Buenos Aires, Argentina
Buenos Aires, Argentina

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Quiroga M.A.,Instituto Nacional Of Limnologia Inali Con1Cet Unl | Reboreda J.C.,Genetica y Evolucion | Beltzer A.H.,Instituto Nacional Of Limnologia Inali Con1Cet Unl
Revista Mexicana de Biodiversidad | Year: 2012

We studied host use by parasitic botflies (Philornis sp.) in a passerine community in central Argentina and analyzed characteristics of nests and hosts associated with botfly parasitism. We conducted a four-year field study as well as a bibliographical survey where we determined: presence of botfly parasitism, type of nest, presence of green material and small sticks in the nest, average height of the nest, date of last nesting attempt during the breeding season and egg volume (as a surrogate of species body mass). Our field study of 3 birds species showed that botflies parasitized Troglodytes aedon (25% of nests), but not Sicalis flaveola and Tachycineta leucorroha in spite of nesting in similar boxes, at the same place and during the same time of the year. However T. aedon built nests using dry material while S. flaveola and T. leucorroha used green material.The analysis of published data (35 species considered) showed a negative association between botfly parasitism and presence of green material in the nest, and a positive association between botfly parasitism and presence of small sticks in the nest and date of the last nesting attempt during the breeding season. Our results indicate that the materials used to build the nest and the extent of the breeding season are factors that influence host use by botflies in central Argentina.


Liljesthrom M.,CONICET | Cooper C.,Cornell University | Reboreda J.C.,Genetica y Evolucion
Condor | Year: 2012

Within a population, the sizes of eggs and clutches vary, and the combination of both determines a female's reproductive investment. We investigated females' investment in clutches of the Chilean Swallow (Tachycineta meyeni) at the southern limit of its range, where it breeds in an extreme climate. We analyzed variation in clutch, egg and yolk size in relation to the female's condition, date of laying, and position in the sequence of laying. As predicted by energy/nutrient constraints, clutch size and yolk size decreased over the breeding season, though egg mass increased. Females' investment strategy differed with clutch size: their investment in eggs increased with each successive egg in clutches of 4 and 5 eggs but decreased with each successive egg in clutches of 3 eggs. Eggs that were heavier for their size were more likely to hatch than eggs light for their size. Females may make a strategic decision, with high investment in eggs laid early resulting in a short sequence (small clutch) and delayed investment resulting in a long sequence (large clutch). Alternatively, the shift in clutch investment may simply be a consequence of physiology. Better estimates of female body condition are needed for these options to be distinguished. © The Cooper Ornithological Society 2012.


Frau D.,CONICET | Battauz Y.,CONICET | Sinistro R.,Genetica y Evolucion
Hydrobiologia | Year: 2016

This work explores the reasons why predation plays a minor role in structuring phytoplankton composition in a Neotropical shallow lake. Phytoplankton, zooplankton, and fish were sampled from a shallow lake over the course of a year, and the stomach contents of 80 individuals of the dominant omnivorous–planktivorous fish species were analyzed. The field study was complemented with a 5-day microcosm experiment in which the predation effects of micro, meso, and macrozooplankton were measured. Stomach content analysis revealed that fish predation was high, and primarily comprised by Cladocera (Ivlev’s index >0.75). Both meso and macrozooplankton fractions are able to feed on colonial cyanobacteria, silica cell-wall organisms (<35 µm), and mixotrophic flagellate (>35 µm). Macrozooplankton, however, can feed on single cells, mucilaginous colonies, non-mucilaginous colonies, and silica cell-wall organisms (>35 µm) (P < 0.05 in all cases). Our results support the idea that absence of predation on phytoplankton is mainly mediated by fish predation on zooplankton and morpho-functional characteristics of algae which prevent zooplankton predation; showing fish a lack of direct predation effect on phytoplankton. © 2016 Springer International Publishing Switzerland


Liljesthrom M.,CONICET | Schiavini A.,CONICET | Reboreda J.C.,Genetica y Evolucion
Emu | Year: 2012

We analysed growth of nestling Chilean Swallows (Tachycineta meyeni) over four consecutive breeding seasons and determined the factors that explain variation in growth rate, asymptotic body mass and length of the nestling period. As the breeding season advanced nestlings grew more slowly and attained lower asymptotic mass, but the length of the nestling period and nestling survival did not show any seasonal trend. Asymptotic body mass of nestlings increased with female body condition, which was negatively correlated with time of breeding, suggesting that a seasonal decline in asymptotic body mass could be the result of changes in environmental conditions or lower quality of females breeding later in the season. There was no relationship between average minimum ambient temperature and either growth rate or asymptotic mass during the nestlings first 10 days. However, short periods of poor weather and snowfall had a significant effect on nestling survival. Growth rate (0.43) was lower than that of other Tachycineta species nesting at similar latitudes in the northern hemisphere but similar to those of subtropical species of the genus, suggesting that the factors that have influenced the evolution of this life-history trait differ between Chilean Swallows and other species of Tachycineta. © 2012 BirdLife Australia.


Cardo M.V.,Genetica y Evolucion | Vezzani D.,Genetica y Evolucion | Carbajo A.E.,Genetica y Evolucion
Bulletin of Entomological Research | Year: 2012

Wetlands have traditionally been associated with harbouring mosquitoes, a well-known nuisance and vectors of diseases. Within mosquito life cycle, oviposition is a determinant event by shaping their individual fitness and vectorial capacity. The study was conducted in one of the main temperate wetlands in South America. We used Generalized Linear Models to study the relation between temperature, precipitation, tidal regime, land use, microenvironment, and the occurrence of floodwater (Ochlerotatus and Psorophora spp.) and raft-laying (Culex and Uranotaenia spp.) mosquitoes using temporary pools as larval habitats. Pool occurrence was negatively associated with temperature, and positively related to precipitation and high tides. As regards the land use, it was lowest in domestic areas and plantations, intermediate in secondary forests, and highest in marshes. Each oviposition strategy was best modelled as a function of different environmental factors. The occurrence of floodwater mosquitoes was positively associated with high cumulative precipitation and low tide records. Raft-laying mosquitoes were related to low temperature records, while the effect of flooding varied with the land use. In view of these results, physical (water inputs and movement), chemical, and biological (egg and larval flushing, and predatory interactions) considerations are given to provide insight in the oviposition patterns of mosquitoes occurring in this complex wetland. We finally propose the generation of a tidal flow as a control measure against floodwater mosquitoes, which are the most anthropophilic in the study area. © 2012 Cambridge University Press.


Hurtado J.,Genetica y Evolucion | Iglesias P.P.,Genetica y Evolucion | Lipko P.,Genetica y Evolucion | Hasson E.,Genetica y Evolucion
Molecular Ecology | Year: 2013

Sperm competition (SC) is a major component of sexual selection that enhances intra- and intersexual conflicts and may trigger rapid adaptive evolution of sexual characters. The actual role of SC on rapid evolution, however, is poorly understood. Besides, the relative contribution of distinctive features of the mating system to among species variation in the strength of SC remains unclear. Here, we assessed the strength of SC and mating system factors that may account for it in the closely related species Drosophila buzzatii and Drosophila koepferae. Our analyses reveal higher incidence of multiple paternity and SC risk in D. buzzatii wild-inseminated females. The estimated number of fathers per brood was 3.57 in D. buzzatii and 1.95 in D. koepferae. In turn, the expected proportion of females inseminated by more than one male was 0.89 in D. buzzatii and 0.58 in D. koepferae. Laboratory experiments show that this pattern may be accounted for by the faster rate of stored sperm usage observed in D. koepferae and by the greater female remating rate exhibited by D. buzzatii. We also found that the male reproductive cost of SC is also higher in D. buzzatii. After a female mated with a second male, first-mating male fertility was reduced by 71.4% in D. buzzatii and only 33.3% in D. koepferae. Therefore, we may conclude that postmating sexual selection via SC is a stronger evolutionary force in D. buzzatii than in its sibling. © 2013 John Wiley & Sons Ltd.


Di Giacomo A.G.,Aves Argentinas Asociacion Ornitologica Del Plata | Di Giacomo A.S.,Genetica y Evolucion | Reboreda J.C.,Genetica y Evolucion
Bird Conservation International | Year: 2011

The north-east of Argentina contains a high number of globally threatened grassland birds and is increasingly managed for livestock, with annual burning in remaining natural grasslands. The Strange-tailed Tyrant Alectrurus risora, a globally threatened grassland specialist, has suffered a 90% contraction in its original range. From 1996 to 2008 we monitored a breeding population in Formosa, north-east Argentina, and explored the effect on breeding of four accidental and one prescribed fires. The plant most frequently used for nesting was Imperata brasiliensis, but the frequency of use was lower after a fire than before. In years with a fire, the height of the plant used for nesting and the height of the nest were lower than in those without a fire. Females avoided nesting in the burned plot in the breeding season immediately after the prescribed fire, but they started to return to the burned plot by the second breeding season and did not discriminate between plots by the third breeding season after the fire. Movements of females after the prescribed fire did not affect nest survival, clutch size, hatchability or chick survival indicating this species was adapted to regular fires. However, our results also show that annual burning in the grassland negatively affects the settlement for reproduction of Strange-tailed Tyrants and that the intervals between burns in the same grassland should be longer than two years. © 2011 BirdLife International.


Goenaga J.,Genetica y Evolucion | Fanara J.J.,Genetica y Evolucion | Hasson E.,Genetica y Evolucion
Genetics Research | Year: 2010

Food shortage is a stress factor that commonly affects organisms in nature. Resistance to food shortage or starvation resistance (SR) is a complex quantitative trait with direct implications on fitness. However, surveys of natural genetic variation in SR at different geographic scales are scarce. Here, we have measured variation in SR in sets of lines derived from nine natural populations of Drosophila melanogaster collected in western Argentina. Our study shows that within population variation explained a larger proportion of overall phenotypic variance (80%) than among populations (72%). We also noticed that an important fraction of variation was sex-specific. Overall females were more resistant to starvation than males; however, the magnitude of the sexual dimorphism (SD) in SR varied among lines and explained a significant fraction of phenotypic variance in all populations. Estimates of cross-sex genetic correlations suggest that the genetic architecture of SR is only partially shared between sexes in the populations examined, thus, facilitating further evolution of the SD. Copyright © Cambridge University Press 2010.


Fallis L.C.,Kansas State University | Fanara J.J.,Genetica y Evolucion | Morgan T.J.,Kansas State University
Genetica | Year: 2011

Spatial or temporal differences in environmental variables, such as temperature, are ubiquitous in nature and impose stress on organisms. This is especially true for organisms that are isothermal with the environment, such as insects. Understanding the means by which insects respond to temperature and how they will react to novel changes in environmental temperature is important for understanding the adaptive capacity of populations and to predict future trajectories of evolutionary change. The organismal response to heat has been identified as an important environmental variable for insects that can dramatically influence life history characters and geographic range. In the current study we surveyed the amount of variation in heat tolerance among Drosophila melanogaster populations collected at diverse sites along a latitudinal gradient in Argentina (24°-38°S). This is the first study to quantify heat tolerance in South American populations and our work demonstrates that most of the populations surveyed have abundant within-population phenotypic variation, while still exhibiting significant variation among populations. The one exception was the most heat tolerant population that comes from a climate exhibiting the warmest annual mean temperature. All together our results suggest there is abundant genetic variation for heat-tolerance phenotypes within and among natural populations of Drosophila and this variation has likely been shaped by environmental temperature. © 2012 Springer Science+Business Media B.V.


Segura L.N.,Genetica y Evolucion | Reboreda J.C.,Genetica y Evolucion
Behaviour | Year: 2012

Avian brood parasites reduce the reproductive success of the host, which favours the evolution of antiparasitic defences, such as aggression towards parasites or rejection of their eggs. The red-crested cardinal, Paroaria coronata, is a potential good-quality host of the shiny cowbird, Molothrus bonariensis. However, the frequency of cowbird parasitism in cardinal nests is very low and there are no records of this host raising parasite's chicks, which suggest that it may have evolved effective antiparasitic defences. We studied cardinal antiparasitic defences by: (1) presenting dummy models of a female cowbird and non-predator and predator control species to nests during laying and incubation, and (2) conducting experiments of artificial parasitism with natural cowbird eggs of different morphs and conspecific eggs during laying and early and late incubation. We found that: (1) the frequency of cowbird parasitism in cardinal nests was 7%, (2) cardinals did not exhibit aggressive behaviours towards cowbird or nonpredator models but responded aggressively towards a predator model, (3) they rejected parasite eggs in 98.5% of the cases (mostly through egg ejection), but conspecific eggs in only 6% of the cases, (4) there were no costs (breakage or ejection of their own eggs) associated with ejection of the parasite's eggs, and (5) a relatively low frequency of parasitism is enough selection pressure to maintain egg rejection at a high level. The antagonistic expression of antiparasitic defences in red-crested cardinals suggests that they may have lost the behaviour of aggression towards the parasite as a result of associated costs. © 2012 Koninklijke Brill NV, Leiden.

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