Deep time extinction of largest insular ant predators and the first fossil Neoponera (Formicidae: Ponerinae) from Miocene age Dominican amber.

BACKGROUND: Ponerine ants are almost exclusively predatory and comprise many of the largest known ant species. Within this clade, the genus Neoponera is among the most conspicuous Neotropical predators. We describe the first fossil member of this lineage: a worker preserved in Miocene-age Dominican amber from Hispaniola. RESULTS: Neoponera vejestoria sp. nov. demonstrates a clear case of local extinction-there are no known extant Neoponera species in the Greater Antilles. The species is attributable to an extant and well-defined species group in the genus, which suggests the group is older than previously estimated. Through CT scan reconstruction and linear morphometrics, we reconstruct the morphospace of extant and fossil ants to evaluate the history and evolution of predatory taxa in this island system. CONCLUSIONS: The fossil attests to a shift in insular ecological community structure since the Miocene. The largest predatory taxa have undergone extinction on the island, but their extant relatives persist throughout the Neotropics. Neoponera vejestoria sp. nov. is larger than all other predatory ant workers known from Hispaniola, extant or extinct. Our results empirically demonstrate the loss of a functional niche associated with body size, which is a trait long hypothesized to be related to extinction risk.

Biogeography of mutualistic fungi cultivated by leafcutter ants.

Leafcutter ants propagate co-evolving fungi for food. The nearly 50 species of leafcutter ants (Atta, Acromyrmex) range from Argentina to the United States, with the greatest species diversity in southern South America. We elucidate the biogeography of fungi cultivated by leafcutter ants using DNA sequence and microsatellite-marker analyses of 474 cultivars collected across the leafcutter range. Fungal cultivars belong to two clades (Clade-A and Clade-B). The dominant and widespread Clade-A cultivars form three genotype clusters, with their relative prevalence corresponding to southern South America, northern South America, Central and North America. Admixture between Clade-A populations supports genetic exchange within a single species, Leucocoprinus gongylophorus. Some leafcutter species that cut grass as fungicultural substrate are specialized to cultivate Clade-B fungi, whereas leafcutters preferring dicot plants appear specialized on Clade-A fungi. Cultivar sharing between sympatric leafcutter species occurs frequently such that cultivars of Atta are not distinct from those of Acromyrmex. Leafcutters specialized on Clade-B fungi occur only in South America. Diversity of Clade-A fungi is greatest in South America, but minimal in Central and North America. Maximum cultivar diversity in South America is predicted by the Kusnezov-Fowler hypothesis that leafcutter ants originated in subtropical South America and only dicot-specialized leafcutter ants migrated out of South America, but the cultivar diversity becomes also compatible with a recently proposed hypothesis of a Central American origin by postulating that leafcutter ants acquired novel cultivars many times from other nonleafcutter fungus-growing ants during their migrations from Central America across South America. We evaluate these biogeographic hypotheses in the light of estimated dates for the origins of leafcutter ants and their cultivars.

A global database of ant species abundances.

What forces structure ecological assemblages? A key limitation to general insights about assemblage structure is the availability of data that are collected at a small spatial grain (local assemblages) and a large spatial extent (global coverage). Here, we present published and unpublished data from 51 ,388 ant abundance and occurrence records of more than 2,693 species and 7,953 morphospecies from local assemblages collected at 4,212 locations around the world. Ants were selected because they are diverse and abundant globally, comprise a large fraction of animal biomass in most terrestrial communities, and are key contributors to a range of ecosystem functions. Data were collected between 1949 and 2014, and include, for each geo-referenced sampling site, both the identity of the ants collected and details of sampling design, habitat type, and degree of disturbance. The aim of compiling this data set was to provide comprehensive species abundance data in order to test relationships between assemblage structure and environmental and biogeographic factors. Data were collected using a variety of standardized methods, such as pitfall and Winkler traps, and will be valuable for studies investigating large-scale forces structuring local assemblages. Understanding such relationships is particularly critical under current rates of global change. We encourage authors holding additional data on systematically collected ant assemblages, especially those in dry and cold, and remote areas, to contact us and contribute their data to this growing data set.

Climate mediates the effects of disturbance on ant assemblage structure.

Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 9°C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.

Taxonomic Additions to the Neotropical Subgenus Camponotus (Myrmobrachys) Forel 1912 (Hymenoptera: Formicidae) with Emphasis on the dimorphus-Group.

We provide updated diagnoses for the senex-, burtoni- and dimorphus-groups of Camponotus (Myrmobrachys). Dichotomous keys for the C. (Myrmobrachys) groups and species of the dimorphus-group, based on type-specimens are provided. Two new species of the dimorphus-group are described, Camponotus cameloides sp. nov. and Camponotus hyalus sp. nov. We classified C. dolabratus and C. lancifer as members of the dimorphus-group and C. crassicornis, C. subcircularis, and C. championi as members of the senex-group. Scanning Electron Microscopy was used to describe the branched pilosity of C. cameloides and this is the first description of it for adult workers of Camponotini tribe.

Evolution and functional implications of stinger shape in ants.

Trait diversification is often driven by underlying performance tradeoffs in the context of different selective pressures. Evolutionary changes in task specialization may influence how species respond to tradeoffs and alter diversification. We conducted this study to investigate the functional morphology, evolutionary history, and tempo and mode of evolution of the Hymenoptera stinger using Ectatomminae ants as a model clade. We hypothesized that a performance tradeoff surface underlies the diversity of stinger morphology and that shifts between predatory and omnivorous diets mediate the diversification dynamics of the trait. Shape variation was characterized by X-ray microtomography, and the correlation between shape and average values of von Mises stress, as a measure of yield failure criteria under loading conditions typical of puncture scenarios, was determined using finite element analysis. We observed that stinger elongation underlies most of the shape variation but found no evidence of biomechanical tradeoffs in the performance characteristics measured. Additionally, omnivores have increased phenotypic shifts and accelerated evolution in performance metrics, suggesting the evolution of dietary flexibility releases selection pressure on a specific function, resulting in a greater phenotypic evolutionary rate. These results increase our understanding of the biomechanical basis of stinger shape, indicate that shape diversity is not the outcome of simple biomechanical optimization, and reveal connections between diet and trait diversification.

The global distribution of known and undiscovered ant biodiversity.

Invertebrates constitute the majority of animal species and are critical for ecosystem functioning and services. Nonetheless, global invertebrate biodiversity patterns and their congruences with vertebrates remain largely unknown. We resolve the first high-resolution (~20-km) global diversity map for a major invertebrate clade, ants, using biodiversity informatics, range modeling, and machine learning to synthesize existing knowledge and predict the distribution of undiscovered diversity. We find that ants and different vertebrate groups have distinct features in their patterns of richness and rarity, underscoring the need to consider a diversity of taxa in conservation. However, despite their phylogenetic and physiological divergence, ant distributions are not highly anomalous relative to variation among vertebrate clades. Furthermore, our models predict that rarity centers largely overlap (78%), suggesting that general forces shape endemism patterns across taxa. This raises confidence that conservation of areas important for small-ranged vertebrates will benefit invertebrates while providing a "treasure map" to guide future discovery.

Predation and patchiness in the tropical litter: do swarm-raiding army ants skim the cream or drain the bottle?

1. Swarm-raiding army ants have long been considered as episodic, catastrophic agents of disturbance in the tropical litter, but few quantitative data exist on their diets, preferences, and, critically, their ability to deplete prey. 2. Here, we provide such data for two common species of swarm raiders broadly sympatric throughout the Neotropics: the iconic Eciton burchellii and the more secretive, less studied Labidus praedator. In Ecuador, Costa Rica, Venezuela and Panama, patches of forest floor were sampled for litter invertebrates immediately before and after army ant raids. These invertebrates have been shown to regulate decomposition and vary 100-fold in local densities across the forest floor. 3. Contrary to Eciton's popular image, only Labidus consistently reduced the biomass of litter invertebrates and only then by an average of 25%. Eciton's impacts were concentrated on rich patches of invertebrates, while Labidus prey depletion showed no such density dependence. Labidus reduced the biomass of some invertebrates-isopods, larviforms and coleoptera-by up to 75%; Eciton showed no such prey preferences. 4. Our results suggest that Eciton specializes on high biomass patches, while Labidus feeds profitably from any litter patch. Combined, these swarm raiders sum to be chronic, but not catastrophic, predators of common litter invertebrates of the brown food web.

Morphological and genetic evidence supports the separation of two Tapinoma ants (Formicidae, Dolichoderinae) from the Atlantic Forest biome.

The taxonomic boundaries of many Neotropical ant species of the genus Tapinoma are still unclear. Tapinoma atriceps and T. atriceps breviscapum are two morphologically similar taxa which occur sympatrically in the southern Atlantic Forest of Brazil. Some characters such as the scape length and head shape suggest that these taxa may be different species. We used DNA analysis and morphological evidence, including scanning electron microscopy, to evaluate the taxonomic validity of these taxa. We found distinct morphological characteristics that allow separating them as two different species, Tapinoma atriceps and Tapinoma breviscapum status novo, and this decision is supported by the DNA results, where Tapinoma atriceps was recovered as a lineage independent of T. breviscapum.

Revealing male genital morphology in the giant ant genus Dinoponera with geometric morphometrics.

Genitalia include some of the most complex and morphologically diverse structures in insects, finding extensive use in taxonomy, but ant taxonomy is female biased and knowledge of the males is little explored, potentially depriving ant taxonomy of valuable information. We examine the male genital morphology of six species of Dinoponera and the variation among species and within species is described. We performed geometric morphometric analyses for the penisvalvae and lateropenite of the volsella. The results from the descriptions and statistical analyses show the genitalia offer valuable characters for species delimitation. What is presently known as Dinoponera australis can be differentiated into discrete populations, perhaps some representing cryptic species. The similarities between D. australis and D. snellingi suggest a close relation between them as well as between D. gigantea and D. quadriceps. We conclude that several genital characters, especially those of the penisvalvae, can be used to differentiate the species and might be useful to clarify the taxonomy of Dinoponera.

Odontomachus davidsoni sp. nov. (Hymenoptera, Formicidae), a new conspicuous trap-jaw ant from Ecuador.

One of the largest species in its genus, Odontomachus davidsoni Hoenle, Lattke & Donoso, sp. nov. is described from workers and queens collected at lowland forests in the Chocó-Darién bioregion in coastal Ecuador. The workers are characterized by their uniform red coloration, their large size (16-18 mm body length), and their frontal head striation that reaches the occipital margin. DNA barcodes (COI) and high resolution 2D images of the type material are provided, as well as an updated key for the Neotropical species of Odontomachus. In addition, a three-dimensional digital model of the worker holotype and a paratype queen scanned with DISC3D based on photogrammetry is presented, for the first time in a species description. Findings of large and conspicuous new species are uncommon around the world and suggest that these Ecuadorian rainforests may conceal many more natural treasures that deserve conservation.

ResumenDescribimos una especie nueva, entre las más grandes conocidas del género Odontomachus. La nueva especie, Odontomachus davidsoni Hoenle, Lattke & Donoso, sp. nov., es descrita a partir de obreras y reinas recolectadas en bosques de tierras bajas en la bioregión Chocó-Darién de la costa del Ecuador. Las obreras se caracterizan por su coloración rojiza uniforme, su grande tamaño (largo del cuerpo 16­18 mm), y la estriación del frente cefálico que alcanza el margen occipital. Proveemos códigos de barras de DNA (COI) e imágenes 2D de alta resolución para el material tipo y así como una guía de identificación actualizada para las especies neotropicales del género Odontomachus. Por primera vez en una descripción de especies, se proveen imágenes 3D de un escáner fotogramétrico DISC3D. Los hallazgos de especies grandes y conspicuas son poco comunes alrededor del mundo y sugieren que estos bosques lluviosos ecuatorianos pueden contener muchos más tesoros naturales que merecen ser conservados.

Leptogenys pujoli, a new amazonian species, and the redescription of Leptogenys famelica Emery, 1896 (Formicidae: Ponerinae)

ABSTRACT We provide an update on the famelica species group, redescribing Leptogenys famelica Emery, 1896 and describing a new species, Leptogenys pujoli n. sp., based on worker specimens. The new species is smaller than L. famelica and can be distinguished by the indistinct mesometanotal suture, and the petiolar node with an anterodorsal margin mostly straight anterior to spiracle in lateral view. Leptogenys famelica is distributed from Costa Rica to Panama, while L. pujoli n. sp. is distributed throughout the Brazilian Amazon, from French Guiana to Bolivia. Some records previously attributed to L. famelica remain uncertain, potentially being either L. famelica or L. pujoli n. sp., or perhaps representing one or more undescribed species. We update the key to Leptogenys workers by Lattke (2011) and include images. We synthesize available knowledge about the possible biology of these species and propose that both L. famelica and L. pujoli n. sp. are generalist predators and that their reproduction is dependent on gamergates.

Two new species of Leptogenys from southern Brazil (Hymenoptera: Formicidae).

Two new species of ants belonging to the genus Leptogenys are described: L. academica n. sp., and L. carioca n. sp., both belonging to the crudelis group. The former species is known from the city of Curitiba while the other species occurs in montane forests of the Itatiaia Plateau. We provide descriptions based on the worker caste, images, as well as a modification of the key presently used for identifying the New World workers of Leptogenys.

Taxonomy and Natural History of Strumigenys thaxteri Wheeler and Strumigenys reticeps (Kempf) (Hymenoptera: Formicidae).

We report finding Strumigenys thaxteri Wheeler in the Amazonian foothills of southeastern Ecuador, over 2000 km to the west of previously known records for the species in Trinidad and Guyana. Field observations suggest it is a sit and wait ambush predator that captures insects that alight on the vegetation upon which they position themselves. Once prey is subdued they descend with it to ground level, where they presumably nest. Their massive mandibles, robust claws, dense body cover of long silky hairs, and sting may all contribute to detecting, trapping, and subduing larger sized, flying prey. This type of predation is hitherto unreported for the genus. Strumigenys reticeps (Kempf), an apparently closely related species from southern Brazil, may share the same behavior but its key morphological traits are of a lesser degree of development than in S. thaxteri. Both species are redescribed and their morphological variability is discussed. High resolution images of both species are provided. The more frequent use of vegetation beating for ant-collecting is urged. Strumigenys lojanensis Lattke Aguirre is synonymized as a junior synonym of S. onorei Baroni Urbani De Andrade.

Discovery of the Dinoponera lucida male (Hymenoptera, Formicidae), a threatened giant ant from the Atlantic rain forest.

The male of the endangered ant Dinoponera lucida Emery is described, providing morphometric measurements, high-resolution images, and a distribution map of the species. This ant inhabits the Brazilian Atlantic forest, an ecosystem strongly impacted by fragmentation. The males show clear morphological differences from the known males of other species of Dinoponera. We briefly discuss the relevance of the male description for the conservation strategies of this ant.

Review of the Leptogenys unistimulosa species group (Hymenoptera: Formicidae) with the description of a new Amazonian species

ABSTRACT Leptogenys elzasoares new species, is described from workers and a male collected near Manaus in the Brazilian Amazon. The worker is recognizable by the presence of 12 chaetae (stout setae) on the clypeal median lobe, the straight mandible, and its bicolored body; the head and mesosoma are black while the gaster is brightly ferruginous. For the first time, the males of L. bohlsi Emery, 1896, L. unistimulosa Roger, 1863, and L. parensis Lattke, 2011 are described. A new key to the males of the unistimulosa species group is provided, and the key to workers of Lattke (2011) is updated to include the new species. Finally, we also report new records of L. parensis from French Guiana, expanding the known distribution by over 780 km northwest.

Timeless standards for species delimitation.

Recently a new species of bombyliid fly, Marleyimyia xylocopae, was described by Marshall & Evenhuis (2015) based on two photographs taken during fieldwork in the Republic of South Africa. This species has no preserved holotype. The paper generated some buzz, especially among dipterists, because in most cases photographs taken in the field provide insufficient information for properly diagnosing and documenting species of Diptera.

A new species and new records of minuta-group Gnamptogenys from Brazil (Hymenoptera: Formicidae)

ABSTRACT We report new records of Gnamptogenys caelata Kempf (1967) and Gnamptogenys minuta (Emery, 1896) from Brazil. We also describe Gnamptogenys piei n. sp. from Southeast Brazil. This distinctive new species is known only from a single worker found in leaf litter from montane forests of the Mantiqueira mountains in Itatiaia National Park, Rio de Janeiro State, Brazil. The specimen was collected at 1991 m above sea level, an infrequent altitude for minuta-group ants, usually more common at lower altitudes. The new species is imaged, compared with other minuta-group species, and an updated identification key for all known species of the minuta-group is included.

Army ants in four forests: geographic variation in raid rates and species composition.

1. The New World army ants are top predators in the litter of tropical forest, but no comprehensive studies exist on variation in assemblage-wide activity and species composition. We used standardized protocols to estimate foraging raid rates and species composition of army ant communities in four Neotropical forests. The study sites spanned approximately 10 degrees latitude, with two sites each in Central and South America. 2. We recorded a total of 22 species of army ants. The four sites varied in observed and estimated species richness. Species overlap was highest between the Central American sites, and lowest between the South American sites. 3. Raid activity varied significantly among sites. Raid activity per kilometre of trail walks was over four times higher at the most active site (Sta. Maria, Venezuela) than at the least active site (Barro Colorado Island, Panama). Furthermore, each site showed a different diel pattern of activity. For example, raid activity was higher during daylight hours in Costa Rica, and higher at night in Venezuela. Raid activity relationships with ambient temperature also varied significantly among sites. 4. The overall rate of army ant raids passing through 1 m(2) plots was 0.73 raids per day, but varied among sites, from 0 raids per day (Panama) to 1.2 raids per day (Venezuela). 5. Primarily subterranean species were significantly more abundant in Venezuela, and above-ground foragers that form large swarm fronts were least abundant in Panama. The site heterogeneity in species abundance and diel activity patterns has implications for army ant symbionts, including ant-following birds, and for the animals hunted by these top predators.