The Atlantic Forest harbors 7% of global biodiversity and possesses high levels of endemism, but many of its component taxa remain unstudied. Due to the importance of tropical forests and the urgency ...to protect them, there is a compelling need to address this knowledge gap. To provide more information on its arthropod fauna, a Malaise trap was deployed for 12 months in a semi-degraded area of the southern Upper Paraná ecoregion of the Atlantic Forest. All specimens were DNA barcoded and the Barcode Index Number (BIN) system was employed to assign each specimen to a species proxy. DNA barcodes were obtained from 75,500 arthropods that included representatives of 8,651 BINs. Nearly 81% of these BINs were first records, highlighting the high rates of endemism and lack of study of arthropods from the Atlantic Forest. Diptera was the most abundant order, followed by Hemiptera, Lepidoptera and Hymenoptera. Diptera was also the most species-rich order, followed by Hymenoptera, Lepidoptera, and Coleoptera, a result consistent with studies in other biogeographic regions. Insects were most abundant in winter and most diverse in autumn and winter. This pattern, however, was caused mainly by the dynamics of dipteran diversity as other orders differed in their seasonal variation. The BIN composition of the insect community varied sharply through the year and also differed between the two consecutive summers included in the sampling period. The study of the 38 commonest BINs showed that seasonal patterns of abundance were not order-specific. Temperature had the strongest impact on seasonal abundance variation. Our results highlight the striking and understudied arthropod diversity of the highly fragmented Atlantic Forest, the predominance of dipterans, and the fact that abundance and richness in this insect community peak in the coolest months. Standardized studies like this generate fast and reliable biodiversity inventories and unveil ecological patterns, thus providing valuable information for conservation programs.
1. The characterisation of energy flow through communities is a primary goal of ecology. Furthermore, predator–prey interactions can influence both species abundance and community composition. The ...ant subfamily Ponerinae includes many predatory species that range from generalist insectivores to highly specialised hunters that target a single prey type. Given their high diversity and ubiquity in tropical ecosystems, measuring intra‐ and interspecific variation in their trophic ecology is essential for understanding the role of ants as predators of insect communities.
2. The stable isotopic composition of nitrogen of 22 species from the ant subfamily Ponerinae was measured, relative to plants and other predatory and herbivorous insects at two Atlantic Forest sites in Argentina. The study tested the general assumption that ponerine ants are all predatory, and examined intra‐ and interspecific variation in trophic ecology relative to habitat, body size and cytochrome c oxidase subunit 1 sequences (DNA barcoding).
3. Stable isotope analysis revealed that most ponerines occupy high trophic levels (primary and secondary predators), but some species overlapped with known insect herbivores. Species residing at low trophic levels were primarily arboreal and may rely heavily on nectar or other plant‐based resources in their diet. In addition, larger species tend to occupy lower trophic positions than smaller species.
4. Although some of the species were divided into two or more genetic clusters by DNA barcoding analysis, these clusters did not correspond to intraspecific variation in trophic position; therefore, colony dietary flexibility most probably explains species that inhabit more than one trophic level.
Stable isotope analysis revealed that most ponerines occupy high trophic levels (primary and secondary predators), but some species overlapped with known insect herbivores.
Species residing at low trophic levels were primarily arboreal and may rely heavily on plant‐based resources. Additionally, larger species tend to occupy lower trophic positions than smaller species.
Intraspecific variation in trophic position was not attributed to the presence of cryptic species. Therefore, colony dietary flexibility most probably explains species that inhabit more than one trophic level.
Associating morphological features with ecological traits is essential for understanding the connection between organisms and their roles in the environment. If applied successfully, functional trait ...approaches link form and function in an organism. However, functional trait data not associated with natural history information provide an incomplete picture of an organism's role in the ecosystem. Using data on the relative trophic position of 592 ant (Formicidae) samples comprising 393 species from 11 subfamilies and 19 widely distributed communities, we tested the extent to which commonly used functional proxies (i.e., morphometric traits) predict diet/trophic position as estimated from stable isotopes (δ15N). We chose ants as a group due to their ubiquity and abundance, as well as the wealth of available data on species traits and trophic levels. We measured 12 traits that have previously been identified as functionally significant, and corrected trait values for size and evolutionary history by using phylogenetically corrected trait residuals. Estimated trophic positions varied from 0.9 to 4.8 or roughly 4 trophic levels. Morphological data spanned nearly the entire size range seen in ants from the smallest (e.g., Strumigenys mitis total length 1.1 mm) to the largest species (e.g., Dinoponera australis total length 28.3 mm). We found overall body size, relative eye position, and scape length to be informative for predicting diet/trophic position in these communities, albeit with relatively weak predictive values. Specifically, trophic position was negatively correlated with body size and positively correlated with sensory traits (higher eye position and scape length). Our results suggest that functional trait‐based approaches can be informative but should be used with caution unless clear links between form and function have been established.
Identifying and associating morphological features with ecological traits are essential for understanding the connection between organisms and their roles in the environment. Using data on the relative trophic position of 592 ant (Formicidae) samples comprising 393 species from 11 subfamilies and 19 widely distributed communities, we tested the extent to which commonly used functional proxies (i.e., morphometric traits) predict diet/trophic position as estimated from stable isotopes (δ15N). We found overall body size, relative eye position, and scape length to be informative for predicting diet/trophic position in these communities, albeit with relatively weak predictive values.
Ants are abundant and ecologically dominant insects in most terrestrial communities. In subtropical ecosystems, there is a high turnover of species from the canopy to the top layers of the soil. ...Additionally, ant communities are often influenced by inter-specific competition. Collectively, these two processes (abiotic filtering and competition) make ants ideal for studies of community structure. We examined composition, co-occurrence, and species interactions in a sub-tropical forest ant community to examine how ground-foraging ant species partition microhabitats. We used four methods: pitfall traps, litter samples, surface baits, and subterranean baits. Surface baiting was employed at three different time periods to examine how foraging activity and species interactions at baits varied with time of day and temperature. Each method sampled a particular assemblage of the 97 total ant species. Pitfall traps shared ∼50% of species with surface baits and litter samples. Subterranean baits had the fewest total species but included some uncommonly sampled ants. The majority of interactions between species at baits were neutral, but a few agonistic interactions were also observed when bait occupancy was highest. Species co-occurrence patterns suggest that this ant community may not be heavily influenced by interspecific competition. Our results reinforce the advantages of applying complementary sampling techniques to examine ant community structure, and suggest that competition and dominance is best considered in the context of resource type, foraging strategy and time of sampling. Finally, we discuss the lack of two conspicuous Neotropical groups in our samples, leaf-cutting ant and army ants.
A central goal of ecology is to understand the mechanisms behind variation in the abundance of species. Food web theory predicts higher biomass for animals at lower trophic levels. However, some high ...trophic level species may reach great abundance via highly efficient foraging behaviors. We evaluated ecological and behavioral traits of the giant tropical ant Dinoponera australis related to these mechanisms. We determined its distribution and abundance, documented its foraging behavior, and measured its trophic position in a population at P.N. Iguazú, Argentina. We report that D. australis colonies are overdispersed, and the species reaches a wet biomass of more than 2.5 kg/ha at this site. Dinoponera australis foraging behavior is characterized by route fidelity of individual workers, with different individuals specializing on different areas around the nest. Finally, stable isotopic evidence and direct observation suggest these ants are among the top predators in this terrestrial invertebrate community. We interpret our findings in the context of how the behavior of an abundant top predator creates an exception to the usual trade‐off between biomass and trophic level. Together these data provide insight into the biology of one of the world's largest ants and why they may be able to attain such high densities where they occur.
A central goal of ecology is to understand the mechanisms behind variation in the abundance of species. Food web theory predicts higher biomass for animals at lower trophic levels. However, some high ...trophic level species may reach great abundance via highly efficient foraging behaviors. We evaluated ecological and behavioral traits of the giant tropical ant Dinoponera australis related to these mechanisms. We determined its distribution and abundance, documented its foraging behavior, and measured its trophic position in a population at P.N. Iguazú, Argentina. We report that D. australis colonies are overdispersed, and the species reaches a wet biomass of more than 2.5 kg/ha at this site. Dinoponera australis foraging behavior is characterized by route fidelity of individual workers, with different individuals specializing on different areas around the nest. Finally, stable isotopic evidence and direct observation suggest these ants are among the top predators in this terrestrial invertebrate community. We interpret our findings in the context of how the behavior of an abundant top predator creates an exception to the usual trade-off between biomass and trophic level. Together these data provide insight into the biology of one of the world's largest ants and why they may be able to attain such high densities where they occur. Resumen Uno de los aspectos centrales de la ecología es comprender los mecanismos que modulan la variación de la abundancia de las especies. La teoría trófica de redes predice una mayor biomasa en los niveles tróficos inferiores. Sin embargo, algunas especies de los niveles tróficos superiores son abundantes a través de su eficiencia de forrajeo. En el P. N. Iguazú, Argentina, se evaluaron ciertas características ecológicas y comportamentales de la hormiga tropical gigante Dinoponera australis, relacionadas con estos mecanismos. Se determinó su distribución y abundancia como así también, se documentó su comportamiento de forrajeo y se estimó su posición trófica. Las colonias de D. australis están sobre-dispersadas y la biomasa fresca de esta especie alcanza valores mayores a 2.5 kg/ha en el área. El comportamiento de forrajeo de D. australis está caracterizado por una alta fidelidad de los individuos a un área de forrajeo, estando algunos individuos especializados en ciertos sectores alrededor del nido. La evidencia aportada por el análisis de los isótopos estables y las observaciones directas de forrajeo sugieren que esta hormiga se encuentra entre los predadores tope de la comunidad de invertebrados terrestres. Los resultados se discuten en el contexto de cómo el comportamiento de un predador tope genera una excepción a la compensación usualmente encontrada entre biomasa y nivel trófico. En conjunto, estos resultados proveen información sobre la biología de una de las hormigas más grandes del mundo y brindan una posible explicación acerca de la alta densidad que esta especie puede alcanzar en las áreas donde ocurre. PUBLICATION ABSTRACT
Background: The ant subfamily Ponerinae consists of primarily predatory species that often exhibit "ancestral" characters including small colonies, worker fertility, and solitary foraging. In ...addition to diversity in their ecology and reproductive behavior, this subfamily has also been a challenge for taxonomists in terms of determining relationships among genera, placing species in appropriate genera, and estimating diversity in genera with many cryptic species (e.g., Hypoponera). In this study, we examined the systematics and distribution of ponerine ants in Argentina. We used DNA barcodes to test hypotheses regarding the delineation of species currently recognized only by morphology, to assess genetic linages among different biogeographic regions, and to link reproductive castes with worker castes. We collected samples from 10 different regions in Argentina, including from Malaise traps from Formosa and Misiones provinces that were active over two years. Additionally, we reviewed material from five museum collections. Results: We obtained 340 COI sequences from 434 individuals belonging to more than 40 species from over 10 genera, including difficult to collect genera like Thaumatomyrmex and Platythyrea. Among identified workers, the mean intraspecific sequence divergence was 1.7%, six times lower than the mean distance to the nearest neighbour (11%). We found more Barcode Index Numbers (BINs) (63) than the identified species (41), with only one case of BIN sharing by morphological species. Eight species showed deep intraspecific divergence (>6%), and half of the cases were within the genus Hypoponera. Significance: Our results suggest that barcodes are useful for identifying species boundaries and cryptic diversity of ants from a group that has historically been taxonomically challenging. We were also able to associate reproductive castes with their corresponding workers. We discuss how the diversity of reproductive strategies in ponerines might influence genetic structure, highlighting the need to take into account species natural history when interpreting COI results in this group.
Background: Understanding patterns of species diversity can only be achieved by long-term research and the integration of taxonomical, ecological, and behavioral data. Here, we studied the diversity ...and ecology of ants of Iguazu National Park (INP), Argentina, using six sampling techniques. DNA barcodes were used to uncover cryptic diversity, test species/morphospecies delimitation accuracy, and link unidentified male and queen specimens with their worker caste. Results: INP houses 195 described ant species and an additional 49 morphospecies. Leaf litter sampling and pitfall traps were the most efficient sampling methods, while surface baiting revealed the prevalence of large predatory species at different times of the day. Comparing baiting to other sampling methods provided information on species co-existence and the presence of possible dominance hierarchies among ant species. We obtained the DNA barcodes of 312 specimens from 124 species (51% of the ants of INP). Our analyses evidenced a clear barcode gap in all species but two, with an average distance to the nearest neighbour of 15.75%, almost eight times larger than the mean distance to the furthest conspecific (2.07%). Eighty-three percent of the sequence clusters obtained with different clustering algorithms (ABGD, RESL, TCS) matched the reference species or morphospecies, while 10% highlighted possible cryptic diversity. In terms of efficacy, this barcode library allowed a correct identification in more than 94% of the species/morphospecies, and to assign a species name to 69% of the unidentified males and queens. Significance: This study evidences that DNA barcodes are a valuable tool for identifying the ants of the Atlantic Forest, a global diversity hotspot. Furthermore, our project provides a framework for understanding the ecology and the taxonomic diversity of the ants of this region, including the identification of currently undescribed reproductive castes and the discovery of possible cryptic species.
Background: The Atlantic Forest in South America is one of the most biodiverse ecosystems on Earth, harboring around 7% of the species of our planet. Because this biodiversity hotspot possesses high ...rates of endemism and has been extremely disturbed, it is a priority for conservation efforts. Arthropods are good indicators of biodiversity and ecosystem integrity of forests. Therefore, a comprehensive assessment of their species composition through time and space is crucial for biomonitoring. DNA barcoding can support this activity. In the context of the Global Malaise Program, Argentina deployed a Malaise trap in Misiones province, in the southern Atlantic Forest, and insects were collected weekly for a year starting in February 2013 to evaluate local diversity and patterns of temporal succession. Results: Overall, 75 589 specimens were collected (67 565 barcode sequences recovered). These represented 8753 Barcode Index Numbers (BINs) (proxy for species), of which 81% had not been previously barcoded. Diptera was the most abundant order (76%), followed by Hemiptera (7%) and Lepidoptera (5%). We assessed the temporal distribution of the 38 most abundant BINs, which constitute conspicuous components of this ecosystem and identified six clusters of BINs with similar time series distributions. Each of these clusters included representatives from different orders, showing that demographic patterns through time are not order specific. We also analyzed which environmental variables (temperature, precipitation, wind speed) can best explain the abundance distribution of each BIN. Significance: Thousands of new species were added to the DNA barcode library. In addition, we dramatically increased access to biodiversity information for this region (currently the Global Biodiversity Information Facility (GBIF) only includes 321 species of insects in the area). Based on these results, the possible role of these BINs as biological indicators for this ecosystem can be further investigated, supporting both biomonitoring and the assessment of changes in community structure due to ongoing climate change and environmental disturbance.
Global biodiversity gradients are generally expected to reflect greater species replacement closer to the equator. However, empirical validation of global biodiversity gradients largely relies on ...vertebrates, plants, and other less diverse taxa. Here we assess the temporal and spatial dynamics of global arthropod biodiversity dynamics using a beta-diversity framework. Sampling includes 129 sampling sites whereby malaise traps are deployed to monitor temporal changes in arthropod communities. Overall, we encountered more than 150,000 unique barcode index numbers (BINs) (i.e. species proxies). We assess between site differences in community diversity using beta-diversity and the partitioned components of species replacement and richness difference. Global total beta-diversity (dissimilarity) increases with decreasing latitude, greater spatial distance and greater temporal distance. Species replacement and richness difference patterns vary across biogeographic regions. Our findings support long-standing, general expectations of global biodiversity patterns. However, we also show that the underlying processes driving patterns may be regionally linked.
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