Fabiana Cuezzo

An Optimality Criterion to Determine Areas of Endemism

A formal method was developed to determine areas of endemism. The study region is divided into cells, and the number of species that can be considered as endemic is counted for a given set of cells (= area). Thus, the areas with the maximum number of species considered endemic are preferred. This is the first method for the identification of areas of endemism that implements an optimality criterion directly based on considering the aspects of species distribution that are relevant to endemism. The method is implemented in two computer programs, NDM and VNDM, available from the authors.

Detecting areas of endemism with a taxonomically diverse data set: plants, mammals, reptiles, amphibians, birds, and insects from Argentina

The idea of an area of endemism implies that different groups of plants and animals should have largely coincident distributions. This paper analyses an area of 1152 000 km2, between parallels 21 and 32°S and meridians 70 and 53°W to examine whether a large and taxonomically diverse data set actually displays areas supported by different groups. The data set includes the distribution of 805 species of plants (45 families), mammals (25 families), reptiles (six families), amphibians (five families), birds (18 families), and insects (30 families), and is analysed with the optimality criterion (based on the notion of endemism) implemented in the program NDM/VNDM. Almost 50% of the areas obtained are supported by three or more major groups; areas supported by fewer major groups generally contain species from different genera, families, or orders.

Can insect data be used to infer areas of endemism?: An example from the Yungas of Argentina

El objetivo principal de este trabajo es analizar si las areas de endemismo pueden ser caracterizadas cuantitativamente utilizando insectos, los cuales generalmente se encuentran mucho mas pobremente muestreados que vertebrados y plantas. La busqueda de areas de endemismo fue realizada utilizando un criterio de optimalidad sobre aproximadamente 1,100 georreferencias de 288 especies de insectos holometabolos presentes en la region de estudio. Esta corresponde al noroeste de la Argentina, especificamente en las Yungas (un bosque lluvioso montano muy humedo). El software NDM/VNDM, que aplica dicho criterio de optimalidad, fue usado para buscar areas de endemismo (i.e. conjuntos de celdas definidos por dos o mas especies). Se utilizaron cinco tamanos de grilla: tres cuadrados (Io, 0.5° y 0.25°) y dos rectangulares (0.25° x 0.5° y 0.5° x 0.25°). Los resultados de este estudio indican que las Yungas pueden ser caracterizadas como una unidad biogeografica con identidad propia y estos resultados concuerdan con propuestas biogeograficas previas. Se obtuvieron 26 areas de endemismo con 23 especies endemicas de insectos (en 14 familias) restringidas a Yungas y 46 especies (en 10 familias) endemicas, presentes en Yungas y habitats adyacentes. Nuestro analisis sugiere que el uso de insectos puede ser una herramienta poderosa para identificar areas de endemismo, aun considerando lo fragmentario del conocimiento actual de estos grupos en America del Sur. El uso de diferentes tamanos de grilla fue crucial. Tamanos pequenos y medianos son altamente recomendados para identificar patrones diferentes. El metodo cuantitativo utilizado permitio identificar areas de endemismo dificiles de reconocer con metodos biogeograficos tradicionales, tales como areas disyuntas o parcialmente superpuestas.

Ground ant diversity (Hymenoptera: Formicidae) in the Iberá Nature Reserve, the largest wetland of Argentina.

ABSTRACT The Iberá Nature Reserve in northeastern Argentina protects one of the largest freshwater wetlands and reservoirs of species in South America. However, key invertebrate groups such as the ants (Hymenoptera: Formicidae) remain almost unknown. The main objective of this work was to study the ground ant diversity in four main habitats of Iberá: grasslands, savannas, forests, and floating islands. Pitfall traps were used to characterize ground foraging ant assemblages, compare ant diversity among environments, and establish habitat associations. We also used bait traps, manual collections, and Winkler and Berlese extractors on the ground, vegetation, and litter strata to increase the species inventory. In total, 94 species in 30 genera were captured, representing the highest number of species reported from a survey of a protected area of Argentina. The richest genus was Pheidole Westwood with 23 species including three species reported for the first time in Argentina. The most common species was Solenopsis invicta Buren. Overall, the savanna was the richest and most diverse habitat with the highest number of exclusive species and functional groups. The grassland showed the highest number of rare species, but only half of the expected species were captured. The forest showed the lowest ant richness, diversity, and equitability, but one half of the species were exclusive to forest habitat. Generalized myrmicines were predominant and dominant in all habitats. Our findings indicate that habitat specialization could be an important factor determining the organization of ant assemblages in Iberá. The protection of each of these unique and threatened natural habitats of Argentina is needed to ensure the long-term preservation of their exclusive ant species.

Environmental determinants of the distribution and abundance of the ants, Lasiophanes picinus and L. valdiviensis, in Argentina

Abstract The distribution and abundance variation of the terrestrial ants, Lasiophanes picinus and Lasiophanes valdiviensis Emery (Formicinae: Lasiini), which are endemic in Patagonia (Argentina and Chile), are described and a set of environmental factors are examined to explain the observed patterns. Ants were collected using 450 pitfall traps arranged in 50, 100 m2 grid plots each with nine traps within a roughly 150 × 150 km area representative of the subantartic-patagonian transition of Argentina. Five sampling periods each 8-days long were carried out between November 2004 and March 2006. To understand the distributional patterns and their link to environmental variables discriminant analysis was used. Path analysis was performed to test for direct and indirect effects of a set of environmental variables on species abundance variation. L. picinus was more frequently captured and attained higher abundance in the forests, while L. valdiviensis was more frequently captured and more abundant in the scrubs. The maximum daily temperature and mean annual precipitation explained L. picinus distribution (i.e. presence or absence) with an accuracy of 90%. L. valdiviensis distribution was predicted with almost 70% accuracy, taking into account herbal richness. The maximum daily temperature was the only climatic variable that affected ant abundance directly; an increase in temperature led to an increase of L. picinus abundance and a decrease of L. valdiviensis abundance. The amount of resources, as indicated by the percent plant cover, explained the variation of the abundance of both species better than the variety of resources as indicated by plant richness (i.e. models including plant richness had low fit or no fit at all). A direct effect of habitat use by cattle was found, as indicated by the amount of feces in the plots, only when variables related to the amount of resources were replaced by variables with less explanatory power related to the variety of resources. This study provides new data on the ecology of Lasiophanes species in relation to existing hypotheses proposed to explain patterns of abundance variation. Evidence is provided that changes in temperature (i.e. global climate change) may have important consequences on populations of these species.

Habitat and Grazing Influence on Terrestrial Ants in Subtropical Grasslands and Savannas of Argentina

ABSTRACT The maintenance of species diversity in modified and natural habitats is a central focus of conservation biology. The Iberá Nature Reserve (INR) protects highly diverse ecosystems in northeastern Argentina, including one of the largest freshwater wetlands in South America. Livestock grazing is one of the major disturbances to these ecosystems; however, its effect on ant diversity is poorly known. The objective of this work was to study the effect of savanna versus grassland and grazing on the structure and composition of subtropical terrestrial ants focusing on the particular response of the native red imported fire ant, Solenopsis invicta Buren. Unbaited pitfall traps were used to capture worker ants in 25 grazed and 20 nongrazed sites. Fifty ant species were collected. The savanna showed more species, individuals, biomass, and functional groups of ants than the grassland. S. invicta was the most frequently captured (61.4%) and numerically dominant species; however Camponotus punctulatus punctulatus Mayr showed the highest biomass. Grazing simplified vegetation structure in both habitats, but its impact on vegetation seemed only to promote a higher total biomass especially in the grassland, and/or functional groups, favoring occurrence of hot-climate specialists in the savanna. This study revealed that habitat type strongly affected the organization of the terrestrial ant assemblages at the INR. However, as in other studies, we did not find clear evidence that habitat modification by grazing significantly affected terrestrial ant assemblages. The weak grazing influence could be the consequence of the short enclosure time as to recover the original ant communities, the differential response of ant species to habitat type, and/or the resilience of ants.

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.

Organic linings in nests of the fire ants Solenopsis electra Forel and Solenopsis nr. macdonaghi Santschi from Argentina

Although fire ants have been extensively studied, not much has been published about the structure and building material of their nests and even less on the lining of chamber walls. Nests built in unconsolidated sandy soils of Solenopsis electra and Solenopsis nr. macdonaghi, studied in La Pampa and Chubut (Argentina), respectively, show organic linings, which are reported herein for the first time. It is hypothesized that these organic linings may be of fecal origin, since there is no organic rich horizon in those soils. Apart from its significance as regards ant architecture and nest function, the presence of organic linings in ant nests is important for interpreting fossil nests, which have been often assigned to termites based on the presence of organic linings.

Environmental Harshness Decreases ant β-Diversity Between Salt Marsh and Neighboring Upland Environments

Understanding how wetland organisms interact with neighbor habitats along environmental gradients is important to recognize wetland integrity and its connectivity at landscape-level. We evaluated whether assemblage characteristics (e.g. α-diversity) of marsh-ants are associated with geographic changes in environmental conditions, and if these factors are associated with marsh-upland dissimilarity in ant species composition (β-diversity). Ant-samples were collected both in the marsh and in the neighboring upland habitat at 5-sites along the South-west Atlantic (SWA) coastline (36°S to 40°S), encompassing two-distinct biogeographic regions. Generalized Linear Models showed that at the marsh scale, ant occurrence increased with maximum temperature and Spartina densiflora cover, but decreased with total-plant cover. Ant richness increased with salinity, S. densiflora cover and marsh area; and ant α-diversity increased with S. densiflora cover and decreased with total marsh plant cover and plant height. Composition of ant assemblages differed between the marsh and the upland habitat depending on the site, and β-diversity decreased with precipitation, salinity, tidal amplitude and α-diversity of the herbaceous stratum. Then, the abundance and α-diversity of ants varied along SWA marshes in relation to changes in local environmental factors and the regional landscape. Moreover, changes in species characteristics across coastal-landscape seem to interact with environmental gradients, resulting in reduced β-diversity values with increasing environmental harshness. Thus, our results suggest that the link of geographic changes in the physical environment with the changes in species traits drives the variation in marsh-upland dissimilarity across the space.