Aquatic Terrestrial Linkages Along a Braided-River: Riparian Arthropods Feeding on Aquatic Insects

Rivers can provide important sources of energy for riparian biota. Stable isotope analysis (δ¹³C, δ¹⁵N) together with linear mixing models, were used to quantify the importance of aquatic insects as a food source for a riparian arthropod assemblage inhabiting the shore of the braided Tagliamento River (NE Italy). Proportional aquatic prey contributions to riparian arthropod diets differed considerable among taxa. Carabid beetles of the genus Bembidion and Nebria picicornis fed entirely on aquatic insects. Aquatic insects made up 80% of the diet of the dominant staphylinid beetle Paederidus rubrothoracicus. The diets of the dominant lycosid spiders Arctosa cinerea and Pardosa wagleri consisted of 56 and 48% aquatic insects, respectively. In contrast, the ant Manica rubida fed mainly on terrestrial sources. The proportion of aquatic insects in the diet of lycosid spiders changed seasonally, being related to the seasonal abundance of lycosid spiders along the stream edge. The degree of spatial and seasonal aggregation of riparian arthropods at the river edge coincided with their proportional use of aquatic subsidies. The results suggest that predation by riparian arthropods is a quantitatively important process in the transfer of aquatic secondary production to the riparian food web.     

The role of invertebrates in seedling establishment in a heterocarpic plant,Atriplex sagittata

Seed heteromorphism is a marked character of many Chenopodioideae (Amaranthaceae). Seed morphs differ in dormancy, germination and seedling biology, but differences in their predation have not yet been studied. Atriplex sagittata produces small black dormant and large brown non‐dormant seeds. In this study, the timing of seed release and seedling establishment were ascertained, and their consumption by invertebrates (carabids, isopods and slugs) was studied. Seeds dispersed in the autumn passed the winter on the ground surface, protected from invertebrate predation by low temperatures. In the following vegetative season, ungerminated black seeds exposed to predation on ground surface were preferred by a large carabid species, Pseudoophonus rufipes. Some black and all brown seeds escaped predation by germinating in early spring. The seedlings were little endangered by carabids and isopods but were preferred by an invasive slug, Arion vulgaris, the feeding of which can exterminate seedlings at places in which slugs are abundant. Invertebrate predation is important factor of seed and seedling mortality of A. sagittata and seed heteromorphism modifies its intensity and timing.     

Ecological response hides behind the species abundance distribution: Community response to low‐intensity disturbance in managed grasslands

Land‐use and management are disturbance factors that have diverse effects on community composition and structure. In traditional rural grasslands, such as meadows and pastures, low‐intensity management is maintained to enhance biodiversity. Maintenance of road verges, in turn, creates habitat, which may complement traditional rural grasslands. To evaluate the effect of low‐intensity disturbance on insect communities, we characterized species abundance distributions (SAD) for Carabidae, Formicidae, and Heteroptera in three grassland types, which differed in management: meadows, pastures, and road verges. The shape of SAD was estimated with three parameters: abundance decay rate, dominance, and rarity. We compared the SAD shape among the grassland types and tested the effect of environmental heterogeneity (plant species richness) and disturbance intensity (trampling in pastures) on SADs. The shape of SADs did not differ among the grassland types but among the taxonomic groups instead. Abundance decay rate and dominance were larger for Formicidae, and rarity smaller, than for Carabidae and Heteroptera. For Carabidae and window‐trapped Heteroptera, rarity increased with increasing plant species richness. For Formicidae, dominance increased with trampling intensity in pastures. Although the SAD shape remained largely unchanged, the identity of the dominant species tended to vary within and among grassland types. Our study shows that for a given taxonomic group, the SAD shape is similar across habitat types with low‐intensity disturbances resulting from different management. This suggests that SADs respond primarily to the intensity of disturbance and thus could be best used in monitoring communities across strong disturbance and environmental gradients. Because taxonomic groups can inherently have different SADs, taxon‐specific SADs for undisturbed communities must be empirically documented before the SAD shape can be used as an indicator of environmental change. Because the identity of the dominant species changes from management type to another, the SAD shape alone is not an adequate monitoring tool.     

Morphological variation in <Emphasis Type="Italic">Laboulbenia polymorpha</Emphasis> (Laboulbeniales)

Specimens of the type collection of Laboulbenia polymorpha Sugiyama (1978) were reexamined. The holotype, M. Ishikawa 673, is composed of three slides and includes three morphologically different forms of thalli, of which two forms were illustrated (Sugiyama 1978, fig. 1-D, 1-E). On the other hand, one of the paratypes, M. Ishikawa 674, has now been lost but photographs were made earlier from this slide, in which one mature individual illustrated as fig. 1-C (Sugiyama 1978) is included. This individual was not correctly shown in Sugiyamas illustration, but actually has a strong resemblance to a form in slide 673-b that was not illustrated by Sugiyama (1978). Thus, three different forms have been recognized as variations of L. polymorpha. In the present article, each variation was termed C-form, D-form, and E-form because Sugiyama (1978) used the same notation in his figures. A mature specimen of C-form in slide 673-b has been selected as a lectotype. Slide 673-d includes only young thalli, one of which was illustrated as fig. 1-G (Sugiyama 1978). This young thallus undoubtedly belongs to another species; mature thalli of the same species were also found in slide 673-b. Another paratype, K. Sugiyama 2101, includes C- and D-forms of L. polymorpha. Infection sites of the C- and D-forms have been determined: the C-form grows mainly on the lateral margins of the elytra of the host, and the D-form occurs mainly on the basal part of the elytra and the mesothorax.     

Differentiation of spring carabid beetle assemblages between semi‐natural habitats and adjoining winter wheat

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中国沟胸步甲属分类研究及一新种描述(鞘翅目： 步甲科： 壶步甲族)

【目的】沟胸步甲属Holcoderus属于鞘翅目(Coleoptera)步甲科(Carabidae)壶步甲族(Lebiini)。本研究旨在对该属在中国分布的各个种进行分类厘定。【方法】基于中国科学院动物研究所的馆藏标本以及欧洲多家博物馆的模式标本,采用形态比较学方法开展研究。【结果】共发现中国沟胸步甲属5种,其中包括新种1种(双毛沟胸步甲H. bisetus sp. n.,模式产地：云南西双版纳),中国新纪录种3种(雅沟胸步甲H. gracilis、绿沟胸步甲H. smaragdinus和红腿沟胸步甲H. aeripennis)。提供了中国所有种类的形态描述及特征图,并编制了分种检索表。【结论】至此,我国所分布的沟胸步甲属物种从此前记录的1种增加至5种。     

All-year reproduction and possible thermal melanism in <Emphasis Type="Italic">Amblystogenium pacificum</Emphasis> (Coleoptera: Carabidae) on the sub-Antarctic Ile de la Possession (Iles Crozet)

In the fell-field habitat at 140–270 m altitude on the sub-Antarctic Ile de la Possession, Iles Crozet, the dimorphic beetle Amblystogenium pacificum Putzeys (Coleoptera: Carabidae) was studied monthly throughout the southern year 1993–1994 by timed hand collections involving turning stones on the rocky fell-field. There were many mating couples and females containing well-developed eggs in every month and the species reproduced throughout the year, with no evidence of a winter cessation of egg production. However, the frequency of mating couples was about twice as great in the summer half-year (October–March) as in the winter half (April–September). Relatively small differences in monthly mean temperatures between the summer and winter at Iles Crozet render all-year reproduction not unexpected when comparisons are made with the temperatures and phenology of Carabidae in cool habitats in other parts of the world. Mating pairs were collected at unusually high frequencies for carabids. The frequency of such pairs, taken per unit effort by hand collecting, was highest in October–December, lower from January to May and intermediate from June to September. Comparison of beetles taken as solitary, non-mating individuals with those taken as mating couples showed that in summer, females of the black morph of this dimorphic species were more frequently involved in mating than expected, but no differences were detected in winter. Female beetles were divided into younger individuals (putative age 1–2 years) and older females (putative age 3–5 years or more) by the amount of claw-wear on individuals of this species. This division indicated that about 40% of the older females showed no egg development when captured, but only about 20% of the younger females were non-breeding. However, of the reproducing beetles, young and old females matured similar numbers of eggs. An altitude transect showed that the proportion of the black morph increased significantly with altitude. Studies at 140–270 m showed that a significantly smaller proportion of the older females of the brown morph were breeding than in the younger brown individuals, and this effect was particularly evident in the colder winter period. No such age differences existed amongst the black morph.     

Carabid beetle (Coleoptera: Carabidae) assemblages in the intermediate successional stage after Mt. Bandai eruption of 1888: Effects of environmental variables on carabid beetles in the Urabandai area

We studied carabid beetle assemblage structure and species diversity in an intermediate successional stage (seral) forest established in areas affected by the 1888 eruption of Mt. Bandai and a climax forest that had not been affected by the eruption at the Urabandai area, Fukushima Prefecture, Japan. In total, 2,131 carabid beetles representing 31 species were collected using pitfall traps without bait. A comparison of carabid beetle assemblages between the two forest types revealed that the number of species observed was comparable, but their abundance was greater in the seral forest. The assemblage structure clearly differed between the two forest types. In the seral forest, forest generalists, such as Synuchus arcuaticollis and Pterostichus prolongatus, along with forest specialists including Carabus vanvolxemi and Pterostichus asymmetricus, were collected. In the climax forest, forest generalists, such as Synuchus cycloderus and Carabus albrechti tsukubanus, were more abundant than forest specialists. This suggests that the current seral forest in the Urabandai area possesses environmental variables that enable the coexistence of both forest specialist and generalist beetle species. A redundancy analysis showed that six species from the genera Synuchus and Pterostichus were associated with high canopy openness and high understory vegetation cover, whereas species recorded only in the climax forest were associated with deep litter. Therefore, it seems likely that carabid beetles in the Urabandai area were affected by these three environmental variables.     

Behaviour‐driven micro‐scale niche differentiation in carabid beetles

Carabid beetles form rich and abundant communities in arable landscapes. Their generalist feeding behaviour and similar environmental requirements raise questions about the mechanisms allowing the coexistence of such species‐rich assemblages. We hypothesized that subtle niche partitioning comes into play on spatial, temporal, or trophic basis. To test this, we performed experiments and made observations on the behaviour of two sympatric carabid species of similar size and life cycle, Bembidion quadrimaculatum L. and Phyla obtusa Audinet‐Serville (both Coleoptera: Carabidae: Bembidiini). We compared plant climbing behaviour, daily activity patterns, and trophic preferences between the two carabid species under laboratory conditions. Whereas no clear difference in trophic preference was observed, our results suggest temporal niche differentiation at the nychthemeron scale (a period of 24 consecutive hours), with one of the species being more diurnal and the other more nocturnal, and spatial differentiation in their habitat use at the plant stratum scale. Intra‐specific variation suggests that micro‐scale spatio‐temporal niche differentiation could be mediated by behavioural plasticity in these two carabid species. We speculate that such behavioural plasticity may provide carabid beetles with a high adaptive potential in intensively managed agricultural areas.     

New records of the carabidicolous Laboulbeniales (Ascomycetes) of Japan (II)

Six carabidicolous species of Laboulbeniales are reported as new for the Japanese mycoflora. They areLaboulbenia finitima, L. separata, L. borneensis, L. manubriolata, Dimeromyces caribaeus, andDixomyces ornatus. In Japan, the former three species are parasitic onMochtherus luctuosus and the latter three species onPerigona nigriceps. Laboulbenia finitima occurs on the left legs (tarsi and tibiae);L. separata on the left elytral margin:L. borneensis on the pronotum;L. manubriolata on the pronotum and elytra;Dimeromyces caribaeus on the right inferior posterior surface of the prothorax (pronotal hypomeron); andDixomyces ornatus on the outer margin of the right elytron. Comments and photographs are given for each fungus.