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Dejean, A., Compin, A., Delabie, J. H. C., Azémar, F., Corbara, B., & Leponce, M. (2019). Biotic and abiotic determinants of the formation of ant mosaics in primary Neotropical rainforests. Ecol Entomol, 44(4), 560–570.
Abstract: 1. Ants are widespread in tropical rainforests, including in the canopy where territorially dominant arboreal species represent the main part of the arthropod biomass.
2. By mapping the territories of dominant arboreal ant species and using a null model analysis and a pairwise approach this study was able to show the presence of an ant mosaic on the upper canopy of a primary Neotropical rainforest (c. 1ha sampled; 157 tall trees from 28 families). Although Neotropical rainforest canopies are frequently irregular, with tree crowns at different heights breaking the continuity of the territories of dominant ants, the latter are preserved via underground galleries or trails laid on the ground.
3. The distribution of the trees influences the structure of the ant mosaic, something related to the attractiveness of tree taxa for certain arboreal ant species rather than others.
4. Small-scale natural disturbances, most likely strong winds in the area studied (presence of canopy gaps), play a role by favouring the presence of two ant species typical of secondary formations: Camponotus femoratus and Crematogaster levior, which live in parabiosis (i.e. share territories and nests but lodge in different cavities) and build conspicuous ant gardens. In addition, pioneer Cecropia myrmecophytic trees were recorded.
Keywords: Ant mosaics; connections on the ground; host tree attractiveness; indicators of disturbance; primary Neotropical rainforest; territoriality
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Talaga, S., Dejean, A., Mouza, C., Dumont, Y., & Leroy, C. (2018). Larval interference competition between the native Neotropical mosquito Limatus durhamii and the invasive Aedes aegypti improves the fitness of both species. Insect Science, 25, 1102–1107.
Abstract: Abstract Interspecific competition with native species during biological invasions can sometimes limit alien expansion. We aimed to determine the potential ecological effects of Limatus durhamii Theobald 1901, a native Neotropical mosquito (Diptera: Culicidae) species, on the invasive species Aedes (Stegomyia) aegypti (Linnaeus 1762) that breeds in the same artificial water containers. Development time and adult dry mass were measured in 3 rearing conditions: control (a single larva), intraspecific competition (2 conspecific larvae), and interspecific competition (2 heterospecific larvae). Food was provided ad libitum to eliminate exploitative competition. For Ae. aegypti, development time was not affected by interspecific interference competition (nonsignificant differences with the control) and the adult dry mass was significantly higher, meaning that individual fitness likely increased. Yet, because previous studies showed longer development time and lighter adults during competition with other invasive mosquitoes, it is likely that Ae. aegypti can express a different phenotype depending on the competing species. The similar pattern found for Li. durhamii females and the nonsignificant difference with the control for males explain in part why this species can compete with Ae. aegypti.
Keywords: Aedes aegypti; increased fitness; interference competition; Limatus durhamii; phenotypic plasticity; resistance to invasion
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Bastin, J. - F., Rutishauser, E., Kellner, J. R., Saatchi, S., Pélissier, R., Hérault, B., et al. (2018). Pan-tropical prediction of forest structure from the largest trees. Global Ecol Biogeogr, 27(11), 1366–1383.
Abstract: Abstract Aim Large tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan-tropical model to predict plot-level forest structure properties and biomass from only the largest trees. Location Pan-tropical. Time period Early 21st century. Major taxa studied Woody plants. Methods Using a dataset of 867 plots distributed among 118 sites across the tropics, we tested the prediction of the quadratic mean diameter, basal area, Lorey's height, community wood density and aboveground biomass (AGB) from the ith largest trees. Results Measuring the largest trees in tropical forests enables unbiased predictions of plot- and site-level forest structure. The 20 largest trees per hectare predicted quadratic mean diameter, basal area, Lorey's height, community wood density and AGB with 12, 16, 4, 4 and 17.7% of relative error, respectively. Most of the remaining error in biomass prediction is driven by differences in the proportion of total biomass held in medium-sized trees (50?70 cm diameter at breast height), which shows some continental dependency, with American tropical forests presenting the highest proportion of total biomass in these intermediate-diameter classes relative to other continents. Main conclusions Our approach provides new information on tropical forest structure and can be used to generate accurate field estimates of tropical forest carbon stocks to support the calibration and validation of current and forthcoming space missions. It will reduce the cost of field inventories and contribute to scientific understanding of tropical forest ecosystems and response to climate change.
Keywords: carbon; climate change; forest structure; large trees; pan-tropical; Redd+; tropical forest ecology
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Franklin, J., Andrade, R., Daniels, M. L., Fairbairn, P., Fandino, M. C., Gillespie, T. W., et al. (2018). Geographical ecology of dry forest tree communities in the West Indies. J Biogeogr, 45(5), 1168–1181.
Abstract: Abstract Aim Seasonally dry tropical forest (SDTF) of the Caribbean Islands (primarily West Indies) is floristically distinct from Neotropical SDTF in Central and South America. We evaluate whether tree species composition was associated with climatic gradients or geographical distance. Turnover (dissimilarity) in species composition of different islands or among more distant sites would suggest communities structured by speciation and dispersal limitations. A nested pattern would be consistent with a steep resource gradient. Correlation of species composition with climatic variation would suggest communities structured by broad-scale environmental filtering. Location The West Indies (The Bahamas, Cuba, Hispaniola, Jamaica, Puerto Rico, US Virgin Islands, Guadeloupe, Martinique, St. Lucia), Providencia (Colombia), south Florida (USA) and Florida Keys (USA). Taxon Seed plants?woody taxa (primarily trees). Methods We compiled 572 plots from 23 surveys conducted between 1969 and 2016. Hierarchical clustering of species in plots, and indicator species analysis for the resulting groups of sites, identified geographical patterns of turnover in species composition. Nonparametric analysis of variance, applied to principal components of bioclimatic variables, determined the degree of covariation in climate with location. Nestedness versus turnover in species composition was evaluated using beta diversity partitioning. Generalized dissimilarity modelling partitioned the effect of climate versus geographical distance on species composition. Results Despite a set of commonly occurring species, SDTF tree community composition was distinct among islands and was characterized by spatial turnover on climatic gradients that covaried with geographical gradients. Greater Antillean islands were characterized by endemic indicator species. Northern subtropical areas supported distinct, rather than nested, SDTF communities in spite of low levels of endemism. Main conclusions The SDTF species composition was correlated with climatic variation. SDTF on large Greater Antillean islands (Hispaniola, Jamaica and Cuba) was characterized by endemic species, consistent with their geological history and the biogeography of plant lineages. These results suggest that both environmental filtering and speciation shape Caribbean SDTF tree communities.
Keywords: beta diversity; Caribbean; community composition; seasonally dry tropical forest; species turnover; tropical dry forest; West Indies
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González, A. L., Céréghino, R., Dézerald, O., Farjalla, V. F., Leroy, C., Richardson, B. A., et al. (2018). Ecological mechanisms and phylogeny shape invertebrate stoichiometry: A test using detritus-based communities across Central and South America. Funct Ecol, 32(10), 2448–2463.
Abstract: Stoichiometric differences among organisms can affect trophic interactions and rates of nutrient cycling within ecosystems. However, we still know little about either the underlying causes of these stoichiometric differences or the consistency of these differences across large geographical extents. Here, we analyse elemental (carbon, nitrogen, phosphorus) composition of 872 aquatic macroinvertebrates (71 species) inhabiting tank bromeliads (n = 140) from five distantly located sites across Central and South America to (i) test phylogenetic, trophic and body size scaling explanations for why organisms differ in elemental composition and (ii) determine whether patterns in elemental composition are universal or context dependent. Taxonomy explained most variance in elemental composition, even though phylogenetic signals were weak and limited to regional spatial extents and to the family level. The highest elemental contents and lowest carbon:nutrient ratios were found in organisms at high trophic levels and with smaller body size, regardless of geographical location. Carnivores may have higher nutrient content and lower carbon:nutrient ratios than their prey, as organisms optimize growth by choosing the most nutrient-rich resources to consume and then preferentially retain nutrients over carbon in their bodies. Smaller organisms grow proportionally faster than large organisms and so are predicted to have higher nutrient requirements to fuel RNA and protein synthesis. Geography influenced the magnitude, more than the direction, of the ecological and/or phylogenetic effects on elemental composition. Overall, our results show that both ecological (i.e. trophic group) and evolutionary drivers explain among-taxa variation in the elemental content of invertebrates, whereas intraspecific variation is mainly a function of body size. Our findings also demonstrate that restricting analyses of macroinvertebrate stoichiometry solely to either the local scale or species level affects inferences of the patterns in invertebrate elemental content and their underlying mechanisms.
Keywords: body size scaling; carnivores; detritivores; ecological stoichiometry; macroinvertebrates; nitrogen; phosphorous; phylogenetic signal
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Dlouhá, J., Alméras, T., Beauchene, J., Clair, B., & Fournier, M. (2018). Biophysical dependences among functional wood traits. Funct Ecol, 32(12), 2652–2665.
Abstract: Abstract Wood properties and especially wood density have been used as functional traits organized along major axes of species life history and strategy. Beyond statistical analyses, a better mechanistic understanding of relationships among wood traits is essential for ecologically relevant interpretation of wood trait variations. A set of theoretical relationships mechanistically linking wood basic density with some other wood traits is derived from cellular material physics. These theoretical models picture basic physical constraints and thus provide null hypotheses for further ecological studies. Analysis is applied to data from two original datasets and several datasets extracted from the literature. Results emphasize the strong physical constraint behind the link between basic density and maximal storable water on the one hand, and elastic modulus on the other hand. Beyond these basic physical constraints, the developed framework reveals physically less expected trends: the amount of free water available for physiological needs increases in less dense wood of fast-growing species, and the cell wall stiffness decreases with density in temperate hardwoods and is higher in sapling stages in the rainforest understorey where competition for light is associated with high mechanical risk. We emphasize the use of theoretically independent traits derived from models of cellular material physics to investigate the functional variation of wood traits together with their environmental and phylogenetic variations. Although the current study is limited to basic density, green wood lumen saturation and wood specific modulus, we further emphasize the identification of complementary independent wood traits representing other biomechanical functions, nutrient storage, hydraulic conductance and resistance to drought. A plain language summary is available for this article.
Keywords: basic density; biomechanical traits; hydraulic traits; wood traits
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Clair, B., Ghislain, B., Prunier, J., Lehnebach, R., Beauchene, J., & Alméras, T. (2019). Mechanical contribution of secondary phloem to postural control in trees: the bark side of the force. New Phytol, 221(1), 209–217.
Abstract: Summary To grow straight, plants need a motor system that controls posture by generating forces to offset gravity. This motor function in trees was long thought to be only controlled by internal forces induced in wood. Here we provide evidence that bark is involved in the generation of mechanical stresses in several tree species. Saplings of nine tropical species were grown tilted and staked in a shadehouse and the change in curvature of the stem was measured after releasing from the pole and after removing the bark. This first experiment evidenced the contribution of bark in the up-righting movement of tree stems. Combined mechanical measurements of released strains on adult trees and microstructural observations in both transverse and longitudinal/tangential plane enabled us to identify the mechanism responsible for the development of asymmetric mechanical stress in the bark of stems of these species. This mechanism does not result from cell wall maturation like in wood, or from the direct action of turgor pressure like in unlignified organs, but is the consequence of the interaction between wood radial pressure and a smartly organized trellis structure in the inner bark.
Keywords: bark; Malvaceae; maturation stress; secondary phloem; tree biomechanics
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Zinger, L., Taberlet, P., Schimann, H., Bonin, A., Boyer, F., De Barba, M., et al. (2019). Body size determines soil community assembly in a tropical forest. Mol Ecol, 28(3), 528–543.
Abstract: Tropical forests shelter an unparalleled biological diversity. The relative influence of environmental selection (i.e., abiotic conditions, biotic interactions) and stochastic?distance-dependent neutral processes (i.e., demography, dispersal) in shaping communities has been extensively studied for various organisms, but has rarely been explored across a large range of body sizes, in particular in soil environments. We built a detailed census of the whole soil biota in a 12-ha tropical forest plot using soil DNA metabarcoding. We show that the distribution of 19 taxonomic groups (ranging from microbes to mesofauna) is primarily stochastic, suggesting that neutral processes are prominent drivers of the assembly of these communities at this scale. We also identify aluminium, topography and plant species identity as weak, yet significant drivers of soil richness and community composition of bacteria, protists and to a lesser extent fungi. Finally, we show that body size, which determines the scale at which an organism perceives its environment, predicted the community assembly across taxonomic groups, with soil mesofauna assemblages being more stochastic than microbial ones. These results suggest that the relative contribution of neutral processes and environmental selection to community assembly directly depends on body size. Body size is hence an important determinant of community assembly rules at the scale of the ecological community in tropical soils and should be accounted for in spatial models of tropical soil food webs.
Keywords: DNA metabarcoding; eDNA; French Guiana; multitaxa; neutral assembly; niche determinism; propagule size; soil diversity
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Servigne, P., Orivel, J., Azémar, F., Carpenter, J., Dejean, A., & Corbara, B. (2020). An uneasy alliance: a nesting association between aggressive ants and equally fierce social wasps. Insect Science, 27(1), 122–132.
Abstract: Although the Neotropical territorially dominant arboreal ant Azteca chartifex Forel is very aggressive towards any intruder, its populous colonies tolerate the close presence of the fierce polistine wasp Polybia rejecta (F.).
In French Guiana, 83.33% of the 48 P. rejecta nests recorded were found side by side with those of A. chartifex. This nesting association results in mutual protection from predators (i.e., the wasps protected from army ants; the ants protected from birds).
We conducted field studies, laboratory-based behavioral experiments and chemical analyses to elucidate the mechanisms allowing the persistence of this association. Due to differences in the cuticular profiles of the two species, we eliminated the possibility of chemical mimicry.
Also, analyses of the carton nests did not reveal traces of marking on the envelopes. Because ant forager flows were not perturbed by extracts from the wasps' Dufour's and venom glands, we rejected any hypothetical action of repulsive chemicals. Nevertheless, we noted that the wasps 'scraped' the surface of the upper part of their nest envelope using their mandibles, likely removing the ants' scent trails, and an experiment showed that ant foragers were perturbed by the removal of their scent trails. This leads us to use the term 'erasure hypothesis'. Thus, this nesting association persists thanks to a relative tolerance by the ants towards wasp presence and the behavior of the wasps that allows them to 'contain' their associated ants through the elimination of their scent trails, direct attacks, 'wing-buzzing' behavior and ejecting the ants.
Keywords: Azteca chartifex ants; interspecific association; mutualism; Polybia rejecta wasps; scent trail erasure
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Mirabel, A., Marcon, E., & Hérault, B. (2021). 30 Years of postdisturbance recruitment in a Neotropical forest. Ecology and Evolution, 11(21), 14448–14458.
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