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The soil microbial food web plays a vital role in soil health, nutrient cycling and agricultural productivity. Notably, there is a distinct paucity of information regarding the effects of heavy metal contamination on trophic-level interactions within the microbial food web of agricultural soils, which experience appreciably metal contamination worldwide. Herein, we investigated trophic interactions among predators (protists), their preys (bacteria and fungi) and competitors (nematodes) under four metal contamination levels using high-throughput sequencing and a laboratory verification experiment. Metal contamination decreased growth of protist-preferential prey (e.g., small-sized and gram-negative bacteria), increased the growth of protist-nonpreferential prey (e.g., pathogenic fungi and Actinobacteria), and had a limited effect on the soil protist-competitor (i.e., nematodes). This resulted in a considerable decrease in the diversity and abundance of protistan consumers and a re-arrangement of their interactions with other organisms. From a systemic view, the direct link was weaker between heavy metal contamination and the protist community than the indirect linkage, i.e., metal-induced changes in the prey community. We further validated these results with laboratory incubation trials that documented growth inhibition of protist (Colpoda) and protist-preferential prey (Spingomonas) versus growth stimulation of protist-nonpreferential prey (Arthrobacter) under metal contamination. These findings indicate that metal contamination collapses trophic-level interactions within the soil microbial food web via bottom-up regulation, providing important implications for managing trophic interactions to maintain agricultural ecosystem services under the challenge of worldwide metal contamination.

Drought events are increasingly affecting the planet's biodiversity. While shrinking body size in response to drought has been observed in many vertebrate animals, whether this rule applies to microscopic animals and the mechanisms during this process remains largely unknown. To address this knowledge gap, we conducted a regional-scale investigation and a microcosm experiment to systematically evaluate the impact of drought stress on the body size of the most abundant soil animals on Earth – nematodes – across various biological scales, including community, population and individual levels. Our results showed that nematode body size declined with drought stress at all biological scales, including a community shift toward smaller-sized species, a smaller body size at the population scale, and a decrease in size-at-age of individuals. Additionally, we designed a petri dish experiment to examine the reversible plasticity of body size under drought stress using a drought-tolerant nematode species. We found that while nematode body size could not be fully reversed when drought stress was alleviated in the offspring generation, offspring from parents that experienced severe drought conditions could acquire tolerance, leading to a relatively smaller reduction in overall body size compared to those from parents that suffered no or light drought conditions. Overall, our study suggests that the increasing frequency of drought events at the global scale will lead to a reduction in soil nematode body size, potentially causing far-reaching consequences for additional changes in the climate, as well as nutrient cycling in soils.

Bacterial persisters are phenotypic variants that tolerate exposure to lethal antibiotics. These dormant cells are responsible for chronic and recurrent infections. Multiple mechanisms have been linked to persister formation. Here, we report that a complex, consisting of an extracellular poly(dC) and its membrane-associated binding protein RmlB, appears to be associated with persistence of the opportunistic pathogen Pseudomonas aeruginosa. Environmental stimuli triggers a switch in the complex physiological state (from poly(dC)/RmlB to P-poly(dC)/RmlB or RmlB). In response to the switch, bacteria decrease proton motive force and intracellular ATP levels, forming dormant cells. This alteration in complex status is linked to a (p)ppGpp-controlled signaling pathway that includes inorganic polyphosphate, Lon protease, exonuclease VII (XseA/XseB), and the type III secretion system. The persistence might be also an adaptive response to the lethal action of the dTDP-l-rhamnose pathway shutdown, which occurs due to switching of poly(dC)/RmlB., The mechanisms underlying bacterial persisters formation remain poorly understood. Here, Chen et al. identify a complex formed by extracellular poly(dC) and the binding protein RmlB that controls Pseudomonas aeruginosa persister formation in response to environmental stimuli.

Tomocerus nabanensis sp. nov. Figs 1C, 6, 7 Type material. Holotype: female on slide, Naban River National Nature Reserve, Xishuangbanna, Yunnan Province, China, 100°39'E, 22°8'N, alt. 1225 m, vii.2017, litters and humus, leg. Shengjie Liu (17BN1). Paratypes: 3 females and 2 males on slides, 15 adults and juveniles in alcohol, same data as holotype. All types in NJAU. Description. Body length 2.1–3.5 mm. General background colouration of body dirty brownish yellow, antero-lateral margin of thoracic terga darker. Ant. I and Ant. II distally with purple pigment, Ant. III and Ant. IV purple. Eye patch black. Purple pigment around antennal bases and mouthparts. All leg segments with diffuse purple pigment, tibiotarsi darker (Fig. 1C). Antenna 0.8–1.0× length of body. Length ratio of Ant I:II:III:IV = 1.0:1.3–1.4:9.0–9.3:1.2–1.4. Cephalic dorsal macrochaetotaxy: anterior area: 2 (A2), 4 (A3, A5); interocular area: 2 (M2), 7 (S0, S2, S5, S 5i); postocular area: 2+2 (Pa5, Pa6); posterior area: 1+1 (Pa2). Posterior margin of head with 35–40 chaetae on each side (Fig. 6A). Pattern of body chaetotaxy as in Fig. 6B. Th. II with macrochaetae a3, a4a and a5a behind anterior marginal macrochaetae cluster; central area with macrochaetae a2, a5, m1, m2 (rarely absent) and m3. Trochantero-femoral organ with 1, 1 slender chaetae. Tibiotarsi I, II, III ventrally with 7–9, 6–9, 7–9 strong chaetae, 2–4, 2–4, 3–5 of them blunt (Fig. 6C). Tenent hair 0.64–0.74× length of inner edge of unguis; anterior accessory chaeta shorter than pretarsal chaetae, posterior accessory chaeta longer than pretarsal chaetae; guard chaetae subequal to or slightly longer than tenent hair. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with basal tooth and more distal tooth at about 1/3 distance from base. Unguiculus lanceolate, about 0.58–0.71× length of unguis, its inner edge with one tooth (Fig. 6D). Ventral tube scaled on both faces. Anterior face with 20–30 chaetae on each side, posterior face with 40–90 chaetae, each lateral flap unscaled, with 45–95 chaetae. Anterior face of tenaculum with 5–11 chaetae and without scales (Fig. 6E). Ratio of manubrium:dens:mucro = 2.6–3.0:3.5–3.9:1.0. Manubrium ventrally scaled without chaetae; laterally with large round scales and 10 chaetae, proximal 1–2 chaetae slender and almost smooth, distal chaetae strong and slightly serrated; each dorsal chaetal strip with 95–145 chaetae of different sizes, an irregular row of scales from base to about 2/3 length of manubrium along inner edge, and 6–14 pseudopores on lateral side; a pair of pointed prominent chaetae near distal end of manubrium (Fig. 7A); distal corner chaeta as large as small mesochaetae in chaetal strip. Dens basally with pointed prominent dorsal chaeta. Dental spine formula as 4–5/3–7, 1, 1, 1 (Fig. 7B); denticles on spines unevenly distributed, all spines with basal moderate to large denticles, large spines ventrally with additional small denticles (Fig. 7C). Mucro with 3–7 intermediate teeth (Fig. 7D). Etymology. Named after type locality Naban River National Natural Reserve. Habitat. Mixed forest, in leaf litters and humus. Remarks. Tomocerus nabanensis sp. nov. is characterised by absence of cephalic macrochaeta Pp3 and mesothoracic macrochaetae a4 and m4, presence of two inner teeth on the unguis, 1+1, 1 pointed prominent chaetae on the furca, dorsal scales on the manubrium, a small spine between two large distal spines and uneven distribution of denticles on the dental spines. The new species resembles cave species T. postantennalis, Tomocerus dong Yu & Li, 2016 and Tomocerus deharvengi Yu & Li, 2016 in dental spine formula and number of the ungual teeth, but differs from the latter species in absence of the large PAO, different pattern of the dorsal chaetotaxy and presence of stronger tenent hairs. The general appearance and dental spine formula of the new species are also similar to those of T. folsomi, but the latter has more teeth on the unguis and smaller denticles on dental spines (Denis 1929). Critical characters discriminating T. nabanensis sp. nov. from similar species are listed in Table 1. Malformed dental spine formulas are found in one female, with 9/4, 1, 3, 1 on the right side and 6/7, 1, 1 on the left side, and in this case proximal spines on both sides are irregularly arranged, distal small spines on the right side are arranged in two rows.

Genus Tomocerus Nicolet, 1842 Common characters for three new species. PAO absent. Eyes 6+6. Both dorsal and ventral sides of head scaled. Mouthparts normal for Tomocerus. Labral formula 4/5, 5, 4, distal edge of labrum with 4 curved spine-like papillae. Maxillary lamella 5 without beard-like appendage. Both dorsal and ventral sides of Ant. I and Ant. II scaled, Ant. III unscaled or occasionally with 1–2 basal scales, Ant. IV unscaled. Macrochaetae densely arranged along anterior margin of Th. II and sparsely on each terga, most mesochaetae laterally and posteriorly on terga. Number of macrochaetae or large mesochaetae in posterior row as 3 (p2, p3, p4), 3 (p1, p3, p5)/ 3 (m2, m3, m4), 3 (m2, m3, m4), 4 (p1, p3, p6, p7), 2 (p6, p7), 4 (m2, m3, m5, m6) from Th. II to Abd. V. Th. III with anterior macrochaeta a4; Abd. III with two anterior macrochaetae m3 and m6; Abd. IV with antero-lateral macrochaeta m6; Abd. VI with numerous chaetae of different sizes. Bothriotricha 2 (a6, m6), 1 (m6)/ 0, 0, 1 (a5), 2 (a2, a5), 0, 0 on Th. II—Abd. VI. Tergal pseudopores 1, 1/ 1, 1, 1, 1, 0, 0 from Th. II to Abd. VI near body axis. Each tibiotarsus with distal whorl of 11 chaetae, ventral 6 as ordinary chaetae, dorsal 5 modified as a central clavate tenent hair, a pair of short accessory chaetae and a pair of slender guard chaetae. Dens basally without outer strong chaetae as Plutomurus or inner large differentiated scales as Pogonognathellus. Dental spines compound, with numerous secondary denticles on surface. Dens dorsally with ordinary chaetae and plumose chaetae, ventrally with dense scales and several apical chaetae. Mucro elongated, bearing numerous chaetae with elongated sockets (not shown in figures); apical tooth subequal to or slightly longer than subapical tooth; two dorsal lamellae running from proximal edges of subapical tooth, outer lamella ending in distal edge of inner basal tooth, inner lamella ending freely at base of mucro, intermediate teeth located on outer lamella; both basal teeth with proximal lamellae, outer basal tooth with toothlet., Published as part of Yu, Daoyuan, Yang, Xiaodong & Liu, Manqiang, 2018, Three new species of Tomocerus from tropical zone of China (Collembola, Tomoceridae), pp. 225-236 in Zootaxa 4508 (2) on page 226, DOI: 10.11646/zootaxa.4508.2.5, http://zenodo.org/record/2607034, {"references":["Nicolet, H. (1842) Recherches pour servir a l'histoire des Podurelles. Nouveau Memoires de la Societe Helvetique des Sciences Naturelles, 6, 1 - 88."]}

Tomocerus tropicus sp. nov. Figs 1A, 2, 3 Type material. Holotype: female on slide, Mt. Wuzhishan National Nature Reserve, Shuiman Township, Wuzhishan, Hainan Province, China, 109°41'15"E, 18°54'11"N, alt. 901 m, 29.xii.2015, litters and humus on rocks, leg. Daoyuan Yu and Chunyan Qin (15HN5). Paratypes: 2 females, 1 male and 1 subadult on slides, 11 adults and juveniles in alcohol, same data as holotype. All types in NJAU. Description. Body length 3.3–3.9 mm. General background colouration of body white to light yellow. Ant. I and Ant. II distally with purple pigment, Ant. III and Ant. IV purple. Eye patch black. Diffuse purple pigment around mouthparts. Tibiotarsi purple and other segments occasionally with light purple pigment (Fig. 1A). Antenna 0.8–0.9× length of body. Length ratio of Ant I:II:III:IV = 1.0:1.3–1.5:8.8–10.0:0.7–0.9. Cephalic dorsal macrochaetotaxy: anterior area: 2 (A2), 4 (A3, A5); interocular area: 2 (M2), 7 (S0, S2, S5, S 5i); postocular area: 2+2 (Pa5, Pa6); posterior area: 2+2 (Pa2, Pp3). Posterior margin of head with 30–40 chaetae on each side (Fig. 2A). Pattern of body chaetotaxy as in Fig. 2B. Th. II with macrochaetae a3, a4, a4a and a5a behind anterior marginal macrochaetae cluster; a2, a5, m3 and m 4 in central area. Trochantero-femoral organ with 1, 1 slender chaetae subequal in length (Fig. 2C). Tibiotarsi I, II, III ventrally with 6–7, 6–7, 6 strong chaetae, 3–4, 4, 6 of them blunt (Fig. 2D). Tenent hair 0.8–1.0× length of inner edge of unguis; accessory chaetae slightly longer than pretarsal chaetae; guard chaetae subequal to tenent hair in length. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with basal tooth and 4–6 more distal teeth, sub-basal tooth stronger. Unguiculus lanceolate, about 0.6–0.8× length of unguis, its inner edge with one tooth (Fig. 2E). Ventral tube scaled on both faces. Anterior face with 16–20 chaetae on each side, posterior face with 50–65 chaetae, each lateral flap unscaled, with 50–115 chaetae. Anterior face of tenaculum with 8–18 chaetae and without scales (Fig. 2F). Ratio of manubrium:dens:mucro = 2.9–3.4:4.0–4.4:1.0. Manubrium ventrally scaled without chaetae; laterally with large round scales and 10–11 chaetae, proximal 1–2 chaetae slender and almost smooth, distal chaetae strong and slightly serrated; each dorsal chaetal strip with 125–180 chaetae of different sizes, an irregular row of scales from base to 1/3–1/2 length of manubrium along inner edge, and 10–15 pseudopores on lateral side; 2 pairs of blunt prominent chaetae at centre and near distal end of manubrium, respectively, proximal prominent chaeta longer (Fig. 3A); distal corner chaeta as about size of small mesochaetae in chaetal strip (Fig. 3B). Dens basally with blunt prominent dorsal chaeta. Dental spine formula as 4–5/3–5, 2, sizes of spines gradually increase on basal subsegment (Fig. 3C); denticles on spines unevenly distributed, small spines with basal large denticles and a few small denticles, moderate and large spines dorsally mainly with basal large denticles, ventrally with basal moderate and distal small denticles (Fig. 3D). Mucro with 6–9 intermediate teeth (Fig. 3E). Etymology. Latin word tropicus: tropical. Habitat. Mixed forest, in leaf litters and thin layer of humus on rocks. Remarks. Tomocerus tropicus sp. nov. is characterised by the presence of 4 central macrochaetae a2, a5, m3 and m4 on Th. II, 2+2, 1 blunt prominent chaetae on the furca, dorsal scales on the manubrium, and uneven distribution of different-size denticles on large dental spines. The species resembles Tomocerus pseudocreatus Yu, 2018 in cephalic chaetotaxy, claw complex and furca prominent chaetae, but the latter has mesothoracic central macrochaetae m1 and m2 but not m4, no scales on the dorsal side of manubrium, and almost evenly distributed denticles on large dental spines. Critical characters discriminating T. tropicus sp. nov. from similar species are listed in Table 1., Published as part of Yu, Daoyuan, Yang, Xiaodong & Liu, Manqiang, 2018, Three new species of Tomocerus from tropical zone of China (Collembola, Tomoceridae), pp. 225-236 in Zootaxa 4508 (2) on pages 227-229, DOI: 10.11646/zootaxa.4508.2.5, http://zenodo.org/record/2607034, {"references":["Yu, D. Y., Qin, C. Y., Ding, Y. H., Hu, F., Zhang, F. & Liu, M. Q. (2018) Revealing species diversity of Tomocerus ocreatus complex (Collembola: Tomoceridae): integrative species delimitation and evaluation of taxonomic characters. Arthropod Systematics & Phylogeny, 76 (1), 147 - 172."]}

Tomocerus nan sp. nov. Figs 1B, 4, 5 Type material. Holotype: female on slide, Mt. Diaoluo National Nature Reserve, Lingshui Autonomous County, Hainan Province, China, 109°52'3"E, 18°43'40"N, alt. 933 m, 25.xii.2015, litters and rotten woods, leg. Daoyuan Yu and Chunyan Qin (15HN2). Paratypes: 2 females, 3 males and 1 subadult on slides, 9 adults and juveniles in alcohol, same data as holotype. All types in NJAU. Description. Body length 2.2–3.1 mm. General background colouration of body light yellow. Ant. I and Ant. II distally with light purple pigment, Ant. III and Ant. IV purple. Eye patch black. Tibiotarsi and distal half of hind femur purple (Fig. 1B). Antenna 0.8–1.0× length of body. Length ratio of Ant I:II:III:IV = 1.0:1.2–1.3:8.8–9.8:1.1–1.3. Cephalic dorsal macrochaetotaxy: anterior area: 2 (A2), 4 (A3, A5); interocular area: 2 (M2), 6 (S2, S5, S 5i); postocular area: 2+2 (Pa5, Pa6); posterior area: 1+1 (Pa2). Posterior margin of head with 20–35 chaetae on each side (Fig. 4A). Pattern of body chaetotaxy as in Fig. 4B. Th. II with macrochaetae a3, a4, a4a and a5a behind anterior marginal macrochaetae cluster; central area with single macrochaeta m3. Trochantero-femoral organ with 1, 1 slender chaetae. Tibiotarsi I, II, III ventrally with 6, 5–7, 6–7 strong chaetae, 3–4, 4–5, 4–6 of them blunt (Fig. 4C). Tenent hair 1.0–1.1× length of inner edge of unguis; accessory chaetae shorter and thinner than pretarsal chaetae; guard chaetae subequal to tenent hair in length. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with basal tooth and 3–5 more distal teeth, sub-basal tooth slightly stronger than more distal teeth. Unguiculus lanceolate, about 0.60–0.85× length of unguis, its inner edge with one tooth (Fig. 4D). Ventral tube scaled on both faces. Anterior face with 14–20 chaetae on each side, posterior face with 50–70 chaetae, each lateral flap unscaled, with 25–45 chaetae. Anterior face of tenaculum with 3–6 chaetae and without scales (Fig. 4E). Ratio of manubrium:dens:mucro = 2.4–2.9:3.2–3.7:1.0. Manubrium ventrally scaled without chaetae; laterally with large round scales and 9–11 chaetae, proximal 1–2 chaetae slender and almost smooth, distal chaetae strong and slightly serrated; each dorsal chaetal strip with 95–120 chaetae of different sizes, an irregular row of scales from base to 1/2–3/5 length of manubrium along inner edge, and 8–13 pseudopores on lateral side; without distinct prominent chaetae (Fig. 5A); distal corner chaeta as large as small mesochaetae in chaetal strip. Dens basally without prominent dorsal chaeta. Dental spine formula as 3–6/2–5, 2 (Fig. 5B); denticles on spines unevenly distributed, all spines with mainly basal moderate to large and a few small denticles, large spines ventrally with additional distal small to moderate denticles (Fig. 5C). Mucro with 4–8 intermediate teeth (Fig. 5D). Etymology. Chinese word nan: south. Habitat. Mixed forest of Dacrydium pierrei and broad leaf trees, in litters and on rotten woods. Remarks. Tomocerus nan sp. nov. can be diagnosed by absence of macrochaetae S0 and Pp3 on the head, presence of only one central macrochaeta m3 on Th. II, absence of distinct prominent chaetae on the furca, presence of dorsal scales on the manubrium and uneven distribution of denticles on large dental spines. The new species resembles most Tomocerus virgatus Yu, 2018 in absence of cephalic macrochaeta S0, presence of single mesothoracic central macrochaeta m3 and absence of prominent chaetae on the furca, but differs from the latter in colour pattern on the body and legs, absence of cephalic macrochaeta Pp3, presence of manubrial dorsal scales and pattern of denticles on large dental spines. Critical characters discriminating T. nan sp. nov. from similar species are listed in Table 1. A malformed dental spine formula is found on only one side of dens in two individuals as 5/3– 4, 1, with proximal spines irregularly arranged., Published as part of Yu, Daoyuan, Yang, Xiaodong & Liu, Manqiang, 2018, Three new species of Tomocerus from tropical zone of China (Collembola, Tomoceridae), pp. 225-236 in Zootaxa 4508 (2) on pages 230-232, DOI: 10.11646/zootaxa.4508.2.5, http://zenodo.org/record/2607034, {"references":["Yu, D. Y., Qin, C. Y., Ding, Y. H., Hu, F., Zhang, F. & Liu, M. Q. (2018) Revealing species diversity of Tomocerus ocreatus complex (Collembola: Tomoceridae): integrative species delimitation and evaluation of taxonomic characters. Arthropod Systematics & Phylogeny, 76 (1), 147 - 172."]}

Tomocerus tropicus sp. nov. Figs 1A, 2, 3 Type material. Holotype: female on slide, Mt. Wuzhishan National Nature Reserve, Shuiman Township, Wuzhishan, Hainan Province, China, 109°41'15"E, 18°54'11"N, alt. 901 m, 29.xii.2015, litters and humus on rocks, leg. Daoyuan Yu and Chunyan Qin (15HN5). Paratypes: 2 females, 1 male and 1 subadult on slides, 11 adults and juveniles in alcohol, same data as holotype. All types in NJAU. Description. Body length 3.3–3.9 mm. General background colouration of body white to light yellow. Ant. I and Ant. II distally with purple pigment, Ant. III and Ant. IV purple. Eye patch black. Diffuse purple pigment around mouthparts. Tibiotarsi purple and other segments occasionally with light purple pigment (Fig. 1A). Antenna 0.8–0.9× length of body. Length ratio of Ant I:II:III:IV = 1.0:1.3–1.5:8.8–10.0:0.7–0.9. Cephalic dorsal macrochaetotaxy: anterior area: 2 (A2), 4 (A3, A5); interocular area: 2 (M2), 7 (S0, S2, S5, S 5i); postocular area: 2+2 (Pa5, Pa6); posterior area: 2+2 (Pa2, Pp3). Posterior margin of head with 30–40 chaetae on each side (Fig. 2A). Pattern of body chaetotaxy as in Fig. 2B. Th. II with macrochaetae a3, a4, a4a and a5a behind anterior marginal macrochaetae cluster; a2, a5, m3 and m 4 in central area. Trochantero-femoral organ with 1, 1 slender chaetae subequal in length (Fig. 2C). Tibiotarsi I, II, III ventrally with 6–7, 6–7, 6 strong chaetae, 3–4, 4, 6 of them blunt (Fig. 2D). Tenent hair 0.8–1.0× length of inner edge of unguis; accessory chaetae slightly longer than pretarsal chaetae; guard chaetae subequal to tenent hair in length. Unguis slender, with baso-internal ridges about 1/4–1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with basal tooth and 4–6 more distal teeth, sub-basal tooth stronger. Unguiculus lanceolate, about 0.6–0.8× length of unguis, its inner edge with one tooth (Fig. 2E). Ventral tube scaled on both faces. Anterior face with 16–20 chaetae on each side, posterior face with 50–65 chaetae, each lateral flap unscaled, with 50–115 chaetae. Anterior face of tenaculum with 8–18 chaetae and without scales (Fig. 2F). Ratio of manubrium:dens:mucro = 2.9–3.4:4.0–4.4:1.0. Manubrium ventrally scaled without chaetae; laterally with large round scales and 10–11 chaetae, proximal 1–2 chaetae slender and almost smooth, distal chaetae strong and slightly serrated; each dorsal chaetal strip with 125–180 chaetae of different sizes, an irregular row of scales from base to 1/3–1/2 length of manubrium along inner edge, and 10–15 pseudopores on lateral side; 2 pairs of blunt prominent chaetae at centre and near distal end of manubrium, respectively, proximal prominent chaeta longer (Fig. 3A); distal corner chaeta as about size of small mesochaetae in chaetal strip (Fig. 3B). Dens basally with blunt prominent dorsal chaeta. Dental spine formula as 4–5/3–5, 2, sizes of spines gradually increase on basal subsegment (Fig. 3C); denticles on spines unevenly distributed, small spines with basal large denticles and a few small denticles, moderate and large spines dorsally mainly with basal large denticles, ventrally with basal moderate and distal small denticles (Fig. 3D). Mucro with 6–9 intermediate teeth (Fig. 3E). Etymology. Latin word tropicus: tropical. Habitat. Mixed forest, in leaf litters and thin layer of humus on rocks. Remarks. Tomocerus tropicus sp. nov. is characterised by the presence of 4 central macrochaetae a2, a5, m3 and m4 on Th. II, 2+2, 1 blunt prominent chaetae on the furca, dorsal scales on the manubrium, and uneven distribution of different-size denticles on large dental spines. The species resembles Tomocerus pseudocreatus Yu, 2018 in cephalic chaetotaxy, claw complex and furca prominent chaetae, but the latter has mesothoracic central macrochaetae m1 and m2 but not m4, no scales on the dorsal side of manubrium, and almost evenly distributed denticles on large dental spines. Critical characters discriminating T. tropicus sp. nov. from similar species are listed in Table 1.

A friction welding machine, which improves the connection performance of two different metals by generating heat of relative movement of friction, could increase the maximum contact area and lower energy and human labor consumption. The machine’s control system reaches the manufacturing process’s demands with its design and exerts its promising prospects.

1. Subterranean detritivores such as earthworms can increase soil nutrient availability through their burrowing and casting activities. A number of recent studies have explored whether these changes caused by earthworms may in turn affect plant performance and resistance to herbivores, but no formal synthesis of this literature has been conducted to date. 2. We tested for the effects of earthworms on plant growth, resistance and chemical defences against insect herbivores by performing a meta-analysis of the existing literature up to 2016. We also explored ecological factors that might explain among-studies variation in the magnitude of the earthworm effects on plant growth and resistance. 3. We found that earthworm presence increases plant growth (by 20%) and nitrogen content (by 11%). Overall, earthworms did not affect plant resistance against chewing herbivores (caterpillars, slugs and rootworms), and even led to a 22% decrease in plant resistance against phloem-feeding herbivores (aphids). However, earthworm presence increased production of chemical defences by 31% when plants where attacked by cell-feeders (thrips), and resulted in an 81% increase in resistance against thrips. The magnitude of earthworm effects was stronger when earthworm inoculations consisted of a mix of species and ecological types, and when densities of earthworms were high. 4. These results suggest that earthworm presence is an important factor underlying natural variation in plant defences against herbivores, and call for a better integration of the soil fauna in the studies of plant-herbivore interaction, both for applied and fundamental research.

Darwin's naturalization hypothesis (DNH), which predicts that alien species more distantly related to native communities are more likely to naturalize, has received much recent attention. The mixed findings from empirical studies that have tested DNH, however, seem to defy generalizations. Using meta-analysis to synthesize results of existing studies, we show that the predictive power of DNH depends on both the invasion stage and spatial scale of the studies. Alien species more closely related to natives tended to be less successful at the local scale, supporting DNH; invasion success, however, was unaffected by alien–native relatedness at the regional scale. On the other hand, alien species with stronger impacts on native communities tended to be more closely related to natives at the local scale, but less closely related to natives at the regional scale. These patterns are generally consistent across different ecosystems, taxa and investigation methods. Our results revealed the different effects of invader–native relatedness on invader success and impact, suggesting the operation of different mechanisms across invasion stages and spatial scales.

Tomoceridae is common but among the most problematic groups of Collembola. Its position within Collembola and the relationships within the family remain obscure. This also extends to the generic division of the subfamily Tomocerinae that remains controversial. This study examines these issues by integrating both molecular and morphological evidence. Our molecular phylogeny based on rDNA sequences supports the monophyly of Tomoceridae and the sister relationship between Tomocerinae and Lepidophorellinae. Reconstructions and tree topology tests constraining monophyly did not resolve the relationships between Tomoceridae and other collembolan groups. We also examined the morphology of the first instar (primary) larvae, which has significant phylogenetic value among higher Collembola. Mapping primary chaetotaxy onto our molecular phylogeny provided further evidence for the unique position of Tomoceridae within Entomobryomorpha and Collembola. The monophyly and subfamilial classification within Tomoceridae were validated here, whereas its position among Collembola will need further studies in a broader consideration across the major collembolan orders. Within Tomocerinae, the monophyly of Pogonognathellus was demonstrated, but the status of Tomocerus and Tomocerina is still to be resolved. Refereed/Peer-reviewed