Linking size spectrum, energy flux and trophic multifunctionality in soil food webs of tropical land-use systems.

Many ecosystem functions depend on the structure of food webs, which heavily relies on the body size spectrum of the community. Despite that, little is known on how the size spectrum of soil animals responds to agricultural practices in tropical land-use systems and how these responses affect ecosystem functioning. We studied land-use-induced changes in below-ground communities in tropical lowland ecosystems in Sumatra (Jambi province, Indonesia), a hot spot of tropical rainforest conversion into rubber and oil palm plantations. The study included ca. 30,000 measured individuals from 33 high-order taxa of meso- and macrofauna spanning eight orders of magnitude in body mass. Using individual body masses, we calculated the metabolism of trophic guilds and used food web models to calculate energy fluxes and infer ecosystem functions, such as decomposition, herbivory, primary and intraguild predation. Land-use change was associated with reduced abundance and taxonomic diversity of soil invertebrates, but strong increase in total biomass and moderate changes in total energy flux. These changes were due to increased biomass of large-sized decomposers in soil, in particular earthworms, with their share in community metabolism increasing from 11% in rainforest to 59%-76% in jungle rubber, and rubber and oil palm plantations. Decomposition, that is the energy flux to decomposers, stayed unchanged, but herbivory, primary and intraguild predation decreased by an order of magnitude in plantation systems. Intraguild predation was very important, being responsible for 38% of the energy flux in rainforest according to our model. Conversion of rainforest into monoculture plantations is associated by an uneven loss of size classes and trophic levels of soil invertebrates resulting in sequestration of energy in large-sized primary consumers and restricted flux of energy to higher trophic levels. Pronounced differences between rainforest and jungle rubber reflect sensitivity of rainforest soil animal communities to moderate land-use changes. Soil communities in plantation systems sustained high total energy flux despite reduced biodiversity. The high energy flux into large decomposers but low energy fluxes into other trophic guilds suggests that trophic multifunctionality of below-ground communities is compromised in plantation systems.

Leaf Litter Chemistry Drives the Structure and Composition of Soil Testate Amoeba Communities in a Tropical Montane Rainforest of the Ecuadorian Andes.

We investigated the role of leaf litter chemistry and richness in affecting testate amoeba communities of tropical rainforest in the Ecuadorian Andes. Litterbags containing leaf litter from four dominating tree species (Clusia sp., Myrcia pubescens, Graffenrieda emarginata, and Cecropia andina) with richness 1, 2, and 4 species were established and exposed in the field for 12 months at 2000 m a.s.l. Chemical elements and compounds of leaf litter were analyzed before exposure. At the end of exposure, microbial biomass and litter mass loss were measured, and living testate amoeba species number, density, biomass, and community composition were determined. In total, 125 testate amoeba species colonized the litter in litterbags. The results suggest that high litter nitrogen and low lignin concentrations are indicators of high litter quality for testate amoebae density and species richness. Their species number and density significantly declined in the order 1 > 4 > 2 leaf litter species and varied with leaf litter chemistry being at a maximum in high-quality single leaf litter species and low in low-quality leaf litter. Further, the addition of litter of high-quality to low-quality litter increased testate amoebae biomass and density; however, the values did not exceed the ones in single high-quality litter treatments. Moreover, the structure of testate amoeba communities varied with litter chemistry, with Fe, Na, lignin, and litter C-to-N ratio being of major importance, and indicating that litter chemistry reflects habitat quality for testate amoebae. Overall, the data show that leaf litter chemistry overrides leaf litter richness in structuring testate amoeba communities.

Three new species of the genus Sternoppia (Acari: Oribatida: Sternoppiidae) from Ecuador.

Three new oppioid mite species of the genus Sternoppia, S. paraincisa sp. nov., S. paramirabilis sp. nov. and S. fissurata sp. nov., are described. Sternoppia paraincisa sp. nov. is most similar morphologically to Sternoppia incisa Balogh & Mahunka, 1977 from Bolivia, however, it differs from the latter by smaller body size, presence of notogastral setae c, location of lyrifissures ia, presence of granules on anal plates, and setiform sensilli. Sternoppia paramirabilis sp. nov. is most similar morphologically to Sternoppia mirabilis Balogh & Mahunka, 1968 from Argentina, however it differs from the latter by larger body size, presence of two or three sensillar branches only, and long interlamellar setae. Sternoppia fissurata sp. nov. differs from all species of the genus by the nine pairs of notogastral setae, location of lyrifissures iad in inverse apoanal position, and the presence of large tectum on anterior part of ventral plate. Sternoppia brasiliensis is for the first time recorded in Ecuador. An identification key to all known species of Sternoppia is provided.

New taxa and new records of oribatid mites of the family Galumnidae (Acari: Oribatida) from Ecuador.

The new genus Neoctenogalumna gen. nov. with Ctenogalumna moresonensis Engelbrecht, 1972 as a type species and the new subgenus Neoctenogalumna (Paractenogalumna) subgen. nov. with Neoctenogalumna (Paractenogalumna) longiciliata sp. nov. as a type species are proposed. Four new species Allogalumna ampla sp. nov., Galumna miniporosa sp. nov., Pergalumna ornamenta sp. nov. and Neoctenogalumna (Paractenogalumna) longiciliata sp. nov. are described from Ecuadorian soils. Neoctenogalumna moresonensis (Engelbrecht, 1972) comb. nov. and N. congoensis (Starý, 2005) comb. nov. are transferred in the genus Neoctenogalumna gen. nov. from Ctenogalumna. An identification key to known species of Neoctenogalumna gen. nov. is provided. An annotated checklist of identified Ecuadorian Galumnidae is presented. Four species Allogalumna borhidii Balogh & Mahunka, 1979, A. cubana Balogh & Mahunka, 1979, Pergalumna australis Pérez-Íñigo & Baggio, 1980, Galumna laselvae Balogh, 1997--are recorded for the first time from Ecuador. One genus and one species Trichogalumna Balogh, 1960 and Trichogalumna nipponica (Aoki, 1966) are recorded for the first time from the Neotropical region.

Consequences of exclusion of precipitation on microorganisms and microbial consumers in montane tropical rainforests.

The structure and functioning of decomposer systems heavily relies on soil moisture. However, this has been primarily studied in temperate ecosystems; little is known about how soil moisture affects the microfaunal food web in tropical regions. This lack of knowledge is surprising, since the microfaunal food web controls major ecosystem processes. To evaluate the role of precipitation in the structure of soil food web components (i.e., microorganisms and testate amoebae), we excluded water input by rain in montane rainforests at different altitudes in Ecuador. Rain exclusion strongly reduced microbial biomass and respiration by about 50 %, and fungal biomass by 23 %. In testate amoebae, rain exclusion decreased the density of live cells by 91 % and caused a shift in species composition at each of the altitudes studied, with ergosterol concentrations, microbial biomass, and water content explaining 25 % of the variation in species data. The results document that reduced precipitation negatively affects soil microorganisms, but that the response of testate amoebae markedly exceeds that of bacteria and fungi. This suggests that, in addition to food, low precipitation directly affects the community structure of testate amoebae, with the effect being more pronounced at lower altitudes. Overall, the results show that microorganisms and testate amoebae rapidly respond to a reduction in precipitation, with testate amoebae-representatives of higher trophic levels-being more sensitive. The results imply that precipitation and soil moisture in tropical rainforests are the main factors regulating decomposition and nutrient turnover.

Differences in leaf and root litter decomposition in tropical montane rainforests are mediated by soil microorganisms not by decomposer microarthropods.

Background: Plant litter decomposition is a key process in carbon and nutrient cycling. Among the factors determining litter decomposition rates, the role of soil biota in the decomposition of different plant litter types and its modification by variations in climatic conditions is not well understood. Methods: In this study, we used litterbags with different mesh sizes (45 µm, 1 mm and 4 mm) to investigate the effect of microorganisms and decomposer microarthropods on leaf and root litter decomposition along an altitudinal gradient of tropical montane rainforests in Ecuador. We examined decomposition rates, litter C and N concentrations, microbial biomass and activity, as well as decomposer microarthropod abundance over one year of exposure at three different altitudes (1,000, 2,000 and 3,000 m). Results: Leaf litter mass loss did not differ between the 1,000 and 2,000 m sites, while root litter mass loss decreased with increasing altitude. Changes in microbial biomass and activity paralleled the changes in litter decomposition rates. Access of microarthropods to litterbags only increased root litter mass loss significantly at 3,000 m. The results suggest that the impacts of climatic conditions differentially affect the decomposition of leaf and root litter, and these modifications are modulated by the quality of the local litter material. The findings also highlight litter quality as the dominant force structuring detritivore communities. Overall, the results support the view that microorganisms mostly drive decomposition processes in tropical montane rainforests with soil microarthropods playing a more important role in decomposing low-quality litter material.

Leaf litter identity rather than diversity shapes microbial functions and microarthropod abundance in tropical montane rainforests.

In tropical forest ecosystems leaf litter from a large variety of species enters the decomposer system, however, the impact of leaf litter diversity on the abundance and activity of soil organisms during decomposition is little known. We investigated the effect of leaf litter diversity and identity on microbial functions and the abundance of microarthropods in Ecuadorian tropical montane rainforests. We used litterbags filled with leaves of six native tree species (Cecropia andina, Dictyocaryum lamarckianum, Myrcia pubescens, Cavendishia zamorensis, Graffenrieda emarginata, and Clusia spp.) and incubated monocultures and all possible two- and four-species combinations in the field for 6 and 12 months. Mass loss, microbial biomass, basal respiration, metabolic quotient, and the slope of microbial growth after glucose addition, as well as the abundance of microarthropods (Acari and Collembola), were measured at both sampling dates. Leaf litter diversity significantly increased mass loss after 6 months of exposure, but reduced microbial biomass after 12 months of exposure. Leaf litter species identity significantly changed both microbial activity and microarthropod abundance with species of high quality (low C-to-N ratio), such as C. andina, improving resource quality as indicated by lower metabolic quotient and higher abundance of microarthropods. Nonetheless, species of low quality, such as Clusia spp., also increased the abundance of Oribatida suggesting that leaf litter chemical composition alone is insufficient to explain variation in the abundances of soil microarthropods. Overall, the results provide evidence that decomposition and microbial biomass in litter respond to leaf litter diversity as well as litter identity (chemical and physical characteristics), while microarthropods respond only to litter identity but not litter diversity.

Review of the mite genus Krantzolaspina Datta & Bhattacharjee (Mesostigmata, Parholaspididae) with re-description of K. angustatus comb. nov. (Ishikawa) from Indonesia.

Herein, we update the diagnosis and description of the genus Krantzolaspina Datta & Bhattacharjee and provide a list of the three valid species including new combinations and synonyms, as follows: 1) Krantzolaspina angustatus (Ishikawa, 1987) comb. nov. (= Indutolaelaps jiroftensisHajizadeh et al., 2017syn. nov.), 2) K. rebatii Datta & Bhattacharjee, 1989 and 3) K. solimani (Metwali, 1983) comb. nov. Finally, we re-describe K. angustatus (Ishikawa, 1987) comb. nov. based on the holotype from Japan, voucher specimens from Iran and additional females that we found in soil samples from oil palm plantations in Sumatra, Indonesia.

New and interesting species of sacculonotic Haplozetidae (Acari, Oribatida, Haplozetidae) from Indonesia.

Two new species of haplozetid oribatid mites (Oribatida, Haplozetidae) are described on the basis of adult specimens sampled from litter and soil in Sumatra, Indonesia: Haplozetes bayartogtokhi sp. nov. differs from Haplozetes biheterodactylus Ermilov Tolstikov, 2015 by the presence of minute interlamellar setae, foveolate anterior part of the notogaster, five pairs of genital setae and the localization of adanal lyrifissures in preanal position; Magyaria leonilae sp. nov. differs from Magyaria annobonica Pérez-Íñigo, 1981 and Magyaria ornata Balogh, 1963 by the presence of bidactylous legs, pointed rostrum and reticulate prodorsum. The species Indoribates hauseri (Mahunka, 1997) comb. nov. (Haplozetidae) is recorded in Indonesia for the first time. A supplementary description for this species is given in detail on the basis of adult specimens from Indonesia and its main morphological traits are summarized. The taxonomic status of the genus Bolkiah Mahunka, 1997 is discussed, resulting in the following new taxonomic proposals: Indoribates (=Bolkiah syn. nov.).

Review of the mite genus Ololaelaps (Acari, Laelapidae) and redescription of O.formidabilis Berlese.

A species of laelapid mite, Ololaelapsformidabilis, is redescribed based on male and female adults from soil in Sumatra, Indonesia. This species is distinguished from other Ololaelaps species by its metapodal platelet narrowly fused with the parapodal plate and by its hologastric shield having two inverted-V-like ridges. The genus is redescribed based on a review of the literature and examination of specimens of some species. Valid species of Ololaelaps are listed and accompanied by notes on morphological characters to assist future revision of the genus.