The strength and drivers of bird-mediated selection on fruit crop size: a meta-analysis

In seed-dispersal mutualisms, the number of fruit a plant displays is a key trait, as it acts asa signal for seed dispersers that entails fruit removal and exportation of reproductive units(fruit crop size hypothesis). Although this hypothesis has gained general acceptance,forces driving the shape and strength of natural selection exerted by birds on fruit cropsize remains an unresolved matter. Here, we propose that ecological filters promotinghigh functional equivalence of interacting partners (similar functional roles) translate intosimilar selection pressures on fruit crop size, enhancing selection strength on this trait.We performed a meta-analysis on 50 seed-dispersal systems to test the hypothesisthat frugivorous birds exert positive selection pressure on fruit crop size, and to assesswhether different factors expected to act as filters (fruit diameter, fruit type, fruiting seasonlength, bird functional groups, and latitude) influence phenotypic selection regimes onthis trait. Birds promote larger fruit crop sizes as a general pattern in nature. Shortfruiting seasons and a high proportion of species belonging to the same functional groupshowed higher selection strength on fruit crop size. Also, selection strength on fruit cropsize increased for large-fruited species and toward the tropics. Our results support thehypothesis that fruit crop size represents a conspicuous signal advertising the amount ofreward to visually driven interacting partners, and that both plant and bird traits, as wellas environmental factors, drive selection strength on fruit display traits. Furthermore, ourresults suggest that the relationship among forces impinged by phenology and frugivorefunctional roles may be key to understand their evolutionary stability.Facultad de Ciencias Naturales y Muse

The strength and drivers of bird-mediated selection on fruit crop size: a meta-analysis

In seed-dispersal mutualisms, the number of fruit a plant displays is a key trait, as it acts asa signal for seed dispersers that entails fruit removal and exportation of reproductive units(fruit crop size hypothesis). Although this hypothesis has gained general acceptance,forces driving the shape and strength of natural selection exerted by birds on fruit cropsize remains an unresolved matter. Here, we propose that ecological filters promotinghigh functional equivalence of interacting partners (similar functional roles) translate intosimilar selection pressures on fruit crop size, enhancing selection strength on this trait.We performed a meta-analysis on 50 seed-dispersal systems to test the hypothesisthat frugivorous birds exert positive selection pressure on fruit crop size, and to assesswhether different factors expected to act as filters (fruit diameter, fruit type, fruiting seasonlength, bird functional groups, and latitude) influence phenotypic selection regimes onthis trait. Birds promote larger fruit crop sizes as a general pattern in nature. Shortfruiting seasons and a high proportion of species belonging to the same functional groupshowed higher selection strength on fruit crop size. Also, selection strength on fruit cropsize increased for large-fruited species and toward the tropics. Our results support thehypothesis that fruit crop size represents a conspicuous signal advertising the amount ofreward to visually driven interacting partners, and that both plant and bird traits, as wellas environmental factors, drive selection strength on fruit display traits. Furthermore, ourresults suggest that the relationship among forces impinged by phenology and frugivorefunctional roles may be key to understand their evolutionary stability.Facultad de Ciencias Naturales y Muse

Pedagogía elemental

"Sin contrario no hay progreso. Atracción y repulsión razón y energía, amor y odio, son necesarios a la existencia humana. Brota de esos contrarios lo que las religiones llaman el Bien y el Mal. E Bien es el elemento pasivo, sumiso a la razón. El Mal es el activo que brota de la energía". William Blak

Persona que habla a medias a medias existe

Se me pidió que dictara para los alumnos de los primeros años de la Carrera de Arte Dramático de la USAL, una materia que ayudara a resolver los problemas de "murmuración". Para fundamentarl y aclararme en contenido es que escribí el siguiente artícul

Linking the hierarchical decisionmaking process of fruit choice and the phenotypic selection strength on fruit traits by birds

Aims: Animals in search of fleshy fruits forage mostly according to the number of available fruits and then select individual fruits based on reward quality or advertised subtle traits. This hierarchical pattern of fruit choice would be translated into patterns of selection strength mediated by frugivores on fruit display traits. Thus, frugivores would exert higher selection pressures on fruit crop size and lower selection pressures on within-plant variation of phenotypic traits (infructescence, fruit and seed size). However, no attempt to link this behavioral mechanism of hierarchical trait selection to natural selection patterns has been made. Therefore, we sought to determine the relationship between the hierarchical decision-making process of fruit choice and patterns of natural selection on fruit traits. Methods: We recorded bird visits and measured fruit-related traits (fruit crop size, fruit diameter and seed weight) in a natural population of Psychotria carthagenensis, a bird-dispersed treelet, in a Yungas forest from Argentina. To assess phenotypic selection patterns on fruit display traits, we performed multivariate selection analysis, and to explicitly identify a hierarchy of fruit trait choice we used a classification tree as a predictive model. Important Findings: Selection patterns on fruit display traits were in agreement with a hierarchical process of fruit choice made by birds. The strength of directional selection on the total number of fruits in a plant (i.e. fruit crop size) was nearly two times higher than on fruit size, and the classification tree analysis supported this hierarchical pattern. Our results support previous evidence that seed dispersers shape fruit crop size with higher intensity than subindividual fruit traits. Also, high levels of subindividual phenotypic variation of fruit display traits may be explained by relaxed selection pressures exerted by frugivores. Empirical studies also show that this pattern may constitute a general phenomenon among other plant-animal interactions.Facultad de Ciencias Naturales y Muse

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

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.Los datos utilizados para este trabajo pueden accederse haciendo clic en "Documentos relacionados".Facultad de Ciencias Naturales y MuseoConsejo Nacional de Investigaciones Científicas y Técnica

Anatomy of flower and fruit of Vassobia breviflora (Solanaceae) in the south of the southern Yungas (Argentina)

Solanaceae es una familia con aproximadamente 2400 especies de distribución cosmopolita. Vassobia breviflora es la única especie del género presente en Argentina. El objetivo de este trabajo fue revisar y caracterizar la anatomía de la flor y fruto de V. breviflora a partir de muestras recolectadas en poblaciones de las Yungas del noroeste argentino. Se aplicaron técnicas anatómicas convencionales. Los resultados mostraron que la mayoría de las estructuras de la flor, el fruto y la semilla no difirieron de lo previamente reportado respecto de la organización estructural descripta para otras especies de Solanaceae. No obstante, por primera vez, describimos el androceo, el fruto, la semilla, pedicelo floral y frutal, cinco tipos de tricomas y cinco tipos de estomas en el perianto. Encontramos diferencias en la forma del tejido de transmisión y del tipo de óvulo respecto de lo previamente descripto. Además, localizamos el parénquima y las células epidérmicas secretoras del nectario. En el contexto de la familia Solanaceae, discutimos la función y valor diagnóstico de las estructuras descriptas.Solanaceae is a family with nearly 2400 species of cosmopolitan distribution. Vassobia breviflora is the only species of the genus present in Argentina. The goal of this work was to review and characterize the anatomy of the flower and fruit of V. breviflora from samples collected in populations of Yungas in the argentine Northwest. Conventional anatomical techniques were applied. The results showed that most flower, fruit and seed structures did not differ from those previously reported regarding the structural organization described for other species of the Solanaceae family. However, for the first time, we described the androecium, fruit, seed, floral and fruit pedicels, five types of tricomes and five types of stomata in the perianth. We found some differences in the shape of the transmission tissue and in the type of ovule with respect to that previously reported. Also, we located the parenchyma and the epidermic secretory cells of the nectary. In the context of the family Solanaceae, we discussed the function and diagnostic value of the described structures.Fil: Bernacki, F. G.. Fundación Miguel Lillo; ArgentinaFil: Albornoz, P. L.. Fundación Miguel Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Valoy, M.. Fundación Miguel Lillo; ArgentinaFil: Ordano, Mariano Andrés. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Influence of the site of oviposition on the level of egg parasitism in the corn leafhopper, dalbulus maidis (Hemiptera: Cicadellidae)

The corn leafhopper Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae), transmits three important plant pathogens that adversely affect corn crop and ranges from the USA to Argentina. The vector has a rich natural enemy complex that generates high levels of parasitism, but its populations are persistent and prevalent. We characterized the oviposition sites of D. maidis on young corn plants in order to verify the hypothesis that the vector has an oviposition strategy for mitigating parasitism. Oviposition locations on plants were assessed in the laboratory and eggs within corn plants were exposed to natural parasitism in a cornfield. Eggs were located mostly laid in the unfolded leaves and were attacked by five parasitoid species. Parasitism was significantly affected by the class of leaf and the position of the egg in the leaf. Anagrus virlai Triapitsyn was the most abundant parasitoid species, which emerged significantly higher in the basal blade than other species. Our results suggest that leafhoppers minimize egg parasitism by laying their eggs within concealed locations on the plant.Fil: Luft Albarracin, Erica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Virla, Eduardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Ordano, Mariano Andrés. Fundación Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentin

On the adequacy of fruit removal as a proxy for fitness in studies of bird-mediated phenotypic selection

Premise: In fleshy-fruited plants, fruit removal is widely used as a proxy for plant reproductive success. Nevertheless, this proxy may not accurately reflect the number of seeds dispersed, an assumed better proxy for total fitness (fruit removal × mean number of seeds dispersed per fruit). Methods: We examined under what circumstances fruit removal can be reliable as a proxy for total fitness when assessing bird-mediated selection on fruit traits. In three populations of the Blue Passionflower (Passiflora caerulea), we used the number of fruits pecked per plant as a surrogate for fruit removal to estimate phenotypic selection on fruit and seed traits, and simulations of the effect of the fruit-seed number trade-off on the number of fruits removed. Results: Fruit removal was a good indicator of fitness, accounting for 55 to 68% of the variability in total fitness, measured as total number of seeds removed. Moreover, multivariate selection analyses on fruit crop size, mean fruit diameter and mean seed number using fruit removal as a fitness proxy yielded similar selection regimes to those using total fitness. Simulations showed that producing more fruits, a lower number of seeds per fruit, and a higher variability in seed number can result in a negative relationship between fruit removal and total fitness. Conclusions: Our results suggest that fruit removal can be reliably used as a proxy for total fitness when (1) there is a weak fruit number-seed number trade-off, (2) fruit crop size and fruit removal correlate positively, and (3) seed number variability does not largely exceed fruit number variability.Fil: Palacio, Facundo Xavier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección Ornitología; ArgentinaFil: Cataudela, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Montalti, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Zoología de Vertebrados. Sección Ornitología; ArgentinaFil: Ordano, Mariano Andrés. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Fundación Miguel Lillo; Argentin

Efficacy of selected volatile compounds for organic vine mealybug control

Planococcus ficus (Signoret) (Hemiptera: Pseudo-coccidae) constitutes a high impact pest in vineyards. Synthetic insecticides are inefficient to control the mealybug population and they affect human health and the environment. The insecticidal properties of eight volatile compounds against vine mealybugs and their grapevine leaf phytotoxicity in laboratory conditions were evaluated. 2-decanone, 3-decanone, α-methyl cinnamaldehyde and cinnamaldehyde produced a higher percentage of mealybug mortality in relation to control at a fumigant dose of 300 µL·L-1 air. The 3-octanone, cinnamyl chloride, 1-octen-3-ol and 3-octanol were not effective against P. ficus. Cinnamaldehyde and α-methyl cinnamaldehyde produced a low acetylcholinesterase inhibition (IC50= 2.67 µL·L-1 and 9.10 µL·L-1, respectively), whereas 2-decanone and 3-decanone did not cause enzyme inhibition. Cinnamaldehyde was not phytotoxic for grapevine leaves; therefore, this compound was selected for a contact application to improve its effectiveness, resulting in a LC50 of 394.36 µL·L-1 solution. The results demonstrated the potential of cinnamaldehyde to be developed as a non-phytotoxic natural insecticide for the control of vine mealybugs in vineyards