Thibaut Delsinne

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.

High species turnover of the ant genus Solenopsis (Hymenoptera : Formicidae) along an altitudinal gradient in the Ecuadorian Andes, indicated by a combined DNA sequencing and morphological approach

Abstract. Solenopsis is a widespread ant genus and the identification of its species is notoriously difficult. Hence, investigation of their distribution along elevational gradients is challenging. Our aims were (1) to test the complementarity of the morphological and DNA barcoding approaches for Solenopsis species identification, and (2) to assess species diversity and distribution along an altitudinal gradient in the Ecuadorian Andes. Ants were collected in five localities between 1000 and 3000 m above sea level. In total, 24 morphospecies were identified along the gradient and 14 of them were barcoded. Seven morphospecies were confirmed by the molecular approach. Three others, occurring sympatrically and possessing clear diagnostic characters, showed low genetic divergence. Representatives of a further four morphospecies were split into nine clusters by COI and nuclear wingless genetic markers, suggesting the existence of cryptic species. Examination of gynes revealed potential diagnostic characters for morphological discrimination. Solenopsis species were found up to an altitudinal record of 3000 m. Most morphospecies (20 of 24) were found at a single elevation. Our results suggest a high species turnover along the gradient, and point to the use of morphological and DNA barcoding approaches as necessary for differentiating among Solenopsis species.

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.

Trophic Ecology of the Armadillo Ant, Tatuidris tatusia, Assessed by Stable Isotopes and Behavioral Observations

Abstract Ants of the genus Tatuidris Brown and Kempf (Formicidae: Agroecomyrmecinae) generally occur at low abundances in forests of Central and South America. Their morphological peculiarities, such as mandibular brushes, are presumably linked with specialized predatory habits. Our aims were to (1) assess the Tatuidris abundance in an evergreen premontane forest of Ecuador; (2) detail morphological characteristics and feeding behavior of Tatuidris; and (3) define the position of Tatuidris in the food web. A total of 465 litter samples were collected. For the first time, live Tatuidris individuals were observed. Various potential food sources were offered to them. A nitrogen stable isotope ratio analysis (15N/14N) was conducted on Tatuidris tatusia, other ants, and common organisms from the leaf-litter mesofauna. We found a relatively high abundance of T. tatusia in the site. Live individuals did not feed on any of the food sources offered, as usually observed with diet specialist ants. The isotope analysis revealed that T. tatusia is one of the top predators of the leaf-litter food web.

Influence of Leaf Litter Moisture on the Efficiency of the Winkler Method for Extracting Ants

Abstract The Winkler extraction is one of the two fundamental sampling techniques of the standardized “Ants of the Leaf Litter” protocol, which aims to allow qualitative and quantitative comparisons of ant (Hymenoptera: Formicidae) assemblages. To achieve this objective, it is essential that the standard 48—hour extraction provides a reliable picture of the assemblages under study. Here, we tested to what extent the efficiency of the ant extraction is affected by the initial moisture content of the leaf litter sample. In an Ecuadorian mountain rainforest, the leaf litter present under rainfall—excluded and rainfall—allowed plots was collected, its moisture content measured, and its ant fauna extracted with a mini—Winkler apparatus for a 48—hour and a 96—hour period. The efficiency of the Winkler method to extract ant individuals over a 48—hour period decreased with the moisture content of the leaf litter sample. However, doubling the extraction time did not improve the estimations of the ant species richness, composition, and relative abundance. Although the moisture content of the leaf litter slightly affected the ant sampling, our results indicated that a 48—hour Winkler extraction, as recommended by the “Ants of the Leaf Litter” protocol, is sufficient to allow reliable comparisons of ant assemblages.

Dominance-diversity relationships in ant communities differ with invasion

The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance-impoverishment rule states that high levels of dominance only occur in species-poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non-native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground-dwelling ants distributed across five continents to document the generality of the dominance-impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance-diversity relationship varies greatly, and depends on whether dominant species are native or non-native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance-impoverishment rule applies to invaded communities, we propose an alternative dominance-diversification rule for native communities.

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.

Distribution and Diversity of the Cryptic Ant Genus Oxyepoecus (Hymenoptera: Formicidae: Myrmicinae) in Paraguay with Descriptions of Two New Species

We discuss the diversity and distribution of the ant genus Oxyepoecus in Paraguay. Oxyepoecus inquilinus is recorded for the first time, and new distribution data are given for O. rastratus and O. vezenyii. Published data for O. bruchi, O. rastratus, O. reticulatus, and O. vezenyii are summarized. Two new species are described (O. bidentatus n. sp. and O. striatus n. sp.), and a key to the workers of the seven Paraguayan Oxyepoecus species is provided. At Teniente Enciso National Park, four species cooccur. This locality appears as a promising site for studies documenting the biology of this poorly known ant genus, and because of the IUCN “vulnerable“ Red List classification of O. inquilinus, the importance of the Teniente Enciso National Park for biological conservation is clearly established.