Isopod Communities Research Articles

Facilitation: Isotopic evidence that wood-boring beetles drive the trophic diversity of secondary decomposers

Deadwood heterogeneity is regarded as a primary causal driver of deadwood-associated soil biodiversity, but the underlying mechanisms remain elusive. This is partly due to the technical difficulties in disentangling and quantifying different components (e.g., deadwood is both habitat and food) of heterogeneity to which soil organisms may have context-dependent responses. Furthermore, non-trophic interactions, e.g., facilitation, also add complexity to deadwood heterogeneity-biodiversity relationships, yet their influences are unaccounted for in most deadwood biodiversity studies. To address these research gaps, we sampled isopod communities from 40 logs of two isotopically distinct tree species, which had been cut and incubated reciprocally for eight years in each of two environmentally contrasting sites (e.g., differences in background isotopic signatures and litter turnover rates). We then assessed the extent to which the variation in the biodiversity of isopod communities is explained by deadwood heterogeneity induced by wood-boring beetles. Stable isotope ratios (i.e., δ13C and δ15N) were employed to examine the response of trophic diversity of isopod communities to the rarely tested food facet of deadwood heterogeneity. We hypothesized the deadwood heterogeneity is boosted by wood-boring beetles and thereby positively affects the abundance, taxonomic diversity and trophic diversity of isopod communities. Our results supported this hypothesis: the abundance and Shannon and Simpson diversity as well as trophic diversity of isopods were positively correlated to wood-boring beetle tunnel densities in both sites and across the two tree species. We observed significant tree species and reciprocal treatment effects on the δ15N values of isopods in one of the two sites. This result suggested that the use of deadwood as food sources versus habitats by isopods is environmentally dependent. This study demonstrates that there is substantial heterogeneity within deadwood that promotes the diversity and trophic diversity of macroinvertebrates. This relationship is mediated by saproxylic beetle facilitation, with implications for the roles of saproxylic beetles and within-deadwood heterogeneity in determining microbial wood decomposition in temperate forests.

한려해상국립공원 조간대의 절지동물(등각류) 군집 연구

In this study, we conducted a survey of the intertidal zones at 20 study stations in Hallyeohaesang National Park, Korea to investigate isopod communities related to habitats from July, 2019 to September, 2020. As a result of the study, 50 isopod species of 13 families belonging an order were identified. There was no species of the endangered wild animal. As the legally protected species, three endemic species and two export restricted species were included. The mean value of the density of isopod individuals for a total of 20 stations was estimated as 62.78 ind./㎡. Dominant and subdominant species in the study areas were Chitonosphaera lata and Ligia exotica, respectively. Based on the number of the species occurred and the density of individuals for each species in the isopod community, the dominance, diversity, and richness indices were caculated as 0.23, 2.69, and 11.84, respectively. As a result of the cluster analysis based on isopod communities at each 20 stations, the study stations divided into two groups according to their geographical locations and characteristics of the substrates: the first group (I) was the stations assembled by having soft substrate with dominant mud in basin sea area; the second group (II) was those assembled by having hard substrate or mixture of soft and hard substrates in outer sea. Each of these two groups was divided again into two subgroups of stations according to their geographical locations and characteristics of the substrates.

Comparison of isopod assemblages (Crustacea: Isopoda: Oniscidea) among four different habitats—Evergreen forest, exotic bamboo plantation, grass and urban habitat

Exotic plantations and urbanization are serious threats to biodiversity. This study compared community structures of terrestrial isopods among urban habitat, grass, exotic bamboo forest and broad-leaved forest. A total of 9553 terrestrial isopod specimens from 11 native and 5 exotic species were collected from 102 sites. Nonmetric multidimensional scaling (NMDS) and non-hierarchical clustering showed that the community structure in exotic bamboo forest was similar to that in broad-leaved forest, and the communities were characterized by four native and one exotic species. However, the abundance in exotic bamboo forest was the lowest among the four habitats. The urban habitat was dominated by exotic species, and the species richness was the highest out of the four habitats. The results showed that exotic bamboo forest maintained an isopod community similar to that in broad-leaved forest, and that urbanization encouraged invasion of exotic species and increased species richness at a local scale.

Isopod assemblages in the Bizerte lagoon (SW Mediterranean Sea): composition, structure and environmental relationships

The spatial and temporal distribution, abundance, and structure of isopod assemblages in Bizerte Lagoon (SW Mediterranean Sea) were studied at 22 stations selected from seagrass and macroalgae sampled during four seasons in 2017. A total of 6808 individuals and 17 species of isopods belonging to 5 suborders, 7 families and 12 genera were identified. Six new species were recorded on Tunisian coasts. In addition, and compared to previous studies, nine isopod species were collected for the first time in this lagoon. Analysis of the trophic structure revealed that most stations are strongly dominated by herbivore-deposit feeders (78.3%), followed by deposit-suspension feeders (13.6%) and carnivores (8.01%). Three isopod assemblages were identified (G1, G2 and G3). The distribution of isopod assemblages is influenced by the nature and structure of the substrates. The seasonal variations in the isopod community patterns at 22 stations showed maximum abundance and diversity during spring, whereas the lowest ones were recorded during winter.

Distribuição e abundância de isópodes gigantes Bathynomus (Crustacea, Isopoda, Cirolanidae) da Plataforma Continental Amazônica

The present study focuses on the distribution and abundance of the giant isopod community, based on specimens collected using the bottom shrimp trawling on the Amazon continental shelf during fishery surveys, at depths between 81 m and 626 m, conducted during the REVIZEE/Score-North Program between 1996 and 1998. The study area is located within the exclusive economic zone of Brazil, between the States of Amapá and Pará. In total, 170 specimens were collected, distributed in the two species Bathynomus giganteus (n = 49) and Bathynomus miyarei (n = 121), in which 54% of the material were collected in the northern and 46% in the southern sector of the study area. B. miyarei was considered to be the dominant species in both sectors, whereas B. giganteus was uncommon in the northern sector, but abundant in the southern sector. Both species preferred gravelly bottoms in the northern sector, and gravelly sand in the southern sector and were more abundant during the dry season in the northern sector, but during the rainy season in the southern sector. The smallest female B. giganteus was collected in the northern sector, and the largest in the southern sector, whereas both the largest and the smallest female B. miyarei were captured in the southern sector. All the male specimens collected in this study were captured in the northern sector.

Species richness and functional diversity of isopod communities vary across an urbanisation gradient, but the direction and strength depend on soil type

Urbanisation involves major changes in environmental conditions such as light, temperature, humidity and noise levels, but the effect of urbanisation on soil conditions and soil biodiversity has received less attention. The reported effects on species richness across a rural to urban landscapes are not unequivocal. Positive, negative and neutral effects have been found, but what is causing this ambiguity in the relationship between species richness and urbanisation is poorly understood. Here we tested whether and how urbanisation affects isopod diversity and whether this depends on habitat soil type. We recorded isopod species presence and soil type in each 1 km2 grid cell in a 500 km2 area in and around the city of Amsterdam, the Netherlands. We analysed the relationship between the number of species and the most important traits (body size and drought- and inundation resistance), the percentage built-up area, and soil type (peat or clay) across a rural-urban landscape gradient. Because many studies find a negative effect of urbanization on biodiversity, we expected a decrease in isopod species richness by increasing amount of built-up area. We found a negative association between isopod species richness and the amount of built-up area across the rural-urban landscape gradient when rural soils contained clay, while for rural soils containing peat the highest species richness was found at intermediate levels of urbanisation. Hence, the relationship between isopod species richness and the level of urbanisation was mediated by soil type. We also found a significant relationship between percentage built-up area and functional traits, irrespective of soil type. Specifically, the percentage built-up area showed a positive correlation with isopod drought resistance as well as body size. These results together demonstrate (1) that soil type variation introduces an important, but often overlooked context-dependency in the effect of urbanisation on biodiversity and (2) that a functional trait approach is an important tool for understanding general effects of environmental change on biodiversity, irrespective of context-dependency.

Terrestrial isopods associated with shallow underground of forested scree slopes in the Western Carpathians (Slovakia).

The shallow underground of forested scree slopes represents a little-studied subterranean biotope. In this paper, species diversity and depth distribution of terrestrial isopod communities studied in the depth profile (5–95 cm from the surface) of eight forested scree slopes in the Western Carpathians (Slovakia) is discussed. The southern edge of the Western Carpathians where the study sites are located represents the northernmost limit of distribution of obligate subterranean fauna in Europe. The sites differ from each other in type of bedrock, forest composition, slope aspect, and altitude. To sample isopods, a set of three subterranean pitfall traps consisting of a plastic cylinder (Ø 110 mm) and ten plastic cups was buried in each studied scree slope. In total, 252 isopods belonging to eleven species were sampled (1–5 species per site). Of the species found, the blind and depigmented Mesoniscusgraniger was the sole species closely associated with deeper parts of the depth profile and was present in most of the sites studied. Another ten species were represented by a small number of individuals and their occurrence deeper in the scree slope profile was rather accidental. A comparison between winter and summer periods indicates apparent differences in seasonal activities of isopods. Ethylene glycol seems to be more appropriate fixative solution for trapping isopods than formaldehyde.

Terrestrial isopods (Oniscidea) of the White Carpathians (Czech Republic and Slovakia).

This paper summarizes data regarding the terrestrial isopods of the White Carpathians range in the Western Outer Carpathians based on field research undertaken during the past several decades in natural meadow pasture and forest localities. Using a combination of four collection methods 19 species belonging to nine families were recorded. The most common representatives were ProtracheoniscuspolitusTrachelipusrathkii and Ligidiumhypnorum. In general the biodiversity of isopod communities in the studied area was considerable with half of the localities explored inhabited by six to ten species. The composition of the isopod assemblages was determined by the character of the biotope and its geographical location. Forest habitats were considerably richer in species than the meadow and pasture ecosystems. Some xerotermic localities in the Slovak part of the area were inhabited by Trachelipusnodulosus and Orthometoponplanum thermophilic species typically associated with warmer parts of Europe. Two relic species (Hyloniscusmariae and Ligidiumgermanicum) were confirmed for this area. Except for only one finding of Porcellioscaber no other evidently introduced or synanthropic species were recorded. Based on the data analyzed the high nature conservancy value of the given area is emphasised.

Two new nonindigenous isopods in the Southwestern Atlantic: Simultaneous assessment of population status and shipping transport vector

The Southwestern Atlantic is often perceived as remote region, yet it is not immune to biological invasions. Patchy information on historical community composition hinders our ability to identify introductions to coastal ecosystems in this region. Hull fouling is an under-managed shipping vector that likely continues to transport large numbers of marine species worldwide. The port of Mar del Plata is a comparatively well-studied shipping and commercial hub that may serve as an observatory to monitor new introductions to the Argentine coast. Following detection of nonindigenous isopods during preliminary port sampling in 2007–2008, we organized regular port surveys aimed at assessing the level of population establishment and evaluated hull fouling as a potential introduction vector in the Port of Mar del Plata. In 2011–2012, we conducted 12 monthly dive surveys of port isopod communities in combination with three opportunistic surveys (two in-water, one in dry-dock) of hull fouling communities attached to a domestic research vessel during consecutive port calls at its base in this port. Replicate biofouling samples from underwater dock structures and the vessel's hull were collected by scraping invertebrates in 20 × 20 cm quadrats (even surfaces) and 1000 cm3 of biofouling organisms (uneven surfaces). Both in port- and hull-fouling communities, we discovered the presence of the nonindigenous isopods Dynamene edwardsi and Paracerceis sculpta. This report constitutes the first detection of these two global marine invaders in American and Argentine waters, respectively. They likely represent relatively recent introductions to this corner of the world's oceans, yet our data indicate that both species are currently well established in Mar del Plata. These results demonstrate (for the first time in the case of D. edwardsi) the potential for hull fouling to disperse both species, and raise a warning on their potential expansion to other Southwestern Atlantic ports and Antarctica in a near future. Research on the marine communities of the Southwestern Atlantic is pressingly needed to establish pre-invasion communities and detect new introductions. Simultaneous surveillance of ports (invasion hubs) and vessels (vectors) can effectively detect invaders and inform prevention efforts in this region.

Effects of roads and adjacent areas on diversity of terrestrial isopods of Hungarian highway verges

AbstractTransportation infrastructure may be the most important driver of social and economic development, but it is a major cause of environmental change in landscapes. The main objective of this paper is to report road edge effects on isopods of Hungarian highway verges. We examined the isopod diversity along five highways (M0, M1, M3, M5, M7) while accounting for road edge proximity and the adjacent areas. Double-glass pitfall traps were set in a total of 15 sites and at three distances from the edge of the roads next to different types of adjacent areas. We found differences between ecological parameters of isopod communities in relation to adjacent areas as well as to road edge proximity. The highest diversity was observed near urban areas, while the lowest was near the arable fields. Isopod diversity increased with decreasing distance from a road. Species diversity of different types of verges based on adjacent areas varied strongly in relation to road edge proximity. A medium distance (40 m) from roads had a positive effect on species richness, while verges next to arable fields were the most species-rich habitats. The general conclusion of this study is that highway verges provided suitable environment conditions for generalist isopod species but may be a limiting factor for specialist isopods. Moreover, highway verges function as corridors for isopods. The proximity of roads and urban areas positively affected isopods, and verges close to roads and urban areas are considered as an attractive environment for isopods in heterogeneous roadside verges.

The short- and long-term effects of changes of vegetation structure on isopod (Oniscidea) diversity and composition in Mátra Mountains

Abstract The aim of the present study was to examine the short- and long-term effects of changes in vegetation structure caused by shrub removal and mowing on isopod diversity and composition in Natura 2000 habitats of Mátra Landscape Protection Area. Species richness and isopod diversity increased in the short term as a result of annual changes in vegetation; however, the values of both indices were reduced in the long term. The changes in vegetation structure on a regional scale led to a reduced isopod diversity in the short and long term. The changes in vegetation structure caused alterations in community structure in the long term. We conclude that changes of vegetation structure have a negative effect on species richness and the diversity of isopod communities in the long term.

Diversity and abundance of isopod fauna associated with holdfasts of the brown alga Himantothallus grandifolius in Admiralty Bay, Antarctic

Abstract Fifteen species of isopods, representing 10 families, were recorded on holdfasts of the brown alga Himantothallus grandifolius. Material was collected in the 15–75 m depth range during the austral summer of 1979/80. The isopod community was dominated by Caecognathia antarctica (mean density 12.4 ± 13.1 ind./100 ml) followed by Cymodocella tubicauda (mean density 0.7 ± 2.1 ind./100 ml). Mean total density of isopods reached the value of 16.1 ± 14.0 ind./100 ml. The comparison with the other studies showed that holdfasts are inhabited by a distinctive isopod community that differs from the isopod fauna associated with soft bottom of Admiralty Bay.

Contrasting responses of millipedes and terrestrial isopods to hydrologic regime changes in forested montane wetlands

Forested montane wetlands are subject to changing disturbance regimes. The factors responsible for their hydrologic degradation include drainage for forestry. Few studies have explicitly addressed the effects of changing hydrologic regimes linked with artificial drainage and disruption of these drainage systems on soil fauna communities. Because millipedes (Diplopoda) and terrestrial isopods (Oniscidea) are an important components of the soil macro-decomposer community and exhibit a wide range of ecological requirements, we examined their response to regimes changes in mountain fen sites of Caltho-Alnetum demonstrating different degrees of alteration of hydrologic conditions and classified into three categories: natural, semi-natural and degraded. Our results showed that hydrologic alteration of mountain fens affected terrestrial isopod and millipede communities much less strongly than soil physico-chemical properties. However, the increasing hydrologic disturbances, due to drainage and lowering of groundwater level also led to differential responses of these two groups of soil macro-decomposer communities, and induced significant change of terrestrial isopod community composition in semi-natural conditions but no response of millipede communities. The observed differences in the responses of these two groups correspond to differences in their sensitivity, resistance and resilience to hydrologic changes in mountain fens. We conclude that the significant response of terrestrial isopod community composition documented in semi-natural conditions reflects their low ability to return to the pre-drying state and indicates their higher sensitivity and limited resilience to disturbances related to groundwater withdrawal compared to communities of millipedes. Besides, our results also suggest that in mountain areas altitude acts as a stronger environmental filter on community composition of terrestrial isopods and millipedes than hydrologic conditions.

Plant communities preferences of terrestrial crustaceans (Isopoda: Oniscidea) in a protected coastal area of southeastern Sicily (Italy)

We studied the plant communities preferences of oniscidean isopods in a protected coastal area in southeastern Sicily that is characterized by ponds, dunes and rocky coast. In total, five sites were sampled between March 2003 and February 2004 using pitfall traps. A total of 7,326 specimens were found, belonging to 23 species. The vegetation analysis, using the phytosociological method, recognized a total of 11 types of plant communities, with specific ecological features. Measuring the species richness, diversity and annual activity density (aAD) values of the terrestrial isopod communities from each sampling site revealed differences among the various plant communities. PCA analysis confirmed the correlation between isopods species and specific plant communities. Moreover our results show that the high species richness is associated with a high vegetation cover and number of plants.

Egy heterogén erdőállomány avarlakó szárazföldi ászkarák-közösségeinek (Isopoda: Oniscidea) összehasonlítása

The aim of our research was an ecofaunistic investigation of isopod communities living in different habitats (three different oak woods, two acacia woods, and a pine-grove) of a heterogeneous forest. In particular, we described and compared the species composition, the dominance structure and diversity indices of the communities (Shannon, Rényi) in the habitats. The researched area (“Községi forest”) situated near the Deseda-lake (Kaposvár, Somogy County). Nine Barber pitfall traps were laid in three parallel lines in six sampling patches. The traps had been working from March to November, 2011 and were emptied eleven times during this interval. The traps caught a total of 8769 isopods belonging to 10 species. Protracheonicus politus had the largest (80.21%) proportion of the total sample so this species is the dominant woodlouse of the Községi forest. The ratio of Porcellium collicola (12.77%), Trachelipus rathkii (4.56%) and Trachelipus ratzeburgii (1.96%) were also noticeable. The amount of the other species was low (1-50 specimens). Some of these species (Haplophthalmus danicus, Hyloniscus riparius, Trichoniscus provisorius) live in the soil or in decaying trees so usually they are under-represented in pitfall samples. An average of six species was found in each habitat. The highest numbers of species (7) occurred in the acacia forests and in an oak wood habitat, while the smallest (5) in another oak wood by the lake. The species compositions of an acacia and an oak wood were identical using Sørensen similarity index. The isopod community of the pine-grove was also similar. The sample of the ruderal weed vegetation differed in the highest degree from the woody habitats. By the results, the isopod community could be very similar in different woody habitats. We found the highest Shannon diversity values in the weedy habitat. The Rényi diversity ordering gave the same result.

Isopod communities of Black locust (Robinia pseudoacacia L.) plantations in Transdanubia (Hungary)

Terrestrial isopod communities were studied in 27 Black locust forest in Transdanubia between 1995 and 2011 by hand sampling and pitfall trapping. The investigations yielded 17 species. The most common isopod species of Transdanubia (Porcellium collicola, Armadillidium vulgare, Trachelipus rathkii, T. nodulosus and Hyloniscus riparius) proved to be frequent in the Black locust plantations, too. All of these species are generalists. The assemblages consisted of 4-5 species. Dominant species of the communities were A. vulgare or P. collicola, alternatively. Species diversity and evenness of the assemblages were low. Strong association was pointed out between A. vulgare, P. collicola and T. rathkii while negative association was calculated between T. nodulosus and H. riparius.

Terrestrial isopod community as indicator of succession in a peat bog

Terrestrial isopods were studied in the Dubravica peat bog and surrounding forest in the northwestern Croatia. Sampling was conducted using pitfall traps over a two year period. Studied peat bog has a history of drastically decrease in area during the last five decades mainly due to the process of natural succession and changes in the water level. A total of 389 isopod individuals belonging to 8 species were captured. Species richness did not significantly differ between bog, edge and surrounding forest. High species richness at the bog is most likely the result of progressive vegetation succession, small size of the bog and interspecific relationships, such as predation. With spreading of Molinia grass on the peat bog, upper layers of Sphagnum mosses become less humid and probably more suitable for forest species that slowly colonise bog area. The highest diversity was found at the edge mainly due to the edge effect and seasonal immigration, but also possibly due to high abundance and predator pressure of the Myrmica ants and lycosid spiders at the bog site. The most abundant species were Trachelipus rathkii and Protracheoniscus politus, in the bog area and in the forest, respectively. Bog specific species were not recorded and the majority of the species collected belong to the group of tyrphoneutral species. However, Hyloniscus adonis could be considered as a tyrphoxenous species regarding its habitat preferences. Most of collected isopod species are widespread eurytopic species that usually inhabit various habitats and therefore indicate negative successive changes or degradation processes in the peat bog.

Ecological and zoogeographical significance of terrestrial isopods from the Carei Plain natural reserve (Romania)

In the Carei Plain natural reserve we identified 15 terrestrial isopod species: Haplophthalmus mengii, Haplophthalmus danicus, Hyloniscus riparius, Hyloniscus transsylvanicus, Plathyarthrus hoffmannseggii, Cylisticus convexus, Porcellionides pruinosus, Protracheoniscus politus, Trachelipus arcuatus, Trachelipus nodulosus, Trachelipus rathkii, Porcellium collicola, Porcellio scaber, Armadillidium vulgare and Armadillidium versicolor. The highest species diversity is found in wetlands, while the lowest is in plantations and forests. On the Carei Plain, there are some terrestrial isopods that are normally connected with higher altitudes. Moreover, some sylvan species are present in the open wetlands. Unlike marshes, sand dunes present anthropophilic and invasive species. The diversity of the terrestrial isopods from the Carei Plain protected area is high due to the habitats? diversity and the history of this area. Thus, the composition of the terrestrial isopod communities from the area underlines its distinct particularities, emphasizing the necessity of preserving the natural habitats.

Habitat diversity, ecological requirements of species and the Small Island Effect

ABSTRACTAim To explore the causal factors leading to a significant Small Island Effect (SIE), that is, the absence of the commonly found species–area relationships below an island size, on the terrestrial isopod communities from a large number of islands.Location Ninety islands of the Aegean Sea (Greece).Methods The detection of a significant SIE is assessed through the application of all three methods available in the literature. Species are divided into generalists and specialists. We tested if the minimum area and the area range of each species’ occurrences differ between generalists and specialists. Next, we searched for differences in the ratios of specialists to generalists above and below the SIE threshold, and tested their cumulative ratios when islands are arranged according to increasing area, altitude or habitat diversity in order to identify the threshold where they become statistically indistinguishable from the ratio of the total set of islands.Results Our results indicate a strong effect of habitat availability on the SIE. Communities of islands within the SIE range, host a higher percentage of generalists. An analysis of the specific habitat requirements shows that, for isopods, the crucial factor is the lack of habitats related to inland waters from small islands.Main conclusions The distribution of habitats on islands of different size is of major importance for the occurrence of a SIE. The relative representation of specialist and generalist species on islands of different size plays an important role in shaping SIE‐related patterns. Conservation efforts should pay special attention on freshwater habitats, especially on small Aegean islands. Identifying the causal factors of SIE, combined with a thorough knowledge of the ecological requirements of species can offer insights into identifying habitat types and groups of species that are more vulnerable to alterations of the environment.

Effects of disturbance on the biodiversity and abundance of isopods in temperate grasslands

Connell's ‘intermediate disturbance hypothesis’ was tested using a relatively simple, species poor isopod community in grass heaths and in a coastal sand dune grassland. Variation in diversity resulted from disturbance both to the soil profile and sward structure due to grazing. Predictions from a spatial survey were tested using a 20 years time series. These changes were related to changes in rabbit activity, anthropogenic soil disturbance and on one site, deposition of blown sand. Changes in the soil profile resulted in diversity initially increasing due to decreases in the density of the commonest species, leading to an increase in equitability. Prolonged disturbance to the soil profile both due to sand blowing onto one site and rotavating on another, lead to a reduction in diversity due to one of the species being eliminated. The isopod community was most diverse when least disturbed by grazing, of intermediate diversity under intermediate grazing intensity and least diverse when most heavily grazed. In these simple communities, differences in diversity were mostly determined by differences in equitability rather than in species richness. We conclude that maximising heterogeneity of sward structure could have advantages for the conservation of both invertebrate biodiversity and vertebrates that feed on them.