270 research outputs found
Similar seed preferences explain trophic ecology of functionally distinct, but co-occurring and closely related harvester ants
No full textTo understand how food resource use and partitioning by closely related species allows local coexistence, it is key to determine whether a species’ diet reflects food availability or food preferences. Here, we analysed the diets, seed selection, and seed preferences of three closely related harvester ants: Messor barbarus, M. bouvieri, and M. capitatus. Sympatric within a Mediterranean shrubland, these species differ in foraging behaviour and worker polymorphism. For two years, we studied the ants’ diets and seed selection patterns as well as the local availability of seeds. Additionally, we performed a seed-choice experiment using a paired comparison design, offering the ants seeds from eight native plant species. The three ant species had the same general diet, which was primarily granivorous. Although they all consumed a wide variety of seeds, they mostly selected seeds from a small subset of plant species. Despite their morphological and behavioural differences, the ants displayed similar seed preferences that were highly consistent with their diets and seed selection patterns. Our results support the idea that the trophic ecology of these three harvester ants is driven by similar seed preferences rather than by their morphological and behavioural differences. Seed diversity and abundance was high near the ants’ nests, suggesting that seed availability is not limiting and could in fact favour local species coexistence.Fil: Pol, Rodrigo Gabriel. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales. Departamento de Biología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Lázaro González, Alba. Universidad de Granada. Facultad de Ciencias; EspañaFil: Rodrigo, Anselm. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; EspañaFil: Arnan, Xavier. Consejo Superior de Investigaciones Científicas. Centre de Recerca Ecológica I Aplicacions Forestals; España. Universidade Federal de Pernambuco; Brasi
Continuous grazing disrupts desert grass-soil seed bank composition under variable rainfall
No full textLong-term field studies help unveil mechanisms of grass soil seed bank (SSB) persistence and resilience. We wonder whether grazing is a disruptive force that changes grass SSB composition and size, while heavy rainfall is a positive bottom-up force that restores the grass SSB in grazed areas of the Monte desert, Argentina. We used core sampling to study the grass SSB in cattle-free (17 year) and grazed (10 year) grasslands. The SSB size in cattle-free sites usually responded in a continuous positive fashion to rainfall, and the proportion of palatable grasses in the SSB was similar among years. Most grass species formed a transient SSB, but the presence of a stand of perennial plants would prevent their local extinction. In contrast, the SSB size in the grazed habitats showed a threshold response to rainfall (i.e. it did not increase under low-moderate rainfall), the seeds of palatable grasses were always scarce, and the proportion of seeds of less palatable grasses increased under extreme rainy conditions. Seed production from grasses that grew tillers from axillary buds during a drought was zero, suggesting that the bank of plants could have a role in the replenishment of the grass SSB only in mesic years. Within the time span assessed here, continuous heavy grazing together with scarce as well as heavy rainfall were disruptive forces that reduced the number and proportion of seeds from palatable grasses in the SSB, which are also the species preferred by seed-eating animals.Fil: Marone, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin
Does edge effect and patch size affect the interaction between ants and Croton lachnostachyus Baill. in fragmented landscapes of Chaco forest?
No full textLittle is known about the role of ants visiting extrafloral nectaries (EFNs) of plants in fragmented forests of South America. The aim of this work was to determine whether patch size and edge effect affect the composition and frequency of ants that visit the EFNs of Croton lachnostachyus, and how these changes may alter the reproductive success of plants in a fragmented landscape of the Chaco forest, Argentina. Data were analyzed considering patch size and edge effects? as indicators of fragmentation? on ant assemblages visiting plants and on plant reproductive success through a field experiment. Ant species composition differed between the edge and interior of fragments, but not among fragments of different sizes. Dolichoderinae species and some bigger ants as Camponotus mus (Formicinae) were more abundant at the edges, whereas Myrmicinae ants dominated the interior of fragments. Foliar damage was higher in plants located at interior than edges of fragments. The ant-exclusion experiment showed that seed mass, germinability, and foliar damage did not differ between control and ant-excluded plants. In contrast, fruit (year 2011) and seed production (years 2010 and 2011) was higher in control plants. We highlight the importance of studying ant?plant interactions combining different attributes of biodiversity (composition, structure, and function) to better understand ecological processes in fragmented landscapes.Fil: Pereyra, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Galetto, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentin
Behavioural flexibility does not prevent numerical declines of harvester ants under intense livestock grazing
No full text1. Human-induced rapid environmental change may decrease food resources and create unfavourable conditions for native species. Organisms showing a flexible foraging behaviour can exploit novel or alternative foods and are more likely to persist, whereas less flexible organisms might suffer starvation and numerical reductions. 2. This study assessed whether declines in the quality and availability of seeds prompted by grazing provoke behavioural and numerical responses in Pogonomyrmex mendozanus ants, and aimed to test whether behavioural flexibility buffers habitat degradation and prevents numerical declines. 3. Heavy grazing caused seed reductions, especially of the highly consumed and preferred grass seeds, and triggered two kinds of ant responses. Ants expanded their diet by incorporating a greater proportion of non-seed items, and they reduced foraging activity. As a consequence, the rate of food intake per colony lessened, particularly that of carbohydrate-rich seeds like grass seeds. Colony density under heavy grazing also fell. 4. Habitat degradation triggered a cascade of mechanisms that starts with a decrease in the seed resources and continues with changes in ant behaviour. However, behavioural responses were insufficient to prevent ant numerical declines. The results of this study suggest that the reduction in the colony density under habitat degradation was provoked by ant nutritional deficit and starvation, and predict a deterioration in body condition, colony performance and reproduction of ants, which deserve further assessment.Fil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Vargas, Gabriela Alejandra. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Marone, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin
Ant community patterns in highly fragmented Chaco forests of central Argentina
No full textThe Chaco is the largest dry forest biome in South America and one of the regions most threatened by agricultural intensification. As a consequence, in several areas Chaco forests persist as forest remnants of different sizes embedded in an agricultural matrix. Ants are social insects that have key roles in ecosystem functioning, and the effects of this ongoing land use change process on ant communities are little known for this region. In the present study, we assessed the consequences of land use replacement by monocultures and forest fragmentation on ant communities. Particularly, we assessed whether patch size, patch isolation and edge effect affect species richness and composition of ground-dwelling ants in fragmented landscapes of Chaco forests. We collected ants by combining hand collecting and pitfall traps in 17 forest fragments and the surrounding matrix from two sites in Córdoba, Argentina. Patch size and patch isolation had no effect on ant richness; however, patch isolation and, to a lesser extent, patch size altered ant species composition. The ant community was not affected by edge but it was negatively affected by the crop matrix, which reduced richness and altered species composition. These results indicate that monoculture matrices severely affect ant communities in the Chaco forests, and that the effects of other indicators of habitat fragmentation (patch size and edge effect) are subtler and less relevant. In the present context of land use change, even small fragments could have an important value for the conservation of ant diversity.Fil: Pereyra, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Universidad Nacional de Cuyo; ArgentinaFil: Galetto, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba; Argentin
Colony size and body condition of harvester ants in the central Monte desert, Argentina
No full textFeeding flexibility is believed to reduce species vulnerability to local extinction associated with environmental changes that cause food shortage, but to what extent such behavioural response is enough to cope with global change is scarcely known in insects. The harvester ant Pogonomyrmex mendozanus modifies its feeding behaviour and widens its diet in response to seed scarcity under grazing and reduces the colony food intake. We tested whether lower food intake, in particular of carbohydrate- rich grass seed, reduces worker survival rate, worsens the body condition of workers and reproductive individuals, and reduces the colony size of P. mendozanus. Our goal was to identify likely links between low quality nutrition and low colony density under heavy grazing previously reported. The reduction of food intake did not affect the body condition of workers, but it was associated with a significant decrease in the colony size and body fat content of queens and gynes. A starvation experiment showed that worker survival did not differ between grazing conditions, but seed deprivation increased worker mortality under all conditions. Implications for insect conservation The reduced colony size and deterioration of body condition of reproductive females could impair the survival and reproductive success of P. mendozanus under grazing. These mechanisms may explain the severe decline in colony density in the grazed habitats. In orderFil: Pol, Rodrigo Gabriel. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Miretti, María Florencia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Grupo de Investigación en Ecología de Comunidades del Desierto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marone, Luis. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin
Lower food intake due to domestic grazing reduces colony size and worsens the body condition of reproductive females of harvester ants
No full textFeeding flexibility is believed to reduce species vulnerability to local extinction associated with environmental changes that cause food shortage, but to what extent such behavioural response is enough to cope with global change is scarcely known in insects. The harvester ant Pogonomyrmex mendozanus modifies its feeding behaviour and widens its diet in response to seed scarcity under grazing and reduces the colony food intake. We tested whether lower food intake, in particular of carbohydrate-rich grass seed, reduces worker survival rate, worsens the body condition of workers and reproductive individuals, and reduces the colony size of P. mendozanus. Our goal was to identify likely links between low quality nutrition and low colony density under heavy grazing previously reported. The reduction of food intake did not affect the body condition of workers, but it was associated with a significant decrease in the colony size and body fat content of queens and gynes. A starvation experiment showed that worker survival did not differ between grazing conditions, but seed deprivation increased worker mortality under all conditions. Implications for insect conservation: The reduced colony size and deterioration of body condition of reproductive females could impair the survival and reproductive success of P. mendozanus under grazing. These mechanisms may explain the severe decline in colony density in the grazed habitats. In order to protect harvester ants, we highlight the importance of native grass seeds as key resources for population maintenance.Fil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Miretti, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Marone, Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin
Grazing impact on desert plants and soil seed banks: implications for seed-eating animals
No full textWe assess whether the knowledge of livestock diet helps to link grazing effects with changes in plant cover and soil seed bank size, aiming at inferring the consequences of grazing on seed-eating animals. Specifically, we test whether continuous and heavy grazing reduce the cover, number of reproductive structures and seed reserves of the same grass species whose seeds are selected and preferred by granivorous animals in the central Monte desert, Argentina. Grass cover and the number of grass spikes usually diminished under grazing conditions in the two localities studied (Telteca and Ñacuñán), and soil seed bank was consistently reduced in all three years evaluated owing to a decline of perennial grass and forb seeds. In particular, the abundance of those seeds selected and preferred by birds and ants (in all cases grass species) declined 70e92% in Ñacuñán, and 52e72% in Telteca. Reduction of perennial grass cover and spike number in grazed sites reinforced the causal link between livestock grazing and the decline of grass soil seed reserves throughout failed plant reproduction. Grass seed bank depletion suggests that grazing may trigger a “cascade” of mechanisms that affect the abundance and persistence of valuable fodder species as well as the availability of seed resources for granivorous animals.Fil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Sagario, Maria Cecilia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución. Grupo de Investigación en Ecología de Comunidades del Desierto; ArgentinaFil: Marone, Luis. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentin
Grass seed production in the central Monte desert during successive wet and dry years
No full textIn desert regions, water availability triggers primary production, which determines seed production, the composition and size of soil seed reserves and the abundance and behaviour of seed-eating animals. In the central Monte desert, large precipitation events (≥10 mm) account for a high proportion of growing season's rainfall. Our first objective here was to assess whether and how timing and amount of seed production of C3 and C4 perennial grasses are linked to spring and summer precipitation pulses and to estimate the seasonal and year-to-year variability in seed production. Our second aim was to calculate grass seed production and compare it with seed requirements by granivorous animals to infer whether the animals can exert top-down effects on plant populations. Seed production of C3 and C4 species was triggered by significant spring and summer rainfall, respectively. Such distinct response may be associated with the effect of precipitation during flower development and seed set in both functional groups. In all species, seed production varied among years. Rainfall pulses in the summer triggered and positively affected the magnitude of seed production in most C4 grasses. However, all perennial grasses were able to produce high amount of seeds even during a year subjected to extreme drought, suggesting that perenniality would allow these species to make large reproductive investment despite harsh environmental conditions. The comparative assessment of seed production and consumer demands suggests that it is unlikely that granivory exerts a top-down control on grasses in the Monte desert.Fil: Pol, Rodrigo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Pirk, Gabriela Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad de Buenos Aires; ArgentinaFil: Marone, Luis. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina. Universidad Católica de Chile; Chil
Vt cecinit poeta: the presence of Virgil in Rodrigo de Castro's De uniuersa mulierum medicina
No full textDe uniuersa mulierum medicina, by the Portuguese physician Rodrigo de Castro, is a complex gynaecological treatise that comprises sources concerning various medical aspects, both ancient and contemporary to the author, and also non-technical sources, namely poets from classical antiquity. This being the first article on the presence of Virgil in Castro, the main goal is to see where Virgil's Georgics 4 and Aeneid 6 are used in the De uniuersa mulierum medicina and explore how passages from the Virgilian oeuvre were used by the Portuguese physician.De uniuersa mulierum medicina, by the Portuguese physician Rodrigo de Castro, is a complex gynaecological treatise that comprises sources concerning various medical aspects, both ancient and contemporary to the author, and also non-technical sources, namely poets from classical antiquity. This being the first article on the presence of Virgil in Castro, the main goal is to see where Virgil's Georgics 4 and Aeneid 6 are used in the De uniuersa mulierum medicina and explore how passages from the Virgilian oeuvre were used by the Portuguese physician
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