rectus, Anisolabella marginalis, Niponia nodulosa, and centipede (chilopod) species in community types C and B than in large forest community type A (Table 5). In community type C there were also significantly more individuals of P. nigrocyaneus, Armadillidium vulgare, and Porcellio scaber than in community type A. In contrast, individuals of Duolandrevus ivani and Phloeotrya obscura were significantly more abundant in community type A than in type C. In total, five facultative species preferred urban forest community type C to large forest community type A. Two obligate species, but no facultative species, preferred community type A over type C.

Species preferences for dead wood properties

Among the dead wood properties examined, we included wood diameter and decay stage in the regression analysis, because bark cover, knife penetration strength, and standing or falling were all correlated with either decay stage or wood diameter. Tree species of the dead wood samples were difficult to identify.

Almost all the studied species preferred small-diameter wood (Table 5). Preference for decay stage differed among species: P. vestiflua and P. scaber preferred less decayed wood, whereas A. marginalis and A. vulgare preferred well-decayed wood.

We examined the effects of urbanization on communities of saproxylic arthropods. The forest size as urbanization scale was the most important environmental factor influencing the saproxylic arthropod communities that we studied (Table 3). The urban community (type C) had large numbers of individuals of few facultative saproxylic species, whereas obligate saproxylic species living sparsely in a large volume of dead wood in the large forest (type A) might have led to greater species richness in the type A community in the rarefaction curve based on number of individuals (Fig. 4).

Retained forest patch size can influence the community structure of saproxylic beetle communities in large-scale forest harvesting, especially through the edge effect (Lee et al. 2015). Declining species richness in urban forests has been reported in many studies in taxa such as carabid beetles, a gall-inhabiting moth, and weevils (Ishitani et al. 2003; Rosch et al. 2001; Su et al. 2011). Species richness loss in urban habitats has been caused mainly by small forest area in the case of tenebrionids, roadside hemipterans, and carabid beetles (Fattorini and Galassi 2016; Helden and Leather 2004; Soga et al. 2013).

Although forest size was critical to saproxylic arthropods, our study suggested that its effect on diversity was not simple. Saproxylic arthropod communities may be diverse but spatially sparse in terms of wood volume in large forest communities (see Fig. 4). Responses of diversity differed by functional types. When we considered single samples of dead wood, more facultative individuals of many facultative species were found in urban forests than in large forests (Table 4). Among obligate species, significantly more xylophagous and fungivorous arthropods were found in urban forests than in large forests. However, omnivores and carnivores did not follow this trend and were rich in large forests in some cases.

Few facultative species dominated in small urban forests. A non-native facultative saproxylic arthropod, A. vulgare, was one of most dominant species in community type C (Table 4). According to Kurita and Harada (2011), A. vulgare prefers dry soil of high pH, because this environment is similar to that in the Mediterranean—the original habitat for this species. Such soil occurs in urban environments close to the concrete structure of roads and other urban structures, so that forests adjacent to urban settings are suitable habitats for this species. Urban facultative saproxylic predators such as Anisolabella and chilopods might depend partly on abundant detritivorous species such as A. vulgare and P. scaber.

The abundance of all species, in the case of table 5 was negatively correlated with dead wood diameter (Table 5). A relationship between diameter and saproxylic arthropod abundance has been reported before (Stokland et al. 2012). According to Schiegg (2001), the species richnesses of Diptera and Coleoptera are larger in limbs than in trunks of the same volume. A poor nitrogen and phosphorus content of heartwood (Meerts 2002) might be a reason why many saproxylic arthropods prefer small-diameter wood.

Conservation of saproxylic arthropods in urban landscapes

Low species diversity in the rarefaction curve based on the number of individuals for all species (Fig. 4) suggests that we need to protect large forests to conserve the overall diversity of saproxylic arthropods.

The importance of large-diameter dead wood has often been discussed for conservation of saproxylic species (Stokland et al. 2012). Large-diameter (³30 cm) dead wood accounts for 42% to 53% of the wood volume on the forest floor but only 1.7 to 2.7% in small(<10cm) (Siitonen et al. 2001), and large dead wood contains various environment such as different diameters or moisture content in different parts of it and more resources for saproxylic species (Stokland et al. 2012). However, we found here that almost all species had a negative preference for large-diameter dead wood. Studies of very rare species in large forests might be needed to test the importance of large-diameter wood, because here we analyzed dominant species only (see Table 5).

Stag beetles are culturally very famous in Japan, and preferred by general publics (Goka 2010; Kameoka and Kiyono 2003). A species of stag beetle (D. rectus) was abundant in urban fragmented forests (Table 5). Because public education can help to conserve wide ranges of species and ecosystems (Horák 2018), looking for wild stag beetles in urban parks can be the first experience for a majority of the general public in understanding ecosystems and the importance of preserving their habitat.

Acknowledgments

We thank the staff of the Ecological Laboratory, Graduate School of Environment and Information Sciences, Yokohama National University, for their help. This study was supported by the managers of each forest, who gave permission. We thank them for their help and cooperation.

The authors have no relevant financial or non-financial interests to disclose.

Ethics Declarations

Funding

The authors did not receive support from any organization for the submitted work.

Competing interests

The authors have no relevant financial or non-financial interests to disclose.

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Table 1. Study sites

Forest site	Geographic coordinates (longitude, latitude, altitude)	Area of maximum inscribed circle of forest (km²)	Vegetation type	Vegetation score by PC1	Dead wood accumulation (cm³m^–2)	No. of dead wood samples examined per 300 m²	Total no. of arthropod species in sampled wood	Total arthropod abundance in sampled wood
KSY	35.161205, 140. 138222, 288 m	55.779	Evergreen broadleaf	2.126	11344.484	30	34	205
AON	34.693347, 138.838461, 167 m	22.267	Evergreen broadleaf	1.051	18150.273	30	34	205
FGY	35.272803, 139.618753, 54 m	3.589	Evergreen broadleaf	0.516	4908.445	33	42	224
SKM	35.345627, 139.587393, 99 m	0.497	Coppice broadleaf	–0.706	12987.128	19	32	179
JIK	35.565162, 139.497812, 53 m	0.412	Coppice broadleaf	–1.668	2276.204	23	36	208
NHR	35.516221, 139.513675, 47 m	0.492	Coppice broadleaf	–1.428	1790.450	25	27	135
KBD	35.532619, 139.660043, 35 m	0.004	Coppice broadleaf	–1.421	4880.219	22	38	275
TGM	35.469033, 139.546484, 55 m	0.008	Coppice broadleaf	–1.392	4565.430	6	36	427
YNU	35.472855, 139.587473, 53 m	0.005	Evergreen broadleaf	2.923	5197.465	30	36	281

Table 2. Sampling and measurements in each forest

Plot and objective	Sampling unit	Location	Measurements and sampling
Vegetation survey plot (vegetation plot dataset; summing three plots provided forest site dataset for vegetation)	Three plots of 15 15 m	Each site	Trunk diameter at breast height Tree height, Tree species
Dead-wood accumulation plot as resource for arthropods	Six plots of 7 7 m	Six isolated plots at each forest site	Volume of dead wood (diameter ³3 cm and length ≥30 cm)
Dead-wood arthropod plot (arthropod plot dataset; summing three plots provided forest site dataset for arthropods)	Three plots of 10 10 m	Inside of each vegetation survey quadrat	Sample 10 randomly selected pieces of dead wood (diameter ≥3 cm and length ≥30 cm) if present
Single dead-wood sample to examine arthropods (single-dead-wood- based dataset)	Single dead wood sample	All sampling locations	Species of all arthropod individuals Decay stage: according to Fukasawa et al. (2009) Decay type: white, brown or soft Volume: diameter²/4 × p × length Bark cover: absent 0, complete, 100% Strength: knife penetration depth / diameter of dead wood sample

Table 3. Relationships between environmental variables and arthropod communities

Arthropod community type	ln(forest area) for forest sites	Average no. of tree species in vegetation quadrats	Average vegetation PC1 scores of sites	Average dead wood accumulation in arthropod plots (cm³ m^–2)
A	3.022033^a	16.5	0.746585	11847.58248
B	–0.79407^b	17.5	–1.54799	2033.326825
C	–5.17315^ab	14.3	0.036549	4881.037996

^a P < 0.01, ^bP < 0.05 by Tukey HSD test

Table 4. Functional-type responses to community types detected by many Poisson regressions. Numbers of species or individuals are response variables, community type is the categorical explanatory variable (type A being the reference), and wood sample volume is the offset term. We used the single dead-wood-based dataset.

	Explanatory variable
Response variable	Community A	Community B	Community C
Number of species
All species	0.0	0.44249***	1.06805***
Dependency on dead wood
Obligate	0.0	0.26265	0.48584***
Facultative	0.0	0.8210***	1.8749***
Food habit
Xylophagous, obligate saproxylic	0.0	0.37602*	0.66239***
Fungivorous, obligate saproxylic	0.0	–15.6393	2.0202*
Carnivorous, obligate saproxylic	0.0	–0.09651	–0.43293
Omnivorous, obligate saproxylic	0.0	–16.9419	–0.8701
Carnivorous, facultative saproxylic	0.0	0.9667***	1.7153***
Detritivore, facultative saproxylic	0.0	0.1678	2.2473***
Number of individuals
All species	0.0	0.50330***	1.32120***
Dependency on dead wood
Obligate	0.0	0.31265***	0.53051***
Facultative	0.0	0.94916***	2.24509***
Food habit
Xylophagous, obligate saproxylic	0.0	0.35749***	0.56494***
Fungivorous, obligate saproxylic	0.0	–14.6393	3.1552***
Carnivorous, obligate saproxylic	0.0	0.3536	–0.3846
Omnivorous, obligate saproxylic	0.0	–17.1783	–0.9242*
Carnivorous, facultative saproxylic	0.0	0.8391***	1.8925***
Detritivore, facultative saproxylic	0.0	1.1868***	2.8132***

*** P < 0.001, ** P < 0.01, * P < 0.05

Table 5. Arthropod species (both obligate and facultative) specific to community types and wood property preferences, as detected by Poisson regression assuming community type to be the explanatory variable (type A being the reference). We used the single dead-wood-based dataset. Ecological traits are also shown.

	Community preference		Wood property preference		Ecological traits		Total no. of individuals
Species	type B	type C	Wood diameter	Decay stage	Functional group	Food habit	Total no. of individuals
Duolandrevus ivani		–*	–34.61876***	0.07135	Omnivorous	Obligate	45
Phloeotrya obscura		–***	–38.31980***	0.05046	Xylophagous	Obligate	107
Pseudopyrochroa vestiflua	+***	+***	–34.2619***	–1.4606***	Xylophagous	Obligate	42
Dorcus rectus	+***	+***	–11.78817***	0.06394	Xylophagous	Obligate	114
Anisolabella marginalis	+***	+***	–17.3579***	0.2249*	Carnivorous	Facultative	221
Chilopod spp.	+***	+***	–10.05542***	–0.03115	Carnivorous	Facultative	198
Niponia nodulosa	+*	+***	–12.36558***	–0.02328	Detritivorous	Facultative	37
Plesiophthalmus nigrocyaneus		+***	–2.8914*	–0.2133	Xylophagous	Obligate	96
Armadillidium vulgare		+***	–10.6041***	0.3720*	Detritivorous	Facultative	146
Porcellio scaber		+***	–1.1950*	–0.4817**	Detritivorous	Facultative	181

*** P < 0.001, ** P < 0.01, * P < 0.05

No competing interests reported.

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Community structure of saproxylic arthropods along an urbanization gradient

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