Abstract: Atopomyrmex mocquerysi ANDRE, 1889 is a West-Central African wood-excavating myrmicine species whose colonies construct galleries in the main live branches of their host trees, causing the distal parts of these branches to dry out. In southeastern Cameroon, this species was mainly found in woody savannahs that are burned annually. It was also present in the canopy of a secondary forest, but was relatively rare on trees growing along forest edges and entirely absent from the canopy of an old-growth forest. It was absent from oil palm and coffee tree plantations, rare on cocoa trees. present on 0.2% to 5.3% of the avocado, guava, mango and Citrus spp. trees monitored, and frequent on safoo trees (12.4%). A fire in a mango plantation seems to have favored its presence. The colonies generally exploit Aleyrodidae, Aphididae, Coccidae, and Stictococcidae. Workers forage for prey diurnally, mostly on the ground. Their predatory behavior is characterized by detection through contact. Workers recruit nestmates at short-range (within range of an alarm pheromone), rarely at long-range, after which they spread-eagle the prey and immediately cut it up on the spot. Individual workers retrieve the prey pieces. Unlike other territorially-dominant arboreal ants, A. mocquerysi is a threat to host trees because. in addition to being a wood-excavating species, its workers only slightly protect the foliage of their host tree from herbivorous insects since they mostly hunt on the ground.

Abstract: Ants play essential roles in most terrestrial ecosystems and may be considered pests for agriculture and agroforestry. Recent morphological and molecular data have challenged conventional ant phylogeny and the interpretation of karyotypic variations. Existing Neotropical ant cytogenetic data focus on Atlantic rainforest species, and provide evolutionary and taxonomic insight. However, there are data for only 18 Amazonian species. In this study, we describe the karyotypes of 16 ant species belonging to 12 genera and three subfamilies, collected in the Brazilian state of Amapa, and in French Guiana. The karyotypes of six species are described for the first time, including that of the South American genus Allomerus Mayr, 1878. The karyotype of Crematogaster Lund, 1831 is also described for the first time for the New World. For other species, extant data for geographically distinct populations was compared with our own data, e.g. for the leafcutter ants Acromyrmex balzani (Emery, 1890) and Atta sexdens (Linnaeus, 1758). The information obtained for the karyotype of Dolichoderus imitator Emery, 1894 differs from extant data from the Atlantic forest, thereby highlighting the importance of population cytogenetic approaches. This study also emphasizes the need for good chromosome preparations for studying karyotype structure.

Abstract: The Ecosystem Demography model version 2.2 (ED-2.2) is a terrestrial biosphere model that simulates the biophysical, ecological, and biogeochemical dynamics of vertically and horizontally heterogeneous terrestrial ecosystems. In a companion paper (Longo et al., 2019a), we described how the model solves the energy, water, and carbon cycles, and verified the high degree of conservation of these properties in long-term simulations that include long-term (multi-decadal) vegetation dynamics. Here, we present a detailed assessment of the model's ability to represent multiple processes associated with the biophysical and biogeochemical cycles in Amazon forests. We use multiple measurements from eddy covariance towers, forest inventory plots, and regional remote-sensing products to assess the model's ability to represent biophysical, physiological, and ecological processes at multiple timescales, ranging from subdaily to century long. The ED-2.2 model accurately describes the vertical distribution of light, water fluxes, and the storage of water, energy, and carbon in the canopy air space, the regional distribution of biomass in tropical South America, and the variability of biomass as a function of environmental drivers. In addition, ED-2.2 qualitatively captures several emergent properties of the ecosystem found in observations, specifically observed relationships between aboveground biomass, mortality rates, and wood density; however, the slopes of these relationships were not accurately captured. We also identified several limitations, including the model's tendency to overestimate the magnitude and seasonality of heterotrophic respiration and to overestimate growth rates in a nutrient-poor tropical site. The evaluation presented here highlights the potential of incorporating structural and functional heterogeneity within biomes in Earth system models (ESMs) and to realistically represent their impacts on energy, water, and carbon cycles. We also identify several priorities for further model development.

Abstract: Secondary forests are a prominent component of tropical landscapes, and they constitute a major atmospheric carbon sink. Rates of carbon accumulation are usually inferred from chronosequence studies, but direct estimates of carbon accumulation based on long-term monitoring of stands are rarely reported. Recent compilations on secondary forest carbon accumulation in the Neotropics are heavily biased geographically as they do not include estimates from the Guiana Shield. We analysed the temporal trajectory of aboveground carbon accumulation and floristic composition at one 25-ha secondary forest site in French Guiana. The site was clear-cut in 1976, abandoned thereafter, and one large plot (6.25 ha) has been monitored continuously since. We used Bayesian modeling to assimilate inventory data and simulate the long-term carbon accumulation trajectory. Canopy change was monitored using two aerial lidar surveys conducted in 2009 and 2017. We compared the dynamics of this site with that of a surrounding old-growth forest. Finally, we compared our results with that from secondary forests in Costa Rica, which is one of the rare long-term monitoring programs reaching a duration comparable to our study. Twenty years after abandonment, aboveground carbon stock was 64.2 (95% credibility interval 46.4, 89.0) Mg C/ha, and this stock increased to 101.3 (78.7, 128.5) Mg C/ha 20 yr later. The time to accumulate one-half of the mean aboveground carbon stored in the nearby old-growth forest (185.6 [155.9, 200.2] Mg C/ha) was estimated at 35.0 [20.9, 55.9] yr. During the first 40 yr, the contribution of the long-lived pioneer species Xylopia nitida, Goupia glabra, and Laetia procera to the aboveground carbon stock increased continuously. Secondary forest mean-canopy height measured by lidar increased by 1.14 m in 8 yr, a canopy-height increase consistent with an aboveground carbon accumulation of 7.1 Mg C/ha (or 0.89 Mg C·ha−1·yr−1) during this period. Long-term AGC accumulation rate in Costa Rica was almost twice as fast as at our site in French Guiana. This may reflect higher fertility of Central American forest communities or a better adaptation of the forest tree community to intense and frequent disturbances. This finding may have important consequences for scaling-up carbon uptake estimates to continental scales.

Abstract: Hylesia moths impact human health in South America, inducing epidemic outbreaks of lepidopterism, a puriginous dermatitis caused by the urticating properties of females' abdominal setae. The classification of the Hylesia genus is complex, owing to its high diversity in Amazonia, high intraspecific morphological variance, and lack of interspecific diagnostic traits which may hide cryptic species. Outbreaks of Hylesia metabus have been considered responsible for the intense outbreaks of lepidopterism in Venezuela and French Guiana since the C20, however, little is known about genetic variability throughout the species range, which is instrumental for establishing control strategies on H. metabus. Seven microsatellites and mitochondrial gene markers were analyzed from Hylesia moths collected from two major lepidopterism outbreak South American regions. The mitochondrial gene sequences contained significant genetic variation, revealing a single, widespread, polymorphic species with distinct clusters, possibly corresponding to populations evolving in isolation. The microsatellite markers validated the mitochondrial results, and suggest the presence of three populations: one in Venezuela, and two in French Guiana. All moths sampled during outbreak events in French Guiana were assigned to a single coastal population. The causes and implications of this finding require further research.