Chlorpyrifos and endosulfan degradations were compared at laboratory scale in three different soi... more Chlorpyrifos and endosulfan degradations were compared at laboratory scale in three different soils: a conventional horticultural (SH), an accredited 25 year organic horticultural (SA) and a reference soil (SR) used as control. Chlorpyrifos and α-endosulfan degradation half-lives were, respectively, in the range 7.2 d-9.8 d and 4.4 d-6.6 d, finding no statistical difference for any soil. In the case of β-endosulfan, a difference was found in degradation half-lives, being: SR (25.8 d) < SA (49.1 d) < SH (102.1 d), indicating some difficulty, in the case of the traditional horticultural soil, to biodegrade this isomer. Three different biostimulants: poultry litter (CP), bokashi (fermented organic matter, BKS) and ramial chipped wood (BRF) were added to soil to explore the increase of chlorpyrifos and endosulfan biodegradation. While no improvement was observed for chlorpyrifos, all biostimulants favoured endosulfan degradation. In the case of BKS endosulfan half-life was reduced ca. three times (considering both isomers). Seed germination bioassays were performed using soil and biostimulant to evaluate potential ecotoxicological impacts. CP had a significant inhibitory effect on germination, hypocotyl elongation, radicle length and hypocotyl length, while BKS and BRF parameters were more similar to the control performance.
A B S T R A C T The main objective of this manuscript was to study the bioremediation capacity of... more A B S T R A C T The main objective of this manuscript was to study the bioremediation capacity of okara (a byproduct of soy milk production) in soils contaminated by organic xenobiotics. To this aim, and under controlled laboratory conditions, a soil was contaminated with chlorpyrifos insecticide at a dose of 5 l ha −1. Okara was added to this contaminated soil in two different manners: (1) pure okara (Op); and (2) a biostimulant/biofertilizer made from pure okara using the pH-stat technique. Several enzymatic activities (dehydrogenase, urease, β-glucosidase and phosphatase) and the evolution of the insecticide in soil were studied over an 80-day period. The results suggested that both forms of okara stimulated soil microorganisms and accelerated the degradation of chlorpyrifos in soil. It was, however, the biostimulant/biofertilizer that showed the greatest acceleration in insecticide degradation , possibly due to its higher content in low molecular weight (< 300 Da) peptides, easily available to soil microorganisms.
Annals of the Entomological Society of America, 2010
The Iberá Nature Reserve in northeastern Argentina protects one of the largest freshwater wetland... more 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 ßoating 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 Þrst 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 Þndings 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.
Annals of the Entomological Society of America, 2010
The maintenance of species diversity in modiÞed and natural habitats is a central focus of conser... more The maintenance of species diversity in modiÞed 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 Þre 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 simpliÞed 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 Þnd clear evidence that habitat modiÞcation by grazing signiÞcantly affected terrestrial ant assemblages. The weak grazing inßuence 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.
An important goal of invasion ecology is to understand the colonization, establishment, and sprea... more An important goal of invasion ecology is to understand the colonization, establishment, and spread of exotic species. To accomplish this, it is essential to examine the ecology of introduced species in native populations. We examined organization patterns, spatial structure, and competitive abilities of ground-dwelling ants in different habitats of a protected area in east-central Argentina, where several highly invasive ant species naturally coexist, to determine whether all they are ecologically dominant in their native range as in their introduced range. We sampled ant communities at Otamendi Nature Reserve and found 49 ant species co-occurred with moderate separation among habitats, including five species that are global invaders; but only Solenopsis richteri (the most numerically dominant) and Linepithema humile (the best mass recruiter) were ecologically co-dominant along with another three non-in-vasive species in locally rich assemblages. Their co-occurrence was apparently facilitated by both niche and competitive differences. However, we found no evidence for discovery-dominance trade-offs, and ant diversity and spatial segregation suggested that competition only plays a secondary role in structuring assemblages in arboreal habitats. Despite L. humile and S. richteri were ecologically co-dominant, their hegemony was lower in the reserve than in their introduced range likely due to biotic resistance. The other invasive ants (Wasmannia auropunctata, Brachy-myrmex patagonicus, and Nylanderia fulva) were not dominant. It is possible that their establishment, persistence, and high prevalence in anthropic habitats in native and introduced populations to be attributed to their better physiologic adaptations to disturbed habitats rather than to their superior competitive abilities.
Chlorpyrifos and endosulfan degradations were compared at laboratory scale in three different soi... more Chlorpyrifos and endosulfan degradations were compared at laboratory scale in three different soils: a conventional horticultural (SH), an accredited 25 year organic horticultural (SA) and a reference soil (SR) used as control. Chlorpyrifos and α-endosulfan degradation half-lives were, respectively, in the range 7.2 d-9.8 d and 4.4 d-6.6 d, finding no statistical difference for any soil. In the case of β-endosulfan, a difference was found in degradation half-lives, being: SR (25.8 d) < SA (49.1 d) < SH (102.1 d), indicating some difficulty, in the case of the traditional horticultural soil, to biodegrade this isomer. Three different biostimulants: poultry litter (CP), bokashi (fermented organic matter, BKS) and ramial chipped wood (BRF) were added to soil to explore the increase of chlorpyrifos and endosulfan biodegradation. While no improvement was observed for chlorpyrifos, all biostimulants favoured endosulfan degradation. In the case of BKS endosulfan half-life was reduced ca. three times (considering both isomers). Seed germination bioassays were performed using soil and biostimulant to evaluate potential ecotoxicological impacts. CP had a significant inhibitory effect on germination, hypocotyl elongation, radicle length and hypocotyl length, while BKS and BRF parameters were more similar to the control performance.
A B S T R A C T The main objective of this manuscript was to study the bioremediation capacity of... more A B S T R A C T The main objective of this manuscript was to study the bioremediation capacity of okara (a byproduct of soy milk production) in soils contaminated by organic xenobiotics. To this aim, and under controlled laboratory conditions, a soil was contaminated with chlorpyrifos insecticide at a dose of 5 l ha −1. Okara was added to this contaminated soil in two different manners: (1) pure okara (Op); and (2) a biostimulant/biofertilizer made from pure okara using the pH-stat technique. Several enzymatic activities (dehydrogenase, urease, β-glucosidase and phosphatase) and the evolution of the insecticide in soil were studied over an 80-day period. The results suggested that both forms of okara stimulated soil microorganisms and accelerated the degradation of chlorpyrifos in soil. It was, however, the biostimulant/biofertilizer that showed the greatest acceleration in insecticide degradation , possibly due to its higher content in low molecular weight (< 300 Da) peptides, easily available to soil microorganisms.
Annals of the Entomological Society of America, 2010
The Iberá Nature Reserve in northeastern Argentina protects one of the largest freshwater wetland... more 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 ßoating 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 Þrst 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 Þndings 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.
Annals of the Entomological Society of America, 2010
The maintenance of species diversity in modiÞed and natural habitats is a central focus of conser... more The maintenance of species diversity in modiÞed 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 Þre 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 simpliÞed 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 Þnd clear evidence that habitat modiÞcation by grazing signiÞcantly affected terrestrial ant assemblages. The weak grazing inßuence 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.
An important goal of invasion ecology is to understand the colonization, establishment, and sprea... more An important goal of invasion ecology is to understand the colonization, establishment, and spread of exotic species. To accomplish this, it is essential to examine the ecology of introduced species in native populations. We examined organization patterns, spatial structure, and competitive abilities of ground-dwelling ants in different habitats of a protected area in east-central Argentina, where several highly invasive ant species naturally coexist, to determine whether all they are ecologically dominant in their native range as in their introduced range. We sampled ant communities at Otamendi Nature Reserve and found 49 ant species co-occurred with moderate separation among habitats, including five species that are global invaders; but only Solenopsis richteri (the most numerically dominant) and Linepithema humile (the best mass recruiter) were ecologically co-dominant along with another three non-in-vasive species in locally rich assemblages. Their co-occurrence was apparently facilitated by both niche and competitive differences. However, we found no evidence for discovery-dominance trade-offs, and ant diversity and spatial segregation suggested that competition only plays a secondary role in structuring assemblages in arboreal habitats. Despite L. humile and S. richteri were ecologically co-dominant, their hegemony was lower in the reserve than in their introduced range likely due to biotic resistance. The other invasive ants (Wasmannia auropunctata, Brachy-myrmex patagonicus, and Nylanderia fulva) were not dominant. It is possible that their establishment, persistence, and high prevalence in anthropic habitats in native and introduced populations to be attributed to their better physiologic adaptations to disturbed habitats rather than to their superior competitive abilities.
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