Determining 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 Saül, 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.
The prevalent mode of reproduction among ants is arrhenotokous parthenogenesis where unfertilized eggs give rise to haploid males and fertilized eggs develop into diploid females. Some ant species ...are capable of thelytokous parthenogenesis, a type of asexual reproduction where females develop from unfertilized diploid eggs. Thelytoky is well-documented in more than 20 ant species. Cytogenetic data are available for six species demonstrating that some thelytokous ant species are capable of producing males occasionally as well as maintaining their chromosome numbers and proper chromosome pairings. Mycocepurus smithii is a thelytokous fungus-growing ant species that inhabits large parts of Central and South America. Cytogenetic data are unavailable for M. smithii and male individuals were never documented for this species, although the presence of males is expected because genetic recombination was observed in a few sexually reproducing populations in Brazil and haploid sperm was documented from the spermathecae of M. smithii queens. This study aims at comparatively studying asexual and sexual populations of M. smithii using classical and molecular cytogenetic methods to test whether karyotype configuration is modified according to the mode of reproduction in M. smithii. Moreover, we report the discovery of M. smithii males from a sexually reproducing population in the Brazilian state Pará, diagnose the male of M. smithii, and morphologically characterize their spermatozoa. Karyotypic variation was observed within the asexual population (2n = 9, 10, or 11), whereas the chromosome number was fixed in the sexual population (2n = 14, n = 7). Identical karyotypes were maintained within individual M. smithii colonies and karyotype variation was only observed between colonies. In asexual individuals, the karyomorphs showed a decay of homologous chromosome pairs, especially in individuals with the karyomorph 2n = 11, which is potentially caused by relaxed natural selection on proper chromosome pairing. In contrast, females in the sexual population showed proper homologous chromosome pairings. In individuals of both asexual and sexual populations, we find that heterochromatin was localized in centromeric regions and on the short arms of the chromosomes, GC-rich regions were associated with heterochromatic regions, and 18S rDNA genes were located on the largest chromosome pair. This comparative cytogenetic analysis contributes to our understanding about the cytological mechanisms associated with thelytokous parthenogenesis in ants and suggests the decay of chromosome structure in the absence of meiosis and genetic recombination.
The Brazilian endemic butterfly Eresia erysice erysice (Geyer, 1832) (Lepidoptera: Nymphalidae) has been included in the Official List of Brazilian Endangered Fauna as critically endangered (CR). ...Until now, this rare butterfly has only been known to inhabit Atlantic Forest fragments in the “Hileia Baiana”. This paper presents updated information on occurrences of E. e. erysice. A male and a female specimens were collected in a disturbed forest fragment near the experimental fields of the Centro de Pesquisas do Cacau (CEPEC), Ilhéus, Bahia. These new findings indicate that the distribution boundary of this subspecies extends about 80 km more to the north and suggest that it is not as exclusive to forest habitats as previously thought.
Habitat loss and fragmentation have highlighted the importance of monitoring remaining habitats. For megadiverse groups such as arthropods, of which many species are still being discovered, the use ...of higher taxonomic levels as substitutes for diversity may be a useful tool. The aim of this study was to evaluate the use of substitute taxonomic resolutions to assess the richness and composition of Laniatores harvestmen (Arachnida: Opiliones). The five resolutions selected were as follows: genus, family, subfamily, indicator taxa and intermediate resolution (combination of genus and species identification levels). In addition, we evaluated whether the diversity substitutes provide good estimates of latitudinal gradients. Nineteen Atlantic Forest sites located along a latitudinal gradient in northeastern Brazil were sampled. We recorded a total of 88 harvestmen species/morpho‐species, distributed in 7 families, 15 subfamilies and 36 genera. Genus and intermediate resolution were excellent substitutes for harvestmen species richness. The efficiency differed according to the substitute resolution used. Four resolutions were adequate to replace the harvestmen composition: genus, intermediate resolution, indicator taxa, and subfamily. The number of harvestmen species recorded was significantly different between Seasonal Semideciduous Forest and Costal Atlantic Rainforest. The same relationship was also observed the same relationship was observed when we consider genus and intermediate resolution. Our results suggest the use of genus as a substitute for richness and composition of harvestmen for reducing monitoring costs and providing evaluation in a shorter time and a more practical way.
Some species are more affected than others by edge effects resultant from habitat loss and fragmentation, generally due to human activities. As these specific responses depend on biophysical and ...behavioral traits of organisms, it is expected that the occurrence of species with particular traits will vary between fragment edges and interiors. Edges are also known to often harbor many invasive species. We performed a meta-analysis of the responses of insect species with different life history traits to anthropogenic edges, focusing on the species’ behavioral characteristics and whether they are considered invasive or not. We systematically searched the Web of Science database for papers on this subject published until May 2018. We examined response ratios for 712 comparisons of anthropogenic edge effects on insects. As expected, the responses differed according to the traits evaluated. Soil-foraging and social insects were negatively affected by anthropogenic edges. Conversely, flying and invasive species were favored by edges. Our analyses suggest that edges, by differently affecting different insect groups, have an important role in structuring local insect communities. Finally, the importance of functional traits in studies of edge effects must be highlighted.
One important strategy to conciliate forest conservation and economic development is the use of reduced-impact logging techniques. Here we evaluated the effects of low-intensity forest management on ...ant assemblages and vegetation structure in a managed area in the southeast of Acre State, Brazil. Ground-dwelling and arboreal ants, and several forest-structure descriptors were sampled in nine paired areas located in control (unlogged) and logged areas in 2005, 2007 and 2009. None of the forest structure predictors were related with either the treatment or the time since logging. However, some ant assemblage’ descriptors were related with logging activities. Arboreal and ground-dwelling ant species richness was similar between unlogged and logged areas, but more ground-dwelling ant species were found in areas logged in 2005 compared with areas logged in 2009. Ground-dwelling ant assemblage composition differed between treatments (logged and unlogged) and year of logging, but species composition heterogeneity was similar between areas. Arboreal ant assemblage composition was not related with treatment and year of logging, but assemblage composition was more heterogeneous in managed areas, suggesting that species that forage on the understory vegetation may be more resilient than ground-dwelling species. The general results of functional group approach suggest that changes of species composition between control and managed areas are more related with differences in ant species occurrence than ant species richness. Selective logging had limited effect on both vegetation descriptors and ant assemblage structure, suggesting that the conciliation of impact reduction techniques with low intensity extraction seems a promising alternative for sustainable logging activity in tropical forests.
The state of the art of Formicidae biogeographic studies using distribution modeling tools was reviewed. We aimed to evaluate how and for what purpose such tools were used in ant studies, as well as ...detecting modeling methods, algorithms, and variables selected for these studies. We analyzed papers published from 2001 to 2021 and focused on predicting invasion risks, conservation, and potential distribution of species. We also considered the mechanistic and correlative approaches, types of algorithms, and environmental variables. We observed that modeling is first used to predict invasion risks before conservation. The correlative approach was the most used, although it does not consider biotic or physiological aspects as the mechanistic approach does. The most used algorithm was Maxent, combining data set of occurrences with climatic variables. Nine studies used combinations of algorithms with consensual models. Research using modeling has been conducted more and more. However, it remains still incipient, mainly regarding conservation, as the current distribution of most of the Formicidae species is not well known. Although not frequently used in ant studies, distribution modeling represents an important approach for research in biogeography, ecology, and related areas. Certain perspectives could be useful, for example, for studying climatic changes, since possible variations in ant distributions, if anticipated, could suggest or guide further investigations or decision-making in public policies.
ABSTRACT Regularly spaced earth mounds called “murundus” are scattered in several landscapes in the semi-arid region of Brazil. Although recent evidence indicates that termites are involved in the ...building of murundus, the contribution of these insects to soil-forming processes in those structures remains poorly understood. In this study, we tested a set of hypotheses to examine whether there are consistent evidence for suggesting the participation of termites in the formation of murundus soils. Morphological and physicochemical features of murundus were compared with adjacent soil profiles in the inter-mounds surface and one epigeic nest built by one species of Syntermes Holmgren. The murundus soils had a more clayey texture, higher contents of nutrients (C, N, P, K, Ca, and Mg) and organic matter compared with adjacent soils. We identified a set of recent and ancient traces inside the murundus that reveals the intense building activity of termite colonies (e.g., galleries, tunnels, and royal chambers), confirming that these structures are not only occupied by these insects but also built-up by them. Taken together, our results provide hard evidence that the long-term activity of mound-building termites was the hierarchically dominant process in producing murundus structures in the semi-arid region of Brazil. Based on available empirical data, we propose an explanatory model on how that construction process may have taken place.
Two valid ant species, Camponotus rufipes and Camponotus renggeri, have recently been the subject of a broad discussion with reference to taxa synonymization. Both species are quite common among the ...Neotropical myrmecofauna and share some unique traits, such as the shape of the scape and the pilosity patterns of the tibiae and scapes. A single morphological trait can help distinguish these species; however, only a combination of different approaches can enlighten our view of the complex phylogenetic relationships prevailing in the different populations of these two taxa. Therefore, focusing on the taxonomic issues concerning these two species, a cytogenetic survey including 10 populations of C. rufipes and two populations of C. renggeri was performed. In order to better understand the extent of the relationship between C. rufipes and C. renggeri, two common Neotropical Camponotus species, C. atriceps and C. cingulatus were taken as outgroups. All four species of Camponotus that were studied had 2n = 40 chromosomes (4sm+34st+2t); however, the abundance of chromosome rearrangements observed, combined with several chromosome markers, suggest that C. rufipes and C. renggeri are two good distinct species although closely related. The already reported chromosome translocation 2n = 39 (1m+4sm+32st+2t) for C. rufipes has been found in different populations as in the unprecedented chromosome inversions found both in C. rufipes and in C. renggeri populations. Within the C. renggeri chromosome inversions, both the heterozygous state 2n = 40 (1m+3sm+34st+2t) and the homozygous state, 2n = 40 (2m+2sm+34st+2t) were identified. However, only heterozygous specimens for chromosome inversions were found among C. rufipes, with karyotype configurations distinct from those found in C. renggeri, with 2n = 40 (1m+4sm+34st+2t). None of the populations studied showed signs of mosaic individuals. With respect to rDNA clusters, the 18S rDNA seemed to be more restricted inside the genome, as C. renggeri showed four 18S rDNA clusters, whereas, C. rufipes, C. atriceps, and C. cingulatus showed only two clusters. The chromosome locations of the 5S rDNA clusters were pointed for the first time in Formicidae, and showed itself to be more widely spread over the genome. By combining different chromosome banding approaches it was possible to demonstrate the crucial importance that chromosome inversions played on the karyotype evolution within these ants. The results also showed that chromosome translocations might be a consequence of the chromatin dynamic condition observed among Camponotus species. The homozygosis condition found in a C. renggeri from a Brazilian savanna population for chromosome inversions and the contrasting heterozygous condition for a different kind of chromosome inversion in C. rufipes from the Brazilian coastal rainforest, opens the window for a chromosome race hypothesis within the group C. renggeri and C. rufipes. The wide distribution, rich ecological interactions, genetic diversity, and morphological variability among C. renggeri and C. rufipes justify questioning of the actual taxonomic status of these species. The answer of this puzzle is clear when observing the number of 18S rDNA clusters of these ants, as C. rufipes has only two clusters whereas C. renggeri has four.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Ants cause a series of accidents involving humans. Such accidents generate different reactions in the body, ranging from a mild irritation at the bite site to anaphylactic shock, and these reactions ...depend on the mechanism of action of the venom. The study of animal venom is a science known as venomics. Through venomics, the composition of the venom of several ant species has already been characterized and their biological activities described. Thus, the aim of this study was to evaluate the protein composition and biological activities (hemolytic and immunostimulatory) of the venom of Neoponera villosa (N. villosa), an ant widely distributed in South America. The protein composition was evaluated by proteomic techniques, such as two-dimensional electrophoresis. To assess the biological activity, hemolysis assay was carried out and cytokines were quantified after exposure of macrophages to the venom. The venom of N. villosa has a profile composed of 145 proteins, including structural and metabolic components (e.g., tubulin and ATPase), allergenic and immunomodulatory proteins (arginine kinase and heat shock proteins (HSPs)), protective proteins of venom (superoxide dismutase (SOD) and catalase) and tissue degradation proteins (hyaluronidase and phospholipase A2). The venom was able to induce hemolysis in human erythrocytes and also induced release of both pro-inflammatory cytokines, as the anti-inflammatory cytokine release by murine macrophages. These results allow better understanding of the composition and complexity of N. villosa venom in the human body, as well as the possible mechanisms of action after the bite.
PDF
