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.

Trophic ecology of the armadillo ant, Tatuidris tatusia, assessed by stable isotopes and behavioral observations.

Ants of the genus Tatuidris Brown and Kempf (Formicidae: Agroecomyrmecinae) generally occur at low abundances in forests of Central and South America. Their morphological peculiarities, such as mandibular brushes, are presumably linked with specialized predatory habits. Our aims were to (1) assess the Tatuidris abundance in an evergreen premontane forest of Ecuador; (2) detail morphological characteristics and feeding behavior of Tatuidris; and (3) define the position of Tatuidris in the food web. A total of 465 litter samples were collected. For the first time, live Tatuidris individuals were observed. Various potential food sources were offered to them. A nitrogen stable isotope ratio analysis ((15)N/(14)N) was conducted on Tatuidris tatusia, other ants, and common organisms from the leaf-litter mesofauna. We found a relatively high abundance of T. tatusia in the site. Live individuals did not feed on any of the food sources offered, as usually observed with diet specialist ants. The isotope analysis revealed that T. tatusia is one of the top predators of the leaf-litter food web.

Moderate changes in nutrient input alter tropical microbial and protist communities and belowground linkages.

We investigated the response of soil microbial communities in tropical ecosystems to increased nutrient deposition, such as predicted by anthropogenic change scenarios. Moderate amounts of nitrogen and phosphorus and their combination were added along an altitudinal transect. We expected microorganisms and microbial grazers (testate amoebae) to significantly respond to nutrient additions with the effect increasing with increasing altitude and with duration of nutrient additions. Further, we expected nutrients to alter grazer-prey interrelationships. Indeed, nutrient additions strongly altered microbial biomass (MB) and community structure as well as the community structure of testate amoebae. The response of microorganisms varied with both altitude and duration of nutrient addition. The results indicate that microorganisms are generally limited by N, but saprotrophic fungi also by P. Also, arbuscular mycorrhizal fungi benefited from N and/or P addition. Parallel to MB, testate amoebae benefited from the addition of N but were detrimentally affected by P, with the addition of P negating the positive effect of N. Our data suggests that testate amoeba communities are predominantly structured by abiotic factors and by antagonistic interactions with other microorganisms, in particular mycorrhizal fungi, rather than by the availability of prey. Overall, the results suggest that the decomposer system of tropical montane rainforests significantly responds to even moderate changes in nutrient inputs with the potential to cause major ramifications of the whole ecosystem including litter decomposition and plant growth.

New and little known species of oribatid mites of the family Haplozetidae (Acari, Oribatida) from Ecuador.

We described two new species, Haplozetes paraminimicoma sp. n. and Protoribates ecuadoriensis sp. n. from Ecuador. Additionally, a detailed supplementary description of Trachyoribates (Rostrozetes) glaber (Beck, 1965) is given on the basis of Ecuadorian specimens, which was known previously only from Peru. An annotated checklist of all identified taxa of Haplozetidae from Ecuador is presented.

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.

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.

Tropical Andean forests are highly susceptible to nutrient inputs--rapid effects of experimental N and P addition to an Ecuadorian montane forest.

Tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems. Here, we show that Neotropical montane rainforests respond rapidly to moderate additions of N (50 kg ha(-1) yr(-1)) and P (10 kg ha(-1) yr(-1)). Monitoring of nutrient fluxes demonstrated that the majority of added nutrients remained in the system, in either soil or vegetation. N and P additions led to not only an increase in foliar N and P concentrations, but also altered soil microbial biomass, standing fine root biomass, stem growth, and litterfall. The different effects suggest that trees are primarily limited by P, whereas some processes-notably aboveground productivity--are limited by both N and P. Highly variable and partly contrasting responses of different tree species suggest marked changes in species composition and diversity of these forests by nutrient inputs in the long term. The unexpectedly fast response of the ecosystem to moderate nutrient additions suggests high vulnerability of tropical montane forests to the expected increase in nutrient inputs.

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.