Decay of similarity across tropical forest communities : integrating spatial distance with soil nutrients

Altres ajuts: Acord transformatiu CRUE-CSICUnderstanding the mechanisms that drive the change of biotic assemblages over space and time is the main quest of community ecology. Assessing the relative importance of dispersal and environmental species selection in a range of organismic sizes and motilities has been a fruitful strategy. A consensus for whether spatial and environmental distances operate similarly across spatial scales and taxa, however, has yet to emerge. We used censuses of four major groups of organisms (soil bacteria, fungi, ground insects, and trees) at two observation scales (1-m sampling point vs. 2,500-m plots) in a topographically standardized sampling design replicated in two tropical rainforests with contrasting relationships between spatial distance and nutrient availability. We modeled the decay of assemblage similarity for each taxon set and site to assess the relative contributions of spatial distance and nutrient availability distance. Then, we evaluated the potentially structuring effect of tree composition over all other taxa. The similarity of nutrient content in the litter and topsoil had a stronger and more consistent selective effect than did dispersal limitation, particularly for bacteria, fungi, and trees at the plot level. Ground insects, the only group assessed with the capacity of active dispersal, had the highest species turnover and the flattest nonsignificant distance−decay relationship, suggesting that neither dispersal limitation nor nutrient availability were fundamental drivers of their community assembly at this scale of analysis. Only the fungal communities at one of our study sites were clearly coordinated with tree composition. The spatial distance at the smallest scale was more important than nutrient selection for the bacteria, fungi, and insects. The lower initial similarity and the moderate variation in composition identified by these distance-decay models, however, suggested that the effects of stochastic sampling were important at this smaller spatial scale. Our results highlight the importance of nutrients as one of the main environmental drivers of rainforest communities irrespective of organismic or propagule size and how the overriding effect of the analytical scale influences the interpretation, leading to the perception of greater importance of dispersal limitation and ecological drift over selection associated with environmental niches at decreasing observation scales

Phylogeny of Blattoidea (Dictyoptera: Blattodea) with a revised classification of Blattidae

Blattoidea are comprised of the major lineages Blattidae, Lamproblattidae, Tryonicidae, Anaplectidae, and Cryptocercidae + Isoptera. Despite a number of studies, no consensus exists regarding the relationships between these lineages. Additionally, the current division of Blattidae into Archiblattinae, Blattinae, Macrocercinae and Polyzosteriinae needs phylogenetic testing. We present a molecular phylogeny of Blattoidea recovering all the major lineages as monophyletic with Lamproblattidae as sister to the remaining Blattoidea and Tryonicidae as sister to Cryptocercidae + Isoptera. Contrary to many previous studies, we found a high degree of consistency between analyses, possibly due to improved taxon sampling. We found that none of the currently accepted subfamilies of Blattidae are monophyletic. Mapping of distribution revealed a clear geographic structuring at odds with the current subfamilial classification. Based on results from this and other studies, we present a revised classification of Blattidae: we erect two new subfamilies, Eurycotiinae stat. rev. and Austrostylopyginae subfam. nov., reinstate Duchailluiinae stat. rev. and subsume Macrocercinae in Polyzosteriinae. We also present a division of Polyzosteriinae into tribes: Polyzosteriini, Methanini stat. rev., Rothisilphini trib. nov., and Celatoblattini trib. nov. Within Blattidae, Duchailluiinae is sister to the remaining taxa, while Austrostylopyginae is most likely sister to all other Blattidae except Duchailluiinae

Including Secondary Structure, Fossils and Molecular Dating in the Centipede Tree of Life

A well-corroborated morphological scheme of interrelationships for centipedes, once broadly accepted, has been in conflict with molecular data with respect to deep branching events. Expanded taxonomic coverage compared to previous analyses adds longer fragments for 28S rRNA and a structural alignment as part of a sample of four genes (two nuclear ribosomal and two mitochondrial) for 111 extant species; these sequence data are combined with morphology under parsimony and maximum likelihood, exploring both traditional multiple sequence alignment and direct optimization approaches. Novel automated procedures to incorporate secondary structure information are also explored. The molecular data in combination yield trees that are highly congruent with morphology as regards the monophyly of all centipede orders as well as the major groups within each of the large orders. Regardless of the optimality criterion or alignment strategy, the Tasmanian/New Zealand Craterostigmomorpha is resolved in a different position by the molecular data than by morphology. Addition of morphology overturns the placement of Craterostigmomorpha in favour of the traditional morphological resolution and eliminates the need to posit major character reversals with respect to developmental mode and maternal care. Calibration of the tree with Palaeozoic and Mesozoic fossils for a relaxed clock analysis corroborates the palaeontological signal that divergences between centipede orders date to the Silurian and earliest Devonian, and familial divergences are likewise almost wholly Palaeozoic.Organismic and Evolutionary Biolog

Ants of French Guiana: 16S rRNA sequence dataset

This dataset represents a reference library of DNA sequences for ants from French Guiana. A total of 3931 new sequences from the 16S rRNA gene has been generated. The reference library covers 344 species distributed in 57 genera. Overall, 3920 sequences have been assigned at the species level and 11 at the genus level. All these sequences were submitted to DDBJ/EMBL/GenBank databases in the Bioproject: PRJNA779056: 16S French Guiana Ants (Hymenoptera: Formicidae), sequence identifier KFFS00000000

Ants of French Guiana: a DNA barcode dataset

This dataset represents a DNA barcode reference library for ants from French Guiana. A total of 3931 new sequences from 16S rRNA gene has been generated. The reference library covers 344 species distributed in 57 genera. 3920 sequences are assigned at the species level and 11 at the genus level. All these sequences were submitted to DDBJ/EMBL/GenBank databases in the Bioproject: PRJNA779056: 16S French Guiana Ants (Hymenoptera: Formicidae), sequence identifier KFFS00000000

Shotgun assembly of the assassin bug <em>Brontostoma colossus</em> mitochondrial genome (Heteroptera, Reduviidae)

International audienceThe complete mitochondrial genome of the assassin bug Brontostoma colossus (Distant, 1902) (Heteroptera: Reduviidae) has been sequenced using a genome-skimming approach on an Illumina Hiseq 2000 platform. Fifty-four additional heteropteran mitogenomes, including five assassin bug species, were retrieved to allow for comparisons and phylogenetic analyses. The mitochondrial genome of B. colossus was determined to be 16,625 bp long, and consists of 13 protein-coding genes (PCGs), 23 transfer-RNA genes (tRNAs), two ribosomal-RNA genes (rRNAs), and one control region. The nucleotide composition is biased toward adenine and thymine (A + T = 73.4%). Overall, architecture, nucleotide composition and genome asymmetry are similar among all available assassin bug mitogenomes. All PCGs have usual start-codons (Met and Ile). Three T and two TA incomplete termination codons were identified adjacent to tRNAs, which was consistent with the punctuation model for primary transcripts processing followed by 3' polyadenylation of mature mRNA. All tRNAs exhibit the classic clover-leaf secondary structure except for tRNA(Ser)(AcN) in which the DHU arm forms a simple loop. Two notable features are present in the B. colossus mitogenome: (i) a 131 bp duplicated unit including the complete tRNA(Arg) gene, resulting in 23 potentially functional tRNAs in total, and (ii) a 857 bp duplicated region comprising 277 bp of the srRNA gene and 580 bp of the control region. A phylogenetic analysis based on 55 true bug mitogenomes confirmed that B. colossus belongs to Reduviidae, but contradicted a widely accepted hypothesis. This highlights the limits of phylogenetic analyses based on mitochondrial data only

iDNA screening: Disease vectors as vertebrate samplers

International audienceIn the current context of global change and human-induced biodiversity decline, there is an urgent need for developing sampling approaches able to accurately describe the state of biodiversity. Traditional surveys of vertebrate fauna involve time-consuming and skill-demanding field methods. Recently, the use of DNA derived from invertebrate parasites (leeches and blowflies) was suggested as a new tool for vertebrate diversity assessment. Bloodmeal analyses of arthropod disease vectors have long been performed to describe their feeding behaviour, for epidemiological purposes. On the other hand, this existing expertise has not yet been applied to investigate vertebrate fauna per se. Here, we evaluate the usefulness of hematophagous dipterans as vertebrate samplers. Blood-fed sand flies and mosquitoes were collected in Amazonian forest sites and analysed using high-throughput sequencing of short mitochondrial markers. Bloodmeal identifications highlighted contrasting ecological features and feeding behaviour among dipteran species, which allowed unveiling arboreal and terrestrial mammals of various body size, as well as birds, lizards and amphibians. Additionally, lower vertebrate diversity was found in sites undergoing higher levels of human-induced perturbation. These results suggest that, in addition to providing precious information on disease vector host use, dipteran bloodmeal analyses may represent a useful tool in the study of vertebrate communities. Although further effort is required to validate the approach and consider its application to large-scale studies, this first work opens up promising perspectives for biodiversity monitoring and eco-epidemiology

Habitats shape taxonomic and functional composition of Neotropical ant assemblages

International audienceDetermining assembly rules of co-occurring species persists as a fundamental goal in community ecology. At local scales, the relative importance of environmental filtering vs. competitive exclusion remains a subject of debate. In this study, we assessed the relative importance of habitat filtering and competition in structuring understory ant communities in tropical forests of French Guiana. Leaf-litter ants were collected using pitfall and Winkler traps across swamp, slope and plateau forests near Saul, French Guiana. We used a combination of univariate and multivariate analyses to evaluate trait response of ants to habitat characteristics. Null model analyses were used to investigate the effects of habitat filtering and competitive interactions on community assembly at the scale of assemblages and sampling points, respectively. Swamp forests presented a much lower taxonomic and functional richness compared to slope and plateau forests. Furthermore, marked differences in taxonomic and functional composition were observed between swamp forests and slope or plateau forests. We found weak evidence for competitive exclusion based on null models. Nevertheless, the contrasting trait composition observed between habitats revealed differences in the ecological attributes of the species in the different forest habitats. Our analyses suggest that competitive interactions may not play an important role in structuring leaf-litter ant assemblages locally. Rather, habitats are responsible for driving both taxonomic and functional composition of ant communities

Vector soup : high-throughput identification of Neotropical phlebotomine sand flies using metabarcoding

Phlebotomine sand flies are haematophagous dipterans of primary medical importance. They represent the only proven vectors of leishmaniasis worldwide and are involved in the transmission of various other pathogens. Studying the ecology of sand flies is crucial to understand the epidemiology of leishmaniasis and further control this disease. A major limitation in this regard is that traditional morphological-based methods for sand fly species identifications are time-consuming and require taxonomic expertise. DNA metabarcoding holds great promise in overcoming this issue by allowing the identification of multiple species from a single bulk sample. Here, we assessed the reliability of a short insect metabarcode located in the mitochondrial 16S rRNA for the identification of Neotropical sand flies, and constructed a reference database for 40 species found in French Guiana. Then, we conducted a metabarcoding experiment on sand flies mixtures of known content and showed that the method allows an accurate identification of specimens in pools. Finally, we applied metabarcoding to field samples caught in a 1-ha forest plot in French Guiana. Besides providing reliable molecular data for species-level assignations of phlebotomine sand flies, our study proves the efficiency of metabarcoding based on the mitochondrial 16S rRNA for studying sand fly diversity from bulk samples. The application of this high-throughput identification procedure to field samples can provide great opportunities for vector monitoring and eco-epidemiological studies