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Worldwide, two of the most harmful invasive ants typical of disturbed sites are Solenopsis geminata (Fabricius) and Wasmannia auropunctata (Roger). Both are natives of the Neotropics and are widely distributed all over the tropics. Within its original geographic range, there are few data on its abundance and potential damage to natural ecosystems. In this study, we recorded their abundance and relationships to diversity and richness of soil ant communities in two localities with different amount of forested area (López Mateos, LM 77% and Venustiano Carranza, VC 27%), at Los Tuxtlas reserve. In each locality, four land use systems (LUS) were sampled: tropical rain forests, agroforestry plantations, annual crops, and pastures. Data were gathered from 360 ant samples obtained from litter squares, pitfall traps, and soil monoliths in 40 sampling points (20 per locality, and five per LUS). Solenopsis geminata was more abundant in LM than in VC; the opposite trend was observed for W. auropunctata. In LM, S. geminata was more abundant in crops than in the other LUS, whereas W. auropunctata tended to have higher abundances in less managed sites of both localities. Abundance and species richness of ant communities were higher in LM than in VC. At regional and local levels, we found negative relationships between the abundance of S. geminata and species richness; the inverse pattern was found for W. auropunctata. We conclude that at Los Tuxtlas, W. auropunctata can be considered as a typical dominant native species, whereas S. geminata is the common exotic invasive ant.

Un lugar no es materia ni forma. Es múltiple, no sólo porque puede ser o devenir, sino también en relación a su duración. Es una dimensión osmótica del espacio que no funciona como manifestación sino como cambio y flujo. Es un territorio en movimiento. Sus continuas traducciones e inscripciones consolidan un valor que es fluido y flotante en la medida en que un lugar no designa una substancia sino que expresa la relación entre fuerzas.

Background: South American birds are known to play a significant role in life cycles of various hard ticks, particularly within Amblyomma genus. However, the tick fauna from the Amazon region has been poorly studied, being limited to very few studies. Objective: To report tick infestations on wild birds captured in a region of the Amazon forest, Acre state, Brazil, and to evaluate rickettsial infection in these ticks. Methods: Wild birds were captured by mist-nets and examined for the presence of ticks, which were all collected and identified to species level by taxonomic keys and/or molecular methods. In addition, part of these ticks was individually tested by PCR targeting portions of three rickettsial genes (gltA, ompA, ompB). Results: Among 1,322 captured birds, 79 individuals (6.0%) were infested by one of the following ticks species: Amblyomma nodosum Neumann, 1899 (72 nymphs), Amblyomma longirostre (Koch, 1844; seven larvae, 13 nymphs), Amblyomma humerale Koch 1844 (four nymphs), Amblyomma geayi Neumann, 1899 (two larvae, two nymphs), and 421 larvae of Amblyomma spp Rickettsia sp strain NOD was detected in 3/26 A. nodosum, and Rickettsia amblyommatis in 5/8 A. longirostre and 1/2 A. geayi ticks tested. Conclusion: This is the first study about ticks parasitizing wild birds in Acre state, adding new host-parasite relationships, new tick species records (A. humerale and A. nodosum) and two rickettsial agents (R amblyommatis and Rickettsia sp strain NOD) for the first time in Acre.

Este artículo analizará los esquemas de percepción y las platafor­mas discursivas a través de los cuales los viajeros extranjeros decimonónicos presentaron, en sus países de origen y a las élites nacionales, el medio natural y el universo sociocultural de las comunidades negras que habitaban en el litoral del Pacífico de la joven República de Colombia. Se verá que la selva húmeda tropical fue percibida como una despensa inagotable de insumos fabriles o como un eje estratégico del comercio mundial. A su vez, se descali­ficó el legado cultural y la trayectoria histórica de los colectivos afropacíficos y fueron tomados como el mayor obstáculo del «progreso» del área, pero igualmente como mano de obra barata para ponerla al servicio del sistema capitalista surgido tras el ocaso del Imperio español.

Comalcalco es un sitio arqueológico localizado en la llanura aluvial tabasqueña, rodeado por una selva tropical, manglares y muy cercano a la costa marina. Las investigaciones efectuadas por el Proyecto Arqueológico Comalcalco en las últimas dos décadas, han permitido identificar a través de diferentes materiales culturales (restos óseos, figurillas cerámicas y esculturas modeladas) que durante el apogeo de esta ciudad maya, ocurrido durante el Clásico Tardío (entre el 550/600-900 d.C.), sus habitantes aprovecharon intensamente los recursos inmediatos para el consumo o elaboración de herramientas y bienes, pero también les integraron como parte de su cosmogonía. Hoy en día, a pesar de la deforestación y modificación de las prácticas culturales, la población local practica algunas actividades que al compararse con la evidencia arqueológica indican la persistencia de una antigua tradición.

Los suelos varían ampliamente en la Amazonia mostrando gran diversidad, diferentes características morfológicas y propiedades físico-químicas del suelo. Las investigaciones llevadas a cabo en relación a las propiedades del suelo en estas áreas ayudan al conocimiento general de los suelos nativos e inexplorados y proporcionan muestras de control para el estudio del suelo. En la literatura existen importantes investigaciones que estudian los bosques amazónicos en un entorno heterogéneo en relación con el suelo y la topografía. En el estudio actual se recolectaron muestras de suelo de 3 profundidades, 9 localidades y altitudes diferentes en la selva amazónica; y proporciona la visión sobre los efectos de la profundidad del suelo así como las variaciones altitudinales sobre el contenido de Fe y la acidez intercambiable (intercambio iónico H-al). Los resultados indicaron que la altitud, en comparación con la profundidad del suelo, puede desempeñar un papel importante en el contenido de Fe y la acidez intercambiable.

Second-growth tropical forests are an important global carbon sink. As current knowledge on biomass accumulation during secondary succession is heavily based on chronosequence studies, direct estimates of annual rates of biomass accumulation in monitored stands are largely unavailable. We evaluated the contributions of tree diameter increment, recruitment, and mortality to annual tree biomass change during succession for three groups of tree species: second-growth (SG) specialists, generalists, and old-growth (OG) specialists. We monitored six second-growth tropical forests that varied in stand age and two old-growth forests in northeastern Costa Rica. We monitored these over a period of 8 to 16 years. To assess rates of biomass change during secondary succession, we compared standing biomass and biomass dynamics between second-growth forest stages and old-growth forest, and evaluated the effect of stand age on standing biomass and biomass dynamics in second-growth forests.  Standing tree biomass increased with stand age during succession, whereas the rate of biomass change decreased. Biomass change was largely driven by tree diameter increment and mortality, with a minor contribution from recruitment. The relative importance of these demographic drivers shifted over succession. Biomass gain due to tree diameter increment decreased with stand age, whereas biomass loss due to mortality increased. In the age range of our second-growth forests, 10-41 years, SG specialists dominated tree biomass in second-growth forests. SG specialists, and to a lesser extent generalists, also dominated stand-level biomass increase due to tree diameter increment, whereas SG specialists largely accounted for decreases in biomass due to mortality. Our results indicate that tree growth is largely driving biomass dynamics early in succession, whereas both growth and mortality are important later in succession. Biomass dynamics are largely accounted for by a few SG specialists and one generalist species, Pentaclethra macroloba . To assess the generality of our results, similar long-term studies should be compared across tropical forest landscapes.

Tropical forest productivity is widely assumed to be limited by soil phosphorus (P), but biogeochemical processes that deplete P also could deplete base cations, suggesting multiple resource limitation. Limitation by several resources could arise from species and functional diversity and from variation among groups in resource requirements, including ecophysiological strategies that minimize P limitation. We hypothesized that tree growth is positively related to soil base cation and P availability and negatively related to local competition; Fabaceae growth is weakly correlated with soil resources if fixed N is used indirectly to acquire other resources; growth of species with low wood density is more strongly related to soil resource availability than that of species with high wood density. Diameter growth and soil resource availability were measured in five mapped stands situated across natural soil resource gradients in lowland wet tropical forest (La Selva Biological Station, Costa Rica). Soil resource availability, and associated uncertainty, was estimated for each tree using a Bayesian multivariate spatial regression model, with individual tree growth being a function of diameter, local neighborhood, and soil resources. Separately, site-level mean tree growth and resource availability were modeled using linear regression. Individual diameter growth and site mean basal area increment correlated with soil base cations and P, but rarely with N; individual growth correlated negatively with neighborhood index for only three species. Growth of Fabaceae was unrelated to soil resources at both individual and site levels. When species were categorized by wood density, growth was related to soil P or base cation availability, with the strongest correlation between the lowest-density species and soil P. Several resources may limit tropical forest productivity, because tree growth was similarly correlated with soil P and base cations, but functional groups responded differently. Negligible growth relationships with soil resources in Fabaceae suggest that N fixation may alleviate mineral nutrient limitations. Correlations of soil P with growth of species of low wood density and base cations with species of higher density suggests variation in resource demands among functional groups. Thus, tropical tree growth may be limited by base cations and/or P, with degree and type of resource limitation dependent on functional or taxonomic group.

Despite the importance of measuring tropical forest biomass, the accuracy of biomass estimates is poorly constrained due to fundamental weaknesses in the design and implementation of field studies. We identify these issues and propose a radical paradigm shift to advance tropical forest biomass research to a firmer theoretical and empirical basis.

Leaf-cutter ant nests are biogeochemical hot spots where ants live and import vegetation to grow fungus. Metabolic activity and (in wet tropical forests) soil gas flux to the nest may result in high nest CO₂ concentrations if not adequately ventilated. Wind-driven ventilation mitigates high CO₂ concentrations in grasslands, but little is known about exchange for forest species faced with prolonged windless conditions. We studied Atta cephalotes nests located under dense canopy (leaf area index > 5) in a wet tropical rainforest in Costa Rica, where wind events are infrequent. We instrumented nests with thermocouples and flow-through CO₂ sensing chambers. The results showed that CO₂ concentrations exiting leaf-cutter ant nests follow a diel pattern with higher values at night. We developed an efflux model based on pressure differences that evaluated the observed CO₂ diel pattern in terms of ventilation by (1) free convection (warm, less dense air rises out the nest more prominently at night) and (2) episodic wind-forced convection events providing occasional supplemental ventilation during daytime. Average greenhouse gas emissions were estimated through nest vents at about 78 kg CO₂ eq nest⁻¹ year⁻¹. At the ecosystem level, leaf-cutter ant nest vents accounted for 0.2% to 1% of total rainforest soil emissions. In wet, clayey tropical soils, leaf-cutter ant nests act as free convection-driven conduits for exporting CO₂ and other greenhouse gases produced within the nest (fungus and ant respiration, refuse decay), and by roots and soil microbes surrounding the nest. This allows A. cephalotes nests to be ventilated without reliable wind conditions.