Alejandro G. Farji-Brener

National Scientific and Technical Research Council | conicet

Understanding why animals avoid some locations is needed to improve the theory of habitat selection. This is key in semi‐sedentary organisms, such as antlion larvae, because once established they rarely move, and their performance largely depends on local environmental conditions. Antlion larvae are sit‐and‐wait predators that build conical pitfall...

Hypotheses based on allocation theory and herbivore selection offer opposite predictions about how defence levels against herbivores change as the plant tissue grows. The growth differentiation balance hypothesis (GDBH) assumes that defences will be resource-limited in immature tissues and predict that defence levels increase as the plant tissue gr...

The principle of resource allocation states that diversion of resources to attend a function may compromise others. The COVID-19 pandemic required a rapid response with a justifiable relocation of equipment, funds and human resources. Based on the ecological principle of allocation, we tested whether the relocation of resources to support COVID-19...

Placing traits into novel evolutionary contexts may profoundly alter their functional roles. Here, we investigated whether the elaiosome, a lipid‐rich appendage located on seeds, retained its role as a seed dispersal trait promoting mutualisms with insectivorous ants following human‐mediated introduction of the elaiosome‐bearing Carduus nutans into...

Remaining immobile for an unpredictable time following contact with a predator (postcontact immobility) is a successful tactic to reduce predation. However, the mechanisms that may cause this variation are poorly known. We explored whether size, personality, substrate type and predation risk influence the duration of postcontact immobility in antli...

Enhanced soil nutrient availability often favours herbivore performance by bringing the carbon:nutrient ratio of plants closer to herbivore requirements. However, a surplus of nutrients can promote a too low carbon:nutrient ratio in plants, making them of poor quality for herbivores. In addition, increased soil nutrients can trigger cascading effec...

Intraspecific competition is a pervasive phenomenon with important ecological and evolutionary consequences in ants. However, its effect at population level remains less known. We investigated the effect of intraspecific competition on the demography of the leaf-cutting ant Acromyrmex lobicornis using a stochastic matrix demographic model parameter...

Un objetivo fundamental de la ecología como ciencia es determinar patrones en la naturaleza e inferir sus posibles causas. Pese a la importancia y la complementariedad de las aproximaciones descriptivas y deductivas, es común que directores, revisores y organismos de financiación requieran obligatoriamente formular hipótesis en los proyectos de inv...

1. Leaf-cutting ants are major pests of Neotropics forest plantations. The lower delta of the Paraná River contains the main Argentine Salicaceae production, strongly attacked by Acromyrmex lundii and Acromyrmex ambiguus. Nevertheless, there is no damage quantification in willow plantations attributed to leaf-cutting ant species. 2. In an area wit...

Building and testing general principles is key to accelerate scientific progress. Here, we review the studies performed in Argentina in which ants were used as model organisms, in the context of ecological theories, hypotheses and concepts. Specifically, we focus on ant studies performed under the conceptual frameworks of ecological engineering, in...

A key principle of the extended phenotype concept is that the benefit of the structures that an animal builds exceeds its cost. However, some contexts may enhance the costs of structures that often represent a benefit, reversing their adaptive nature. In leaf-cutting ant nests, thatched mounds are extended phenotypes that offer a stable microclimat...

Given that pollinators usually visit flowers for hidden rewards, they need to rely on floral traits that indicate reward status (“honest signals”). However, the relationship between pollination, honest signals, and floral rewards is little documented in natural conditions. The Scotch broom (Cytisus scoparius) is an invasive shrub with polymorphism...

Transportar alimentos desde los centros de producción hacia los centros de consumo es un desafío para las sociedades densamente pobladas. Para evitar retrasos, el sistema desenderos debe ser eficiente y el comportamiento de los transportistas debe reducir la probabilidad de colisiones. En este trabajo se describe cómo las hormigas cortadoras de hoj...

Los investigadores en ecología pretendemos desarrollar proyectos basados en ideas novedosas pero, como todos los seres humanos, tenemos una capacidad de creatividad limitada. Por ende, es común que durante nuestra vida académica se nos ocurran sólo unas pocas ideas realmente originales. Entonces, conocer cómo surgen las ideas se torna vital. Si est...

The biotic resistance hypothesis asserts that native species may hinder the invasion of exotic species, which can occur either directly or indirectly by influencing interactions between exotic and local species. Aphid-tending ants may play a key role in the indirect biotic resistance to plant invasion. Ants may protect aphids, thus increasing their...

First larval stages require adequate feeding to reach subsequent instars. However, the accumulation of reserves is also important in the last larval instar because it is vital to pupate and successfully perform metamorphosis into adulthood. We indirectly determined the presence of changes in the relative importance of prey capture through larval on...

Conocer el efecto de la morfología floral sobre las visitas de los polinizadores y sus consecuencias en la reproducción es vital para comprender la ecología y la evolución de las interacciones planta-polinizador. Determinamos si las variaciones en el área y la simetría del estandarte floral afectan la frecuencia de visitas y la producción de semill...

En 2003 publiqué un artículo en Ecología Austral en el que revelaba que la gran mayoría de sus manuscritos empleaban de forma incorrecta los términos hipótesis y predicciones. En dicho artículo explicaba y ejemplificaba los motivos de dicha confusión, describía los conceptos básicos del método hipotético-deductivo (MHD) y finalizaba con algunos con...

The study of how trap design responds to biotic and abiotic conditions can help to understand the selective forces affecting the foraging of trap‐building organisms. We experimentally tested whether pit design can be modified by intraspecific competition for space in larvae of Myrmeleon crudelis , a common sit‐and‐wait predator that digs conical pi...

Mutualism studies often focus on the service provided by single species, while variation in benefits provided by multiple partners is less understood. Ant‐aphid food‐for‐protection mutualisms are suitable to study the implications of intra‐guild service variation because they often involve several ant species with varying levels of aggressiveness....

A menudo, los polinizadores emplean los colores de las flores como señales indirectas del status de la recompensa. Sin embargo, los visitantes florales pueden percibir patrones del espectro cromático invisibles para el ojo humano. Cytisus scoparius (retama) es un arbusto abundante en bosques perturbados del NO de la Patagonia que presenta variación...

Social organisms express collaborative behaviors, allowing them to solve problems that exceed their individual capabilities. Group coordination and environmental context are some of the factors that may determine the performance of individual and collaborative strategies. Using the trail‐clearing behavior of leaf‐cutting ants, we evaluated experime...

The physical structures built by animals are considered extended phenotypes that reflect how organisms make decisions and deal with changes in their biotic and abiotic environment. We summarize the results of several studies on Myrmeleon crudelis, a neuropteran larva that digs pit-traps in the soil to capture small arthropods (mostly ants) in the t...

El estudio de los mutualismos usualmente considera el servicio ofrecido por una sola especie; sin embargo, estas interacciones frecuentemente incluyen múltiples mutualistas. El mutualismo hormiga-pulgón usualmente involucra numerosas especies de hormiga que defienden a los pulgones a cambio de recompensas azucaradas. Estudiamos la relación entre un...

Para predecir cómo las especies se verán afectadas por el cambio climático es importante comprender el efecto actual de los factores abióticos sobre los organimos. Evaluamos cómo el viento, un factor abiótico poco estudiado, afecta la distribución y abundancia de dos especies de pulgones (Uroleucon aeneum y Brachycaudus cardui; pulgones negros y ve...

A better knowledge of the behaviors that reduce traffic congestions is essential to understand the success of the trail system despite of costs. Leaf-cutting ants use a trunk-trail system to transport leaf fragments into their nests. Some ants carry extra-large leaf fragments and walk slower than the rest of laden workers, thus slowing the ant colu...

La planificación de proyectos de investigación en Entomología es un desafío que muchos estudiantes no superan con éxito. La falta de entrenamiento formal sobre cómo desarrollar proyectos, la excesiva importancia a los análisis en vez de a las ideas y la ausencia de un marco conceptual sencillo son algunas de las posibles causas de este problema. En...

Being social adds another level of defence for organisms: social defences. Beside individual defensive behaviours, social organisms can limit parasite infections by using collective and collaborative behaviours. We evaluated whether the social defence of the leaf-cutting ant Atta cephalotes is specific against phorid parasitoids and the occurrence...

Invasive species may interact with resident species and disrupt previously established interactions, with effects on the whole community. If introduced seeds are selectively consumed by native granivores, this could limit the establishment or spread of invasive plants (biotic resistance), and reduce the predation pressure upon native seeds. We dete...

Planning research projects is a challenge that many students fail to successfully overcome. A lack of formal training in research planning and design, an excessive emphasis on analysis rather than on ideas and a lack of a guide are some of the possible causes of this problem. This essay proposes a conceptual framework that is of didactic utility to...

Dada la importancia de publicar en ciencia, existen numerosos trabajos que brindan consejos sobre cómo escribir manuscritos científicos para que sean leídos por una gran cantidad de colegas. Sin embargo, existen pocas guías que describan cómo escribir para ahuyentar lectores. En ese ensayo pretendo cubrir ese vacío de conocimiento y ofrecer consejo...

Taking bad decisions to solve problems can negatively affect organism fitness, hence, the costs accrued by them should modulate decisions about when and how problems should be solved. We studied the problem of trail maintenance in leaf-cutting ants. We evaluated whether colonies have individuals exclusively dedicated to trail maintenance, and how o...

Several factors may restrict the acquisition of food to below the levels predicted by the optimization theory. However, how the design of structures that animals build for foraging restricts the entry of food is less known. Using scaling relationships, we determined whether the design of the entrances of leaf‐cutting ant nests restricts resource in...

La depredación de nidos es una de las presiones de selección más importantes para las aves, por lo que la elección del sitio de nidifcación es clave para la supervivencia de los polluelos. Evaluamos de manera experimental si la presencia de espinas en arbustos contribuye a la protección contra la depredación de nidos. El trabajo se desarrolló cerca...

Leaf-cutting ants are key organisms because their role as primary consumers and potential agricultural pests. However, their foraging ecology was mostly studied as response of extrinsic factors such as climate and plant species traits. We evaluated the effects of intrinsic factors (i. e., nest size and species identity) on the foraging behavior in...

The nutrient‐rich organic waste generated by ants may affect plant reproductive success directly by enhancing fruit production but also indirectly, by affecting floral traits related with pollinator attraction. Understanding how these soil‐nutrient hot spots influence floral phenotype is relevant to plant–pollination interactions. We experimentally...

Understanding how environmental factors modulate foraging is key to recognizing the adaptive value of animal behavior, especially in ectothermic organisms such as ants. We experimentally analyzed the effect of rain on the foraging of leaf-cutting ants, a key ant group that is commonly found in rainy habitats. Specifically, we experimentally discrim...

This book, containing 18 chapters, combines the hierarchy-of-hypotheses (HoH) approach with hypothesis networks for invasion biology. This book aims to further develop the HoH approach by inviting critical comments (Part I), apply it to 12 major invasion hypotheses (Part II) and explore how it can be expanded to a hierarchically structured hypothes...

Ants are probably the most dominant insect family on earth, and flowering plants have been the dominant plant group on land for more than 100 million years. In recent decades, human activities have degraded natural environments with unparalleled speed and scale, making it increasingly apparent that interspecific interactions vary not only under dif...

Disturbances like biological invasions and fire may affect in unexpected ways plant-animal interactions. In northwestern Patagonia, introduced ungulates (cattle, horses and deers) are widespread and very common occupying more than 50% of forests and shrublands, widely affecting these habitats. In addition, fire play a major role in creating landsca...

The existence of transport networks is vital for leaf-cutting ant foraging but may generate overcrowding, reducing the input of food into the nest. We studied how ants turn at branching points, a problematic sector for ant traffic, in leaf-cutting ant species that vary in ant flow and trail design. If the walking of turning ants reduces the chance...

Empirical data about food size carried by central-place foragers do not often fit with the optimum predicted by classical foraging theory. Traditionally, biotic constraints such as predation risk and competition have been proposed to explain this inconsistency, leaving aside the possible role of abiotic factors. Here we documented how wind affects...

Dominant herbivores, like leafcutter ants, have a strong impact on the ecosystems they inhabit. Understanding which factors regulate their foraging rates is crucial for understanding ecosystem dynamics. In desert habitats, environmental factors, such as temperature, play a major role in regulating ants' behavior. We studied the role of ground tempe...

Ants are recognized as one of the major sources of soil disturbance world‐wide. However, this view is largely based on isolated studies and qualitative reviews. Here, for the first time, we quantitatively determined whether ant nests affect soil fertility and plant performance, and identified the possible sources of variation of these effects. Usin...

One advantage of sociality is to mitigate environmental restrictions through collective behavior. Here we document a colony-level response of leaf-cutting ants to wind, an environmental factor that impedes foraging. Given that larger ants adhere more strongly to the substrate, increasing forager size in windy conditions should reduce the negative e...

A better understanding of plant–herbivore relationships should integrate negative and positive effects of consumers on plant fitness. We studied the effect of a major insect herbivore (leaf-cutting ants, LCA) on plant fitness in several species of Monte Desert, assessing both the direct negative effect of ant defoliation and the indirect positive r...

Adequate waste management is vital for the success of social life, because waste accumulation increases sanitary risks in dense societies. We explored why different leaf-cutting ants (LCA) species locate their waste in internal nest chambers or external piles, including ecological context and accounting for phylogenetic relations. We propose that w...

Adequate waste management is vital for the success of social life, because waste accumulation increases sanitary risks in dense societies. We explored why different leaf-cutting ants (LCA) species locate their waste in internal nest chambers or external piles, including ecological context and accounting for phylogenetic relations. We propose that w...

The fitness and survival of organisms ultimately depend on their feeding. Therefore, foraging behaviors should be selected to maximize cost-benefit ratio. Wind may restrict and modify animal movements increasing the cost of foraging, especially when the animal carries resources that intercept wind. We quantified the effect of wind on the foraging o...

The study of the intraspecific variability in the flower color may help us to better understand the role of pollinators as selective agents end their effect on the local abundance of floral morphs. We studied the influence of intraspecific variation of flower color on the floral visitation rate and the fitness of Sarothamnus scoparius, a common exo...

The activity of herbivores may depend on resource characteristics as well as on interactions with other organisms that consume leaves. We analyzed the effect of leaf toughness and the probability of leaf damage on the activity and efficiency of leaf miners in the shrub Azara microphylla. Basal sectors of the leaves showed higher toughness and lower...

El estudio de la variación intraespecífica del color de las flores nos permite comprender mejor el papel de los polinizadores como agentes de selección, y su efecto sobre la abundancia de las variantes florales. Estudiamos la influencia de la variación en los colores florales sobre la tasa de visita a las flores y la reproducción de Sarothamnus sco...

La actividad de los herbívoros puede depender tanto de las características de los recursos como de las interacciones con otros organismos que dañan las hojas. Analizamos el efecto de la dureza de la hoja y la probabilidad de daño foliar sobre el recorrido y la eficiencia de las larvas del minador de hojas en el arbusto Azara microphylla. En compara...

Understanding the responses of natural communities to disturbances remains a challenging task in ecology. In northwestern Patagonia, the most important disturbances are fire and introduced ungulates. Although these disturbances have been present in this region since late eighteen century, their effects on arthropods diversity have been poorly studi...

Ant-aphid relationships provide excellent opportunities to study how changes in resource availability may affect the outcome of competitive interactions. Variations in soil fertility may affect host plant quality, with concomitant effects on aphid abundance and the amount/quality of aphid honeydew. This may determine the intensity at which tending...

1. Leaf‐cutting ants ( LCA s) are considered as one of the most important agents of soil disturbances that affect vegetation patterns, but these assertions are based on isolated studies or anecdotal data. In this study, meta‐analysis techniques were used to quantitatively analyse the generality of these effects and determine some of their sources o...

In an earlier work, we found that 66% of manuscripts that suffered editorial rejections were finally accepted in journals of similar ranking to which they were originally submitted. We thus concluded that editors appear to be “poor oracles” with regards to being able to evaluate the quality of a manuscript without the help of external reviewers. Th...

CAPíTULO Los ecosistemas naturales son complejos y dinámicos. Esa com-plejidad se ve reflejada en redes de interacciones formadas por las innumerables relaciones que se establecen entre las especies y entre éstas y el entorno físico que habitan. Estas redes contienen especies y recursos considerados 'clave' debido a su influencia des-proporcionada...

The design of transport paths in consuming entities that use routes to access food should be under strong selective pressures to reduce costs and increase benefits. We studied the adaptive nature of branching angles in foraging trail networks of the two most abundant tropical leaf-cutting ant species. We mathematically assessed how these angles sho...

Fil: Farji Brener, Alejandro Gustavo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue; Argentina

Soil biota activity in arid lands is often limited by the availability of water and organic matter. We experimentally explored whether small changes in soil moisture affect the activity of soil biota in external refuse dumps of the leaf-cutting ant Acromyrmex lobicornis, one of the most important sources of organic matter in a semi-arid land of nor...

Soil microorganisms play a key role in the process of nutrient cycling. Therefore, the knowledge of the factors that infuence its activity is vital for a better understanding of terrestrial ecosystem function. We use external refuse dumps from the leaf-cutting ant Acromyrmex lobicornis such as a model system to determine the influence of the concen...

Ecología Austral, 24:103-110 (2014)Los microorganismos del suelo cumplen un papel relevante en el ciclado de nutrientes. En consecuencia, conocer los factores que influyen sobre su actividad es de fundamental importancia para comprender mejor el funcionamiento de los ecosistemas terrestres. Empleando a los basureros externos de la hormiga cortadora...

Los microorganismos del suelo cumplen un papel relevante en el ciclado de nutrientes. En consecuencia, conocer los factores que influyen sobre su actividad es de fundamental importancia para comprender mejor el funcionamiento de los ecosistemas terrestres. Empleando a los basureros externos de la hormiga cortadora Acromyrmex lobicornis como sistema...

: Successional state of forest and availability of pioneer plants are recognized factors affecting densities of leaf-cutting ants. However little is known about how abiotic factors can shape nest distributions. We investigated the effect of topography, soil, forest successional state and inundation risk on nest density and size of Atta cephalotes c...

Interspecific competition plays a key role in the organisation of ant communities. In ant–plant interactions, individual host plants are usually occupied by a single ant colony, and co‐occurring ant species compete for hosts. Here indirect evidence of competition between three dominant ant species that tend aphids on two biennial thistles in northe...

Compensation, the degree of plant recovery after herbivory, is influenced by nutrient availability. The compensatory continuum hypothesis (CCH) predicts that the more abundant the resources in an environment, the greater the potential for compensation. Nutrient-rich patches generated by leaf-cutting ants near their nests could modify plants’ respon...

Decomposers soil microorganisms play a vital role in terrestrial ecosystems, releasing nutrients for plants and other trophic levels. In arid systems this decomposition is strongly affected by the availability of water, and the abundance, diversity and distribution of organic matter. I studied the effect of refuse dumps of leaf-cutting ants, one of...

Paradójicamente, el artículo en donde critico al número de citas de un manuscrito como estimador de su calidad fue tempranamente citado. Me agrada esta cita: el interlocutor posee experiencia en el tema y la charla promete ser interesante. Adicionalmente, dispara un debate útil para mejorar el actual sistema indirecto de evaluación académica. Aprov...

Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic an...

Los investigadores somos evaluados constantemente para acceder a puestos estables de trabajo, para promover de categoría y para ganar subsidios que nos permitan equiparnos y financiar nuestras investigaciones. Pese a que la calidad de un investigador puede valorarse de maneras diferentes, la cantidad y la calidad de sus publicaciones siguen siendo...

Animals adjust their behaviors in response to changing environmental conditions because the costs and benefits of such behaviors change as conditions change. The reuse of materials from waste (i.e., recycling) rarely occurs in social insects because it may imply significant health risks and behavioral difficulties. However, the benefit of reusing m...

Question Low quantities of soil nutrients often restrict plant establishment and growth in arid lands and have been partially attributed to the scarcity of organic matter in these ecosystems. Refuse dumps from leaf‐cutting ants are a natural source of organic matter; however, their effects on native plant performance have received limited attention...

Abstract. 1. Ants using trails to forage have to select between two alternative routes at bifurcations, using two, potentially conflicting, sources of information to make their decision: individual experience to return to a previous successful foraging site (i.e. fidelity) and ant traffic. In the field, we investigated which of these two types of i...

Leaf-cutting ants, being the principal herbivores and ecosystem engineers in the Neotropics, have been considered to be a keystone species in natural ecosystems and agroecosystems, due to the direct and indirect effects of their plant defoliation activities. This review summarizes current concepts of the biological and ecological importance of leaf...

Studies of herbivory and its consequences on the growth of native and exotic plants could help elucidate some processes involved in plant invasions. Introduced species are likely to experience reduced herbivory in their new range due to the absence of specialist enemies and, thus, may have higher benefits if they reduce the investment in resistance...

We used a simple engineering principle, which suggests that the width of a road needed for a smooth traffic flow is proportional to the peak traffic volume (“engineering hypothesis”), to analyze the adaptive significance of trail width at branching points in the leaf-cutting ant Atta cephalotes. Since the flow of outgoing ants splits at trail bifur...

Soil disturbances that increase nutrient availability may trigger bottom-up cascading effects along trophic chains. However, the strength and sign of these effects may depend on attributes of the interacting species. Here, we studied the effects of nutrient-rich refuse dumps of the leaf-cutting ant, Acromyrmex lobicornis, on the food chain composed...

Exotic species change the structure and composition of invaded communities in multiple ways, but the sign of their impact on native species is still controversial. We evaluated the effects of the thistles Carduus thoermeri and Onopordum acanthium—two of the most abundant exotic plant species in disturbed areas of the Patagonian steppe—on the native...

• It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods f...

• The economic losses associated with crop damage by invasive pests can be minimized by recognizing their potential impact before they spread into new areas or crops. • We experimentally evaluated the preferences of the leaf-cutting ant Acromyrmex lobicornis (Hymenoptera: Formicidae) for the most common conifer species commercially planted in north...

• It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods f...

The foraging behaviour of social insects is highly flexible because it depends on the interplay between individual and collective decisions. In ants that use foraging trails, high ant flow may entail traffic problems if different workers vary widely in their walking speed. Slow ants carrying extra-large loads in the leaf-cutting ant Atta cephalotes...

Impulsivity or patience? What does the Argentinean scientific system stimulate, and select: Some of the present criteria applied to evaluate the academic performance of individuals in the scientific system in Argentina (particularly, in the CONICET) confront the researchers with the dilemma of being patient to obtain larger academic benefits in the...

Objetivou-se avaliar a eficiência de estratégias de artrópodes contra a predação por formigas. Realizamos simulações de estratégias anti-predatórias para testar as seguintes hipóteses: esconder-se entre os componentes da serapilheira é uma boa estratégia para um artrópode evitar a predação por formigas; a estratégia de alguns artrópodes de manterem...