Every organism on Earth must cope with a multitude of species interactions both directly and indirectly throughout its life cycle. However, how selection from multiple species occupying different trophic levels affects diffuse mutualisms has received little attention. As a result, how a given species amalgamates the combined effects of selection from multiple mutualists and antagonists to enhance its own fitness remains little understood. We investigated how multispecies interactions (frugivorous birds, ants, fruit flies and parasitoid wasps) generate selection on fruit traits in a seed dispersal mutualism. We used structural equation models to assess whether seed dispersers (frugivorous birds and ants) exerted phenotypic selection on fruit and seed traits in the spiny hackberry (Celtis ehrenbergiana), a fleshy-fruited tree, and how these selection regimes were influenced by fruit fly infestation and wasp parasitoidism levels. Birds exerted negative correlational selection on the combination of fruit crop size and mean seed weight, favouring either large crops with small seeds or small crops with large seeds. Parasitoids selected plants with higher fruit fly infestation levels, and fruit flies exerted positive directional selection on fruit size, which was positively correlated with seed weight. Therefore, higher parasitoidism indirectly correlated with higher plant fitness through increased bird fruit removal. In addition, ants exerted negative directional selection on mean seed weight. Our results show that strong selection on phenotypic traits may still arise in perceived diffuse species interactions. Overall, we emphasize the need to consider diverse direct and indirect partners to achieve a better understanding of the mechanisms driving phenotypic trait evolution in multispecies interactions.

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Selection on fruit traits is mediated by the interplay between frugivorous birds, fruit flies, parasitoid wasps and seed‐dispersing ants

Transitar hacia una producción de alimentos sostenible a través de los principios de la agroecología implica no una transición, sino varias transiciones simultáneas, a diferentes escalas, niveles y dimensiones; de índole social, biológica, económica, cultural, institucional, política. Este artículo propone utilizar diferentes marcos conceptuales, derivados de la ecología, la agronomía y la ciencia de la innovación, para describir estas transiciones. El artículo aborda a la transición agroecológica como una sucesión de innovaciones emergentes, y analiza las etapas de la transición técnico-institucional y sus forzantes. Se propone demás conceptualizar a la transición como una restauración de las funciones y de la resiliencia del socio-ecosistema. Por último, se explora con un par de ejemplos lo que implica la transición en términos de cambios en las prácticas de manejo agropecuario. La transición agroecológica puede involucrar una optimización de prácticas de manejo para aumentar la eficiencia productiva, una substitución de insumos, o bien el rediseño del sistema. Los ejemplos analizados muestran que la transición no siempre comienza a partir de sistemas altamente industrializados y/o degradados. Muchos productores que no se autodenominan agroecológicos implementan sin embargo muchas de sus prácticas con bases agroecológicas. Se concluye que el tránsito hacia la agroecología implica una transición técnicoproductiva a nivel de los subsistemas de la explotación, una transición socio-ecológica a nivel de la familia rural, su comunidad y su paisaje, y una transición político-institucional a nivel de territorios, regiones y países. Entender a la transición de esta forma, como una interdependencia entre escalas y dimensiones, permite conciliar las miradas de las diferentes ́escuelas ́ de la agroecología, desde las más ecológicas a las más socio-políticas.

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Las transiciones agroecológicas

The Peripampasic Arc is a set of low mountains / hills that connects the Andes, as it scatters to the East forming mountainous areas of lower heights in north-eastern Argentina, with the Atlantic coastal range of the Serra do Mar in Brazil. Numerous studies proved its important biogeographic connection for plant and animal phylogenies, but no information of this pattern is known to lichens. The aim of this work is to establish if the dispersion route of the lichenbiota follows the previously known Peripampasic Arc. For this reason, a comparative study of each area regarding its similarities was analyzed, with emphasis on the biota of the Buenos Aires’ Sierras. We quantified the similarity and β diversity of 104 saxicolous lichens species. There was a strong similarity between the Sierra de la Ventana and Tandil biota, which in turn is linked to the biotas of Uruguay, the Pampean Sierras and the northwest of Argentina. The lack of subgroups in the Peripampasic Arc implies the arc acts as a functional unit of dispersion, which is the most likely cause for the present lichens’ distribution.

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Peripampasic Arc: a route of dispersion for lichens.

Leaf‐cutting ants (LCA) frequently show positive associations with human disturbance in forest biome, explained by habitat opening and increase of pioneer vegetation. However, little is known about LCA response in grassland biome. Agriculture and commercial forestry typically introduce closed habitats and displace pioneer vegetation when occurring in grasslands. The aim of this study was to assess the response of LCA to different land use types developed in a grassland biome. Semi‐natural grassland remnants, soybean crops, cattle pastures and young and mature eucalypt plantations were sampled in Entre Ríos, Argentina. LCA nest abundance and occurrence of workers was obtained by hand sampling and baited pitfall traps. LCA nest abundance significantly decreased in most land use types when compared with the grassland sites. All habitat types were characterized by the presence of different LCA species, which showed different associations with temperature, vegetation and soil structure. Our results suggest that LCA response to human disturbance depends on the biome where it occurs; contrary to what was observed in forests, the LCA assemblage was negatively associated to human disturbance in grasslands. The response of the whole assemblage masked different responses of LCA species, possibly indicating differences in their ecological niche.

Leaf-cutting ant abundance and distribution under different agricultural practices in grassland biome

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Grupos funcionales de hormigas: evaluación de su utilización como indicadores del impacto ambiental producto de la agricultura y el cambio climático

Agroecological transition is a complex process in which different scales (farm, local community, territory) are articulated and that is affected by social, economic, technological, cultural, political and ecological factors. To analyze a transition process initially requires understanding how agro-ecosystems function (structure and processes occurring in it) and the different modes of intervention of human beings, who make management decisions to transform an agricultural ecosystem. It is therefore necessary to consider, simultaneously, at least 3 key criteria of the complex reality that the transition process faces: 1. The internal structural characteristics of the agroecosystem undertaking the process; 2. The singularities of the farmer or farmer family who makes decisions and manages the operation of the system; 3. External factors that influence the transition process. By using two concrete examples the transition process was analyzed in relation to the criteria considered, the initial situation, the changes through time and the implemented strategies.

https://revistas.um.es/agroecologia/article/download/300731/216151

Transición agroecológica: características, criterios y estrategias. Dos casos emblemáticos de la provincia de Buenos Aires, Argentina

The Attini, mainly the genera Atta Fabricius and Acromyrmex Mayr, are called leaf-cutting ants. Acromyrmex has scarce records referring to the geographical distribution of its species in Buenos Aires province. The objective of the present work was to gather existing information, to update these data with our own investigation, and to apply different criteria to establish relations with the use of the land. Of the total records for the province, 87 localities of 56 provincial districts were counted. To perform a hierarchical classification of similarities in the distribution patterns of the species, binary data matrices were constructed, analyzed by the weighted average method, calculating squared euclidean distances. The cophenetic indexes obtained were 0.883 for the geographical subregions, 0.943 for the municipal conglomerates and 0.877 for the agricultural areas. Eleven species of ants of the genus Acromyrmex are present in the province of Buenos Aires: A. ambiguus, A. fracticornis, A. heyeri, A. hispidus, A. hystrix, A. landolti, A. lobicornis, A. lundii, A. rugosus, A. silvestrii and A. striatus . The genus Acromyrmex is characterized by nesting in the soil, whereby anthropic practices for productive, industrial and urban purposes directly affect its pattern of occurrence.

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Nadia Dubrovsky Berensztein

Papers

Transición agroecológica: características, criterios y estrategias. Dos casos emblemáticos de la provincia de Buenos Aires, Argentina

Acromyrmex Mayr (Hymenoptera: Formicidae: Myrmicinae): patrones de distribución de las especies en la provincia de Buenos Aires, Argentina